Download Investigating tectonic-erosion interactions

10th Topo-Europe workshop 2014
Interplay between surface, lithospheric
and mantle processes
ABSTRACTS
Tectonic control on topographic and exhumational
segmentation of the Himalaya
Peter van der Beek(1)
Mallory Baudin(1)
Camille Litty(1,2)
Jonathan Mercier(1)
Xavier Robert(1)
Elisabeth Hardwick(1)
(1)Institut des Sciences de la Terre, Université Joseph Fourier, Grenoble, France
(2)Now at: Institut für Geologie, Universität Bern, Switzerland"
Abstract:
Although the Himalayan range is commonly presented as cylindrical along-strike, geological
structures, topography, precipitation, and exhumation rates as recorded by low-temperature
thermochronology data all vary significantly from west to east. In particular, segments of the belt
that are characterized by a clear topographic step between the Lesser and Higher Himalaya,
associated with a peak in precipitation and focused exhumation (e.g. central Nepal, Himachal
Pradesh) alternate with segments where the topography increases more linearly to the north,
precipitation peaks at lower elevations and exhumation rates appear to be lower (e.g. western
Nepal, Bhutan). The potential climatic or tectonic controls on these spatially variable topographic,
precipitation and exhumational patterns have been widely discussed in recent years but remain
unclear. Thermo-kinematic modelling predicts that the geometry of the main Himalayan detachment
(in particular the presence or absence of a major mid-crustal ramp) strongly controls the kinematics,
exhumation and topography of the orogen. Where a major crustal ramp is present, the topography
shows a steep gradient that focuses exhumation and orographic precipitation whereas the
topography is gentler and exhumation less focused in the absence of a ramp. We test this
prediction by comparing the pattern of topography, river incision and long-term exhumation in
central Nepal with new results from the remote Karnali River transect in far western Nepal. Our
results therefore imply that along-strike climatic variations in the Himalaya respond to tectonics
rather than driving it. The presence or absence of a mid-crustal ramp may be due to inherited
structures on the underthrusting Indian Plate or, alternatively, may reflect transient behaviour of the
accreting Lesser Himalayan thrust stack, which may oscillate between frontal accretion (without a
ramp) or basal accretion in the presence of a ramp.
GEOCHEMISTRY OF ADIGRAT SANDSTONE,
NORTH WESTERN ETHIOPIA
Barsisa Bekele
Wollaga University
Abstract:
Mineralogy, major, traces, and rare earth elements geochemistry of Adigrat Sandstones Formation
from the Blue Nile Basin (BNB), NW Ethiopian plateau have been analyzed to decipher their
provenance composition, paleoweathering and paleoclimatic scenarios. Samples of this sandstone
are slightly variable in composition. Mineralogically the framework grains are quartz (Q), feldspar
(F) and lithic fragments (L) and on QFL diagram; most of the samples are plotted in subarkose and
lithic subarkose fields. Geochemically, Adigrat sandstones are classified as arkose, subarkose,
litharenite, and sublitharenite. The CIA, PIA and CIW values for this sandstone and the A–CN–K
diagram agreeably suggest that source rocks experienced intense chemical weathering under hot
and humid tropical to sub-tropical climate. Mineralogical evidence suggests that plutonic and
metamorphic rocks were major contributing source rocks. Perhaps, multi-cyclic processes reworked
the sediment. Relatively immobile elements have been selected for provenance studies. Ratios and
plots of relatively immobile elements consistently suggest that the Adigrat Sandstone is derived
from compositionally mixed source between mafic and intermediate igneous rocks. Discriminant
function diagram constructed from major oxides, the Chondrite normalized REE plot, Cr/V vs. Y/Ni
ratios, La vs. Th plot and Th-Hf-Co ternary diagram all suggest that the Adigrat Sandstone is
derived from compositionally mixed source. Significant contributions of intermediate supply are also
confirmed by Al2O3/TiO2 ratios and lower Eu/Eu* (0.552) values than that of PAAS (0.65).
Provenance composition and degree of sorting between Adigrat Sandstone in BNB vs. Mekele
Basin (MB) have been compared. The result shows that sediment of the former were highly sorted
and compositionally derived from mafic and intermediate input, where as that of the later was
mainly derived from felsic rocks.
Keywords: Adigrat sandstones, provenance, paleoweathering, paleoclimate and Discriminant
function diagram.
On the use of Luminescence Geochronology to infer uplift and
climatic controls on fluvial incision dynamics, terraces
formation and sediment transport in rivers.
Stéphane Bonnet (1)
Tony Reimann (2)
Dimitri Lague(3)
Jakob Wallinga(2)
Philippe Davy(3)
Uwe Rieser (4)
(1) Université de Toulouse, Géosciences Environnement Toulouse, UMR 5563, France
(2) Netherlands Center for Luminescence Dating, Wageningen University of Technology, The
Netherlands
(3) Geoscience Rennes, CNRS/INSU, UMR 6118, Campus de Beaulieu, 35042 Rennes Cedex,
France
(4) Luminescence Dating Laboratory, School of Earth Sciences, Victoria University, Wellington,
New Zealand
"Poster”
Abstract:
"Luminescence Geochronology (OSL, IRSL) allows to date the burial of sediment particles within
fluvial deposits on the basis of the estimate of the number of electrons trapped at defects in the
crystal lattice in response to natural ionizing radiations. A prerequisite for accurate dating is that all
traps were emptied by exposure to sunlight (a phenomenon referred to as bleaching) prior to
deposition,. Sunlight exposure is very efficient to bleach the luminescence signal, however
incomplete bleaching is ordinary in fluvial settings resulting in overestimation of ages of deposits.
Here we investigate the temporal variability in luminescence single-grain ages distribution and
resulting ages overestimation of sediments of a river during its downcutting into the bedrock during
the Holocene (Rangitikei river, New Zealand). The results we will present will illustrate (1) a sharp
decrease in fluvial incision rate during the Holocene, that we relate to the process of re-equilibration
between incision and uplift following a LGM climatic inhibition of incision, (2) a fluvial incision control
on the formation of fluvial terraces, high incision rates preventing lateral planation and the formation
of fluvial terraces, (3) a control of fluvial incision on single-grain ages distribution and resulting ages
overestimation, related to two complementary processes : attenuation of light in the water column
during fast incision rate periods because of high sediment concentration and turbidity, coupled to
short particle transport and bleaching because of limited cycles of erosion, transport and deposition
when incision rate is high.
Our results will then illustrate the richness of luminescence geochronology to investigate
geomorphic processes.
Strain localization in continental compressional settings:
insights from analogue models
Elisa Calignano (1)
Dimitrios Sokoutis (1, 2)
Ernst Willingshofer (1)
Frédéric Gueydan (3)
Sierd Cloetingh (1)
(1) Faculty of Geosciences, Department of Earth Sciences, Utrecht University, Budapestlaan 4, PO
Box 80021, 3508 TA Utrecht, The Netherlands
(2) Department of Geosciences, University of Oslo, PO Box 1047 Blindern, N-0316 Oslo, Norway
(3) Géosciences Montpellier, Université Montpellier 2, UMR CNRS/INSU 5243, Place Bataillon,
CC60, 34093 Montpellier Cedex, France
Abstract:
The strength of the continental lithosphere is controlled by its depth dependent rheological
structure. Continents, however, are the result of the assemblage of domains that suffered different
tectonic processes. These result in lateral changes in composition and thermal perturbations that
alter the rheology and thus the strength of the lithosphere.
Numerous modelling studies investigated the localization of deformation in compressional settings
in case of lithospheric weak zones flanked by stronger domains.
We used lithospheric scale analogue models to explore strain redistribution and topography
development resulting from the presence of stronger domains in the lithosphere. Such lateral
heterogeneities have been implemented in both weak (crème-brûlée) or strong (jelly sandwich)
lithosphere. Among the investigated parameters, the vertical location of a high viscosity block was
varied and different convergence velocity and thickness of the upper brittle mantle were tested,
both playing an important role in the crust-mantle coupling. Furthermore, we examined different
orientations of the rheological boundaries with respect to the convergence direction, since
reactivated lithosphere heterogeneities are often observed to strike oblique with respect to the main
horizontal stress field.
Experimental results indicate that the presence of strong segments within the lithosphere induce
strong localization of deformation at the rheological boundaries, with associated high relief build-up.
Topography allow for inferring the presence of lateral strength heterogeneities in the lithosphere
with low relief being characteristic for stable regions associated with the strong domains. The
obliquity of the heterogeneity with respect to convergence direction yielded to be an important
factor controlling the polarity of lithospheric mantle underthrusting.
The presented results provide valuable insight for strain localization in collisional settings under
various rheological configurations.
Strain localization during compression of a laterally
heterogeneous lithosphere
Elisa Calignano (1)
Dimitrios Sokoutis (1, 2)
Ernst Willingshofer (1)
Frédéric Gueydan (3)
Sierd Cloetingh (1)
(1) Faculty of Geosciences, Department of Earth Sciences, Utrecht University, Budapestlaan 4, PO
Box 80021, 3508 TA Utrecht, The Netherlands
(2) Department of Geosciences, University of Oslo, PO Box 1047 Blindern, N-0316 Oslo, Norway
(3) Géosciences Montpellier, Université Montpellier 2, UMR CNRS/INSU 5243, Place Bataillon,
CC60, 34093 Montpellier Cedex, France
“Poster”
Abstract:
First order large scale stress fields, associated with active plate tectonic processes, interact with
lateral heterogeneities in the lithosphere and generate strain redistribution. Next to the fact that the
strength of the continental lithosphere is mainly controlled by its depth dependent rheological
structure, continents are often the product of the assemblage of domains that suffered different
tectonic processes, resulting in lateral changes in composition and thermal structure.
We present a series of lithospheric-scale analogue models designed to investigate strain
redistribution resulting from the presence of a stronger rheological heterogeneity embedded in a
weak lithosphere.
The modelled lithosphere consists of a four-layer brittle-ductile rheological structure, representative
of low geothermal gradient conditions. The experiments consist of three domains with different
mechanical properties: two external blocks sharing the same lithospheric stratification and one
narrow central block where a thicker upper crust has been implemented to approximate an increase
in bulk lithospheric strength.
Among the investigated parameters, convergence velocity and thickness of the upper brittle mantle
are varied, both playing an important role in the crust-mantle coupling. Furthermore, we examined
different orientations of the rheological boundaries with respect to the convergence direction, since
reactivated lithosphere heterogeneities are often observed to strike oblique with respect to the main
horizontal stress field.
Experimental outcomes indicate that the presence of a strong lithospheric section induces strong
localization of deformation at the rheological boundaries, with associated high relief build-up. When
the strong domain was oblique to the convergence direction, deformation was partially localized
along the rheological boundaries, due to the along-strike increase in distance from the moving wall.
As a consequence two main thrust systems with opposite underthrusting polarity developed,
connected by a complex transition zone.
The presented results provide valuable insight for strain localization in collisional settings under
various rheological configurations.
Structural and stratigraphic 4D evolution of the Kuh-e-Faghan
fault system: the intraplate response to Arabia-Eurasia
collision in Central Iran
Gabriele Calzolari (1)
Federico Rossetti (1)
Valerio Olivetti (2)
Marta Della Seta (3)
Reza Nozaem (4)
Gianluca Vignaroli (1)
Maria Laura Balestrieri (5)
Domenico Cosentino (1)
Claudio Faccenna (1)
1) Dipartimento di Scienze, Università Roma Tre, Largo S. L. Murialdo 1, 00146 Roma, Italy
2) Centre de Recherche et d’Enseignement de Géosciences de l’Environnement, Avenue Louis
Philibert BP 80, 13545 Aix en Provence, France
3) Dipartimento di Scienze della Terra, “Sapienza” Università di Roma, Piazzale Aldo Moro 5,
00185 Rome, Italy
4) Department of Science, Imam Khomeini International University, 34185-1416 Qazvin, Iran
5) CNR-Istituto di Geoscienze e Georisorse, Via G. La Pira 4, 50121 Firenze, Italy
Abstract:
Central Iran provides an ideal test site to study the morphotectonic response to initiation and
propagation of intraplate faulting. A multidisciplinary approach that integrates structural and
stratigraphic field investigations with geochronological (OSL) and thermochronological (U-Th)/He
apatite, AHe) analyses is adopted to reconstruct the spatio-temporal evolution of the Kuh-e-Faghan
Fault (KFF), in northeaster Central Iran. Structural mapping reveals that KFF defines a narrow, ca.
80 km long, deformation zone consisting of three main, broadly left stepping, E-W striking rightlateral fault strands, which cut through the Mesozoic-Paleozoic substratum and the NeogeneQuaternary sedimentary covers. The structural and depositional architecture of the Neogene
deposits, together with the AHe thermochronology results indicate that the intra-fault blocks along
the KFF experienced two major episodes of fault-related exhumation at ~18 Ma and ~4 Ma. The
major outcomes of this study bear implications on: (i) the understanding the spatio-temporal
evolution of intraplate strike-slip fault systems; and (ii) the Neogene-Quaternary kinematic and
tectonic evolution of Central Iran. (i) A conceptual model of fault initiation and propagation is
proposed. The fault system propagates and evolve from diffuse deformation, accomplished by
distributed en-echelon shears, to localized deformation with development of mature, thoroughgoing
fault strands. Fault zone localization induces widening of the damage zones inhibiting further
length-ward propagation and causing trailing extensional and contractional terminations to develop.
As a result, the fault systems may then propagate by renewed diffuse shear deformation in
undeformed regions of the fault tip. (ii) The two fault-related exhumation episodes, at ~18 Ma and
~4 Ma, well fit with the regional early Miocene collision-enhanced uplift/exhumation and the late
Miocene–early Pliocene widespread tectonic reorganization of the Turkish-Iranian plateau.
Activation and kinematic evolution of the intraplate strike-slip fault systems in Central Iran during
Neogene-Quaternary times may reflect states of far- and near-field stress changes at the collisional
boundaries".
