Download Geology Without Limits Investigation of Lithosphere Deep

17th-22nd May, 2015
Hyatt Regency Hotel
Title: Geology Without Limits Investigation of Lithosphere Deep Structure of the
Caribbean by Seismic Methods
Name of the Authors: Keith H. James1, Nikolay Amelin2 and Laslo Miles3
1
Consultant, Scientist Board, and Lead Scientist, Geology Without Limits Caribbean
program; Department of Geography and Earth Sciences, Aberystwyth University,
SY23 3DB, Wales, UK
2
CEO, 3 Interpretation Manager, Geology Without Limits, Regional Geophysical
Exploration LLC, Shukhova St. 14, Moscow, Russia 115162
The Geology Without Limits consortium conducts regional studies of large marine
basins, crossing international boundaries. It includes the Department of Geology,
Moscow State University, the State Geological Institute of the Russian Federation
Academy of Sciences and the Schmidt Institute of Physics of the Earth. It also
includes scientific institutions/organizations of countries bordering study areas - local
scientists share data, understanding and learnings. Finance comes from Geology
Without Limits and interested petroleum companies.
The group has completed projects in the Arctic and the Black Sea. Caribbean and
Caspian Sea studies are in progress.
The Caribbean study will record the areas first regional seismic grid, extending from
the Gulf of Mexico and the Atlantic and crossing the Caribbean interior, including the
Yucatán Basin and Cayman Trough, across the Caribbean interior (Colombia,
Venezuela and Grenada basins, Cayman, Beata and Aves ridges), northeast onto the
Bahamas Platform via the Greater Antilles, and east and southeast onto the Atlantic
(including the Barbados Ridge and Trinidad-Guyana offshore) via the Lesser Antilles.
It will include some 60,000 km of reflection and refraction seismic plus gravity and
magnetic data. A large air gun, 12 km streamer, independently floating sonobuoys
and 18 second records will provide data to 45 - 60 km depth, to be processed with
state-of-art technology.
Interpretation will be a joint effort and will integrate existing geophysical and
geological data. Data will be available on a distributed access system. Collaboration
will occur via workshops, conferences and field trips. Results will be presented at
international conferences.
Participating countries will receive new data from their exclusive economic zones
cost free for non-commercial use. They will also receive a full, final report.
The new data will record the regional crustal composition and architecture of
submarine Middle America and will allow interpretation of geological evolution and
hydrocarbon potential. Geological learnings should have global significance.
The project will include the following areas (1- current understanding, 2- expected
results).
Bahamas Platform
1- Thick, shallow water limestones on rifted continental crust (oceanic in the SE?).
Crustal thickness 15 – 30 km.
2- Basement composition and tectonic history, tied to eastern North America.
Greater Antilles
1- Hispaniola, Puerto Rico, Virgin Islands. Crustal thickness ~30 km. Jurassic Cretaceous arc and oceanic rocks diachronously (west – east) emplaced northwards.
Bounded south and north by the Muertos Trough and North Hispaniola-Puerto Rico
Trench subduction zones. Major zone of sinistral displacement between the
Caribbean and North America. Cuba: Crustal thickness 20 – 26 km. Bounded to north
by Nicholas/Old Bahama Channel subduction zone. Jurassic – Campanian arc and
oceanic rocks, emplaced northwards onto the southern Bahama Platform Precambrian-Palaeozoic, Triassic-Jurassic (continental clastics in west, salt, tholeites
to east), Jurassic- Cretaceous carbonate (shallow in north, deep in south). SE Cuba
Palaeogene volcanic arc continues west along the Cayman Ridge.
2- Deep structure and composition below obducted rocks (SE Bahamas Platform
extension below Hispaniola – Virgin Islands?). Diachronous or synchronous
collision? Nature of trenches.
Barbados Ridge - Lesser Antilles – Aves Ridge
1- World-class accretionary prism, up to 10 km thick, on Atlantic oceanic crust.
Atlantic oceanic crust subducted below Eocene – Recent active Lesser Antilles and
Cretaceous extinct Aves intra-oceanic volcanic arcs separated by Eocene back-arc
Grenada Basin. Crustal thicknesses 18 - 40 km. Aves Ridge shares 1000s metre post
Eocene-Oligocene subsidence history with Beata and Cayman ridges.
2- Nature of Atlantic crust. Subduction architecture. Deep structure/velocity
composition of arcs and Grenada Basin.
Central America
1- Chortis block, crustal thickness 45 – 35 (W – E) km thick, continental in north,
extended crust in south/east with accreted arc/oceanic rocks. Extends along Upper
Nicaragua Rise to Jamaica. Crustal thickness up to 25 km - carbonate platform on
extended continental crust or Cretaceous arc rocks. Lower Nicaragua Rise (south of
the Pedro Fault) oceanic (numerous volcanoes reported) or highly extended continent.
Chorotega and Choco blocks accreted oceanic/arc rocks. Crustal thicknesses up to 45
km.
2- Structure/composition of Upper and Lower Nicaragua Rise.
Caribbean Interior
1- Colombia – Venezuela basins, separated by Beata Ridge, Jurassic (Pacific) oceanic
crust thickened by (Pacific) late Cretaceous mantle plume into a ~20 km “ocean
plateau”, capped by 88 – 90 Ma basalt, engulfed by westward migrating Americas.
Thin (3km) SE Venezuela Basin.
2- Deep velocity/structural architecture. Wholly oceanic or extended continent.
Northern South America Offshore
1- Metamorphosed distal Jurassic – Cretaceous sediments, volcanic and oceanic
rocks, Eocene – Recent sediments. Crustal thickness diminishes seawards from
craton, 50 – 20 km. Thick Panamá and South Caribbean Deformed belts - northwardverging (?)Eocene – Recent sediment prisms.
2- Extent/geometry of continental crust. Nature of Deformed Belts.
Yucatán Basin
1- Tertiary back-arc basin to Cretaceous volcanic arc accreted to southern margin of
N America (Cuba) in the Eocene. Crustal thickness 8 – 9 km.
2- Internal crustal structure. Older history? Extended continent present?
Cayman Trough
1- Cayman Trough/Ridge - pull-apart basin within sinistral boundary between N
America and the Caribbean. Eocene-Recent ocean spreading between Yucatán Basin
and Upper Nicaragua Rise. Cayman Ridge similar to Nicaragua Rise: abundant
material derived from granitic and metamorphic rocks, possibly pre-Cretaceous.
2- Structure/composition of Cayman Ridge-Nicaragua Rise. Deep crustal structure
Cayman Trough spreading in central part, distal extended continent? Age of
spreading.
Studies
1- Existing seismic data
2- Integrate new geophysical data with outcrop/well data
3- Regional study igneous/metamorphic rocks – their significance, independent of
models
4- Existing dredge/core samples
5- Zircons in arc rocks of Greater and Lesser Antilles, dredge samples from Cayman
Trough, Beata and Aves ridges, DSDP-cored basalts, volcanoes of Caribbean interior,
Atlantic Site 543 basement core
6- Heat flow, gravity/magnetic survey and core “seamounts”; investigate reported salt
diapirs
7- Regional tectonic/geologic synthesis/history based upon the above