Sedimentary characteristics and evolution model of the Middle Cambrian in the Qinglongshan Section,Ordos Basin
Through field outcrops observation and thin sections identification,the lithofacies types and lithofacies assemblage characteristics of the Middle Cambrian in the Qinglongshan Section of the Ordos Basin were studied.The types and characteristics of sedimentary facies and section facies were analyzed,and the sedimentary evolution model was established.The study shows that 13(LF1-LF13)lithofacies types and 8 lithofacies assemblages in the Middle Cambrian of the Qinglongshan Section are identified.The lithofacies assemblages include bright crystal oolitic limestone and khaki argillaceous shale,particle-supported gravel limestone,bright crystal oolitic limestone and khaki argillaceous shale,mud crystal bioclastic limestone and khaki argillaceous shale,mud crystal oolitic limestone and khaki argillaceous shale,gray-green argillaceous shale and mud crystaloolitic limestone,banded limestone and radial grav-el limestone,banded limestone and khaki argillaceous shale,spherulite-bearing powder crystal dolomite and khaki argillaceous shale.The carbonate gentle slope sedimentary system is developed in the Middle Cambrian,which is mainly inner gentle slope facies.It can be divided into 4 subfacies and 10 microfa-cies.The subfacies contain tidal flat,lagoon,inter-beach sea and grain beach.In the Middle Cambrian,the Qinglongshan Section was in a carbonate ramp environment.With the eastward and northward transgression of the Qinqi Trough,the sedimentary center migrated eastward under the influence of the Qingtongxia-Guyuan Fault.The sedimentary facies belt changed from tidal flat-lagoon to grain beach-in-ter shoal sea,and finally changed into tidal flat deposition again due to the signs of sea retreat.The re-sult provides a basis for therestoration in the paleoenvironment in the Ordos Basin.
万方数据
维普
