Chronostratigraphic framework of late Mesozoic terrestrial strata in the Hailar–Tamtsag Basin, Northeast China, and its geodynamic implication

Abstract

The Hailar–Tamtsag Basin (HTB), an important component of the late Mesozoic extensional basin system in Northeast (NE) China, is characterized by episodic rifting, dramatic magmatism, and thick terrestrial sediments, which provides crucial opportunities to understand late Mesozoic tectonomagmatic events in NE China. However, the previously established late Mesozoic chronostratigraphic framework in the basin remains problematic due to limited isotopic chronological constraints. Here, we present 28 new zircon U–Pb ages for the volcanic rocks from the HTB, which allow us to establish a refined chronostratigraphic framework for the late Mesozoic terrestrial strata. Newly calibrated results indicate that the depositional ages of the Tamulangou and Tongbomiao formations are constrained to ca. 157–148 and ca. 142–137 Ma, respectively; the depositional ages of the Lower Nantun and Upper Nantun members are constrained to ca. 131–120 and ca. 117–111 Ma, respectively. Combining these results with previous studies on sedimentation, structural deformation, and magmatism, the Late Jurassic–Early Cretaceous tectonostratigraphic evolution of the HTB is reconstructed, and three major phases of intracontinental deformation are identified. The HTB experienced extensional deformation in the Late Jurassic due to the break‐off of the subducted oceanic slab of the Mongol–Okhotsk Ocean and subsequent gravitational collapse of orogenically thickened crust following the closure of the ocean basin. Then, in the latest Jurassic–earliest Cretaceous, the evolution of the HTB was dominated by compressional deformation related to flat‐slab subduction of the Paleo‐Pacific Plate. During the Early Cretaceous, an extensional regime resumed in the HTB in response to rollback of the subducting Paleo‐Pacific Plate.

Structural characteristics and formation mechanisms of Bayanhushu Sag in Hailar Basin, north‐east China: A study based on structural physical simulation

“…Top of the Nantun Formation (T 22 ): It is a maximum surface of angular unconformity in the early period of the whole region (Ji et al, 2019;Li, Wei, et al, 2020;Z. H. Liu et al, 2009;Min Na et al, 2013;Y.…”

“…Some scholars also refer to this as "uplift denudation unconformity" (Li, Wei, et al, 2020). The overlying strata onlaps the interface layer by layer, and the lower surfaces T 23 and T 4 F I G U R E 2 Structural units of Hailar Basin (modified after Ji et al, 2019 and in the uplift zone are usually truncated at the interface (Figure 6). The stratum thickens in the central sag above the T 22 seismic reflection interface and serves as the centre of subsidence of the overlying structural stage.…”

“…F I G U R E 3 Stratigraphic column of BYHS Sag in Hailar Basin (modified after Li, Wei, et al, 2020 and Top of the Yimin Formation (T 04 ): It is the largest surface of angular unconformity in the whole region formed in the late period (Ji et al, 2019;Li, Wei, et al, 2020;Z. H. Liu et al, 2009;Min Na et al, 2013;Y.…”

“…The basin is located at the junction of the North China Plate and the Siberian Plate (Li, Hu, Shi, & Rao, 2020;Liu, Li, Xiao, & Somerville, 2019) (Figure 1). During the process of tectonic evolution, it was affected by multiple geodynamic systems (W. , resulting in its complicated structural deformation (Ji et al, 2019;. In recent years, with the breakthroughs of industrial oil exploitation from wells such as Chu 5 in the Bayanhushu (BYHS) Sag, it has once again emerged that the basin is an attractive prospect for oil and gas resource extraction.…”

Petrogenesis and Tectonic Setting of Early Cretaceous Intrusive Rocks in the Northern Ulanhot Area, Central and Southern Great Xing’an Range, NE China

“…(3) lithospheric delamination induced by the contribution of westward subduction of the Paleo-Pacific slab [53][54][55][56]; and (4) retreat of the PPO plate and the successive upwelling of the varying degrees of asthenospheric mantle [35,[57][58][59]. The above disputes indicate that the GXR has frequent tectonomagmatic activity and complex tectonic settings [56,[60][61][62].…”