Earth Science Frontiers ›› 2023, Vol. 30 ›› Issue (4): 112-127.DOI: 10.13745/j.esf.sf.2022.10.23

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Tectono-sedimentary characteristics and formation mechanism of the Lishu rift depression, Songliao Basin

WANG Hongyu1(), LI Ruilei2, ZHU Jianfeng2, ZHANG Haoyu1   

  1. 1. School of Energy Resources, China University of Geosciences (Beijing), Beijing 100083, China
    2. Northeast Oil and Gas Branch of Sinopec, Changchun 130062, China
  • Received:2022-08-07 Revised:2022-09-10 Online:2023-07-25 Published:2023-07-07

Abstract:

The Lishu rift depression is a typical wedge-shaped rift lake basin in the Songliao Basin with complex tectono-sedimentary features. This paper, based on tectono-sedimentary analysis using large amounts of 3-D seismic and drilling data, reveals the tectono-sedimentary characteristics and evolution, main controlling factors and formation mechanism of the rift depression. The results provide, on the one hand, a geological basis for the reservoir prediction in this area, and on the other hand, a practical reference for the relevant, in-depth studies of other rift depressions in the Songliao Basin. The Lishu rift depression experienced three sub-rift phases under left-handed tensile stress and multi-extrusion tectonic activities in the Early Cretaceous. It evolved from a small rift sag with few small, steep secondary rifts in the early rift stage, to a lacustrine basin with wedge-shaped half graben, bound by the Sangshutai fault along its western side, in the intense rifting phase, then to the shallow lake basin in the late rifting phase. Each of the sub-rift phases exhibited varied basin configuration and palaeo-geomorphological features. In the early rifting phase, both surface uplifting and fault-block tilting occurred, resulting in various types of unconformities. In the intense rifting phase, angular conformities were more developed due to fault-block rotation and tilting. While in the late-rifting phase paraconformities dominated, reflecting regional uplifting and subsidence. During basin evolution, sedimentary systems in the basin transitioned from lake delta to braided river systems. The sequence stratigraphic framework of the intense-rifting phase was characterized by upward “gradual shrinking of low system tracts (LST) and continuing expansion of high system tracts (HST)”; whilst late-rifting sequence featured transverse continuous sediment deposition and longitudinal alluvial accumulation.

Key words: Lishu rift depression, tectono-sedimentology, basin configuraiton, unconformity, sedimentary filling, sequence stratigraphic framework, control factors

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