Download Mesozoic fill-sequences in Hefei Basin: Implication for Dabie

Vol. 44 No. 1
SCIENCE IN CHINA (Series D)
January 2001
Mesozoic fill-sequences in Hefei Basin: Implication for
Dabie Orogenesis, central China
LI Zhong (' ), SUN Shu (, ×), LI Renwei (')
& JIANG Maosheng (ޓ)
Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
Correspondence should be addressed to Li Zhong (email: [email protected])
Received February 15, 2000
Abstract A research on the Mesozoic fill-sequences of Hefei basin, located at the north foot of
Dabie Mountains, shows two-phase evolution. The first phase, early- to mid-/late-Jurassic, is characterized by terrestrial clastic deposits, with four times of reverse-grading units at least, and forms
greatly thick molass reconstruction in the mid-/late-phase, which reflects gradually strong thrusting-orogenesis in the north Dabie and flexural depression in the north foreland of Dabie Mountains.
The second phase, late-Jurassic to Cretaceous, includes two-episode rifting processes. The first
episode (-) shows calc-alkalic and alkali volcanic rocks interstratified pyroclastic rocks, which may
reflect upwelling igneous magma from mantle-source due to the Yangtze continent slab breakoff
induced by deep subduction process. A suite of lacustrine, fluvial and piemount facies, about 3000
3500 m in thickness, develops in the second episode (J3 -K1), which reflects regional extensional
setting and intense elevator diversity of mountain-basin in the study area. This research renews
and deepens cognition for the Mesozoic Dabie orogenesis.
Keywords: Hefei basin, Mesozoic fill-sequence, basin-mountain relation, orogenesis, Dabie Mountains.
With the development of research on ultra-high pressure metamorphic petrology, geochemistry and their tectonic settings, the Dabie orogenic belt has gradually become one of the highlights
of continental dynamic research. However, a sedimentary research on the Dabie orogenic belt
obviously lags, which seriously restricts further cognition of the Dabie orogenesis. For purposes of
stratigraphy and petroleum investigation, depositional evolution and tectonic framework of the
Hefei basin have ever been studied[1
4]
, otherwise tectonic relationship between the Dabie oro-
genic belt and the Hefei basin was also explored according to geologic-geophysic profiles[5],
which put forward elementary cognition to the evolution of Hefei Basin. Because an embedded
research on the fill-sequences of Hefei basin has not been done, there still lacks a full recognition
on basin types and tectonic dynamic mechanism of regional orogenic belt in the studied area.
Some questions, such as the time of continent-continent collision, the location of suture belt and
the existence of Dabie micro-continent, are still in debate[6
9]
. So many researches, from regional
tectonic views, endowed the Hefei Basin with intermontane basin or rift basin[2, 4, 10, 11], inherited
basin[8] and hinterland basin[5, 12], and so on. Based on detailed field observations, a new research
on fill-sequences and depositional evolution of the Hefei basin are done in this paper, which tries
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to supplement and deepen cognition of the Dabie orogenesis and the basin-mountain relation in
the north part of the Dabie mountains.
1 Regional geological structure of Hefei basin
The Hefei basin, located at the north foot of Dabie Mountains (fig. 1), is bounded with the
Xiaotian-Mozitan fault as its southern edge, the Yinshan-Dingyuan fault at its northern limit, the
Tanlu rift as its eastern limit and the Changshandong fault as its western limit. The strike of Hefei
basin is nearly in east-west. The preserved deposits of Hefei basin are about 180 km in length
from east to west and 125 km in width from south to north.
Fig. 1. Tectonic framework and exposed stratum in the Hefei basin. 1, Cenozoic; 2, Late Jurassic
to Cretaceous volcanic rocks and pyroclastic rocks; 3, Jurassic terrestrial clastic rocks; 4, granite
of Yanshan stage; 5, Foziling group and Meishan group; 6, fault or concealed rift.
Xiaotian-Mozitan fault; Yeji-Shucheng fault; Liuan-Queshan fault; Tanlu fault.
