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ABSTRACT: Genetic Stratigraphic Framework and Depositional System of Q-Y-N Formations in the North Songliao Lacustrine Basin, Northeast of China

Liangqing Xue, William E. Galloway

The depositional complex of Qingshankou, Yaojia, and Nengjian (Q-Y-N) formations in the north of the Songliao basin is the main producing unit and illustrates the application of genetic stratigraphic sequence analysis in a lacustrine basin setting.

The regional, dark mudstones of Member 1 of Qingshankou Formation and Member 1 of Negjian Formation, deposited during maximum lacustrine flooding, are chosen as the bottom and top boundaries of the Q-Y-N genetic stratigraphic sequence. The highly fossiliferous and organic-rich condensed section mudstones are the main petroleum source rocks in Songliao basin.

In the lower part of the sequence, the progradational, lobate delta complex of Members 2 and 3 of Qingshankou Formation was deposited in the north of Songliao basin during a slow fall of lake level. A subaerial, widespread erosion surface was developed at the top of Qingshankou Fm. during maximum regression.

The middle part of the sequence consists of the progradational, bird-foot delta lobes of Member 1 of the Yaojia Formation. These delta lobes were deposited as a result of the rapid fall of the lake level. The widespread Saertu-Putaohua mudstone is the sedimentary product of the first significant migration of the shoreline landward following lowstand.

The upper part of the sequence is composed of the retrogradational delta lobes of Members 2 and 3 of Yaojia Formation. These delta lobes were the result of the step-by-step shoreline migration landward during the rising of lake level. The depositional episode encompassing the Q-Y-N formations was terminated by a maximum lacustrine flooding event and deposition of Member 1 of the Nengjian Formation.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990