## 1 Regional Geological Background
### Regional Tectonic Evolution and Lithoficies' Paleo-Geographic Characteristics  
The structural and sedimentary development of the Mangeshlak Basin was influenced by the closure of the Paleo-Tethys Ocean from the Permian to the Late Triassic, the formation of the Neo-Tethys Ocean from the Jurassic to the Paleogene, and the Indo-Tibetannon-marine collision orogeny since the Paleogene [3]. It can be divided into four stages: basement formation, syn-rift, post-rift depression, and foreland basin.  
The basement of the basin was formed in the Late Paleozoic (Hercynian), which was mainly composed of strongly folded and highly metamorphosed Late Paleozoic (Hercynian) granites, intermediate-basic volcanic rocks, and clastic rocks.  
Late Permian rifting formed a large northwest-trending graben. Sedimentation began in a non-marine environment, with the predominantly clastic red beds deposited. With the continuation of subsidence, the early and middle Triassic transgression gradually established shallow sea conditions and deposited carbonate, clastic, and volcanic stratigraphic sequences [4] and deposited Permian and Triassic with a thickness of up to 10 km.  
At the end of the Triassic, the basin was subjected to strong compression from south to north, which led to the inversion, folding, and erosion of the graben, forming the Mangeshlak-Middle Ustyurt uplift belt and causing an angular unconformity to contact between the Jurassic and Triassic [5,6] (Figure 3a).  
Thermal subsidence of the post-rift depression occurred mainly in the Early Jurassic, and extensive marine transgression occurred in the basin. In the Middle Jurassic, a thick shallow marine clastic rock sequence was deposited in the basin [7]. From the Late Jurassic to the Early Cretaceous, the clastic rock sediments were replaced by carbonate and salt rock sediments. In the Late Cretaceous to Early Paleogene, partial marine regression in the area led to the widespread development of clastic rocks and oolitic limestones, calcareous sandstones, and conglomerates (Figure 3b).  
Figure 1: Structural outline map of Mangeshlak Basin (revised according to IHS).  
Figure 3: _Cont._  
Figure 2: Comprehensive stratigraphic column chart of Mangeshlak Basin (revised according to IHS).  
The foreland stage can be further divided into the compressional tectonic stage and the depression stage. In the late Eocene, the basin was affected by the collision between the Ara  
Figure 3: Tectonic-lithofacies map of the northern margin of the West Asian section of the Tethys Realm during critical periods (revised according to [4]).  
bian Plate and the Eurasian continent, and local uplift and early fault revival occurred [8]. The western part of the basin was uplifted and eroded, forming an uncomformity above the Lower Cretaceous. In the northeast of the basin, the basin edge was uplifted by compression to form the Turkmentai anticline. In the early Miocene and middle Pliocene, continuous compression led to another tectonic uplift and deformation, forming the southern plateau of the Mangeshlak Basin, and the strata were eroded and karstified [9]. After the Pliocene, the offshore area of the basin continued to sink gently, causing the basin to collapse and tilt toward the sea to the west [10]. Under this tilting action, the land part of the southeastern basin gradually rose to the highland, forming strata dominated by non-marine sediments (Figure 3c).