The formation and development of Songliao basin are influenced and controlled by Yanshan movement, and its evolution can be divided into five stages: the initial stage of basin development, the stage of basin development and prosperity, the stage of basin area contraction, the stage of basin structure finalization and the stage of modern Songnen plain finalization.
Early stage of basin development: due to the strong tectonic movement in Yanshan period, discontinuous small graben-type fault basins have appeared since Jurassic, and Jurassic pyroclastic rocks with a thickness of about 2000 m have been deposited.
The prosperous stage of basin development: in the early Cretaceous, a large-scale fault basin was developed on the basis of Jurassic fault basin, and the basin area gradually expanded, and the Lower Cretaceous Denglouku Formation was deposited. Later, the fault basin developed rapidly, forming a unified large-scale depression basin, and the lower Cretaceous Quantou Formation, Qingshankou Formation, Yao Jia Formation and Nenjiang Formation were deposited, with a thickness of about 6000 m and a range of about 20× 104km2, which was the heyday of the development of Songliao Basin. At that time, the lakes in the basin were deep and the sedimentary range was wide. Because the basin is surrounded by mountains, the ancient Songliao basin was the catchment area of the surrounding water bodies at that time, where a large number of debris and soluble salts were deposited and enriched, forming a huge thickness of lacustrine deposits and delta deposits.
Stage of basin area reduction: at the end of early Cretaceous, there was obvious folding movement in the basin between Nenjiang Formation and Sifangtai Formation, which led to the formation of Cretaceous secondary structure and local structural prototype; At the beginning of Late Cretaceous, the basin margin rose, the lake gradually shrank, the basin area shrank, and the Sifangtai Formation was deposited. Since then, the eastern and northern parts of the basin have continued to uplift, and the sedimentary center has moved westward, depositing Mingshui Formation.
Formation stage of basin structure: At the end of Mesozoic, the folding movement in the basin was obvious again, and the secondary structures and local structures in the basin were basically formed. Influenced by two folding movement, especially the last folding movement, Cretaceous strata folds and faults developed, especially in the eastern uplift area, forming a good water storage structure in the axis of anticline and fault zone.
Formation stage of modern Songnen Plain: In the Early Tertiary, Songliao Plain was in the period of uplift and denudation, and the terrain had reached quasi-platformization. The Eocene and Oligocene basins declined slowly, and lacustrine clastic rocks of Yi 'an Formation (E2-3y) were deposited in the vast area north of Binzhou Railway in the middle of the basin. In the early Miocene, on the quasi-leveled Songliao Plain, a centripetal internal water system from the ancient Nenjiang River to the Xiliao River began to form, and the Da 'an Formation with mixed fluvial facies as the main facies was deposited. In the early Pliocene, Songliao basin was controlled by the central depression and Kailu fault depression, and the centripetal water system of Songliao was further developed. In the late Pliocene, Songliao Depression sank greatly, forming the heyday of Songliao Great Lake, forming the largest, widest and deepest lake basin since Paleogene, and depositing Taikang Formation (Table 2-4).
Table 2-4 Evolution Table of Paleogene and Neogene Sedimentary Environment in Songnen Plain
Since Quaternary, the mountains around Songliao Plain have been uplifted, and the basin continues to be dominated by subsidence, but there are some differences, and the plain water system has undergone major changes. At the end of the early Pleistocene or the beginning of the middle Pleistocene, the rivers in the lower reaches of Songhua River crossed the watershed east of Samsung, seized the rivers in the middle reaches of Songhua River and flowed northeast into Heilongjiang. Under the influence of neotectonic movement in the same period, the Lower Liaohe River also passed through Tieling hills and captured the Dongliao River and the West Liaohe River. Songliao water system changed from centripetal to outflow, Songliao Plain split into two, and Songnen Plain began to form. In the Middle Pleistocene, the central depression sank again and the Songnen Great Lake reappeared. After many external forces, the Songnen Great Lake was continuously filled, and by the end of the late Pleistocene, it had all disappeared, and the hydrological network of Songnen Plain was basically formed. Since Holocene, the Songnen Plain has generally uplifted, forming the landform and water system of modern Songnen Plain.