Ramp Delta Deposit and Palaeogeography Evolution of Permian Paralic Basin in Southwest Shandong Province, North China

The paper focuses on the deltaic deposition of Southwest Shandong and studies its sedimentary characteristics and evolution of paleogeography. It can be identified six kinds of lithofacies including drab yellow coarse-sand facies (CS), grayish medium-sand facies (MS), grayish fine-sand facies (FS), dark grey mudstone and siltstone interbedding (MFS), coal (CB), dark mudstone (DM). Eight kinds of sedimentary microfacies are identified which are: distributary channel facies (MS and CS association), mouth bar facies (MS and FS association), natural levee facies (FS and MFS association), crevasse splay facies (MS, FS and MFS association), peat swamp facies (DM and CB association), distal bar facies (MFS), bay or littoral-neritic facies (DM). Isochronous sedimentary contrast is carried out in the delta sedimentary of Southwest Shandong and divided into five cycles. C1 mainly forms bay facies of prodelta in early stage, delta plain and delta front deposition in later stage. C2 develops delta front and prodelta deposition in the southwest and delta plain in the northern of the study area in early stage, delta plain in later stage. C3 develops delta front deposition in early stage, delta plain in later stage, C4 and C5 are mainly formed in delta plain, and Zibo area has evolved into continental fluvial sedimentary.