Continental margin basins in East Asia:tectonic implications of the
Meso-Cenozoic East China Sea pull-apart basins
Y.H.SUO 1,2,S.Z.LI 1,2*,S.J.ZHAO 1,2,I.D.SOMERVILLE 3,S.YU 1,2,L.M.DAI 1,2,L.Q.XU 1,2,
X.Z.CAO 1,2and P.C.WANG 1,2
1
Key Lab of Submarine Geosciences and Prospecting Technique,Ministry of Education,Qingdao,China 2
Institute of Marine Geodynamics,College of Marine Geosciences,Ocean University of China,Qingdao,China
3
UCD School of Geological Sciences,University College Dublin,Bel field,Dublin,Ireland
The East China Sea basins,located in the West Paci fic Continental Margin (WPCM)since the late M
esozoic,mainly include the East China Sea Shelf Basin (ECSSB)and the Okinawa Trough (OT).The WPCM and its adjacent as can be tectonically divided into five units from west to east,including the Min-Zhe Uplift,ECSSB,the Taiwan –Sinzi Belt,OT,and the Ryukyu Island Arc,which record regional tectonic evolution and geodynamics.Among tho tectonic units,the ECSSB and the OT are important composite dimentary pull-apart basins,which experienced two stages of strike-slip pull-apart process.In ismic pro files,the ECSSB and the OT show a double-layer architecture with an upper half-graben overlapping on a lower graben.In planar view,the ECSSB and the OT are characterized by faulted blocks from south to north in the early Cenozoic and by a zonation from west to east in the late Cenozoic.The faulted blocks with planar zonation and two-layer vertical architecture entirely jumped eastward from the Min-Zhe Uplift to the OT during the late Cenozoic.In addition,the whole palaeogeomorphology of the ECSSB changed notably,from pre-Cenozoic highland or mountain into a Late Eocene continental margin with east-tilting topography caud by the eastward tectonic jumping.The OT opened to develop into a back-arc basin until the Miocene.Synthetic surface geological studies in the China mainland reveal that the Mesozoic tectonic tting of the WPCM is an Andean-type continental margin developing many sinistral strike-slip faults and pull-apart basins and the Cenozoic tectonic tting of the WPCM is a Japane-type continental margin developing dextral strike-slip faults and pull-apart basins.Thus,the WPCM underw
石榴花几月开ent a transition from Andean-type to Japane-type continental margins at about 80Ma (Late Cretaceous)and a transition in topography from a Mesozoic highland to a Cenozoic lowland,and then to below a-level basins.Copyright ©2013John Wiley &Sons,Ltd.
Received 12August 2013;accepted 23October 2013KEY WORDS
East China Sea Shelf Basin;Okinawa Trough;East Asia;Mesozoic;Cenozoic;tectonic jumping;topographic inversion;pull-apart basins
1.INTRODUCTION
Rearch on continental margins has highly stimulated many international interests and has become a major focus of the international geoscience community.For example,InterMARGINS and GeoPRISMs,particularly emphasizing rearch on rifted margins and rifting of continental lithosphere,material and energy exchanges of subduction zones and subduction factory process (Cawood,2005;Li et al .,2009),ismogenic zone process,dimentary process,and the source-to-sink system,have already obtained remarkable achievements (/).Many plate reconstructions are cloly associated with the tectonic evolution of continental margins,especially the
机械排烟
最简单快速去除头皮屑evolution of the West Paci fic or East Asian continental margins (Fig.1,Klimetz,1983;Sengör and Natal ’in,1996;Flower et al .,2001;Konstantinovskaia,2001;Deschamps and Lallemand,2002;Hall,2002,2012;Honza and Fujioka,2004;Gaina and Müller,2007;Komiya and Maruyama,2007;Sun et al .,2007;Zhao et al .,2007;Chen et al .,2008;Müller et al .,2008;Faccenna et al .,2009;Isozaki et al .,2010;Li and Van Der Hilst,2010;Martin,2011;Yoshida and Santosh,2011;Seton et al .,2012;Todd et al .,2012).However,most of the tectonic models of plate reconstructions have not yet been tested by the related tectonic evolution of the continental margins in East Asia.