On the static and dynamic contribution
of topography
F. Cammarano (1)
M. Guerri (1)
P.J. Tackley (2)
(1) Department of Geosciences and Natural Resurces Management, University of Copenhagen,
Denmark;
(2) Institute of Geophysics, ETH Zurich, Switzerland
Poster
Abstract:
A large part of current topography is due to isostatically compensated density variations within the
crust and lithospheric mantle, but dynamic topography - i.e. the topography due to adjustment of
surface (as for other internal boundaries) to mantle convection – is an important secondary
component at a global scale.
In order to separate the two components, it is fundamental to estimate: i) crustal and mantle density
structure, ii) mantle viscosity distribution.
We use a multidisciplinary approach involving geophysical observables and mineral physics
constraints. 3-D mantle density structure is inferred from the thermal interpretation of several global
seismic models assuming a depleted continental lithosphere (which accounts for petrological
observations, as in Cammarano et al. 2011). We further constrain the top 150 km by including heatflow data and considering the thermal evolution of the oceanic lithosphere. The density structures
are coupled with 3-D viscosity distributions obtained with various pressure and temperature
viscosity laws. We use StagYY (Tackley 2008) to compute the associated dynamic topographies
and free-air gravity. The crustal density distribution relies on CRUST1.0 (Laske et al. 2013), but we
also test alternative distributions based on various average chemical compositions and a robust
thermodynamic database (Guerri and Cammarano, in preparation).
The statistical analysis of the results (with or without lateral variations in viscosity and at different
spatial scales) and the comparison with the observations shows the importance of lithospheric
densities to correctly determine the static component, thus improving the interpretation of the
topography signal.
Discrepancies between seismic models produce significant differences in the inferred lithospheric
mantle densities already at spatial scales around one thousand kilometers. In addition, crustal
densities are poorly constrained from available crustal models.
A combined interpretation of gravity, seismic, heat-flow and petrologic data in terms of temperature
and composition has the potential to improve current estimates of lithospheric density structure."
Exhumation of the High Himalaya in the Mt. Everest
region and India-Asia collision zone: implications
for Himalayan tectonics
B. Carrapa (1)
P.G. DeCelles (1)
D. Orme (1)
P. Kapp (1)
(1) Department of Geosciences, University of Arizona
Abstract:
The India-Asia collision zone in southern Tibet and the high Himalaya preserves a record of
geodynamic and erosional processes following intercontinental collision. Apatite fission-track and
zircon and apatite (U-Th)/He data from the Oligocene–Miocene Kailas Formation, within the IndiaAsia collision zone, show a synchronous cooling signal at 17 ± 1 Ma, which is younger than the ca.
26–21 Ma depositional age of the Kailas Formation, constrained by U-Pb and 40Ar/39Ar
geochronology, and requires heating (burial) after ca. 21 Ma and subsequent rapid exhumation.
Data from the Gangdese batholith underlying the Kailas Formation also indicate Miocene
exhumation. Significant removal of material from the India-Asia collision zone was likely facilitated
by efficient incision of the paleo–Indus and paleo–Yarlung Rivers in response to drainage
reorganization and/or intensification of the Asian monsoon. AFT and 40Ar/39Ar ages from the
Rongbuk region, north of Mt. Everest, record regional rapid cooling associated with tectonic
exhumation along the South Tibetan Detachment at ca. 16 Ma. The depositional and thermal
history of the Kailas Formation is consistent with rapid subsidence during a short-lived phase of
early Miocene extension during southward rollback of the Indian plate, followed by uplift and
exhumation driven by renewed northward underthrusting of India. The coeval exhumation signal at
Mt. Everest suggests a similar mechanism for the initiation of the STD. Comparison between the
north and south sides of Mt. Everest shows a bimodal exhumation history: the north side was
exhumed by 16 Ma, whereas the south side is characterized by Pliocene (4-1 Ma; Streule et al.,
2012) exhumation, suggesting that tectonic exhumation associated with STD was localized rather
than regional. These results also suggest that exhumational bimodality (older to the north, younger
to the south) may be a persistent feature of the High Himalaya.
Cenozoic surface dynamics of
West Africa
D. Chardon (1)
J.L. Grimaud (1, 2)
A. Beauvais (3)
D. Rouby (4)
(1) IRD, CNRS, GET, Toulouse University, Toulouse, France ([email protected])
(2) St. Anthony Falls Laboratory, University of Minnesota, Minneapolis, Minnesota, USA
(3) IRD, CEREGE, Aix-Marseille University, Aix-en-Provence, France
Abstract:
We evaluate and quantify surface dynamics of West Africa by constraining its evolving regional
topography, river catchment geometries, river long profiles, denudation and yields. Four erosion
periods are considered since 45 Ma as recorded by dated and regionally correlated incision
markers.
The current river catchments of the sub region were acquired by drainage reorganization between ~
45 and ~ 24 Ma (probably before 30 Ma), which triggered Niger delta progradation in the Earliest
Oligocene. The fixed geometry of the West African drainage since then offers the opportunity to
effectively link the inland morphoclimatic and epeirogenic record to offshore sedimentation.
Drainages evolved preferentially by very slow (5 m/my) slope decrease or uniform incision along
river segments comprised between stationary knickzones with no apparent relation to base level
change. Therefore, knickzones’ height of position may not reflect the response of rivers to base
level fall. Very slow incision allowed amplification of the Hoggar hot spot swell and flexural uplift of
the continental margin to be recorded by river long profiles, emphasizing the potential of big rivers
as gauges of dynamic topography.
The subregion underwent a steady state, weathering-limited denudation regime controlled by the
thickness of the lateritic regolith available for stripping. We obtain a regionally averaged volumetric
erosion rate of 5 x 10-3 km3/km2/m.y. corresponding to a denudation rate of 6 m/m.y. that
remained nearly constant for three time spans (45-24, 24-11 and 11-0 Ma) despite spatial variations
due to epeirogenic movements. Denudation is converted into a yield of 20 +/- 6 t/km2/yr with a
minimum solute component of 5 +/- 3 t/km2/yr accounting for the porosity of the regoliths being
eroded, implying a contribution of 2 +/- 0.6 Gt/yr of the non-orogenic landmass to the global
continental yield since the last peak greenhouse.
Effect of surface processes on fold development:
a numerical approach
M. Collignon (1),
B.J.P. Kaus (2),
D.A. May (3),
N. Fernandez (2)
(1) Geological Institute, ETH Zurich, Switzerland
(2) Institut für Geowissenschaften, Johannes Gutenberg-Universität, Mainz, Germany
(3) Institute of Geophysics, ETH Zurich, Switzerland"
Abstract:
In order to understand the interactions between surface processes and multilayer folding systems,
we here present fully coupled three-dimensional numerical simulations. The mechanical model
represents a sedimentary cover with internal weak layers, detached over a much weaker basal
layer representing salt or evaporites. Applying compression in one direction results in a series of
three-dimensional buckle folds, of which the topographic expression consists of anticlines and
synclines. This topography is modified through time by mass redistribution, which is achieved by a
combination of fluvial and hillslope erosion, as well as deposition, and which can in return influence
the subsequent deformation. Model results show that surface processes do not have a significant
influence on folding patterns and aspect ratio of the folds. Nevertheless, erosion reduces the
amount of shortening required to initiate folding and increases the exhumation rates. Increased
sedimentation in the synclines contributes to this effect by amplifying the fold growth rate by gravity.
The main contribution of surface processes is rather due to their ability to strongly modify the initial
topography and hence the initial random noise, prior to deformation. If larger initial random noise is
present, folds amplify faster, which is consistent with previous detachment folding theory. Variations
in thickness of the sedimentary cover (in one or two directions) also have a significant influence on
the folding pattern, resulting in linear, large aspect ratio folds.
Our simulation results can be applied to folding-dominated fold- and thrust-belt systems, detached
over weak basal layers, such as the Zagros Folded Belt.
Physical Parameters Controlling Subduction Dynamics and
Surface Topography in Self-Consistent Global
Models of Mantle Convection
F. Crameri (1)
Carolina R. Lithgow-Bertelloni (1)
Paul J. Tackley (2)
(1) University College London
(2) ETH Zurich
“Poster”
Abstract:
Recent advances in numerical modelling allow global models of mantle convection to realistically
reproduce the behaviour at convergent plate boundaries (Crameri et al., 2012a). This allows for a
more extensive study of subduction that, in contrast to the numerous regional models, incorporates
the complete framework of mantle convection.
Here, we focus on different aspects of mantle convection including (i) slab dip variations, (ii)
variations in radial mantle viscosity, and (iii) the presence of localised mantle upwellings and
discuss their control on the dynamics of Earth-like plate tectonics. Additionally, we present the
effect these parameter variations have on measurable quantities like dynamic topography and plate
velocity.
The models are calculated by the finite-volume code Stag-YY (e.g., Tackley 2008) using a multigrid method on a fully staggered grid. Second, the sticky-air method (Matsumoto and Tomoda
1983; Schmeling et al, 2008) is applied and thus approximates a free surface when the sticky-air
parameters are chosen carefully (Crameri et al., 2012b).
Overall, this study demonstrates the ability of various parameters to significantly influence both
subduction dynamics and surface topography.
REFERENCES
Crameri, F., et al. (2012a), Geophys. Res. Lett., 39(3).
Crameri, F., et al. (2012b), Geophys. J. Int., 189(1).
Matsumoto, T., and Y. Tomoda (1983), J. Phys. Earth, 31(3).
Schmeling, H., et al. (2008), Phys. Earth Planet. Int., 171(1-4).
Tackley, P. J. (2008), Phys. Earth Planet. Int., 171(1-4)."
Hinterland “Bobber” Basins as Recorders of Lithospheric
Removal in the Central Andes
P.G. DeCelles (1)
B. Carrapa (1)
H. Wang (2)
C.A. Currie (2)
(1) Department of Geosciences, University of Arizona, Tucson, USA;
(2) Department of Physics, University of Alberta, Edmonton, Alberta, Canada
Abstract:
The hinterland (Puna and Altiplano) region of the central Andes contains numerous Miocene to
Recent enigmatic sedimentary basins not attributable to thrust-loading or normal faulting. Arizaro
basin in the Puna Plateau of NW Argentina is typical. At 3800-4200 m elevation along the eastern
flank of the magmatic arc, the basin is circular, ~100 km in diameter, and was filled during Miocene
time (ca. 21-9 Ma) by >3.5 km of eolian, alluvial, fluvial, and lacustrine sediment and ashfall tuffs
from the magmatic arc. The basin fill was subsequently shortened in its central part, and has been
uplifted and topographically inverted. Arizaro basin is not related to known basin-bounding faults,
nor does it exhibit a peripheral belt of coarse-grained facies. Sandstone modal framework
compositions are arkosic, but not as rich in volcanic lithic fragments as intra-arc basin sandstones.
Detrital zircon U-Pb age spectra implicate sources in western Argentina and northern Chile and the
local Miocene magmatic arc. Depositional-age zircons are present in most sandstones analyzed,
and zircon U-Pb ages from volcanic tuffs provide independent chronological control. Tectonic
subsidence initiated slowly, accelerated to ~0.6 mm/yr during the medial stage of basin
development, and tapered off to zero as the basin began to shorten internally and topographically
invert after ~10 Ma. The Arizaro basin could have developed by gravitational foundering of a dense
Rayleigh-Taylor-type instability. To match the topographic evolution of the Arizaro basin, numerical
models indicate that the density anomaly must be <60 km in diameter and originate at ~50 km
depth, within the deep part of the thickened orogenic crust. Gravitational removal is accompanied
by shortening of the overlying crust and surface uplift. Mantle removal in this region occurred by
piecemeal processes, rather than wholesale removal. The model developed here may be relevant
for other hinterland basins throughout the central Andes.
Structure of the lithosphere from
analysis of satellite data
J. Ebbing
Department of Geosciences, Kiel University, Germany
Abstract:
Understanding the interplay between mantle and lithosphere dynamics requires an integrated
approach to estimate its physical properties. In recent years, it has become evident that the thermal
structure and composition of the upper mantle have a large influence on topography. Lithospheric
structures are affected by large-scale tectonic processes and are, in turn, expected to influence the
amount, localization and style of surface deformation. Prominent changes in the upper mantle are
expected at the lithosphere-asthenosphere boundary (e.g., partial melting) and at cratonic edges.
These changes can be recorded by a number of different geophysical data sets, sensitive to
seismic wave velocity, electrical resistivity and density.
Despite the increasing amount of geophysical observables, the heterogeneous data distribution is
still a challenge for large scale study areas. Globally available data sets with homogenous coverage
are satellite data, as for example the GOCE gravity gradient mission or the recently launched
SWARM magnetic field mission. These satellite missions add a scale of observation that cannot be
achieved at the Earth’s surface. For example, the gravity gradients from the GOCE mission data
have a depth sensitivity that makes them a useful tool to study the density distribution in the
uppermost mantle. The characteristic of the gradients is that they are not sensitive to the sublithospheric regional trend (unlike terrestrial gravity and the geoid), but especially sensitive to the
uppermost 150 km of the lithosphere. Sensitivity tests show that if reasonable crustal models exist,
with the use of satellite gravity gradients, it enables us to distinguish between density domains
influenced by the thermal structure or composition of the upper mantle, and herby to link crust and
upper mantle in great detail, which makes them an ideal data set to be used in combination with
seismic tomography.
