Responses Of Sedimentary Sources And Paleoclimatic Changes Of The Cretaceous Jiaolai Basin To Coastal Mountains In Eastern China

East China experienced crustal extensions during the Early Cretaceous and the latest Cretaceous-Cenozoic.For a long time,previous studies have recognized a short-lived compressional event between these two extensional regimes during the early Late Cretaceous,but not much attention has been paid to it,although it may shed new light on the tectonic evolution of East Asia and the mechanism of the North China Craton Destruction.A large amount of evidence shows that there are huge coastal mountains on the margin of the Late Cretaceous East Asia continent.however.At present,our understanding of the coastal mountains is very limited.It is unclear when the coastal mountains rise,the range of the mountains,and the ancient elevationHere,we apply integrated sedimentological methods to sandstone samples of the Jiaolai Basin,Which located at the margin of East China.The thin section statistics show that the sandstones of the Lower Cretaceous Laiyang Group are mainly granite and metamorphic rocks,and the sandstones of Upper Cretaceous Wangshi Group are mainly medium-basic volcanic rocks and andesite basalt Statistics of heavy minerals indicate that the heavy mineral assemblages of the Lower Cretaceous Laiyang Group are mainly zircon,rutile,monazite,chlorite,and garnet,showing the origin of metamorphic rocks and granites.The heavy mineral assemblages of the Upper Cretaceous Wangshi Group are mainly hornblende,pyroxene and sphene,showing the origin of medium-basic volcanic rocks.The samples from the Lower Cretaceous Laiyang Group and the Upper Cretaceous Wangshi Group showed similar peaks,but the proportions of the peaks were very different.The peaks of the Late Cretaceous 110-130Ma accounted for more than 90%.Combining the analysis of clastic components,we believe that the Lower Cretaceous Laiyang Group is mainly from granites in the Jiaobei terrane and the Sulu Orogenic belt,and the source of Late Cretaceous is mainly from basalt and andesite in the Qingshan Group in the basin.We speculate that the Jiaolai Basin became a intermontane basin in Late Cretaceous,and the coastal mountains also extended to Shandong Jiaolai Basin.The uplift of the coastal mountain had blocked the relatively distal materials from the Sulu orogenic belt and Jiaobei Terrane,so that the Jiaolai Basin could only receive limited materials from the basin margins.Based on the analysis of clay minerals in the Jiaolai Basin,the paleoclimate of the Jiaolai Basin changed from a warm and humid climate in the Early Cretaceous to a dry climate in the Late Cretaceous,and the cause of the climate change may be the rain shadow effect of the uplift of the coastal mountains.Combined with large-scale northwest-southeast tectonic events in East Asia,as well as the large-scale unconformity of basins in East Asia,we determined the range of coastal mountains.At the Late Cretaceous,including the Nanxiong Basin,Subei Basin,and Jiaolai Basin,large-scale unconformities were formed.We speculate that at this time,the coastal mountains extended from southern China to the Jiaolai Basin.There is transgression in the Songliao Basin indicating the Songliao Basin is at a lower elevation at this time.However,in the central Nanyang Basin and Jianghan Basin,the strata have not formed unconformity,indicating that the coastal mountains have not extended to this range.