The marginal a and the continental shelf basins,mainly situated at the West Paci fic Continental Margin (WPCM,int map of Fig.2),are important components of a complex continental margin system.The basins located at the WPCM and cloly related to subduction of the Paci fic Plate are as follows:the Philippine Sea,the South China Sea,the Sulu
*Correspondence to:Sanzhong Li,College of Marine Geosciences,Ocean University of China No.238,Songling Road,266100,Qingdao,Shandong Province,China.E-mail:sanzhong@ GEOLOGICAL JOURNAL Geol.J.50:139–156(2015)
Published online 22November 2013in Wiley Online Library ().DOI:10.1002/gj.2535
Sea,the Celebes Sea,the Japan Sea,the Bohai Bay,the East China Sea Continental Shelf,the Yellow Sea,and the Okinawa Trough basins.They record the detailed tectonic evolution and some transitional process among different types of continental margins.The East China Sea Shelf Basin (ECSSB)and the Okinawa Trough (OT)are particu-larly important in the WPCM becau of their abundant information on the Meso-Cenozoic formation and evolution of the continental margin in East Asia (Fig.1).Especially since the Mesozoic,the formation of the east-tilting topography of East Asia,the geomorphologic switch between West and East China (Wang,1998;Wang et al .,2005;Li et al .,2007;Zheng et al .,2008),and the coastward younger igneous rocks in eastern South China following tectonic eastward jumping (Wang and Shen,2003;Zhou,
2003;Li and Li,2007;Wang and Shu,2012)are gradually being focud on.The basic scienti fic issues,especially rearch on tectonic jumping and the detailed tectonic pro-cess of topographic inversion,have been gradually attracting much attention for the needs of oil and gas explo-ration in their corresponding areas.
Tectonic jumping is a common geological process in the tectonic evolution of oil-bearing basins and orogenic belts (Jiang,2009).It means that deformation,magmatism,dimentation,the associated source-rervoir-cap rocks,migration,trap,and hydrocarbon accumulation of oil and gas display a spa
tially regular migration or jump following an ori-ented propagation of basins and orogenic belts,in a certain geodynamic tting.The identi fication of tectonic jumping in the ECSSB and the OT is signi ficant for (i)
驳论和悖论evaluating
Figure 1.Schematic structural map and tectonic units of the ECSSB.Areas filled with light blue are depressions and sags.Areas filled with pink are uplifts.Black solid lines are con firmed tectonic unit boundaries,and black dotted lines are suppod boundaries inferred from ismic pro files.Red thick lines reprent Palaeocene faults,orange lines reprent Eocene –Oligocene faults,yellow lines reprent Miocene faults,and red thin lines reprent new NW-oriented faults.Green lines are anticlines bad on ismic pro files.Thick blue lines labelled with triangles show the subduction zone of the Paci fic Plate subducting under the Eurasian Plate.Thin blue lines are locations of ismic pro files in Figures 3and 4and identi fied by A to G .See abbreviations of places in Table 1.Int map:Areas filled with yellow are major dimentary basins.BBB,Bohai Bay Basin;NYSB,North Yellow Sea Basin;SYSB,South Yellow Sea Basin;ECSSB,East China Sea Shelf Basin;OT,Okinawa Trough;SCSB,South China Sea Basin;H-J-GFD,Hangzhou –Jiangshan –Ganzhou fault depression;TLF,Tan-Lu Fault.Black solid lines are boundaries between North China Block and South China Block.Red dotted lines are fault zones.F1,Changle-Nanao Fault Zone;F2,Gangjiang Fault Zone;F3,Zhenghe-Dapu Fault Zone;F4,Sihui-Wuchuan Fault Zone;F5,Shaoxing-Jiangshan-Pingxiang Fault Zone.Red arrows show the
strike-slip direction of fault zones.This figure is available in colour online /journal/gj
Y .H .SUO ET AL .