From the surface Topography to the Upper mantle
beneath Central-Iberian-Zone. The ALCUDIA
Seismic Experiments
Siddique Akhtar Ehsan(1)
Ramon Carbonell(1)
Puy Ayarza(2)
David Martí(1)
David Jesús Martínez-Poyatos(3)
José Fernando Simancas(3)
Antonio Azor(3)
Concepción Ayala(4, 1)
Montserrat Torné(1)
Ignacio Marzan(1)
Andrés Pérez-Estaún(1)
1) Department of Structure and Dynamics of the Earth, Institute of Earth Sciences Jaume Almera,
ICTJA-CSIC, Lluis Sole i Sabaris s/n, 08028 Barcelona, Spain
2) Department of Geology, University of Salamanca, 37008 Salamanca, Spain
3) Department of Geodynamics, Faculty of Science, University of Granada, E-18071 Granada,
Spain
4) Instituto Geológico y Minero de España (IGME), C/ La Calera, 1, 28760 Tres Cantos- Madrid"
Poster
Abstract:
Multi-seismic experiments acquired across the central and southern part of the Iberian Peninsula
provide a new insight into the structure and nature of the lithosphere beneath these areas. Normal
incidence and wide-angle seismic reflection data acquired in the area resolve the internal
architecture and constrain the distribution of the physical properties along an almost 280 km long
transect that samples the major tectonic domains of the Central Iberian Zone (CIZ) and the
associated suture (e.g., the Central Unit, CU). A high quality image, ~230 km long, down to 45 km
depth (~15 s TWTT) is provided by the normal incidence data set. Based on the reflectivity
characteristics, the image can be divided into an upper and mid-lower crust, ~13 km and ~18 km
thick, respectively. The wide-angle seismic transect extended the crustal section towards the north
across the Madrid Basin. This, latter data set also sample the CIZ until the CU. This is ~280 km
long profile which provides very strong constraints on the distribution of physical properties (P wave
and S wave velocities, Poisson's ratio) of the upper lithosphere. The PiP and PmP seismic phases
constrain two discontinuities: the brittle to ductile discontinuity at ~13-19 km and the Moho
boundary at ~31-35.5 km. Currently both appear to act as decoupling surfaces and are interpreted
to represent levels of lithological/rheological variations. The internal structure of the Moho is further
discussed taking into account the characteristics of the PmP reflections. Furthermore, low fold
wide-angle P and S wave stacks reveal a marked crust-mantle transition which is most probably 5-6
km thick and relatively complex structure. The geometrical relationships of this structure with the
crustal fabrics of the normal incidence image suggest that the Moho is most probably a result of the
re-equilibration and/or other lithospheric processes active after the Variscan collision.
Crustal and Upper Mantle Structural Constraints on
the Topography of the southern Central
Iberian Zone
Siddique Akhtar Ehsan(1),
Ramon Carbonell(1),
Puy Ayarza(2),
David Martí(1),
David Jesús Martínez-Poyatos(3),
José Fernando Simancas(3),
Antonio Azor(3),
Concepción Ayala(4, 1),
Montserrat Torné(1),
Ignacio Marzan(1)
Andrés Pérez-Estaún(1)
1) Department of Structure and Dynamics of the Earth, Institute of Earth Sciences Jaume Almera,
ICTJA-CSIC, Lluis Sole i Sabaris s/n, 08028 Barcelona, Spain
2) Department of Geology, University of Salamanca, 37008 Salamanca, Spain
3) Department of Geodynamics, Faculty of Science, University of Granada, E-18071 Granada,
Spain
4) Instituto Geológico y Minero de España (IGME), C/ La Calera, 1, 28760 Tres Cantos- Madrid"
Institution of Earth Sciences Jaume Almera (ICTJA-CSIC)
Abstract:
Multi-seismic experiments ALCUDIA which include normal incidence and wide-angle seismic
reflection data reveal detailed crustal and lithospheric structure of the central to the southwestern
Iberia. The experiments provided an opportunity to analyse the nature and possible origin of the
Mohorovicic discontinuity and map in cross-section the distribution of the physical properties across
the Central Iberian Massif. The normal incidence deep seismic reflection transect, acquired in
summer 2007 provides a detailed image of an intra-continental Variscan orogenic crust (the Central
Iberian Zone, CIZ) and its suture zone with the Ossa-Morena Zone in southwest Iberia. This
seismic image shows a slightly less reflective upper crust, which has been interpreted to be ~13 km
thick. The deformation patterns in the mid-lower crust appear to correspond to ductile boudinage
structures, thrusting and an upper mantle wedge. The Mohorovicic discontinuity has been
interpreted to be the sharp, sudden decrease in reflectivity identified at 10.5 s TWTT (~31-33 km
depth). The velocity structure, P and S waves was constrained by conventional iterative forward
model of the travel time picks digitized from the high-resolution wide-angle seismic reflection data
acquired in early May 2012. The P wave velocity model reveals significant lateral velocity variations
in the upper crust down to ~20 km depth. The mid-lower crust is identified by a sharp gradient in
velocity at ~13 km and ~20 km beneath the CIZ in the south and the Madrid Basin in the north,
respectively. The base of the crust is well constrained by the high amplitude PmP arrivals and it is
located at ~31 km in the southern end and at ~35.5 km below the northern end of the profile. These
data provides for the first time a significant piece of evidence for a smooth and gradual increase of
crustal thickness beneath the Madrid Basin, Central Iberian Peninsula.
Small-scale subduction in
odd margins
M. Fernandez
M. Torne
J. Vergés
E. Casciello
Institute of Earth Sciences Jaume Almera - CSIC, Barcelona, Spain
Abstract:
Subduction is a prime consequence of plate tectonics where, an oceanic plate subducts beneath a
continental or an oceanic upper plate. Common observations in subducting regions, characterized
by large oceanic subducting plates, are: i) long and quasi-linear subduction trenches, ii) active
seismicity and a well-defined Wadati-Benioff zone, iii) unique subduction polarity, and iv) orogenic
volcanism and HP-LT metamorphism in the upper plate. Depending on the balance between
convergence and subduction rates, shortening or extension takes place in the upper plate, and
vertical and horizontal sublithospheric mantle flow develops. These simple observations can be
dramatically modified when the subducting plate formed at odd plate margins, dominated by very
slow spreading rates, strong transtensional regimes, and a high degree of margin segmentation.
Examples of odd margins are the Ligurian-Tethys, which developed during Jurassic-early
Cretaceous times due to the opening of the Central Atlantic Ocean, forming a series of en-echelon
margins with a thin crust of continental to oceanic nature and, occasionally, exhumed upper mantle.
The subsequent Africa-Eurasia convergence resulted in the consumption of these odd margins
becoming characterized by diffuse seismicity, well developed back-arc basins, uneven distribution
of metamorphism and volcanism, and transform faults separating small-scale subduction domains
that may show opposite polarities.
Tectonic controls on the Mesopotamian foreland
basin evolution: coupled tectonic/surface
processes modeling
C. Fillon (1)
D.Garcia-Castellanos (1)
J. Vergés (1)
(1) Institute of Earth Sciences Jaume Almera -CSIC, Barcelona, Spain
Abstract:
Identifying how changes in plate configuration affect wide and long-lived drainage systems is key to
decipher between climate and tectonic forcing on sedimentary basins evolution. The Mesopotamian
basin is a plate-scale foreland basin presumably linked to the tectonic load of the Zagros mountain
belt. The current drainage pattern shows the two main river systems (Tigris and Euphrates) draining
the basin longitudinally, likely to be influenced by other large-scale geodynamic events as well,
such as the uplift of the Anatolian Plateau (Middle Miocene) to the NW and/or the Red Sea opening
and flank tilting to the W, starting in early Miocene. In addition to these lithospheric-scale
processes, the Mesopotamian basin developed where the Neogene closure of the gateway
between Mediterranean sea and Indian ocean occurred, therefore recording the continentalization
of the area. By using an integrated modeling of surface processes, lithospheric flexure and
kinematic fault deformation, we test the influences of each main tectonic units on the basin
evolution. The numerical model is particularly designed to study the 3D foreland basin evolution
and to identify large-scale relationships between tectonic movements and sediment transport and
deposition. We specifically aim at reproducing the drainage conditions in the basin, the flexural
profile and the sediment thicknesses and geometry of deposition, by investigating the basin history
at the scale of the Arabian plate (3000 km x 1200 km), over a long period of time (i.e. since 35 Ma
to present day), and with integrating realistic climatic conditions. The main results reveal the need
for an external load in addition to the Zagros to reproduce the flexural profile of the basin,
suggesting a significant contribution from deep geodynamic events occurring in early to middle
Miocene times in shaping the present day Mesopotamian basin.
Coeval thrusting and strike-slip faulting during
Early Miocene collision in the Western Betics
(Southern Spain)
Gianluca Frasca (1)
Frédéric Gueydan (2)
Jean-Pierre Brun (1)
(1) Géosciences Rennes, UR1, France
(2) Géosciences Montpellier, UM2, France
Abstract:
"In recent years, researchers have been debating about the tectonic origin of the arcuate Betic-Rif
orogenic belt, which surrounds the Alboran Sea at the western end of the Mediterranean Sea. In
this talk, we investigate the tectonic units cropping out in the Western Betics (Malaga region,
Southern Spain) with the main goal of reconstructing the Miocene evolution of the area.
New structural data and geological mapping together with available data allow us to identify the
main structural features of the area. Two strike-slip corridors outline two E-W elongated tectonic
blocks with different lithological composition. The northern block is mainly composed by a lower
Miocene basin and by Mesozoic sediments, while the southern block mostly by mantle and
metamorphic rocks. Both the orientation of folds and of fault slip-vectors in the two corridors and the
foliation trajectories in the surrounding rocks are compatible with a dextral movement.
We will demonstrate that the main actors of the Miocene tectonics of the Western Betic Cordillera
are these E-W strike-slip corridors. The corridors terminate in coeval N50 directed thrusts that we
interpret as horse-tail splays. We consider then these strike-slip corridors as lateral ramps of the
thrust system observed in the area. We conclude that corridors and thrusts are responsible for the
westward emplacement of the Alboran thinned lithosphere on top of the Iberian margin.
Two enigmas in lithospheric dynamics: initiation of subduction
zones and ridge-transform spreading patterns
T. Gerya
"Institute of Geophysics, ETH-Zurich, Sonneggstrasse 5, Zurich Switzerland,
Abstract:
Global networks of subduction trenches and ridge-transform spreading patterns represent inherent
surface features of terrestrial plate tectonics. A fundamental unresolved problem is how these
topographic networks formed and why they are maintained.
Although most of the presently active intra-oceanic subduction zones are relatively young and
initiated during the Cenozoic, subduction initiation process remains controversial. We investigated
spontaneous intra-oceanic subduction initiation with new numerical hydro-thermo-mechanical
approach, in which solid rock deformation and fluid percolation are fully coupled (Dymkova and
Gerya, 2013). With laboratory-measured brittle rock strength, subduction can naturally start only in
the presence of porous fluid inside oceanic crust and pre-existing fracture zones. Fluid percolation
is localized along a system of multiple listric propagating thrusts with coalescing nearly horizontal
roots located near the oceanic Moho of the forming subducting slab. High fluid pressure along this
forming subduction interface controls rheological decoupling between the plates.
Initiation of orthogonal ridge-transform spreading patterns remains contentious. We investigated
this process with the use of high-resolution 3D petrological-thermo-mechanical numerical models
(Gerya, 2013). The resulting geometry of an oceanic spreading pattern depends strongly on the
initial offset of spreading centers and the magnitude of fracture healing rate. Three different
characteristic long-term spreading modes are obtained: (1) ridge-transform patterns, (2) single
ridges and (3) spreading centers with an intermediate plate. Orthogonal ridge-transform oceanic
spreading patterns form gradually from moderate initial offsets of 40-60 km and become fully
established several million years after the plate breakup. We demonstrated that the ridge-transform
system is a long-term plate growth pattern that is generally different from an initial plate rifting
pattern. Steady-state orthogonal geometry of the ridge-transform system is governed by 180o
rotational symmetry requirement for open space occupation.
Citations:
Dymkova, D., Gerya, T. (2013) Geophys. Res. Lett., 40, 5671–5676.
Gerya, T. (2013) Phys. Earth Planet. Interiors, 214, 35–52
African lithosphere geometry: Geoid and elevation
constraints on Moho and LAB topography.
Jan Globig (1)
Manel Fernandez (1)
Montserrat Torné (1)
Claudio Faccenna (2)
(1) Institute of Earth Sciences Jaume Almera - CSIC, Group of Dynamics of the Lithosphere
(G.D.L.), Barcelona, Spain ([email protected])
(2) University Roma TRE, Dept. of Geological Sciences, Italy"
Abstract:
The African continent offers provoking conditions to investigate the relation between its lithospheric
structure and its anomalous regional long wavelength topography. The variable topography of the
continent has been intensively studied and is strongly discussed in terms of its age and origin. To
our understanding of surface topography knowledge of crustal thickness is of first-oder importance,
which is still incomplete for vast areas of the African continent. Here we present insights into the
continent’s crustal and lithospheric thickness which are major requirements in investigating the
evolution of African topography and mainly come from global and continental models often missing
a proper relation between elevation, density and depth to the Moho and LAB. For this purpose we
address the 1D study of the detailed structure of the African lithosphere (Moho and LAB geometry)
applying a four-layered model composed of crust and lithospheric mantle plus sea water and
asthenosphere, assuming Airy isostasy and using, as constraints, elevation, geoid and thermal
data. To better verify our crustal thickness model we test it against a comprehensive compilation of
existing Moho depth estimates from active and passive seismic studies across the continent.
Relating better the surface topography with the depth to the Moho and the LAB our approach is
seen to support the discussion around the strongly debated processes responsible for the today’s
bimodal distribution of basin-and swell topography.
From topography to topography: Surface elevation,
Moho geometry and African
lithosphere dynamics
Jan Globig (1)
Manel Fernandez (1)
Montserrat Torné (1)
Claudio Faccenna (2)
(1) Institute of Earth Sciences Jaume Almera - CSIC, Group of Dynamics of the Lithosphere
(G.D.L.), Barcelona, Spain ([email protected])
(2) University Roma TRE, Dept. of Geological Sciences, Italy
Poster
Abstract:
"Despite increasing efforts in seismic surveying and geophysical studies to unravel the structure of
the African lithosphere,vast areas of the African continent, especially in the central part, still lack
reliable data on Moho and LAB depth. As Africa offers provoking conditions to investigate the
relation between deep and upper mantle thermal and/or compositional anomalies and its
anomalous regional long wavelength topography we present insights into the continent’s crustal
and lithospheric thickness. For this purpose we address the 1D study of the detailed structure of the
African lithosphere (Moho and LAB geometry) applying a four-layered model composed of crust
and lithospheric mantle plus sea water and asthenosphere, assuming Airy isostasy and using, as
constraints, elevation, geoid and thermal data. Furthermore, to better verify the crustal thickness
model we test it against a comprehensive compilation of existing Moho depth estimates from active
and passive seismic studies across the continent.