The Hefei basin is characterized by zonation from south to north. The south zone, namely the
east part of Beihuaiyang region, which is also called “Beihuaiyang fault-fold belt”, is referred to
as an elongated, nearly east-west orientation zone, which is restricted by the Liuan-Qieshan fault
at the north, the Xiaotian-Mozitan fault at the south, the Yuxi fault at the west and the Tanlu fault
at the east. This belt is 400 km in length and 20
40 km in width, of which the basement consists
of the Foziling group and Meishan group, mainly greenschist facies of low metamorphism and
intensive tectonic deformation. The Jurassic-Cretaceous clastic rocks interbedded with volcanic
and volcaniclastic rocks are found on the basement. The Beihuaiyang belt lies between the Huabei
plate and the Dabie orogenetic belt and experienced complicated evolution history, about which
tectonic attributes have been in debate for a long time[8, 13
17]
. The north zone is bounded by the
Liuan- Queshan fault in the south (fig. 1), of which the basement consists of the Huoqiu group and
Wuhe group, mainly migmatitized kata-metamorphite and shows distinct tectonic evolutional
properties from the south belt. The Jurassic-Cretaceous strata of the north zone, overlying the
above mentioned basement, can be correlated with those of the south zone[2, 18], but their lithofacies and thickness are obviously different. It is necessary to note that a small basin, named Xiao-
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tian, occurs at the south part of Yeji-Shucheng fault, which is also filled by the Jurassic-Cretaceous and has a similar lithofacies with that of the south zone of Hefei basin, in which
the intermediate-acid volcanic rocks directly overlie the metamorphic basement of Foziling group.
2 Basin-fill and sedimentary lithofacies
2.1
The south zone
The Jurassic-Cretaceous of the south zone of Hefei basin, which has a relatively good exposure in the Huoshan-Jinzhai region, is composed of a suite of terrigenous clastic deposits interbedded with volcanic-volcaniclastic rocks of the Mesozoic with 5 000
7 000 m in thickness, in-
cluding the Sanjianpu Formation (J2s), the Fenghuangtai Formation (J2f), the Maotanchang Formation (J3m), the Heishidu Formation (K1h) and the Xiaotian Formation (K1x) from bottom to top
in the stratum section (fig. 2).
The Sanjianpu Formation, larger than 1 700 m in thickness, overlies with unconformity different horizons of the Foziling group, and includes three sedimentary-genetic units from bottom to
top. Based on the sedimentary-process types for fluvial deposits presented by Miall[19], these units
may be approximately classified into the fourth and/or fifth rank, with indeterminacy due to the
lack of effective time calibration for these deposits. J2s1: low mottled conglomerates, mainly composed of paraconglomerate the gravels of which are generally less than 0.3 m in size, and sorting
and roundness of gravels are very low; the upper section of J2s1 is grey muddy siltstones
interstratified with thick sandstones. J2s2: grey and brown silty mudstones and siltstones interstratified with fine conglomerates and sandstones, in which trough and wedge-shaped cross bedding are developed, and small-scale inclined bedding and biological escape traces are frequent.
J2s3: the lower section shows grey, dark brown silty mudstones interbedded with conglomerate-bearing sandstones, in which calcareous concretions are developed and small-scale inclined
bedding occurs occasionally; but, in the upper section, grey, light brown-red conglomerate-bearing
sandstones and sandy conglomerates interbedded with medium-fine sandstones occur, in which
large cross and wedge beddings are developed. As a whole, this formation shows alluvial deposition of wandered-braided streams, in which J2s1 and J2s2 represent two normal-grading depositional units, J2s3 constitutes one reverse-grading depositional unit with major paleocurrent of
northeastern direction (fig. 3 (a)).
The Fenghuangtai Formation, more than 1 800 m in thickness, consists of three sedimentary-genetic units. J2f1: mottled and grey-purple conglomerates, mainly orthoconglomerates, at the
low section, in which lenticular sandstone bodies and large-scale inclined bedding are developed
and scouring surfaces occur frequently; the upper section shows paraconglomerates in great
thickness. J2f2: the low section shows grey and grey-purple conglomerates, mainly orthoconglomerates with huge gravels, interbedded with small conglomerates and lenticular gravelly sandstone
bodies, in which main paleocurrent points to north (fig. 3(b), (c)); the upper one is mainly composed of paraconglomerates in great thickness, with the largest gravel-size of 1.3 m. J2f3 is similar
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Fig. 2. A column chart showing typical strata and depositional lithofacies of Hefei basin.
to J2f2, in which gravelly sandstones, 0.5
1.0 m in thickness, occasionally occur in the upper sec-
tion as an interlayer. The Fenghuangtai Formation shows typical alluvial fan deposits characterized by debris flow[19], in which three reverse-grading depositional processes are represented by
J2f1, J2f2 and J2f3, respectively.