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hydrocarbon and gas hydrate potential,(ii)forecasting rer-voirs in new exploration areas,(iii)deepening exploration in a mature exploration region,and (iv)understanding the geodynamics of oil-bearing basins.Tectonic jumping occurring in the continental margin of East Asia is related to the rollback of the subduction of the Paci fic Plate (Santosh et al .,2009).However,Santosh et al .(2009)did not prent any evidence of tectonic jumping in the East Asian continental margin.
In this study,we have taken the ECSSB and the OT as an example to address the above-mentioned issues through a detailed analysis of the geological architectures and structures,as well as their migrations and transitions,as revealed by ismic pro files covering the ECSSB and the OT.
2.GEOLOGICAL SETTING
The Mesozoic (Jurassic –Cretaceous)granitoid belt (Sagong et al .,2005;Z.X.Li et al .2012;Wang and
Shu,2012;Fig.2),ca .500km wide and veral thousand kilometres long,parallels the WPCM in East Asia,being considered to have formed above a subduction zone in a crustal compressive tectonic regime (Uyeda and Miyashiro,1974;Charvet et al .,1994;Maruyama et al .,1997).Recent
rearch reveals that it has emingly generated diachronous activity (Kinoshita,1995;Sagong et al .,2005),rather than a single contemporaneous magmatic activity of the belt,bad on the age distribution of granitoid plutons.The propod models for the generation of the huge belt are (i)ridge subduction (Uyeda and Miyashiro,1974;Kinoshita,1995;Sun et al .,2007),(ii)magmatism in a continental back-arc environment,and (iii)magmatism in association with extension of the lithosphere (Li,2000;Wang and Shu,2012)or by plume activity (Okada,1999).
In East Asia,Mesozoic tectonics are traditionally considered as basin and range-type tectonics,such as metamorphic core complexes in the North China Craton during the Late Cretaceous,and the associated magmatism is the reprentative of an extensional tectonic tting during the Middle Jurassic to Late Cretaceous (Wang and Shu,2012).The coastward migration and zonation of magmatism of early post-orogenic granites to late intracontinental syn-extensional A-type granites and bimodal volcanic rocks developed in East China (Wang and Shu,2012)and South Korea (Sagong et al .,2005),which are located to the west of the ECSSB.The granitoid ages and kinematic
analys of the Mesozoic structures in South Korea suggest that dextral strike-slip ductile shear zones formed becau of the途成语
northwest
Figure 2.Pre-Cenozoic structural units and magmatism of the ECSSB.Data for South China mainland are modi fied after Z.X.Li et al .(2012).Data for offshore basins are from ismic pro files in this study.Int map:TLF,Tan-Lu Fault;WPCM,West Paci fic Continental Margin.This figure is available in
colour online /journal/gj
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(orthogonal)subduction of the palaeo-Pacific Plate in the Middle Jurassic(180–170Ma),and sinistral faults formed becau of the northward(oblique)subduction of the palaeo-Pacific Plate in the Cretaceous.This mostly agrees with the propod reconstruction of plate motions around East Asia(Sagong et al.,2005).The geodynamic evolution of the South China Block during the Late Mesozoic is also considered to be derived from a polypha tectonic evolution,mainly constrained by subduction of the palaeo-Pacific Plate since the Late Mesozoic,leading to the formation of various magmatic events in a back-arc extensional tting(Wang and Shu,2012).In fact,a similar zone of magmatism also happened in the ECSSB,the OT, and east of the South China Block in the Cenozoic.
The ECSSB is located on the wide continental shelf off East China,with the Min-Zhe Uplift to the west and the Taiwan–Sinzi Belt to the east(Fig.1,Table1).The OT is located east of the ECSSB(Zhang et al.,2008)(Fig.1, Table1).Their evolution is a key linkage of the Mesozoic evolution of the South China Block with the Cenozoic evo-lution of the West Pacific Subduction Zone,controlled by subduction of the Pacific Plate.