Additionally existing models of thermo-tectonic age of crust, sediment thickness and the thermochemical state of mantle domains from global and regional tomography are used to discuss the
strongly debated processes responsible for the today’s bimodal distribution of basin-and swell
topography."
A single cause for uplift of the Central and
Eastern Anatolian plateau?
R. Govers (1)
J. Bartol (1)
(1) Department of Earth Sciences, Utrecht University, Netherlands,
Abstract:
Regional observations suggest that the Central Anatolian plateau (central Turkey) has risen by
more than 1 km since the Tortonian (~8 Ma) while significant crustal shortening did not occur. This
uplift was preceded by the onset of widespread volcanism (~14-9Ma). The lithospheric context of
these events is however unknown. For the Eastern Anatolian plateau, similar events have been
attributed to the late-stage evolution of the northern Neotethys slab, resulting in delamination and
slab break-off. Recent tomographic results indicate that this slab extended beneath both below the
Eastern and Central Anatolian plateau just prior to delamination. We propose a new lithospheric
scenario for the regional evolution in the Aegean-Anatolia-Near East region that combines a recent
compilation of surface geology data with the structure of the upper mantle. Following CretaceousEocene closure of the northern Neotethys, Africa-Eurasia convergence was accommodated by
horizontal subduction at a trench that was located south of Anatolia. Like before the closure, the
northern Neotethys slab continued to sink into the deeper mantle beneath the Izmir-AnkaraErzincan suture. In the early Miocene (~20-15Ma), the northern Neotethys slab started to retreat
southward to the trench, resulting in delamination of the lithospheric mantle. The last part of this
scenario is testable, whether delamination can explain the uplift of both the Central and Eastern
Anatolian plateau. In the east, uplift due to collision of Arabia is included. We use a coupled
thermal-flexural model of the lithosphere. Delamination can explain the average present-day longwavelength topography of the Central Anatolian plateau. For the Eastern Anatolian plateau,
delamination explains half the present-day elevation: the other half resulted from crustal thickening.
We therefore propose to refer to central and east Anatolia since the middle Miocene as "the
Anatolian plateau".
Cretaceous to Miocene long wavelength landforms of Africa
and NW Europe: climate, mantle dynamics and
lithosphere deformations controls.
F. Guillocheau and TopoAfrica working group
Géosciences Rennes - UMR 6118 Université de Rennes1-CNRS, Campus de Beaulieu, 35042
Rennes cedex
Abstract:
"In addition to the mountain belts and the rift shoulders, the Earth relief is characterized by
planation surfaces preserved as plateaus or plains, later more or less incised by rivers.
Africa is characterized by a succession of plateaus (Kalahari) and swells (Central-African, HoggarTibesti…) alternating with “basins” (Congo, Chad, Sudan...) with a wavelength of few thousands
years (very long wavelength). NW Europe displays a similar pattern with “highs” (French Massif
Central, Ardennes, Cornwall, Ardennes-Eifel…) and “lows” (Aquitaine, Paris-London, Western
Approaches..) with a lower wavelength of one order of magnitude (x100 km).
In both cases the landforms are similar: weathered planation surfaces (etchplains) degraded by
pediments and or pediplains, more or less weathered.
The uplift history is based on (1) the stepping of the different landforms and (2) the available age
constraints (dated weathering profiles, relationships between sediments, volcanism and landforms,
basin siliciclastic sediment budget..).
African reliefs are Cenozoic in age, younger than the Early-Middle Eocene (55-40 Ma). The only old
relief of Africa is the Southern African (Kalahari) Plateau that experienced a two steps evolution, a
first uplift during Late Cretaceous contemporaneous with high erosion under humid climatic
conditions, followed by a second uplift during Late Eocene – Early Oligocene. The paroxysm of
Africa uplift was during Miocene times (20-10 Ma) in response to mantle-scale processes.
In contrast, NW European reliefs have a much more complex history, exhumation and burial during
Cretaceous and two times uplift during Cenozoic times. Those quite “old” relief (compared to Africa)
recorded the lithospheric deformations due to the relative movements of Africa, Iberia and Eurasia.
Multiphase halokinematic deformation and
changing transport direction in the
Levant Basin
Zohar Gvirtzman (1, 2)
(1) Geological Survey of Israel, Jerusalem, Israel
(2) Hebrew University, Jerusalem, Israel"
Abstract:
"The Levant Basin provides a unique opportunity to study the early evolution of a salt giant when it
still behaves as an intact layer. Newly-acquired high-quality three dimensional seismic surveys
reveal previously undetected features on the seabed as well as weak reflections within the buried
Messinian salt.
The weak, yet observable, reflectors within the salt open the gate for classical stratigraphic analysis
that enables distinguishing between syn- and post-depositional deformations. While numerous
studies have shown that salt related deformation in the Levant Basin began in the Late Pliocene or
Early Pleistocene, these reflectors indicate that the first salt related deformation event occurred 3-4
my earlier, in the middle of the Messinian Salinity Crisis.
This interpretation reopens another question regarding the observed SW-NE shortening direction,
which is approximately orthogonal to the gliding direction expected from the northwestward tilting of
the basin. Whereas previous studies related this shortening direction to salt flow away from the Nile
Cone, our data indicate that this early deformation predates the accumulation of the Nile Cone and
therefore requires a different explanation.
On the other hand, the present day seabed morphology offshore Sinai with its circum Nile fold belt
confirms that the recent tectonic transport pattern is indeed controlled by squeezing away salt from
under the Nile Cone. Moreover, we show that additional folds previously explained by westward
gliding of the Plio-Quaternary section downdip the Israeli slope are, in fact, caused by updip
climbing of this section eastwards as a result of the far field salt flow pattern.
In general, we show that the contractional domain related to salt tectonics is far more complex than
previously thought and that the overburden and the salt deform synchronously, but not necessarily
harmonically.
Linking lithosphere deformation and sedimentary
basin formation over multiple scales
Ritske S. Huismans
Department of Earth Science, University of Bergen, Allégaten 41, N-5007 Bergen, Norway
Abstract:
Here we focus on the relationships between tectonic deformation and sedimentary basin formation.
Resolving the interaction and feedback between tectonic crust-lithosphere scale deformation and
surface processes through erosion of elevated areas and formation of sedimentary basins over
multiple scales has been a long-standing challenge. While forward process based models have
been successful at showing that a feedback is expected between tectonic deformation and
redistribution of mass at the earth’s surface by erosion, transport, and deposition, demonstrating
this coupling for natural systems has been an even greater challenge and is strongly debated.
Observational constraints on crust-lithosphere deformation and surface processes are typically
collected at highly varying spatial and temporal scales, while forward process based models are
typically run at either very large lithosphere-mantle scale, or at the scale of the sedimentary basin
making it difficult to investigate and explore the detailed interaction and feedback between these
systems. Here I will report on recent advances in forward modelling linking crust-lithosphere
deformation with surface processes over a large range of scales resolving tectonic plate scale
deformation and sedimentary basin formation at stratigraphic scales. The forward numerical models
indicate a linkage and interaction between the structural style of thick-skinned large-scale mountain
belt and rift-passive margin formation, erosion-transport-deposition processes operating at the
surface, and the thin-skinned deformation occurring in the associated sedimentary basins.
Dynamic ups and downs of mountain belts:
the Himalaya
L. Husson
ISTerre, CNRS, Univ. Grenoble Alpes, Grenoble, France
Abstract:
"In many mountain belts, the record of uplift and subsidence is often at odds with crustal tectonics
and shortening history. The canonical explanations that are based on lithospheric flexure or
removal of the mantle lithosphere also often fail to explain all observations. Transient dynamic
topography above evolving subduction slabs is an alternative mechanism that reconciles all
observations.
The Himalaya provide a good example. There, fast uplift and exhumation of the Himalaya and Tibet
and fast subsidence in the foreland basin portray the first order Neogene evolution of the IndianEurasian collision zone. Dynamic topography over the southward folded Indian slab explains the
modern location of the foreland depocenter. Backwards in time, that deflection was located
underneath the Himalaya and S. Tibet. The Neogene relative southward drift of the slab and
associated dynamic topography explains the uplift of the Himalaya and the fast subsidence of the
foreland basin.
While competing with other processes, transient dynamic topography may thus explain to a large
extent both the uplift and subsidence history of the Himalaya and of foreland basin, without any a
priori need for removal of the lithospheric mantle nor for the elastic flexure of the Indian plate.
Similar reasoning, with different subduction histories, equally applies to the Andes, the Carpathians,
or the Aegean."
Dynamics of lithospheric thinning and mantle melting
by edge-driven convection: Application to
Moroccan Atlas mountains
L. Kaislaniemi (1)
J. van Hunen (1)
(1) Department of Earth Sciences, University of Durham, Durham, United Kingdom
Abstract:
Edge-driven convection (EDC) forms in the upper mantle at locations of lithosphere thickness
gradients, e.g., craton edges. In this study we show how the traditional style of EDC, a convection
cell governed by the cold downwelling below an edge alternates with another style of EDC, in which
the convection cell forms as a secondary feature with a hot asthenospheric shear flow from
underneath the thicker lithosphere. These alternating EDC styles produce episodic lithosphere
erosion and decompression melting. Three-dimensional models of EDC show that convection rolls
form perpendicular to the thickness gradient at the lithosphere-asthenosphere boundary. Stagnantlid convection scaling laws are used to gain further insight in the underlying physical processes.
Application of our models to the Moroccan Atlas mountains region shows that the combination of
these two styles of EDC can reproduce many of the observations from the Atlas mountains,
including two distinct periods of Cenozoic volcanism, a semicontinuous corridor of thinned
lithosphere under the Atlas mountains, and piecewise delamination of the lithosphere. A very good
match between observations and numerical models is found for the lithosphere thicknesses across
the study area, amounts of melts produced, and the length of the quiet gap in between volcanic
episodes show quantitative match to observations.
Seismic imaging of the Pacific slab beneath Japan and
northeast China: deep water transportation
and enigma of the off-arc volcanism
Hitoshi Kawakatsu
Earthquake Research Institute, the University of Tokyo, Tokyo, Japan
Abstract:
We present seismic image indicating the transportation of water into the mantle wedge of the
subduction zone beneath northeastern Japan (Kawakatsu & Watada, 2007, Science). The
reflectivity profiles of seismic waves obtained from migrated receiver functions (RFs) of teleseismic
earthquakes recorded by the dense Japanese seismic network, Hi-net, show strong signature of the
dehydration of the subducting oceanic crust in the depth interval of 50-90km. Below this depth
range, a low-velocity layer on the top of the subducting plate, which we infer as a channel of
serpentinite that brings water into the deep mantle, is observed. Our result indicates that a
significant amount of water (several weight percent H2O) is transported at least to a depth ~130150km through this channel. Further signature corresponding the low-velocity channel atop of the
slab can be traced as deep as ~350km, suggesting at least water may be transported to the depth.
Below 350km right beneath central/southwestern Japan, there also exist signatures inside of the
slab which we attribute to those originated from the postulated meta-stable olivine wedge (MOW).
The existence of the MOW indicates insignificant amount of water (~100ppm) present in the
subducting slab in the region, thus a deep "dry" cold slab (Kawakatsu & Yoshioka, 2011, EPSL).
Water seems mainly transported along the top surface of the subducting plate. To investigate the
fate of the deep slab that often stagnates in the transition zone beneath Japan and NE China, we
deployed 120 broadband stations in northeast China (NECESSArray). Tomographic and various
images of stagnating Pacific slab using NECESSArray data brought a surprising result: the absence
of a long flat stagnating slab beneath NE China. We speculate its relation to the enigmatic off-arc
volcanism associated with the Changbaishan volcanism (Tang et al., 2014, Nature Geoscience).
Coupling surface and mantle dynamics using
laboratory experiments
A. Kiraly (1)
C. Faccenna (1)
F. Funiciello (1)
A. Sembroni (1)
(1) LET, Laboratory of Experimental Tectonics, Department of Sciences, Università degli Studi
Roma Tre, Rome, Italy
Abstract:
Thermal or density anomalies located beneath the lithosphere are thought to generate dynamic
topography to compensate the viscous stresses originating from the anomaly driven mantle flow. In
addition, recent modeling shows that surface processes, such as erosion and sedimentation, may
influence the deformation of the Earth’s surface, interfering with deeper crustal and mantle signals.
To study the link between the surface and deep processes and related effects on topographic
signals, we designed a three-dimensional (3-D) laboratory apparatus made of a thin multilayer
viscous sheet floating on a uniform Newtonian viscous fluid where a buoyant sphere progressively
rises up. The setup is constituted and scaled down to natural gravity field, with mantle and
lithosphere simulated by Newtonian viscous glucose syrup and silicon putty, respectively. Surface
processes are simulated assuming a simple diffusive erosion law producing the downhill motion of
a thin viscous material away from high topography. The deep mantle upwelling is triggered by the
rise of a buoyant sphere.
The model is able to re-create the movements of shallow material from topographic highs to basins
triggered by the dynamic uplift of the lithosphere. The diffusion of the surface material creates
isostatic uplift and subsidence on the center of - and externally from the loading area, respectively.
The results of these models along with the parametric analysis show the possibility to successfully
couple surface and deep processes within a single 3-D model.