The Maotanchang Formation, about 900
1000 m in thickness, consists of three ge-
netic-stratigraphic units and overlies with unconformity the Fenghuangtai Formation. J3m1 shows
six cycles of intermediate-acid volcanic eruption, which are made up of andesite, andesite tuff,
volcanic breccia and ashy sandstone and conglomerate, with gravels generally less than 0.2 m in
size. J3m2: grey silt-bearing mudstones of thin-layer, in which the Estheria is found, reflects lacustrine depositional facies formed during intermittent period of volcanic eruption. J3m3 shows three
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cycles of intermediate-acid volcano eruption that consists of andesites, trachytic crystallinoclastic
tuffs.
Fig. 3. A rose-diagram showing depositional paleocurrent of the Jurassic detrital rocks. (a)
Cross-bedding in the Sanjianpu Formation (n = 8); (b) cross-bedding in the Fenghuangtai Formation
(n = 18); (c) dip of imbricated gravels (n = 9); (d) axial strike of gravels in the Zhougongshan Formation (n = 128); (e) cross-bedding in the Zhougongshan Formation (n = 10); (f) axial strike of gravels in the Zhougongshan Formation (n = 56).
The Heishidu Formation comprises two sedimentary-genetic units. K1h1: mottled sandy conglomerates and breccias interbedded with lenticular sandstones, which reflects piedmont alluvial
fan and gravel-sandy meandering deposition, in which the greatest size of gravel reaches 0.55 m.
K1h2: grey silty mudstones interbedded with gravel-bearing sandstones and fine sandstones, in
which interlayer gliding structures and cross bedding are developed, represents deposition of shallow lacustrine. Both K1h1 and K1h2 show normal-grading.
Grey and dark grey muddy shales, interbedded with thin-layer siltstones and fine sandstones,
occur at the lower section (unit K1x1) of Xiaotian Formation, in which small-scale cross bedding
and plant fragments are developed, which shows typical lacustrine facies; the upper section, however, is partly or all denuded. The Xiaotian Formation underlies, with angular unconformity, purple-red and thick sandy conglomerates of the Tertiary.
2.2
The north zone
The Jurassic-Cretaceous of the south zone of Hefei basin, which has a relatively good exposure in the Liuan-Feixi region, includes the Fanghushan Formation (J1f), the Yuantongshan Formation (J2y), the Zhougongshan Formation (J2-3z), the Maotanchang Formation (J3m), the
Zhuxiang Formation (K1z), the Xiangdaopu Formation (K2x) and the Zhangqiao Formation (K2z)
from bottom to top, which is composed of a suite of terrigenous clastic deposits of Mesozoic interbedded with volcaniclastic rocks in thickness of 4 000
5 500 m (fig. 2).
The Fanghushan Formation, about 400 m in thickness, overlies, with unconformity, the
grey-black graphite-schist and grey mica-quartz schist, which consists of three sedimen-
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tary-genetic units. J1f1: mainly grey, brown grey sandy conglomerates and orthoconglomerates in
the lower section, 30 40 m in thickness, in which the gravels are generally smaller than 0.2 m in
size with the medium sorting and roundness, and the imbricated structure of gravels can be found,
reflects deposition of sandy-gravel wandering streams[19]; on the other hand, grey muddy siltstones,
interbedded with thin-layer shale and coal bed, occurs at the upper section of J1f1, shows flood
plain deposition. J1f2: greyish-white gravel-bearing sandstones interbedded with thin layers of siltstones-fine sandstones and conglomerates, with the comparatively high component maturity of
sandstones and large-scale cross-bedding, reflects sand-bar deposition of wandering streams, in
which the main paleocurrent is northeast by east.
The Yuantongshan Formation, about 1 000 3 000 m in thickness, on the whole, is a suite of
interbedded assemblage of purple-red siltstones, silty mudstones and greyish-green silty mudstones, in which two upward-fining depositional units (J2y1, J2y2) and one reverse-grading unit
(J2y3) may be identified, and gravel-containing medium-fine sandstones, as an interlayer, occasionally occur. It is found that climbing bedding, bioturbate structure, burrow and interference
ripple are developed in the unit, which reflects typical deposition of the fine-grained meandering
streams[19] and alluvial flood plain.