Five Late Mesozoic,regional NE-and ENE-trending strike-slip faults developed in the eastern part of the South China Block(Xu and Shu,2001,Shu et al.,2011)(Figs.1and2), including,from west to east,the ENE-trending Shaoxing-Jiangshan-Pingxiang Fault Zone(F5),the Sihui-Wuchuan Fault Zone(F4),the Zhenghe-Dapu Fault Zone(F3),the Gangjiang Fault Zone(F2),and the Changle-Nanao Fault Zone(F1).The NE-trending Gangjiang Fault Zone marks the western boundary of Early Cretaceous volcanic rocks (Shu et al.,2009b;Wang and Shu,2012),and the Changle-Nanao Fault Zone controlled the broad distribution of100–120Ma orthogneiss and gneissic granodiorite (Wang and Lu,2000)(Fig.2).Granitic magmatism occurred(Charvet et al.,1994)and alkaline basalts erupted during the Late Cretaceous–Palaeogene in respon to the oblique subduction of the palaeo-Pacific Plate(Wang and Shu,2012).A t of Late Cretaceous–Palaeogene pull-apart basins are also controlled by the NE-striking Sihui-Wuchuan Fault Zone(F4),accompanied by succes-sive lava erupti
ons between92–38Ma from the Maoming Basin to the Sanshui Basin(Zhu et al.,2004)(Fig.2).It indicates a transition from Early Cretaceous intracontinental sinistral strike-slip faulting to Late Cretaceous normal and dextral strike-slip faulting.
Regional disconformities also record multiple-stage tectonic evolution in basins(S.Z.Li et al.,2012).The angular unconfor-mities in the Xuefeng Intracontinental Tectonic System during the Triassic–Early Cretaceous interval are characterized by a westward migration.Correspondingly,the deformation ranges and the boundary lines between high-angle and low-angle un-conformities migrated westward,and the deformation intensity in the Xuefeng Intracontinental Tectonic System simulta-neously decreas from east to west during the Early Mesozoic. Five deformation belts can be recognized(S.Z.Li et al.,2012),
Table1.Division of tectonic units of the ECSSB Y.H.SUO ET AL.
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from east to west,and they resulted in different stages of this diachronously progressive deformation.Jin et al.(2009)pro-pod that the controls to the progressive propagation and thrusting events result from detachment layers and coeval magmatism in the South China region un
der the subduction-related compression of the palaeo-Pacific Plate.However,the eastward tectonic migration started since the Late Cretaceous. All the migrations are also recorded by angular unconformities among the Palaeozoic,Mesozoic,and Cenozoic strata in the ECSSB and its neighbouring basins.From bottom to top, the Cenozoic strata(Table2)in the ECSSB contain(i)the Palaeocene Yueguifeng(T010–T09,the abbreviated symbols of T010/T09mark the interface between different units in ismic profiles,and between the adjacent formations),the Lingfeng(T09–T58),and the Mingyuefeng(T58–T08)formations; (ii)the Eocene Oujiang(T08–T05),the Wenzhou(T05–T04),and the Pinghu(T04–T03)formations;(iii)the Oligocene Huagang Formation(T03–T02);(iv)the Miocene Longjing(T02–T61), the Yuquan(T61–T21),and the Liulang(T21–T01)formations; (v)the Pliocene Santan Formation(T01–T0);and(vi)the Quaternary Donghai Group(T0–prent)(Table2).Since the Late Cretaceous,the ECSSB underwent multi-stage movements,which include the Jilong(T g),the Yandang
(T010),the Oujiang(T08),the Yuquan(T03),the Huagang (T02),the Longjing(T21),and the Okinawa Trough(T0) tectonic movements(Xu and Le,1988;Xiao and Zhou,1995) (Table2).Therefore,the relationship among the Cenozoic stratigraphic units is complex due to the multi-stage tectonic movements in the ECSSB.
