Geothermal evidence of Meso-Cenozoic lithosphere thinning in the Jiyang sub-basin, Bohai Bay Basin, eastern North China Craton

The Bohai Bay Basin is at the center of lithosphere destruction and thinning in the eastern North China Craton (NCC). In this paper, the thermal lithospheric thicknesses of the Meso-Cenozoic Jiyang sub-basin in the Bohai Bay Basin were calculated by reconstructing the thermal history of the sedimentary basin using apatite fission track and vitrinite reflectance data. The results show that the Jiyang sub-basin experienced two heat flow peaks in the late Early Cretaceous and in the Middle to Late Paleogene, with heat flow values of 84 ~ 88 mW/m2 and 85 ~ 88 mW/m2, respectively. The thermal lithosphere thicknesses of the Jiyang sub-basin, calculated from the modeled thermal histories, experienced two thinning stages in the Cretaceous and in the Paleogene. The lithosphere began with an initial thickness of 150 km in the Early Mesozoic and reached a thinning peak of 51 km in the late Early Cretaceous. The thickness then increased to approximately 80 km at the end of the Cretaceous. A second thinning peak occurred in the Middle and Late Paleogene, with a thickness of only 48 km, which corresponds to a rift phase in the Bohai Bay Basin. The lithosphere thickened thereafter and is 78 km at present. The North China Craton now has a thin lithosphere. Our research provides new geothermal evidence for the lithospheric thinning of the NCC.