The Zhougongshan Formation, 900 1 300 m in thickness, includes four sedimentary-genetic
units. J2-3z1: purple-red gravel-bearing coarse sandstones and sandstones, in which both washing
surface and cross-bedding are developed. J2-3z2: interbedded sandstones and siltstones at the lower
section of this unit, about 150
200 m in thickness, in which more bioturbate structure can be
found; turning into the upper section then, interbedded light brown, grey thick sandy conglomerates, medium-coarse sandstone and siltstone occur, in which washing sedimentary-structure with a
combination of lage-scale cross-bedding, wave diagonal bedding and wave lamination are developed. It is also found that the sorting and roundness of gravels is between the medium rank to the
low one, and the gravels are generally smaller than 0.2 m. J2-3z3: thick grey sandy conglomerates
and medium-coarse sandstones, interbedded with siltstones, with upwardly increased proportion
of gravel component, washing structure and large-scale trough cross-bedding in this unit, in which
mainly eastern paleocurrent is found (fig.3(d), (e), (f)). J2-3z4: brown grey fine sandstones interbedded with siltstones and silty mudstones, with omission in the top strata. The J2-3z1, J2-3z2 and
J2-3z3 represent three reverse-grading depositional units respectively, and, on the whole, result
from sedimentary environments of gravel-sandy braided river and alluvial flood plain.
The Maotanchang Formation, about 350 m in thickness, consists of two incomplete volcanic
eruption cycles, in which rock types are mainly made up of grey, brown grey andesitic tuff breccia,
lava and tuff.
The Zhuxiang Formation, about 1 500 m in tkickness, consists of two sedimentary-genetic
units. K1z1: dark brown silty mudstones interbedded with grey, dark-grey mudstones and silt-fine
sandstones, in which brownish red conglomerates, gravel-bearing coarse sandstones are developed
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at the bottom of this unit, but depositional gypsums are found at the top stratum. The K1z1 principally shows one upward-fining cycle. K1z2: interbedded dark brown/brownish grey silty mudstones and volcaniclastic fine sandstones in unequal thickness, in which thin-layers of greyish
green mudstone and marl concretion occasionally occur. The Zhuxiang Formation principally
shows deposition of sandy wandering river and/or meandering river and alluvial plain, in which
coarse clastic alluvial deposits gradually decrease from the K1z1 to the K1z2.
The Xiangdaopu Formation, 800
900 m in thickness, generally shows one ge-
netic-stratigraphic unit, represented by K2x1, interbedded dark-greyish brown silty mudstone layers, fine sandstones and siltstone ones in unequal thickness. It is found that gypsum lamina or lenticle frequently occur, and horizontal and wavy bedding are developed, which reflects deposition
of flood plain and restricted playa environment.
The Zhangqiao Formation, 900 1 000 m in thickness, consists of two sedimentary-genetic
units. K2z1
interbedded dark brown silt-fine sandstones and silty mudstones, with more frequent
wavy diagonal bedding. K2z2: brownish red, greyish purple thick-layer conglomerates and sandstones interbedded with silty mudstones in thin-layer, in which trough cross-bedding and washing
surfaces frequently occur at the bottom of this unit. The upward-fining depositional processes are
developed in the Zhangqiao Formation, which represents deposition of sandy braided river and
alluvial plain. However one complete reverse-grading unit occurs from the K2z1 to the K2z2, with
increasing influence of high-energy fluvial process.
3 Basin-fill sequence and evolution
It is found that the fill-sequences of Hefei basin show obviously distinct lithofacies, depositional architectures and regional geodynamics in the Jurassic and the late Jurassic-Cretaceous respectively, which may be divided by angular unconformities (fig. 4).
3.1 The evolutionary phase of Jurassic
The Jurassic of the studied area mainly shows a facies-assemblage of alluvial fan, fluvial and
flood plain. In the early-Jurassic, deposition of meandering streams is developed under the condition of relatively small topographic relief. With the increase of mountain-basin topographic relief
in the medium-Jurassic, the depositional systems turn from the combination of braided river and
alluvial plain into the combination of alluvial fan and flood plain, with obviously intensified overcompensation sedimentation. In this phase, an extreme development of paraconglomerates shows
transportation medium characterized by flood and debris flow. Later, intensive uplift of the north
Dabie Mountains and the south Hefei basin results in sedimentary depocenter migrating northward,
and erosion of the middle-Jurassic strata at the south Hefei basin also provides partial provenance
for deposition of the upper section of Zhougongshan Formation at the north part of Hefei basin[18].
