Development Characteristics of Mesozoic-Cenozoic Tectonic Strata in the Jiyang Depression and Their Response to Tectonic Evolution

Based on the latest drilling, logging, and seismic data, and using key tectonic interfaces as markers, this study divides tectonic strata in combination with regional tectonic movements, establishes a vertical stratigraphic framework, and reconstructs erosion amounts. It clarifies the present-day preservation, post-depositional erosion, original distribution characteristics, and their spatiotemporal variations for each stratum, systematically revealing how their development features respond to the basin's tectonic evolution. The results indicate that the Mesozoic tectonic layer in the Jiyang Depression can be subdivided into three sublayers: Early-Middle Triassic, Early-Middle Jurassic, and Early Cretaceous. The Cenozoic tectonic layer can be subdivided into five sublayers: Kongdian–Lower Es4, Upper Es4–Lower Es2, Upper Es2–Dongying, Guantao–Minghuazhen, and Pingyuan Formations. The distribution of preserved strata from bottom to top is uneven, with significant variations among different tectonic units and layers, reflecting the combined effects of original deposition and subsequent erosion. The Early-Middle Triassic period inherited the tectonic framework and sedimentary characteristics since the Late Hercynian, forming a large-scale inland depositional system. The Early-Middle Jurassic represented a transitional period from the Paleo-Asian tectonic domain to the circum-Pacific tectonic domain, characterized by early-stage filling and late-stage draping. The Early Cretaceous exhibited reverse fault depression, trending northwest, with greater depositional thickness near the Zhangjiakou–Penglai fault zone. The Cenozoic was marked by mantle upwelling and lithospheric thinning, with the Paleogene characterized by multi-episodic extensional fault depression and the Neogene–Quaternary by regional sag depression. The Jiyang Depression underwent multiple phases of complex tectonic evolution during the Mesozoic and Cenozoic, leading to widespread erosion at the tops of the Late Triassic, Late Jurassic, Late Cretaceous, Lower Es4, and other tectonic sublayers.