| The East Asian continental Margin has undergone complex tectonic evolution since the Late Mesozoic.forming a complex basin-mountain system,and at the same time,the Sulu orogenic belt has also entered the post-orogenic stage.How to reproduce the plate subduction.intracontinental deformation,and post-orogenic exhumation of ultra-high pressure metamorphic rocks in the East Asian continental Margin since the Late Mesozoic has long been an important issue of concern to geologists.Basin is an important window to explore regional tectonic evolution,which preserves the information of regional tectonic deformation history.subsidence,uplift,and denudation.Jiaolai basin.located on the north side of the Sulu orogenic belt,is a Mesozoic rift basin that has undergone multi-stage tectonic evolution.The sedimentary strata and related tectonic tracks in the basin have recorded the intense extensional activities in East Asia and the evolution of Sulu orogenic belt during the post-orogenic stage since the Cretaceous.However,there are still Many controversies and deficiencies in the understanding of the basin evolution,the source-sink system.and their genetic relationship between the Paleo-Pacific plate subduction.Therefore,this article focused on the Cretaceous sedimentary records of the Jiaolai Basin,based on the relationship between the basin and the mountain,combining the study of sedimentology,isotopic chronology,provenance analysis,structural analysis,and paleostress inversion.through the detailed field investigation and data statistical analysis,to demonstrates the deposition-structure evolution of the Jiaolai basin during the Cretaceous.The research results show that during the deposition of the Laiyang Group,the north and south strata of the basin were asynchronous:During the early Early Cretaceous(ca.135-131 Ma),under the control of the E-W extension,the southern area initially rifted and gradually expanded northward;During the late Early Cretaceous(ca.121-113 Ma),the northern part of the basin was strongly stretched due to the near-NW-SE extension.And in this process,Zhucheng-Gaomi Sag and Laiyang Sag developed alluvial fan-fluvial delta/fan delta-lacustrine sedimentary systems successively.The NW-SE extension lasted until the end of the Qingshan Group(ca.93 Ma),and then,the NE-SW compression(ca.93-88 Ma)fold the Qingshan Group and its underlying strata.During the Late Cretaceous.under the control of S-N extension(88-65 Ma),the basin re-accepted sediments and formed the alluvial fan-fluvial delta/fan delta-lacustrine sedimentary system of the Wang Group.The reconstruction of the source-to-sink system shows that during the Cretaceous,the Sulu orogenic belt during its post-orogenic stage experienced two rapid uplifts at ca.121 Ma and ca.83 Ma,respectively.In addition,during the deposition of the Laiyang Group,the supply of sediments derived from ultrahigh-pressure metamorphic rocks showed differences in the source-to-sink systems of different sags in the basin,indicating that the high-ultrahigh-pressure rock units were uplifted in the form of multiple independent rock slices:At about 121 Ma,the high-ultrahigh-pressure rock slices in the northern section of the Sulu orogenic belt have been uplifted to the surface;while in the southern section of the Sulu orogen,the high-ultrahighpressure rock slices May not be exposed until about 113 Ma.The analysis results,including the basin deposition process,source-sink system evolution,and the paleo-stress field inversion consistently show that the Jiaolai Basin has undergone a multi-stage evolution accompanied by a change in the extension direction.Comparing the evolution of the basin with the history of the Paleo-Pacific subduction,it is revealed that the dynamic adjustment of the subduction of the PaleoPacific plate during the Cretaceous is the first-order driving force,which induced the tectonic evolution of the East Asian continental margin and formed the complex basin-mountain system. |