The statistic of the sedimentary-genetic units presented above shows two three normal-grading
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Fig. 4. The fill-sequences of Hefei basin.
depositional-processes in the early-Jurassic, and at least four reverse-grading ones in the mid-late
Jurassic (fig. 2). On the other hand, principal paleocurrent of the Jurassic deposits northward and
northeastward respectively in the south Hefei basin and the north one, reflects that transverse river
system is developed in the Huoshan-Jinzhai region of the south basin, but, northward, axial river
system in the Liuan-Feixi region.
In conclusion, an evolutionary sequence, from fluvial-flood plain clastic to molasse reconstruction, exists in the Jurassic section, in which there are frequent uplift, exposure and washing
erosion records. Especially, for the mid-upper Jurassic, reverse-grading depositional units, lithofacies distributed mainly from south to north, fault border in the south of basin and stratum onlap at
the north one, and depositional depocenter confined to the south basin[18], and so on, principally
show that the basin-fill was obviously influenced by thrust processes within the north Dabie orogenic belt, which may be main factors controlling intensive provenence erosion and cyclic progradation during the Jurassic phase. So it is presented that pressing tectonic regime once has an
important effect on the Hefei basin, which results in episodic thrusting, at least four times, in the
arc-continent collision orogenic belt formed in early stage[18], and further intracontinent uplift-orogenesis. This process also provides ample provenance condition for deposition of the Fenghuangtai Formation.
It should be pointed out that, as presented in the research[18], main provenances are similar to
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“the Beihuaiyang flysch” types in the early-middle Jurassic of Hefei basin, but “the north Dabie
complex” types in the middle-late Jurassic, which means that the former provenance block may be
superposed by the latter through thrusting process. However, on the whole, the mixed provenance
types, with complicated components of lithoclast and gravel, frequently occur through the Jurassic
section. So more integrated research is needed to define paleotectonic-geographic significance of
the four times of thrusting processes mentioned above.
3.2
The evolutionary phase of late Jurassic-Cretaceous
This phase begins with a suite of calc-alkaline and alkali andesitic volcanic lava. In the
Jinzhai-Huoshan region, an assemblage of andesitic lava, trachyliparite and volcanic arenite of the
Maotanchang Formation occurs during the rifting-episode I; and the Heishidu Formation and the
Xiaotian Formation, made up by dark brown, browny grey, thick-layer fine clastic rocks interbedded with dark grey mudstones, form during the rifting-episode II (fig. 4). The volcanic rocks of
Maotanchang Formation originated from the upper mantle, but were contaminated by intensive
alkali and calcareous material[10] which is obviously related with rifting in postorogenesis, and no
relation to synorogenic volcanic activity. Then alluvial and lacustrine deposits make up one
rounded normal-reverse grading unit in the episode II, showing marked extentional and rifting
process.
In the Huoshan-Jinzhai region, no depositional record of the late-Jurassic exists probably due
to intensively late erosion, therefore the rifting cycle mentioned above is incomplete. In the
Liuan-Feixi region or its north, however, the rifting-episode I and the rifting-episode II, respectively constituted by the Maotanchang Formation and the Zhuxiang-Xiangdaopu Formation, can
be compared with the two rifting-episodes in the Jinzhai-Huoshan region. In addition, the top section of this region, represented by the Zhangqiao Formation made up by brownish red, greyish
purple, thick-layer fine conglomerates and sandstones interbedded with silty mudstones, results
from the post-rift sedimentation after the rifting-episode II.
4 Discussion on the relation between Hefei basin formation and Dabie orogenesis
Regionally there are distinct evolutionary processes between the southern part of North
China (namely the Nanhuabei), and the northern part of North China, which may be related with
the influence of intracontinental subduction of the Yangtze plate and their obvious exchange of
material-energy-momentum on the southern part of North China. It has been pointed out that the
Dabie Mountains and its adjacent region had gone through an tectonic transform process from
pressing uplift scenario to extensional rift one. However, the cognition on time boundary and
geodynamics of the above evolutionary process, especially the Jurassic tectonic-dynamic environment of Hefei basin, is very obscure. For the Beihuaiyang region, it was considered that the
time boundary of tectonic scenario change is at the late-Triassic[5, 8, 10, 11] or the end of
early-Jurassic[2], that is, the Hefei basin is a fault basin, of which the formation environment is
generally regarded as tensile setting.
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For the transform process of tectonic systems of Hefei basin in the Mesozoic, especially in
the Jurassic, and its relation with the Dabie orogenesis, new research information and recognition
are presented in this paper.
