Research progress on main controlling factors and classification schemes of lacustrine gravity flow deposits
FAN Hongjun, WANG Xiabin, CHEN Fei, ZHAN Shengyun, YUE Dali, LIU Jingyang, LI Wei, REN Keyu, ZHANG Shuqi
1 CNOOC Research Institute Co., Ltd., Beijing 100028, China 2 National Key Laboratory of Petroleum Resources and Engineering, China University of Petroleum-Beijing, Beijing 102249, China 3 College of Geosciences, China University of Petroleum-Beijing, Beijing 102249, China
Deep-water gravity flow sedimentation is topical in global petroleum and natural gas exploration. In the past 30 years, great achievements have been made in the sedimentary characteristics, controlling factors and sedimentary models of lacustrine gravity flow. However, due to the complex structure of continental sedimentary basins and the diverse development of gravity flow types, lacustrine gravity flow classification is still lacking. By systematically sorting out the development history and research into gravity flow, this paper summarizes a sedimentary classification scheme of lacustrine gravity flows based on sedimentary genesis and the main controlling factors, and summarizes the research into lacustrine gravity flows into the following three aspects. 1) Research into the main controlling factors of gravity flow: the sedimentary characteristics and models of lacustrine gravity flow in different types of basins are obviously different. These are mainly controlled by intra-basin factors and extra-basin factors. The intra-basin factors mainly include basin types (such as topographic slope), sedimentation rate and water density, while the extra-basin factors mainly include the composition and sources of sediments. 2) Gravity flow sand body distribution in source-sink systems: the formation and evolution of lacustrine gravity flow and the distribution pattern of sand bodies are usually controlled by the source-channel-sink system. This system effectively connects internal and external factors within the basin. 3) Lacustrine gravity flow classification: Continental lacustrine basins, compared to marine basins, are characterized by smaller scale, shallower water bodies, and intense tectonic activity. These characteristics result in diverse controlling factors and complex sedimentary features of gravity flow deposition. According to different research purposes, it can be classified according to sedimentary origin, development location or provenance supply, but the classification scheme of lacustrine gravity flow has not been unified. In this paper, lacustrine gravity flow depositions are classified into three major types and seven subtypes, by comprehensively considering the causal mechanisms and main controlling factors of gravity flows. Specifically, lacustrine gravity flow depositions are classified into flood-type (gentle slope sand-rich type, gentle slope sand-mud hybrid type, gentle slope mudrich type, steep slope sand-rich type, steep slope sand-mud hybrid type), slump-type (flexural slump type, fault-controlled slump type), and flood-slump coexisting type. There are plenty of research in the gravity flow of lacustrine facies at present. However, there is still much room for progress in fluid, flow transformation and genetic mechanisms of deep water channels. Therefore, the study of the formation, evolution and genesis mechanism of lacustrine gravity flows by integrating dynamics and sedimentology has become a current research and development trend.
Key words：
gravity flow deposits; slump-induced gravity flow; flood-induced gravity flow; main control factors; deposition model