New Mesozoic pelitic eclogites from the western
Rhodope (Chalkidiki, northern Greece)
Konstantinos Kydonakis (1)
Evangelos Moulas (2,3)
Dimitrios Kostopoulos (4)
Elias Chatzitheodoridis (5)
Jean-Pierre Brun (1)
(1) Géosciences Rennes, UMR 6118, Université Rennes1, Campus de Beaulieu, 35042 Rennes,
France
(2) Institut des sciences de la Terra, Université de Lausanne, 1015 Lausanne, Switzerland
(3) Department of Earth Sciences, ETH Zurich, Sonneggstrasse 5, 8092 Zurich, Switzerland
(4) Faculty of Geology, Dep. of Mineralogy and Petrology, National and Kapodistrian University of
Athens, Panepistimioupoli, Zographou, Athens 15784, Greece
(5) National Technical University of Athens, School of Mining and Metallurgical Engineering,
Department of Geological Sciences, Laboratory of Mineralogy"
Poster
Abstract:
"The Chalkidiki block of Northern Greece is the southwesternmost part of the Rhodope and both
are located at the most internal part of the Aegean. The eastern part of the Chalkidiki block is a
basement complex made largely of Palaeozoic orthogneisses and intercalated paragneisses that
were metamorphosed during the Mesozoic. The basement has been considered as part of the
Rhodopean hanging-wall, an assignment which is supported by the lack of HP relicts and the
regional medium-pressure/high-temperature (MP/HT) amphibolite-facies metamorphic imprint. The
basement is juxtaposed, to the west, to units that carry evidence for an early Mesozoic highpressure/low-temperature (HP/LT) event through a sharp NW-trending contact. The questions set
are based around i) the nature of the contact that brings together HP and Barrovian MP/HT rocks
and ii) the possibility of the existence of a largely erased HP event from the basement before the
regional Barrovian MP/HT overprint.
Toward that direction, we studied garnet-staurolite-mica schists from the eastern part of the MP/HT
basement by means of micro-textures, mineral chemistry and isochemical phase diagram sections
in the system NCKFMASHTiMn (Na2O-CaO-K2O-FeO-MgO-Al2O3-SiO2-H2O-TiO2-MnO). Model
results suggest the existence of a high-pressure/medium temperature metamorphic event
(P≈1.9GPa, T≈520°C) that preceded the re-equilibration at MP/HT conditions (P≈1.2GPa,
T≈620°C).
Our concluding remark concern the existence, in a Barrovian complex of northern Greece, of a
largely erased HP mineral assemblage due to re-equilibration under higher temperature conditions.
In the light of our findings, the basement complex of the Chalkidiki block fits a common tectonometamorphic evolution with both the HP units, to the west, and the high-grade Rhodopean
gneisses, to the northeast. The model involves a Jurassic northward subduction and subsequent
Cretaceous HT overprint with the metamorphic intensity increasing toward the transport direction
(i.e., toward northeast)."
Mesozoic Tectonics of the Aegean
Konstantinos Kydonakis (1)
Jean-Pierre Brun (1)
Dimitrios Sokoutis (2,3)
Frédéric Gueydan (4)
(1) Géosciences Rennes, UMR 6118, Université Rennes1, Campus de Beaulieu, 35042 Rennes,
France
(2) Utrecht University, Faculty of Earth Science, Budapestlaan 4, 3584 CD Utrecht, The
Netherlands
(3) University of Oslo, Department of Geosciences, PO Box 1047 Blindern, NO-316 Oslo, Norway
(4) Géosciences Montpellier, UMR 5243, Université Montpellier II, place E. Bataillon, 34095
Montpellier, France"
Abstract:
The Aegean started forming during middle Eocene back-arc extension superimposed on the
previously formed Hellenic Thrust Wedge. The latter was made by Jurassic - Cretaceous accretion
of three continental fragments and the closure of two intervening oceanic domains. The thickened
crustal-scale wedge collapsed, in a process driven by the Hellenic slab rollback, triggering largescale extension of core complex type localised at the beginning to the hinterland of the system
known as the Rhodope.
In the Rhodope, the Mesozoic convergence-related fabrics were partly reworked during Cenozoic
extension. However, the relatively unexplored southwesternmost part of the Rhodope, namely the
Chalkidiki block, behaved as a coherent block during Cenozoic extension and largely escaped the
related deformation. For the purpose of this work we have selected to study the Chalkidiki block.
We carried out field mapping measuring the geometry of the deformation fabrics. We evaluated the
intensity of the metamorphic conditions using isochemical phase diagram sections and
demonstrated the existence of an early eclogite-facies event before the regional amphibolite-facies
overprint. We performed high- (U/Pb in zircon and monazite) and medium-temperature (40Ar/39Ar
on micas) geochronology coupled with low-temperature thermochronology and inverse thermal
history modelling and defined the complete thermal path (T-t) of the study area from Cretaceous
cooling to Eocene near surface exposure.
We modelled the geological evolution of the Rhodope with reference to the exhumation of the lower
crust during core complex formation. In particular, using small-scale laboratory experiments we
tested whether the gravity spreading of a crustal-scale thrust wedge that undergoes extension is a
suitable process for the development of the Rhodopean core complexes during the early opening of
the Aegean. We exemplified that strain localisation and core complex development near the
backstop of the area affected by extension is intrinsic to the pre-collapse geometry of the orogenic
wedge."
North Aegean core complexes, the gravity
spreading of a thrust wedge
Konstantinos Kydonakis (1)
Jean-Pierre Brun (1)
Dimitrios Sokoutis (2,3)
(1) Géosciences Rennes, UMR 6118, Université Rennes1, Campus de Beaulieu, 35042 Rennes,
France
(2) Utrecht University, Faculty of Earth Science, Budapestlaan 4, 3584 CD Utrecht, The
Netherlands
(3) University of Oslo, Department of Geosciences, PO Box 1047 Blindern, NO-316 Oslo, Norway"
“Poster”
Abstract:
The North Aegean core complexes formed at the rear of the Aegean back-arc domain (Rhodope)
and started their development soon after the end of continental convergence and pilling up of the
Hellenic Thrust Wedge when the subducting slab started to rollback.
A series of laboratory experiments were performed to test whether the gravity spreading of a thrust
wedge is a suitable process for the development of the North Aegean core complexes during early
back-arc extension. Wedge-shaped models were built with sand and silicone putty to represent the
brittle and the ductile crust, respectively, and variable boundary velocities and sand-layer
geometries were tested. Extension was applied at constant rate at the wedge front and,
simultaneously, the wedge base was tilted toward horizontal to simulate the isostatic re-adjustment
due to wedge thinning. The models exemplify that extension can be either distributed (i.e., wide rift
mode) or localised (i.e., core complex mode) but always located at the wedge rear. Because in
gravity spreading the amount of horizontal stretching directly depends on layer thickness, the
wedge rear that is thicker undergoes stronger stretching. Core complexes developed in models with
thicker brittle layer (higher frictional strength) and lower stretching rates (lower ductile strength).
Both core complex location, at the wedge rear, and detachment location/dip are interdependent and
intrinsically related to the initial wedge shape of the extending system.
The experimental model displays striking similarities with the extensional pattern of the North
Aegean in terms of: i) location, size and shape of core complexes as well as their sequence of
development, and ii) detachment location and dip. The model suggests that it is the initial wedge
geometry of the system and the hot and thick (i.e., weak) nature of the crust at the onset of
extension that controlled the extensional pattern of the North Aegean Domain."
Thermal perturbation, mineralogical assemblage and rheology
variations induced by dyke emplacement in the crust
A. Lavecchia (1, 2)
S. Clark (1)
F. Beekman (2)
S. Cloetingh (2)
(1) Simula Research Laboratory, Fornebu, Norway
(2) Utrecht University, Utrecht, The Netherlands
Poster
Abstract:
Our model consists of a two-dimensional physical model, simulating a thermal perturbation induced
by a sequence of basaltic dykes along a two-layered crustal section. The geometry of the model is
similar to sequence thicknesses registered in rift areas, such as in the Afar Rift case, and a
temperature-dependent thermal conductivity is considered.
Results take into account metamorphic reactions in a MnKFMASH system, relative to
disappearance of chlorite, appearance of garnet and staurolite, disappearance of staurolite,
appearance of allumosilicate and muscovite and biotite dehydration reactions. The reaction
enthalpies are calculated and considered in the total thermal balance. Subsequently, variations in
mineralogical associations with temperature are used to obtain the averaged values of rheological
parameters for the multiphase rocks and to calculate the variation in the rheological behavior during
the simulation time.
We have investigated: 1) a quartz-feldspatic crust (QF), 2) a micaschists crust (M), and 3) a crust
whose mineralogical assemblage approximates estimations of chemical composition occurring in
literature (CC).
We find that temperature profiles are strongly influenced by metamorphism, with variations in the Tt paths higher than 30 °C. The effect is pronounced in the lower crust, where temperature peaks are
retained for longer periods, and negligible (but still occurring) in the upper crust.
The rheology of the crust is strongly dependent on mineralogical association variation during time.
In the M and CC case, we observe a weak upper crust, but a strong and partially brittle lower crust:
these strong rheology contrasts may lead to strain partitioning and decoupling.
Regarding the dykes aureole, it increase its strength at the very early phases of emplacement. It
may cause a switch in dykes emplacement location and, with a repeated injection in time, an
increased strength of the rifting area, with subsequent transition from crust thinning rifting to magma
assisted rifting mechanism."
Seismic Structure, Anisotropy and Dynamics
of the Lithosphere and Asthenosphere
S. Lebedev (1)
(1) Dublin Institute for Advanced Studies
Abstract:
"Seismic anisotropy reflects complex patterns of deformation and flow within the Earth. The
rheological behaviour of the lithosphere displays large variations, radial, lateral, and in time. The
coldest upper crust is brittle; the lower crust and lithospheric mantle will flow like viscous fluids
when relatively warm but will resist deformation when cold. Below the lithosphere, the viscous
asthenosphere undergoes continuous, three-dimensional flow. The layered, evolving deformation
within the lithosphere and asthenosphere thus results in a complex distribution of anisotropic fabric,
which varies in the 3 spatial dimensions as well as in its age.
Surface-wave data, in particular from dense arrays of broad-band seismic stations, can constrain
3D distributions of seismic velocities and azimuthal and radial anisotropy in the entire lithosphereasthenosphere depth range. Beneath the reworked and stretched crust of Tuscany, for example,
the isotropic-average shear speeds show a decrease around 60 km depth, while azimuthal
anisotropy changes at the same depth from an E-W to NNW-SSE orientation. The two lines of
evidence are thus consistent and suggest a 60-km deep lithosphere-asthenosphere boundary. This
implies that the new mantle lithosphere has formed very recently, following the westward accretion
of Tuscany’s crust; both the lithospheric thickening and the concurrent crustal stretching must have
resulted in subsidence.
Beneath Tibet, very low crustal seismic velocities suggest partial melting and low viscosity,
consistent with conditions for mid-crust channel flow, proposed previously. Seismic anisotropy,
however, shows that crustal flow is determined by the regional patterns of deformation rather than
crustal viscosity. Layered anisotropy reveals different deformation within the crust and the
asthenosphere, with the dominant deformation pattern in the deep crust similar to that seen at the
surface.
Low denudation recorded by 10Be in
Southern Peninsular India
Sanjay Kumar Mandal
Maarten Lupker
Jean-Pierre Burg
Marcus Christl
“Geological Institute, ETH Zurich, Switzerland”
Poster
Abstract:
The persistence of high elevation topography observed along many passive margins remains one
of the outstanding problems in landscape evolution. In the Southern Peninsular India, this question
is marked in the outstanding problem of whether the anomalous topographic relief is in a quasiequilibrium state, decaying slowly through time, or whether the relief has gained during the late
Cenozoic. It has long been hypothesized that topography, as well as climate and rock strength,
exert first order controls on erosion rates. Here we use detrital cosmogenic 10Be from 43 basins
ranging in size from 4 to 68768 km2, to measure millennial basin averaged erosion rates along and
across the Western Ghat Mountains in Southern India. The Western Ghat is characterized by W-E
gradient in relief and rainfall compared to weak variation in lithology allow us to isolate the
relationship between erosion rate and topographic form. Cosmogenic 10Be inventories of modern
stream sediment indicate that erosion rates are spatially variable, ranging from ~8 to 77 mm/Ka on
the western side and 8 to 51 mm/Ka on the eastern plateau side. The rugged topography of
Western Ghats and Nilgiri Mountains of Southern Peninsular India exhibit an alpine-like topography
in conjunction with slowest denudation rates. This presents an exception to the often-cited coupling
of topography and denudation rates and suggests that in Passive margin settings steep slopes and
high relief are not sufficient to record high denudation rates with which they are commonly
associated. The differences in denudation rates along and across the Western Ghats is very well
correlated with local relief, hence it exerts a first order control that in Passive margin paleo relief
influences the topographic development. Although the catchments in Western Ghats receives mean
annual precipitation ~ 5 m due to SW monsoon, it records the slow denudation rates. This data
suggests that due to the lack of tectonic forcing climate is not sufficient enough to denude the
landscape faster in Passive margins.
Crustal imaging across the Northern Scandinavian
Mountains from seismological and
Magnetotelluric data analysis
Walid Ben Mansour (1)
Richard W. England (1)
Max Moorkamp (1)
(1)Department of Geology, University of Leicester, University Road Leicester LE1 7RH, UK
"Poster (95 cmts * 140 cmts)”
Abstract:
"The Scandinavian passive margin and craton have been studied in the past by active seismic
experiments. These experiments provided the first constraints on the crustal thickness beneath
Scandinavia; on the West coast (30-36 km) and beneath the Baltic Shield (44-50 km).
However the central part of Scandinavia dominated by Caledonian structure and high topographies
(> 2 km) crossing into the Baltic Shield (~ 400-500 m) is poorly understood. In order to understand
this topography anomaly (Scandinavian Mountains), a number of passive seismic experiments were
deployed first in Southern Scandinavia. These experiments show a thickening of the crust from
South-West to North-East in Southern Scandinavia.
From 2007, two new seismological networks (SCANLIPS2 and SCANLIPS3D) have been deployed
in Northern Scandinavian in order to have a complete view of the lithosphere across the region. At
the same time a magnetotelluric array (MaSca project) has been set up in this region in order to
image the electric Moho (e-Moho) and electric LAB (e-LAB) in a transition zone between a passive
continental margin and a stable Precambrian craton.
We use these two kinds of data in order to build a new crustal model across the Northern
Scandinavian Mountains. From ZRT receiver function analysis we have a new Moho depth map
beneath the Northern Scandinavian Mountains. We will show a new crustal velocity model from
ZRT receiver functions and ambient seismic noise analysis. First results for the e-Moho show
similarity (Moho depth) with the seismic Moho from ZRT receiver functions and indicate that will be
possible to use a joint inversion of Receiver function data and magnetotelluric data for our new
crustal model. We will show first results from this technique for the Northern Scandinavian
Mountains.