Firstly, the Hefei basin is characterized by terrestrial clastic deposits with multiple reverse-grading units in the middle-late Jurassic, with molasse reconstruction in greater thickness,
which reflects gradually strong episodic thrusting-orogenesis in the north Dabie and flexural depression in the north foreland of the Dabie
Mountains. From the late-Jurassic to the Cretaceous, Two-episodic rifting processes are
identified. The first-episode (J3) shows accumulation of intermediate-acid volcanic
rocks interstratified pyroclastic rocks. A suite
of lacustrine, fluvial and piemount facies,
about 3 000
3 500 m in thickness, develops
in the second-episode (J3-K1), which reflects
regional extensional setting and intense differential elevator of mountain-basin in the
study area (fig. 5). This conclusion is basically consistent with the viewpoints presented by Chen[20] and Yang[21], that is, intensive uplift of the Dabie Mountains occurs
during 140
120 Ma. In other words, the
main episode of vertial uplift of the Dabie
Mountaina does not correspond to the mid- Fig. 5. Tectonic relationship and evolutionary phases of the
dle-late Jurassic, during which molasse re- Hefei basin and the Dabie Mountains. (a) Early Jurassic; (b) middle-late Jurassic; (c) late Jurassic to early Cretaceous; 1, gravel
construction in greater thickness develops in clastic rock; 2, sandy clastic rock; 3, mudstone/fine-clastic rock; 4,
volcanic/pyroclastic rock; 5, eclogite; 6, granite.
the south of Hefei basin.
Secondly, the Jurassic tectonic-stratum framework is characterized by “fault and stratum
onlap respectively occurring in the south border of the basin and the north border”. According to
published research[18, 22], both maximum depth and temperature of the Jurassic ever experienced in
the southern part of Hefei basin are far greater than that of the northern part, and main provenances are from the Dabie orogenic belt. In addition, it is also found that the Meishan group
and/or the Foziling group overthrust on the Jurassic in some area, though their genetic mechanisms are presented by different explanations. So it is certain that sole stretch fault model is very
difficult to explain the Mesozoic basin-fill, especially Jurassic sedimentary sequences, genesis and
occurrence of the Hefei basin.
Obviously, due to the further intracontinental subduction of Yangtze plate after the Triassic,
strong pull of deep subduction-slab may become the major drive force on flexural depression in
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the north foreland of the Dabie Mountains. At the same time, regional pressing thrusting-orogenesis once predominated the area, which accordingly results in the northwards progradation and onlap of Jurassic detritus, and forms multiple reverse-grading fill-sequences in the Hefei
basin. Afterwards, with the beginning of andesitic and trachyte lava of Maotanchang Formation,
the late-Mesozoic rifting cycles occur in the basin, which regionally are comparable in the east
China[23], and of which the deep geodynamic process may relate with mantle upwelling induced
by deep thermal-flow increase due to the Yangtze continent slab breakoff and subduction termination. Because the Hefei basin is adjacent to the Dabie orogenic belt, of which the evolution is controlled by the orogenic tectonic framework early formed, the strikes of extensional structures of
this episode show mainly northwest by west or east-west in the basin, not northeast-northeast by
north that is common in eastern China.
So, two distinct evolutionary stages of the Mesozoic Hefei basin have profound implications
of regional geodynamics. It is convincing that the different tectonic dynamic systems in the Hefei
basin and the Beihuaiyang region, during moutain-basin transform, cannot be simply delimited by
the late-Triassic. Although the two-phase evolution of Hefei basin and their geodynamic implication are objective and reasonable, further and detailed research will be necessary.
Acknowledgements Thanks to Prof. Jin Fuquan, Hefei Industrial University, for his enthusiastic support and help to our
field work. This work was supported by the Key Project of the Chinese Academy of Sciences (Grant No. KZ951-Al-401-07).
References
1.
2.
Jin, H. Q., Yian, X. H., New progress of stratigraphic research in Beihuaiyang, Journal of Hefei Industrial University (in
Chinese), 1987, (9): 3.
Han, S. F., Analysis of Mesozoic and Cenozoic Sedimentary Basins in North Anhui (in Chinese), Beijing: Geological Publishing House, 1996, 89
3.
4.
94, 117
129.
Liu, D. L., Shen, X. Z., Li, X. X. et al., Deep nappe-extentional structure and oil-gas controlling analysis, Journal of Nanjing University (in Chinese), 1993, 5(2): 208.
