Meso-Cenozoic Lithosphere Thinning in the Eastern North China Craton: Evidence from Thermal History of the Bohai Bay Basin, North China

The formation and evolution of a rift basin is the shallow response of deep geodynamic processes. The Bohai Bay Basin is at the center of lithosphere destruction and thinning in the eastern North China Craton (NCC). In this article, the Meso-Cenozoic thermal lithospheric thickness of the Bohai Bay Basin was calculated by reconstructing the thermal history of the sedimentary basin using apatite fission track and vitrinite reflectance data. The Meso-Cenozoic thermal modeling results show that the basin experienced four evolutionary stages with two heat flow peaks in the late Early Cretaceous and in the Middle to Late Paleogene, which had heat flow values of 82-86 and 81-88 mW/m(2), respectively. Accordingly, the thermal lithospheric thicknesses of the basin, calculated from the thermal histories, experienced two thinning stages in the Cretaceous and the Paleogene. The lithosphere began with an initial thickness of 150 km in the Early Mesozoic and was thinned to approximately 51-61 km in the late Early Cretaceous. The thickness then increased to approximately 80-90 km at the end of the Cretaceous. A second thinning phase occurred in the Middle to Late Paleogene, resulting in a thickness of only 43-55 km. The lithosphere thickened thereafter, and the NCC now has a thermal lithosphere of 75-97 km. The lithospheric thinning in the Cenozoic was dominated by extension rather than thermal erosion. At the same time, there existed some differences in the thermal evolution and lithospheric thinning evolution among different sub-basins, but the time of peak heat flow and peak lithosphere thinning in the Cenozoic is consistent with the migration of the depocenter of the basin. Therefore, the thermal history of sedimentary basins may provide continuous temporal and spatial evidence to reveal deep geodynamic processes. Our research provides new geothermal evidence for the lithospheric thinning of the NCC.