Earthquake-induced landslides: Processes,
rates and implications
O. Marc (1)
N. Hovius (1)
P. Meunier (2)
T. Uchida(3)
T. Gorum(4)
(1) : German Research Center for Geosciences (GFZ), Telegrafenberg, 14473 Potsdam, Germany.
(2) : École Normale Supérieure de Paris, Laboratoire de Géologie, 75231 Paris CEDEX 5, France.
(3) : National Institute for Land and Infrastructure Management, Research Center for Disaster Risk
Management, 1 Asahi, Tsukuba City,8 Ibaraki Prefecture 305-0804, Japan.
(4) : Faculty of Geo-Information Science and Earth Observation (ITC), University of Twente, PO
Box 217, 7500 AE, Enschede, The Netherlands."
Abstract:
"We present several progress in our understanding of co-seismic and post-seismic landsliding.
First, we propose a new physically based relationship predicting the total volume of landslide
caused by an earthquake. 12 comprehensive inventories and 18 partially constrained case of
earthquake-induced landslides caused mainly by thrust fault earthquakes, but also strike slip and
normal fault earthquakes with magnitudes between 5.1 to 7.9 were compared to our prediction. We
found that, when normalized for landscape steepness, all but one of our best cases were predicted
within a factor of two and about 3/4 of all data are within a factor of 4. The remaining outliers might
be caused by lithological variations that are yet to be included in our model. Our data suggest that
the 3 principal parameters, moment, depth and landscape steepness are effectively accounted for.
As every parameters can be measured or described a-priori for a given earthquake scenario our
prediction could have important application both in terms of assessing secondary hazards and in
modelling the impact of earthquake-induced landslides in landscape evolution model.
Second, we present evidences of a global long term geomorphic response to earthquakes. We
documented four cases of persistent elevated landslide rates after Mw6.7 – 7.6 earthquakes. These
rates could not be explained by climatic events of aftershocks and recovered exponentially over 1.5
to 4.5 years. We additionally show that, seismometers recorded seismic velocity decrease and
exponential recovery over similar period for the shallow layers of the epicentral area. This suggest a
damage mechanism could be at the source of both observations and that seismometers could be
used to monitor landslide rates after earthquakes that can be another, less recognized, source of
hazards."
3D mechanical structure of the lithosphere below the
Alps and the role of gravitational body forces in
the regional present-day stress field
Anna Maria Marotta (1)
Raffaele Splendore (1)
(1) Università degli Studi di Milano, Department of Earth Sciences “Ardito Desio”, c/o Cicognara 7,
20129 Milano, Italy
“Poster”
“
Abstract:
"The present study aims to investigate how the tectonic compression due to Africa–Eurasia
convergence is transmitted up to Central Europe via a thermo-mechanical model, in which a highresolution rheological analysis is performed in the surroundings of the Alpine domain and the
predicted heterogeneous lithosphere strength is accounted for to reproduce the surface strain
pattern. Our rheological analysis reveals a strongly heterogeneous lithosphere strength that is
characterised by steep strength gradients across the Periadriatic Lineament and the occurrence of
non-competent crustal layers located below the Northern Alps, where the upper crust controls the
total lithosphere strength. When the predicted lithosphere strength is included within a spherical thin
sheet model to investigate the propagation of the tectonic compression due to Africa–Eurasia
convergence toward Central Europe, our analysis supports the hypothesis that the N–S
compressive stress dominates the gravitational body forces in the Southern Alps up to the
Periadriatic Lineament. This lineament defines an abrupt transition from the strong mantle
belonging to the Adriatic lithosphere to the softer mantle below the Eastern Alps, which is
mechanically decoupled from the relatively stronger upper crust, thus preventing stress
transmission toward the surface. Thus, in the Eastern Alps, the transmitted S–N compression would
remain lower than the E–Wextensional stress induced at crustal levels by the body gravitational
forces associated with thick crustal layers.
Marotta and Splendore, 2014. Tectonophysics, doi: 10.1016/j.tecto.2014.04.038."
Continent-arc collisions: an overlooked factor in
explaining North American topography
during Jura-Cretaceous times
Mitchell G. Mihalynuk (2)
K. Sigloch (1)
(1) University of Oxford, Oxford, United Kingdom
(2) Geological Survey and Resource Development Branch, British Columbia Ministry of Energy and
Mines, Victoria, BC, Canada
Abstract
The viscous drag of lithosphere subducting into the mantle should create dynamic topography at
the surface. This includes slabs that have already sunk into the lower mantle – a depth associated
with subduction during Mesozoic times. The dynamic topography due to such slabs has been
estimated, from observational constraints of gravity anomalies, of seismically imaged slab
geometries, and of geological subsidence records.
Correct translation of sinking slabs into dynamic topography also depends on the knowledge of
paleo-trench locations over time. North America is among the regions that have been scrutinized
most closely for tectonic and dynamic topography linked to subduction, because the continent
overlies massive piles of lower-mantle slabs.
However, Sigloch & Mihalynuk (2013) recently found that Jura-Cretaceous paleo-trench locations
for North America seem to be much less certain than generally assumed, even to first order. The
widely accepted scenario of “Andean-style”, ocean-beneath-continent subduction since at least 175
Ma does not fit newer geophysical observations of slab geometries and quantitative plate
reconstructions. Moreover, Andean-style subduction does not explain why 70% of the North
American Cordillera consists of accreted terranes, mainly island arcs. Hence we hypothesized a
fundamentally different paleo-geography, and successfully tested it against the data:
The seas west of Cretaceous North America must have resembled today’s western Pacific, strung
with island arcs. All proto-Pacific plates initially subducted into almost stationary, intra-oceanic
trenches, and accumulated below as the massive vertical slab walls imaged today. Above the
slabs, long-lived volcanic archipelagos and subduction complexes grew. Crustal accretion occurred
when North America overrode the archipelagos, causing major episodes of Cordilleran mountain
building.
This seems to explain all North American observations, including accreted terranes, but is
incompatible with the widely accepted continental Farallon trench since 175+Ma. Hence intraoceanic subduction had gone unrecognized, and thus also a potent mechanism for generating
flexural and dynamic topography: continent-arc collision. Unraveling the history the Tethyan
(Alpine-Himalayan) margin, that other major accretionary belt of the Mesozoic, is likely hampered
by similar “unknown unknowns” about paleo-trench configurations."
Accurate imaging of the sub-surface and retrieval of
rock properties with joint inversion
M. Moorkamp (1)
B. Heincke (2)
M. Jegen (2)
(1) University of Leicester, Department of Geology, Leicester, UK
(2) Geomar, Helmholtz Centre for Ocean Sciences, Kiel, Germany"
Poster
Abstract:
Understanding geodynamic processes requires detailed images of the sub-surface and accurate
information on the types of rock present. Only then can we obtain meaningful input for geodynamic
simulations, relate them to observations of topography and predict its evolution. In recent years,
joint inversion of different geophysical datasets has established itself as a method to obtain
improved images of the sub-surface compared to individual analyses. Although it is computationally
challenging and great care has to be taken to establish an adequate connection between the
different types of data, the combination of seismic/seismological data and electromagnetic data in
particular has the potential to substantially improve our understanding of sub-surface processes.
We will show successful examples of joint inversion in different geological settings, demonstrate the
improvement in resolution that we can obtain with joint inversion and show how we can extract
additional information such as rock property relationships from the joint inversion results.
Investigating tectonic-erosion interactions:
a Himalayan case study
Y. Najman (1)
L Bracciali (1 and 2)
R. Parrish (2)
I. Millar (2)
H. Akhter (3)
(1) LEC, Lancaster University, Lancaster LA1 4YQ, UK.
(2) NIGL, BGS Keyworth, Nottingham, UK
(3) Dept of Geology, Dhaka University, Dhaka, Bangladesh."
Abstract:
Has been proposed that the rapid exhumation and anomalously young metamorphism of the
eastern Himalayan syntaxis in the Plio-Pleistocene resulted from river capture of the Yarlung River
by the Brahmaputra (the “tectonic aneurysm” model; e.g. Zeitler et al.GSA Today 2001). In order to
test this hypothesis, the occurrence of river capture, and its timing, must be ascertained. Today, the
Yarlung River flows east along the Indus-Yarlung suture before taking a 180º turn at the eastern
Himalayan syntaxis to flow south across the Himalaya as the Brahmaputra. Whether this river
pattern results from river capture, or whether the river is antecedent to orogenesis, is much
debated. The Yarlung River drains the Jurassic-Paleogene Trans-Himalayan arc of the Asian plate
north of the suture and the Tethyan Himalaya of the Indian plate to the south of the suture. The
Brahmaputra prior to any capture would have drained the southern Himalayan slopes composed
only of Precambrian-Palaeozoic Indian crust, much of which metamorphosed to high grade during
the Oligo-Miocene. Hence, the first occurrence of Trans-Himalayan arc detritus which is distinctive
of the Yarlung River, in the Neogene palaeo-Brahmaputra deposits in the Bengal Basin,
Bangladesh, is key to date the river capture. We have applied a multi-disciplinary provenance study
to these sediments and identify the earliest occurrence of detritus from the arc in the Early Miocene.
These data allow us to explore the proposed interaction between the snytaxial evolution and the
timing of river capture. Given we have now dated the time of this river capture at 18 Ma, the
modelled coupling between capture and onset of rapid exhumation (dated <10 Ma) would need to
accommodate a lag time of 8 Ma for this hypothesis to hold true and thus we consider the proposed
tectonic-erosion untenable.
On the evolution of Subduction-Transform Edge Propagators
(STEPs): consequences for the Calabrian arc
Nicolai Nijholt (1)
Rob Govers (1)
(1) Department of Earth Sciences, Utrecht University, Netherlands; [email protected]
Abstract:
Passive margins are first order strength contrasts between ocean and continents, and they may
therefore play a critical role in steering the propagation direction of STEPs. Subduction history
potentially is also relevant because it is a decisive factor for the forces that drive continued
subduction. In this study we explore these factors with mechanical models.
Results show that a STEP will follow a passive margin as long as variations in the strike remain
within 20 degrees. A change in strike of the passive margin ahead of the STEP of less than 15
degrees results in propagation along the passive margin. If the change in strike of the margin is
greater than 15 degrees, the STEP will propagate into the direction that it had before reaching the
change in margin strike. Surprisingly, subduction history and strength contrast are less relevant.
The results shed light on the evolution of the Calabrian arc after the Miocene: slab rollback towards
the ESE was facilitated by a roughly W-E oriented STEP that followed the Africa-Ionian passive
margin along the north coast of Sicily. The geology of NE Sicily suggests that this passive margin
changed orientation here and was parallel to the present-day Sisifo fault. Given that this
corresponds to a moderate orientation change, the active STEP continued to follow the margin. The
next orientation change of the passive margin, to the one that is bounded by the Malta Escarpment,
was approximately 50 degrees. Based on our model results, we therefore predict that the STEP
propagated into the Ionian basin in a direction that was approximately parallel to the Sisifo fault.
Interestingly, the predicted location of the present-day STEP fault in the basement at the SW
termination of the Calabrian trench appears to correspond with a significant discontinuity within the
accretionary wedge."
Exploring the topography and time scale in volcanic regions:
Numerical and analogue modelling
Mehdi Nikkhoo (1)
Thomas R.Walter (1)
Valerio Acocella (2)
(1) Section 2.1: Physics of Earthquakes and Volcanoes, GFZ Potsdam, Germany
(2) Dip. Sc. Geologiche, Universita Roma Tre, Rome, Italy
“Poster”
Abstract:
Topography is known as the geometry of the surface features and their corresponding load above a
reference datum. These two characteristics of the topography affect the surface deformation as well
as the development of volcanic and tectonic processes in different ways. The topographic loads
perturb the uppermost stress field of the Earth, which has a major control on the initiation and
development of magma pathways and associated faults. The geometry of the topography on the
other hand, localizes and controls the stress transfer that promotes the aforementioned effects on
the sources and also influences the surface displacements.
To include such “topographic effects” in models, we developed a new code based on the boundary
element method (BEM), which incorporates the triangular dislocations (TDs) as the basic elements.
Utilizing the code, we can simulate surfaces of any 3D complex geometry along with displacement
or traction boundary conditions. The modelling code is fast enough to allow simulations based on
real observations derived from satellite radar interferometry (InSAR) methods. To infer the volcanic
source parameters and also to simulate the observed InSAR surface displacements, we applied the
BEM code to well suited case studies: the Lastarria volcano in the Lazufre volcanic region in Chile,
the Tendürek volcano in Turkey and Volcán de Colima in Mexico. While in all cases the BEM code
allows for multiple interacting sources, the results of the first and the third cases reveal large
topographic effects that are due to shallow inferred magma bodies.
Analogue models were then developed in order to test and challenge made in the field and by
numerical methods, and to explore distinct parameter changes. By injecting dyed-water into a
gelatin tank with a defined topography, we examined the effect of the topographic loads on the
propagation paths of magma dikes. These analogue models can partly explain the rotation of
intrusive fissures as well as off-rift magmatism.
Keywords: Topographic effects, Boundary Element Method (BEM), Volcano source Modelling"
Controls on deltaic sedimentation in an active
rift setting: a source to sink approach from
the Sperchios delta, central Greece
Sofia Pechlivanidou (1)
Patience Cowie (1)
Bjarte Hannisdal (1)
Rob Gawthorpe (1)
(1) Department of Earth Science, University of Bergen, Allégaten, 41, N-5007 Bergen, Norway
“Poster”
Abstract:
This study presents an integrated source to sink approach to assess the Holocene sedimentary
record of the Sperchios delta, central Greece. The Sperchios delta has developed as an axial
depositional system within an active rift, which is characterized by a half-graben geometry. Detailed
sedimentological analysis (grain size, macro/micro faunal, geochemical and mineral magnetic
analysis) in conjunction with 14C age constraints reveal the stratigraphic evolution of the area,
including the presence of a Holocene transgressive - regressive wedge overlying Late Pleistocene
alluvial deposits. The process-based stratigraphic model SedFlux2D is used to simulate the delta
evolution and model scenarios are compared with the measured data. A series of sensitivity tests
are used to explore uncertainties associated with variations in sediment supply, tectonic subsidence
rate, and Holocene relative sea level. We discuss the effects of the major controls, in particular the
rate of relative sea-level rise and tectonic subsidence rate, on accommodation creation and thus
delta architecture in this active rift setting during the Holocene. The transition from transgression to
regression is found to be mainly controlled by the slowing rate of relative sea level rise that
occurred approximately 5500 kyrs ago. Finally, we compare the sediment flux estimates derived
from the SedFlux2D modelling of the Sperchios delta to the spatial distribution of onshore erosion
rates inferred from analysis of the drainage network as well as lithologically controlled variations in
erodibility. This comparison, when combined with information on relative uplift/subsidence patterns
due to active extensional tectonics, allows us to develop a semi-quantitative source-to-sink model
for this area.
