Sequence Architecture, Depositional Systems, and Controls on Development of Lacustrine Basin Fills in Part of the Erlian Basin, Northeast China

Abstract Sequence architecture and depositional systems of a Jurassic-Cretaceous lacustrine rift succession in the Wuliyashitai subbasin, and Erlian basin in northeastern China were investigated using seismic profiles, complemented by well logs and cores. Five second-order or composite sequences are identified on the basis of basin-scale unconformities. Constituent third-order sequences are defined by unconformities along the basin margins and correlative conformities within the central basin. Lowstand-transgressive and highstand systems tracts are separated by major lake flooding surfaces. Depositional systems identified in the basin include alluvial fan, incised valley, fan delta, braid delta, and sublacustrine fan. Three types of lacustrine sequences, consisting of distinctive depositional systems, formed during different tectonic stages: (1) alluvial-shallow-lacustrine sequences (type A) developed during the initial rifting stage; (2) shallow-lacustrine to deep-lacustrine sequences (type B) formed during the early and late periods of rifting; and (3) deep-lacustrine sequences (type C) developed in response to rapid tectonic subsidence during the middle, maximum-rifting stage. Uplift following each rifting episode related to changes in the paleostress field appears to have been the major control on the formation of high-order sequence boundaries (second-order and some third-order sequences). Block rotation, coupled with lake level fluctuations, controlled the formation of most third-order sequence boundaries. Forward simulation modeling suggests that development of different lacustrine sequence types can be related to a balance between tectonic subsidence and sediment input. Deltaic sandstone bodies and incised valley fills along the hinged margins within the shallow-lacustrine and deep-lacustrine sequences and sublacustrine-fan sandstones in the central basin are the economically most important reservoir sandstones in the basin. Fan-delta deposits along the escarpment margin constitute another potential reservoir type.