Abstract:

Detailed sample collections and descriptions have been made from upper Qingshankou to lower Yaojia formations in well Xu-22 of Daqing Oilfield. The thickness of collected well core is 12.20 m. Careful identification and analysis on sporopollen and ostracods fossils have been carried out. Microbiota from the upper part of Qingshankou Formation refers to a deepwater and disoxidation environment. There are large amount of ostracods and other biota. The sporopollen Cythidites is dominant. This shows a relatively warm and moist climate. The color of upper layers turns light, the granularity turns large and the fossil abundance reduces rapidly. This shows the lake became shallower, the climate was drier and heater, and the creatures were suffered by disaster. At the boundary of 1,612.90 m, ostracods completely vanished, and the sporopollen number decreased. Sediments in upper layers become coarse and red. This shows that the lake was shallow, maybe in a delta-silted phase. The climate became more and more dry and heat, and fluctuated frequently, and fossils were rare. Generally, at the boundary, the climate turned to drier and heater from moist and warm conditions; the water became shallower and more fluctuant upwards; as a result, biota declined their abundance rapidly under the climate change.

Key words: Qingshankou and Yaojia formation, sporopollen, ostracods, paleoclimate, Daqing Oilfield