Han, J., Zhu, S., Xu, S., The generation and evolution of the Hefei basin, in The Chinese Sedimentary Basins (ed. Zhu, X.),
Amsterdam-Oxford-New York-Tokyo: Elsevier, 1989, 125
5.
6.
7.
8.
Press, 1994, 1319, 135
9.
10.
12.
137.
Cong, B., Wang, Q., Tectonic framework of the ultrahigh-pressure metamorphic zone from the Dabie mountains, Scientia
Geologica Sinica, 1998, 7(4): 449.
Xu, G. Z., Geotectonics and Gold Mineralization in the Northeastern Dabie (in Chinese), Beijing: Geological Publishing
House, 1994, 1
11.
135.
Wang, Q. C., Cong, B. L., Ma, L., Structural coupling of the Dabie orogen with Hefei Basin, Chinese Science Bulletin,
1997, 42(18): 1566.
Ernst, W. G., Zhou, G., Liou, J. G. et al., High-pressure and superhigh-pressure metamorphic terranes in the Qinling-Dabie
mountain belt, central China: early- to mid-Phanerozic accretion of the western paleo-Pacific Rim, Pacific Sci. Assoc. Information Bull., 1991, 43: 6.
Okay, A. I., Sengor, A. M. C., Sant, M., Tectonics of an ultrahigh-pressure metamorphic terrane: the Dabie Shan/Tongbai
Shan orogen, China, Tectonics, 1993, 12: 1320.
Xu, S. T., Liu, Y. C., Jiang, L. L. et al., Tectonic Regime and Evolution of Dabie Mountain (in Chinese), Beijing: Science
72.
Yang, S. N., Chen, R. Y., Qian, X. H., Orogeny and orogen structure of Dabie Mountain in Mesozoic, Earth Science (in
Chinese), 1987, 12(5): 495.
Li, Y. J., Hu, S. L., Jin, F. Q. et al., The genetic type of Yangshan upper Paleozoic basin and its relation to the Tong-
No. 1
13.
14.
15.
16.
17.
18.
MESOZOIC FILL-SEQUENCE: IMPLICATION FOR DABIE
63
bai-Dabie orogenic belt, Scientia Geologica Sinica (in Chinese), 1997, 32(1): 19.
Yang Zhijian, The characteristics of geological and tectonic evolution of the Tongbai-Dabie Mountian, Acta Geologica
Sinica (in Chinese), 1982, (2): 123.
Xu, G. Z., Hao, J., The characteristics of Foziling group and geotectonic environment of its formation in the northern foot
of the Dabie mountain, Scientia Geologica Sinica (in Chinese), 1988, (2): 97.
Wang, D. X., Tectonic properties and evolution in Beihuaiyang, Journal of Hefei Industrial University (in Chinese), 1987,
(9): 29.
Ma Wenpu, The carboniferous at the northern foot of the Dabie mountain and its tectonic implication, Acta Geological
Sinica (in Chinese), 1991, 65(1): 17.
Dong, S., Sun, X., Zhang, Y. et al., The basic structure of Dabie collisional orogen, Chinese Science Bulletin, 1993, 38(22):
1884.
Li, Z., Li, R. W., Sun, S. et al., Detrital composition and provenance tectonic attributes of Jurassic sandstones, South Hefei
Basin, Acta Petrologica Sinica (in Chinese), 1999, 15(3): 438.
98, 191
250.
19.
Miall, A. D., The Geology of Fluvial Deposits, Berlin: Springer-Verlag, 1996, 75
20.
Chen, J., Xie, Z., Liu, S. et al., Cooling age of Dabie orogen, China, determined by 40Ar-39Ar and fission track techniques,
Science in China, Ser. B, 1995, 38(6): 749.
Yang, K. G., Ma, C. Q., Xu, C. H. et al., Differential uplift between Beihuaiyang and Dabie orogenic belt, Science in
China, Ser. D, 2000, 43(2): 193.
Xue, A., Yang, X., Inversion of thermal history and evolution of subsidence and erosion rates using apatie fission track
data in Hefei basin, Anhui province, Acta Geophysica Sinica (in Chinese), 1994, 37(6): 787.
Ma, X. Y., Liu, H. F., Wang, W. X. et al., Rifting and extensional tectonics, Acta Geologica Sinica (in Chinese), 1983, (1):
22.
21.
22.
23.