Sedimentary Geology Of The Wufoshan Group In The Southern Margin Of North China Block And Its Tectonic Implications

Songshan area,Henan Province,belongs to the south margin of North China Craton,which is widely developed in Mesoproterozoic-Neoproterozoic stable sedimentary formations.It is an important "window" to understand the structural paleogeographic pattern and its evolution,paleo plate tectonics and geodynamic environment of the south margin of North China paleocontinent.In this paper,we selected the Wufoshan group and Bingmagou group to carry out the comprehensive research of isotope chronology,sedimentary geology,geotectonics and other disciplines,and made the following new progress:1.Based on the LA-ICP-MS U-Pb dating of detrital zircons of the sandstones of Luotuopan formation and Heyao formation in the Wufoshan group,it is confirmed that the age of 1.6¹.0Ga is the largest,and the minimum peak value ²⁰⁷Pb/²⁰⁶ Pb is 1020±47Ma,indicating that the lower age of Luotuopan formation and Heyao formation is not more than 1020 ± 47 Ma,suggesting that the geological age may be extended to the early Neoproterozoic.2.The U-Pb ages of the upper part of the Wufushan group are mostly concentrated in the range of 1.8-1.0ga,which is similar to the Qinling group,and the peak ages are consistent with the records of the Precambrian tectonic thermal events in the North Qinling structural belt,indicating that the Greenville orogenic belt in the North Qinling may be the provenance of the Luotuopan formation and the Heyao formation.3.In the Heyao formation,we can identify the soft sedimentary deformation structures,such as hill-trough structure,ball-pillow structure,liquefying vein,fluidizing conglomerate,diapir structure and seismic fracture fault.Based on the research results of "molar tooth" structure and the comparative study of typical sections,analyz the temporal and spatial development patterns of soft sedimentary deformation structures,discuss the geodynamic conditions of their formation,we suggest that the earthquake is the most likely trigger mechanism.4.Based on the comprehensive study of the sedimentary facies,oblique bedding position and zircon age spectrum of Wufoshan group and Bingmagou group,it is determined that the unconformity between Bingmagou group and overlying Ma'anshan group,Puyu group and overlying Luotuopan group are the most important structural transition surfaces in Songshan area,indicating that the structural paleogeographic pattern and plate tectonic environment of the southern margin of the North China ancient land experienced twice important conversion in the late Precambrian.5.Based on the above new achievements and previous data,this paper analyzes the sedimentary geological process of the Wufushan group and its response to the Mesoproterozoic-Neoproterozoic orogenic process of the northern Qinling Mountains,and discusses the Mesoproterozoic-Neoproterozoic tectonic paleogeographic pattern and its evolution of the Songshan area and its adjacent areas.