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3.STRUCTURAL UNITS OF ECSSB AND OT The ECSSB can be subdivided into three parts,from west to east:the West Depression Group(WDG),the Central Uplift Group(CUG),and the East Depression Group(EDG) (Chen,1994;Liu et al.,2003).All three parts are compod of a ries of cond-order tectonic units(Fig.1,Table1). The OT is also subdivided into three parts,from west to east: the Frontal Continental Shelf Depression(FD),the Longwang Ridge(LR),and the Tokara Depression(TD) (Zhang et al.,2008)(Fig.1,Table1).Further east,the Taiwan–Sinzi Belt acted as a buttress against the compres-sional tectonism.The LR may be the youngest of the relict arcs or buried ridges in the OT(Gungor et al.,2012). Previous studies(Wang,1987;Guo,1988)have shown that the overall geological architecture of the Cenozoic ECSSB and the OT is characterized by faulted blocks from south to north,and by a zonation from west to east in plan view,and obvious multiple-layer architectures(Liu et al.,2003)in verti-cal profiles.In this study,we have recognized that the detailed architectures of the ECSSB and OT are faulted blocks and basins from south to north at the early stage and characterized by a zonation from west to east in plan view at the late stage. The profiles show a double-layer architecture comprising a half-graben overlaying a graben,and this architectural evolu-tion of the EDG is later than that of the WDG in the ECSSB.
3.1.Subdivision of structural units in the ECSSB
心得体会格式The ECSSB,recording more long-term information of its geodynamics than the OT,is a more important link between the eastern marginal rifting of the South China Block and the westward subduction of the Pacific Plate.Therefore,we need more detailed subdivision of its structural units. Some faults in the WDG are a ries of NE-trending,left-stepping,en echelon-arrayed Palaeocene normal faults.The major faults rve as the boundary between uplifts and adjacent depressions,resulting in the left-stepping,faulted blocks from south to north in the WDG(Fig.1).
The CUG is a relatively fault-undeveloped area who boundary is controlled by NE-trending border faults in the depressions of the WDG and NNE-trending faults or western slopes in the EDG(Yang and Li,2003).The left-stepping en echelon pattern in the CUG is also dominated by activity of the NE-trending faults in the WDG.合肥学院分数线
The NNE-trending and N–S-trending faults are Eo-cene–Oligocene in age,commonly en in the EDG, and identified by the cross-cutting relationship between the fault activity and the strata,some of which control the two-sided boundaries of this depression group.The EDG,which was also previously known as the Zhedong Depression(ZD),compris three parts,from north to south:the Fujiang Sag(FJ),the Xihu Sag(XH),and the Diaobei Sag(DB;Fig.1).The Fujiang and Diaobei sags can be divided into the West gentle slope(WS), the Central sub-sag(CS),and the East sharp slope(ES), resp
ectively.However,the Xihu Sag is divided into the West gentle slope(WS),the Central Anticline belt(CA),and the East sharp(ES)slope,becau of its late nearly E–W-trending faults(Song,2007),as well as NNE-trending and N–S-trending faults,and a ries of right-stepping en echelon folds in the centre of the sag(Fig.1).The large-scale coverage and the particularity of the Xihu Sag determine the right-stepping en echelon pattern and unobvious faulted blocks style from south to north in the EDG.
In summary,faulted blocks from south to north controlled by the Palaeocene NE-trending faults mainly developed in the WDG,and the zonation from west to east controlled by the Eocene-Oligocene NNE-trending faults developed in the CUG and EDG.Thus,the architecture of the ECSSB is characterized by faulted blocks from south to north at the early stage and by a zonation from west to east at the late stage,which specifically behaves as the left-stepping WDG,the left-stepping CUG,and the right-stepping EDG.
MESO-CENOZOIC EAST ASIAN CONTINENTAL MARGIN143