Isostatic and dynamic support of topography
in the Norwegian region
V.K. Pedersen
R.S. Huismans
Department of Earth Science, University of Bergen, Bergen, Norway
Poster
Abstract:
Substantial controversy surrounds the recent evolution of high topography along the North Atlantic
passive margins. Particularly the origin and age of the Norwegian mountains remain elusive, with
suggested formations ranging from Caledonian orogenesis to neogene uplift of a Mesozoic
peneplain.
In this study we focus on the southern part of the Scandinavian mountains and quantify the relative
contributions of crustal isostasy and dynamic topography in controlling the present topography.
Crustal isostasy is calculated from a three-dimensional density model we base on recently
published seismic data (Stratford et al., 2009) and constrain by gravity modeling. Estimates of
dynamic topography have been generated using a global mantle convection model, constrained by
seismic and geodynamic observations (Moucha et al., 2008).
We find that most of the topography is compensated by the crustal structure, suggesting that the
age of the main topography in western Scandinavia is related to the formation of the current crustal
structure. A small component of dynamic uplift has however affected the western part of southern
Norway rejuvenating existing topography within the last ~ 10 Ma.
Stratford et al., 2009. New Moho Map for onshore southern Norway. Geophys. J. Int. 178, 1755–
1765.
Moucha, et al., 2008. Dynamic topography and long-term sea-level variations: There is no such
thing as a stable continental platform. Earth Planet. Sci. Lett. 271 (1), 101-108.
Probing connections between deep earth and surface Processes
in a land-locked ocean basin transformed into a giant saline
basin: the Mediterranean DREAM-GOLD project
M. Rabineau (1)
S. Cloetingh (2)
J. Kuroda (3)
D. Aslanian (4)
A Droxler (5)
C. Gorini (6)
D. Garcia-Castellanos (7)
G. Nolet (8)
A. Moscariellio (9)
Y. Hello (8)
E. Burov (6)
F. Sierro (10)
F. Lirer (11)
F. Roure (12)
P.A. Pezard (13)
Y. Mart (14)
A. Camerlenghi (15)
and the GOLD and DREAM Working Groups
1 CNRS, UMR6538, Domaines Océaniques, IUEM, 29280 Plouzané, France
2 Dept. of Earth Sciences, Utrecht University, Budapestlaan 4, 3584CD Utrecht, The Netherlands
3 Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima-Cho, Yokosuka-city,
Kanagawa 237-0061, Japan
4 IFREMER, DRO/GM/LGG, BP 70, 29280 Plouzané, France
5 Department of Earth Science | Rice University MS-126 | 6100 Main Street | Houston, Texas
77005, USA
6 Sorbonne Universités, UPMC, Univ. Paris 06, UMR 7193, Institut des Sciences de la Terre de
Paris (iSTeP), F75005, Paris, France
7 Instituto de Ciencias de la Tierra Jaume Almera (ICTJA-CSIC), Solé i Sabarís s/n, 08028
Barcelona, Spain
8 Geoazur, 250, rue Albert Einstein, 06560 Sophia Antipolis, France
9 Earth and Environmental Sciences, University of Geneva, Rue des Maraichers 13, CH-1205
Geneva, Switzerland
10 University of Salamanca, Faculty of Science, Plaza de la Merced s/n, 37008 Salamanca, Spain
11 Istituto Ambiente Marino Costiero (IAMC)-CNR Calata Porta di Massa, interno Porto di Napoli
80133, Napoli Italy
12 IFP-Energies Nouvelles, 4 Avenue du Bois Préau, 92852 Rueil-Malmaison
13 Geosciences Montpellier, CNRS, CC60, Univ. Montpellier 2, Pl. Bataillon, 34095, Montpellier,
Cedex 5, France
14 Univ. Haifa, Mount Carmel, Haifa 31905, Israel
15 OGS Istituto Nazionale di Oceanografia e di Geofisica Sperimentale, Borgo Grotta Gigante
42/C, 34010 Sgonico, Trieste, Italy
Abstract:
"During the last decade, the interaction of deep processes in the lithosphere and mantle with
surface processes (erosion, climate, sea-level, subsidence, glacio-isostatic readjustment) has been
the subject of intense exploration. The use of a multidisciplinary approach linking geology,
geophysics, geodesy, modelling, and geotechnology has lead to the concept of coupled deep and
surface processes. Deep earth dynamics (topography, erosion, tectonics) are strongly connected to
natural hazards such as earthquakes, landslides, and tsunamis; sedimentary mass transfers have
important consequences on isostatic movements and on georesources, geothermal energy
repartitions The ability to read and understand the link between deep Earth dynamic and surface
processes has therefore important societal impacts. Ground-truth investigations through carefullyselected sites of investigation are strongly required to better understand this coupling.
Due to its youth (<30 Ma) and its history of strong subsidence, the almost land-locked Gulf of LionSardinia continental margins system provides a unique record of sedimentary deposition from the
Miocene to present. Palaeoclimatic variations, tectonic events, and subsidence history are all
recorded there at very high resolution. The late Miocene isolation and desiccation of the
Mediterranean, the youngest and most catastrophic event which occurred in the Neogene period,
the Messinian Salinity Crisis (MSC), induced drastic changes in marine environments: widespread
deposition of evaporite (gypsum, anhydrite and halite) in the central basin, and intense subaerial
erosion along its periphery. These extraordinary mass transfers from land to sea imparted strong
isostatic re-adjustments that are archived in the sedimentary record and represents a window to the
lithospheric rheology and the deep processes.
The GOLD project, part of the DREAM Umbrella proposal focused on the MSC, proposes to
explore this unique sedimentary record as well as the nature of the deep crustal structure, providing
valuable information about the mechanisms underlying vertical motions in basins and their margins.
The Miocene formation and the Pliocene deformation
of the Gibraltar Arc System
C. R. Ranero (1)
E. Gràcia (2)
I. Grevemeyer (3)
X. Garcia (2)
WestMed
TopoMed
Geomargen-1
Amelie cruises working groups.
(1) Barcelona Center for Subsurface Imaging, ICREA at CSIC, CSIC, Barcelona, Spain.
(2) Barcelona Center for Subsurface Imaging, CSIC, Barcelona, Spain.
(3) GEOMAR | Helmholtz Centre of Ocean Research, Kiel, Germany.
Abstract:
Four major geological domains form the Gibraltar Arc System (GAS). The GAS is fronted in the Gulf
of Cadiz by a large imbricated wedge of tectonically piled rock slices. At the rear side of the
structural arc, there are several extensional basins, in the Mediterranean portion of the region. The
West Alboran Basin is located overlying Gibraltar stacked units, and the basin sediment infill
appears largely unrelated to normal faulting. Ridges and promontories that, where dredged and
drilled contain abundant volcanic rocks, characterize the seafloor of the East Alboran Basin. Further
east the South Balearic – North Algerian Basin has generally being interpreted as back arc basin.
However, the different tectonic elements of the GAS have regionally poorly characterized
basement, and their age, evolution and geodynamic origin are highly debated. Part of this
uncertainty arises from the scarcity of deep-penetration modern geophysical data in most of the
system.
The goal of this contribution is to present a summary of results recently produced from models and
images from the data collected in 4 recent marine experiments. We present P-wave velocity models
across key areas of the system and new reflection images of the tectonic and sediment structures
of the crust. Further we present magnetotellutic 3D models of the lithospheric structure. These
results are use to interpret the Miocene formation of the GAS and Plio-Pleistocene continent
collision that might explain the crustal-lithospheric structure.
We conclude that a geodynamic process that is no longer active formed the geological domains of
the GAS, and that a new deformation regime -active since about the Pliocene times- is controlling
the currently active deformation.
A global crustal model from the inversion of
GOCE gravity observations
M. Reguzzoni(1)
D. Sampietro(1,2)
(1) DICA - Politecnico di Milano, Milan, Italy
(2) GReD s.r.l., Como, Italy
Poster
Abstract:
The boundary between Earth crust and mantle, the so called Moho, is commonly estimated by
means of seismic or gravimetric methods. The former methods can be locally very accurate since
seismic profiles give an almost direct observation of the actual crustal structure, but can be quite far
from reality in large regions where no data are available. The latter methods, although often based
on simplified hypotheses to guarantee the uniqueness of the solution, are nowadays becoming
more and more important thanks to the improved knowledge of the gravitational field. In particular
satellite gravity missions, like the European Space Agency mission GOCE, provide a very accurate
and spatially homogeneous dataset that can be used to validate the existing global crustal models
or to estimate a new one by constraining the relation between Moho depth and crustal density.
In this work the GEMMA1.0 crustal model with a spatial resolution of 0.5°x0.5° and constrained with
GOCE observations is presented. For this purpose several additional external information has been
used, such as topography, bathymetry and ice sheet models from ETOPO1, a recent 1°x1°
sediment global model and some prior hypotheses on crustal density. In particular the main
geological provinces, each of them characterized by its own relation between density and depth,
have been considered. A model describing lateral density variations of the upper mantle is also
taken into account. Starting from this prior information, an inversion algorithm is applied to the
GOCE space-wise grid of second radial derivatives of the gravitational potential to estimate the
bottom of the crust. The computed Moho global model is well consistent not only with other
global/regional models, but also with the actual gravity field, thus overcoming the main limitation of
seismic Moho models, like the CRUST1.0.
Impact of early inversions and recent lithospheric deformations
on erosional surfaces and unroofing in circum-Mediterranean
thrust belts and margins
F. Roure (1, 2)
(1) IFP Energies nouvelles, Geosciences Dpt, Rueil-Malmaison, France
(2) Utrecht univ., Tectonic Group, the Netherlands"
Abstract:
Ealy inversions operating in the North African-Apulian passive margin prior to the Tethyan-Alpine
ophiolitic sutures and the final collision stage have lead to local emersion and strong erosion of both
platform and basinal series in numerous portions of the foreland, prior to the onset of thrust
stacking, tectonic loading and foreland flexure development.
Post-collision asthenospheric rise and slab detachments have in turn controlled more recent
lithospheric unflexing, resulting in the back-tilting and rapid uplift and erosion of numerous
segments of the former flexural basins.
Various case studies taken from the Mediterranean will document the effects of these processes,
which deviate strongly from the classical models of thrust belt evolution."
Accretionary wedge evolution seen as a competition
between minimum work and critical taper
Tasca Santimano (1)
Matthias Rosenau (1)
Onno Oncken (1)
1)German Research Center for Geosciences (GFZ), Potsdam, Germany
Abstract:
"The evolution of accretionary wedges has been described by two theories: The critical taper theory
(CTT, Davis et. al., 1983) and the minimum work concept (MWC, Masek & Duncan, 1998). CTT is
based on force balance and predicts the ideal shape (critical taper) of an accretionary wedge
system. However, the structures that are formed and reactivated to reach the preferred geometry
during accretionary wedge growth can be predicted by MWC. This concept states that deformation
is accommodated in an energetical way by faults that minimize total (frictional plus gravitational)
work. In this study we test the interplay of both concepts and hypothesize that there is a competition
between minimizing work and reaching the critical taper that controls the evolution of accretionary
wedges. The experimental setup consists of creating a plane strain homogeneous compressional
sand wedge with low friction (µ) basal detachment. The evolution of the entire wedge is recorded
and analysed by means of the Particle Image Velocimetry (PIV). This allows for a time-series
collection of the incremental geometries and internal displacement fields (Dx, Dy) that are used to
calculate the gravitational (Wg) and frictional (Wf) work. Observed geometrical evolution and work
history are compared to analytical solutions of a self-similarly growing and critically tapered wedge.
The analysis shows that shortening and uplift steepens the wedge and therefore causes its
departure from the critical state. The latter can only be re-established by forming a new,
energetically unfavorable frontal thrust ahead of the wedge tip lowering the taper. Compared to a
self-similarly growing wedge that follows the CTT, real accretionary wedges are rarely described as
either CTT or MWC. Instead they reflect the competition of reaching criticality and minimum work
and are a mixture between a geometrically versus an energetically preferred state.
References:
Davis, D., Suppe, J., Dahlen, F.A., 1983: Mechanics of Fold-and-Thrust Belts and Accretionary
Wedges. Journal of Geophysical Research 88, 1153-1172.
