Models for Mesozoic sequence stratigraphy of the North Weifang depression

The North Weifang depression located in northern Weifang, Shandong is a small Mesozoic prolific sedimentary basin confined by the Tancheng-Luxian fault. In terms of the seismic reflection boundaries in the depression, six seismic sequence boundaries or five third-order sequences have been recognized in the Kongdian Formation and the fourth member of the Shahejie Formation. The depression originated in the Eocene has experienced several episodes of evolution from rifting apart (latest Late Cretaceous), early subsidence, resubsidence, early collapse (Oligocene), termination and late subsidence (Neogene to Quaternary). Influenced by the intense faulting of the nearly EW-trending Gucheng-Weihekou fault, the strong subsidence of the northern part of the depression resulted in the formation of the half graben-like depression which is relatively gentle in the northern part while steep in the southern part. Two sedimentary models of sequence stratigraphy are put forward: simple fault and duplex fault.