Late Mesozoic-Cenozoic evolution of the Sanjiang Basin in NE China and its tectonic implications for the West Pacific continental margin

This study uses new seismic reflection profiles and exploratory well data to analyze the structural characteristics and evolution of the Sanjiang Basin in eastern Heilongjiang, NE China. The basin sequence was divided into six stratigraphic units, representing discrete Middle-Upper Jurassic, Lower Cretaceous, Upper Cretaceous, Eocene-Oligocene, Miocene and Quaternary phases of development. The Sanjiang Basin initiated as a passive marginal rift flank to the southern Mongol-Okhotsk Ocean during the Middle Jurassic, and primary basin growth was terminated by orogenic deformation related to the Mongol-Okhotsk suture to the north and the accretion of the Nadanhada terrane to the east. Middle-Upper Jurassic strata are controlled by half-graben structures active during this phase of basin growth, and are limited largely to the west Suibin sub-basin. The wider basin experienced renewed rifting and large-scale sag caused by back arc extension along the Eurasian continental margin in the Early Cretaceous, terminating during the Late Cretaceous in a phase of intense compression at the contemporary Andean-type continental margin. This produced a series of thrust-folds through the Lower and Upper Cretaceous successions, and led to the development of a regional-scale erosional unconformity. Minor subsequent Cenozoic extension is attributed to back-arc extension along the West Pacific continental margin, with Eocene-Oligocene, Miocene, and Quaternary deposits unconformably overlying the Mesozoic sequences in half-graben and extensional fault-demarcated depocenters, most prominently in the east Qianjin sub-basin. (C) 2012 Elsevier Ltd. All rights reserved.