Masek, J.G., Duncan, C.C., 1998: Minimum-work mountain building. Journal of Geophysical
Research, 103,907-91
Timing and Mode of Landscape Response to Glacial-Interglacial
Climate Forcing From Fluvial Fill Terrace Sediments:
Humahuaca Basin, E Cordillera, NW Argentina
Taylor F. Schildgen (1)
Ruth Robinson (2)
Sara Savi (1)
Bodo Bookhagen (1)
Stefanie Tofelde (1)
Manfred R. Strecker (1)
(1) Institut für Erd- und Umweltwissenschaften, Universität Potsdam, Potsdam, Germany
(2) Department of Earth and Environmental Sciences, University of St Andrews, St. Andrews,
Scotland UK
Poster
Abstract:
Fluvial fill terraces provide a record of changes in sediment production and/or transport in response
to external forcing. The N-S striking Humahuaca intermontane basin parallels the eastern margin of
the Puna Plateau and is known for frequent landslides/debris flows during the wet season and
protracted past wet periods. Fill terraces along tributaries (20-1100 km2 catchments) to the trunk
stream are dated with OSL to between ~30 and 120 ka. Aggradation phases on the west side of the
basin correlate with past wet periods, and those on the east side with dry periods. The difference
may arise because the river-network geometry of eastern catchments promotes sediment storage,
resulting in delayed sediment delivery to the trunk stream and/or a higher threshold to erosion and
sediment transport. Cosmogenic nuclide (10Be) concentrations of sand (<0.7 cm) and pebbles (1-3
cm) reveal that in modern stream sediments, (1) denudation rates from sand (<0.1 mm/yr) overlap
with bedrock erosion rates, and (2) denudation rates from pebbles are 1.2 to 4x higher, which could
reflect the importance of mass movements. From wet-phase terraces, denudation rates are higher
than those from modern streams, while highly scattered pebble denudation rates of 0.1-10 mm/yr
may reflect an increased frequency of mass movements in past wetter periods. In contrast, dryphase terrace pebble and sand denudation rates overlap with modern rates, 26Al/10Be ratios are
low, and a sample from the sediment storage zone has a relatively high pebble denudation rate of
0.3 mm/yr. We interpret the patterns to imply that mass movements are triggered throughout the
valley during wet climate phases and induce aggradation, but slow re-excavation of stored
sediments from eastern catchments leads to increased 10Be concentrations and delayed sediment
delivery to the main valley. Such behavior at an orogen scale could attenuate or mask landscape
responses to climate forcing.
Deep-Sea Record of Mediterranean Messinian Events (DREAM)
multi-phase drilling project. A new challenge
for deep sea exploration.
Sierro, F. J. (1)
Camerlenghi A. (2)
Aloisi G. (3)
Lofi J. (4)
Hübscher C. (5)
deLange G. (6)
Flecker R. (7)
Garcia-Castellanos D. (8)
Gorini C. (3)
Gvirtzman Z. (9)
Krijgsman W. (6)
Lugli S. (10)
Makowsky Y. (11)
Manzi V. (12)
McGenity T. (13)
Panieri G. (14)
Rabineau M. (15)
Roveri M. (12)
Waldmann N. (11)
1. University of Salamanca
2. OGS, Trieste
3. Université Pierre et Marie Curie, Paris,
4. Université de Montpellier 2,
5. University of Hamburg,
6. Utrecht University,
7. University of Bristol
8. ICTJA-CSIC, Barcelona,
9. Geological Survey of Israel, Jerusalem,
10. University of Modena and Reggio Emilia,
11. University of Haifa,
12. University of Parma,
13. University of Essex,
14. University of Tromsø,
15. CNRS Plouzané Brest.
Abstract:
Since the discovery of large volumes of salt in the deep Mediterranean DSDP Leg 13 the Messinian
salinity crisis has captured the attention of geoscientists from many different disciplines. However,
after thousands of publications over the last decades still many questions remain unanswered. The
biostratigraphic, magnetostratigraphic and cyclostratigraphic study of marginal basins allowed high
resolution correlations throughout the Mediterranean based on the astronomical tuning of rythmic
sections. Unfortunately, most of the sedimentary records recovered in marginal basins are not
continuous, especially during the latest part of the Messinian, making them not suitable for
reconstructing the tectonic, climatic, and biological events that took place in the Mediterranean at
that time. In parallel, geophysical research expeditions have provided excellent, high resolution
seismic records of deep and intermediate Mediterranean basins pointing to the existence of
continuous Messinian successions only in the deepest basins below a thick layer of salt, whereas
major erosive surfaces were identified in the present continental margins and the intermediate
basins. Only drilling these deep water deposits the scientific community will fully understand the
causes, chronology and biological, chemical and tectonic consequences of the MSC. The
Mediterraneran salt giant might be a hotspot for the development of a deep biosphere of microbes,
living off the association of reduced carbon and sulfate contained in mineral gypsum and anhydrite.
The calibration of the vast seismic data from the different Mediterranean basins will shift various
paradigms of the early structural evolution of salt giants and their sealing capability. The
implementation of riser drilling technologies in the Chikyu vessel would allow to drill these deep
Mediterranean sequences, leading a group of scientists to explore and identify locations for
multiple-site drilling (including non-riser and riser-drilling) in different environmental settings
extending from the intermediate to the deep basins of the Mediterranean Sea.
Numerical modelling of terrace staircase formation in the
Quaternary drainage system of the southern
Pyrenees, Ebro basin, NE Iberia
K.M. Stange (1),
R.T. van Balen (1),
D. Garcia-Castellanos (2)
(1) Department of Earth Sciences, Vrije Universiteit Amsterdam
(2) Institute of Earth Sciences Jaume Almera, Spanish National Research Council
Abstract:
"The southern foreland basin of the Pyrenees (Ebro basin) is an exorheic drainage basin since Late
Miocene times. Remnants of an early exorheic Ebro drainage system are not preserved, but
morphology provides evidence for the Pliocene–Quaternary drainage development. The incision
history of the Ebro system is denoted by (i) extensive pediments associated with the denudation of
the southern Pyrenean piedmont around the Pliocene–Quaternary transition, and (ii) deeply
entrenched Quaternary river valleys. The Ebro basin pediments indicate a smooth, low-gradient
palaeo-topography. In the Middle–Late Pleistocene fluvial incision intensified in the Ebro basin,
involving extensive terrace staircase formation. Terrace exposure dating in Ebro tributary rivers
indicates climate-triggered terrace staircase formation in response to glacial–interglacial climate
cycles in the Pyrenean headwaters. The overall (semi)parallel longitudinal terrace profiles argue for
progressive base level lowering for the whole Ebro drainage network.
A landscape evolution model, TISC, is used to evaluate climatic, tectonic, and base level scenarios
for terrace staircase formation in the Ebro drainage system. Model simulations are compared with
morpho-climatic, tectonic, and chronologic data. Results show that climate may trigger terrace
formation, but the modelled incision magnitudes and convergent terrace profiles are not consistent
with the (semi)parallel terraces in the Ebro basin. A model scenario including rapid (late Pliocene)
uplift of the Catalan coastal ranges causes rapid base level lowering and erosion along the Ebro
drainage network, small Middle–Late Pleistocene incision magnitudes, and terrace convergence,
which are not in agreement with observations. Instead, continuous Quaternary uplift of the
Pyrenees and the foreland basins produces (semi)parallel terrace staircases in southern Pyrenean
tributary rivers that are consistent with the longitudinal terrace profiles and Middle–Late Pleistocene
incision magnitudes observed in the Ebro basin. Forward model simulations indicate that the
present Ebro drainage system is actively incising, providing further evidence for uplift.
Isostasy, dynamic topography and the elevation
of the European Alps
P. Sternai (1)
T. Becker (2)
C. Faccenna (3)
S. D. Willett (4)
E. Serpelloni (5)
M. Miller (2)
I . Bianchi (6)
L. Jolivet (1)
(1) Institut des Sciences de la Terre d'Orléans (ISTO), University of Orléans, Orléans, France;
(2) Department of Earth Sciences, University of Southern California (USC), Los Angeles CA, USA;
(3) Laboratory of Experimental Tectonics, Università Roma TRE, Roma, Italy;
(4) Department of Earth Sciences, Swiss Federal Institute of Technology (ETH), Zurich,
Switzerland;
(5) Istituto Nazionale di Geofisica e Vulcanologia (INGV), Centro Nazionale Terremoti, Bologna,
Italy;
(6) Institute fur Meteorologie und Geophysik, Universitat Wien, Vienna, Austria"
Poster
Abstract:
The shape and elevation of an orogen are the result of isostatic and dynamic contributions, which
evolve in space and time depending on the active crustal and mantle processes. We focus on the
European Alps and use representative crustal and mantle models to quantify the isostatic and
dynamic components of the present-day Alpine topography. We find that the observed elevation of
the western and central/eastern Alps is respectively higher and lower than the isostatically
compensated topography as estimated from crustal models, suggesting a major contribution to the
present-day Alpine topography from the mantle dynamics. The expected mantle flow induced
dynamic topography, however, indicates some widespread down welling throughout the orogen,
which is consistent with the negative residual topography in the central and eastern Alps but
opposite to the positive topographic anomaly in the western Alps. Newly acquired geodetic
constraints on the present-day vertical motion provide additional insights on the active processes
across the Alps. In particular, measured vertical displacement rates confirm that the Alps are still
active, with a complex deformation pattern involving uplift in the western and central Alps and
subsidence in the eastern Alps. Since shortening and crustal thickening in the western and central
Alps is to date limited, uplift in this sector seems to be best explained by erosional unloading and
adjustment to the supposed break-off of the European slab, or a combination of both. The
subsidence in the eastern Alps is in contrast with ongoing crustal shortening and thickening,
suggesting that a dynamic pull-down arising by the mantle flow provides a substantial contribution
to the ongoing vertical motion.
How surface processes affect the syn-rift evolution
of passive continental margins
Susanne J.H. Buiter (1,2)
(1) Geological Survey of Norway, Trondheim, Norway ([email protected])
(2) The Centre for Earth Evolution and Dynamics, University of Oslo, Norway.
Abstract:
Seismic observations of passive margins document surface transport of different amounts of
sediments from the onshore to the offshore during the evolution from a continental rift to a post-rift
margin. Thick packages of syn-rift basin sediments are found on the Newfoundland and Norwegian
margins, whereas West Iberia and the Red Sea are examples of sediment-starved margins. What is
the impact of offshore sedimentation and onshore surface erosion on syn-rift margin architecture?
Fundamentally, erosion is always a weakening process, whereas sedimentation can be both
strengthening and weakening. Erosion reduces the overburden, which induces an isostatic surface
uplift, and lowers vertical stress, which reduces pressure-dependent brittle strength. Sedimentation
increases brittle strength because of the increase in vertical stress under the extra load. But
sediments may have a lower density and cohesion, and therefore a lower brittle strength, than the
adjacent crust. Sediments with a low thermal conductivity may also act as a ‘thermal blanket’
preserving heat in the crust below, thereby reducing crustal ductile strength. The feedback effects
between surface processes and tectonic deformation during passive margin formation clearly go
beyond a simple isostatic response and require careful quantification of the contributing processes
in relation to crustal strength evolution.
To explore the dynamic feedback relationships between surface processes and crustal strength, I
perform a series of numerical experiments on continental extension using the finite-element code
SULEC. For a wide range of sediment amounts, a strong lower crust leads to relatively fast
lithospheric break-up and a short margin, accompanied by rift flank uplift and focussed mantle
upwelling. A weak lower crust delays break-up and may produce a wide, hyper-thin crust. I show
that sedimentation may fundamentally alter margin architecture for intermediate strength lower
crust by switching break-up style from fast break-up to prolonged rifting with the development of a
wide domain of hyper-thin crust. For these model margins, the strengthening effect of
sedimentation dominates over its weakening properties."
Depth sensitivity of satellite gravity gradients
to the lithospheric structure of
North America
W. Szwillus (1),
J. Ebbing (1)
(1) Department of geophysics, University of Kiel, Germany
“Poster”
Abstract:
Commonly, lithospheric scale modelling of the gravity field is done primarily by the potential/geoid
or vertical gravity acceleration. We examine how satellite gravity gradient data can help to improve
the quality of crustal models and to distinguish lithospheric and sub-lithospheric sources.
Commonly, the gravity field is divided into lithospheric sub-lithospheric parts by wavelength filtering;
e.g. spherical harmonics degrees 2-9 are identified as the sub-lithospheric gravity field. However,
the lithosphere contains significant density anomalies that cause a strong gravity effect at these
wavelengths. Thus the filtered gravity field is “contaminated” by a considerable crustal effect.
An alternative approach is to strip the total field of the contribution of crustal sources by forward
calculation. This approach requires a well-defined density model. We are developing such a model
for the North American continent, based on the seismological model of the North American Crust
(NaCr 14). Additionally we include information from travel time tomography for the velocity and
resulting density distribution in the upper mantle.
Our first results show that the density contrast at the Moho boundary causes the strongest signal in
both the gravity field and the gravity gradients. Gravity gradients have an increased sensitivity to
inner-crustal density anomalies, whereas the normal, vertical gravity field better reflects sublithospheric anomalies. Thus, gravity gradients can help to improve the accuracy of crustal density
models, which in turn helps to better unveil the sub-lithospheric density structure of the Earth.
Thermal, compositional and strength variations of
the North American lithosphere
M. Tesauro (1, 2)
M. K. Kaban (1)
W. D. Mooney (3)
S. Cloetingh (2)
(1) GeoForschungsZentrum Potsdam (GFZ)
(2) Department of Earth Sciences, Utrecht University
(3) USGS
Abstract:
Using a regional (NA07) and a global (SL201sv) tomography model and gravity data, we apply an
iterative technique, which jointly interprets seismic tomography and gravity data, to estimate
temperature and compositional variations in the NA upper mantle. The results obtained
demonstrate that temperature of the cratonic mantle is up to 150°C higher than when using a
uniform compositional model. The differences between the two tomography models influence the
results more strongly than possible changes of the depth distribution of compositional variations.
Strong negative compositional density anomalies, corresponding to Mg # >92, characterize the
upper mantle of the northwestern part of the Superior craton and the central part of the Slave and
Churchill craton. The Proterozoic upper mantle of the western and more deformed part of the NA
cratons, appears weakly depleted (Mg# ~91) when NA07 is used, in agreement with the results
based on the interpretation of xenolith data. When we use SL2013sv, the same areas are locally
characterized by high density bodies, which might be interpreted as the effect due to fragments of
subducted slabs, as those close to the suture of the Appalachians and Grenville province. We used
the two thermal models to estimate the integrated strength and the effective elastic thickness (Te)
of the lithosphere. In the peripheral parts of the cratons, as the Proterozoic Canadian Platform and
Grenville, the integrated strength for model NA07 is ten times larger than in model SL2013sv, due
to a model-dependent temperature difference of >200˚C in the uppermost mantle. In both models,
Proterozoic regions reactivated by Meso-Cenozoic tectonics (e.g., Rocky Mountains and the
Mississippi Embayment) show a weak lithosphere due to the absence of the mechanically strong
part of the mantle lithospheric layer. Intraplate earthquakes are distributed along the edges of the
cratons, characterized by pronounced contrast of strength and Te.