Late Mesozoic Elevation History Of The North Taihang Mountains

The East China underwent intensive Jurassic to Cretaceous intracontinental deformation,which result in the orogenesis and climate change in the North China.During this period,the Taihang Mountains gradually stand as a geomorphic and ecological separation zone,and separates the NC into regions with different landform,tectonic setting,and climatic regimes.Reconstructing the paleo-elevation changes of the THM in the late Mesozoic can effectively constrain the uplift history of the mountain range,and critical to constrain the paleogeography and geodynamic models of orogen evolution in NC.Besides,the drastic surface topography changes and paleoclimate fluctuations may have led to the rapid turnover of the late Mesozoic biomes in the North China,global/regional climate change,dramatic geomorphologic changes and intense volcanic activity may be the causes of these changes,but the research on the climatic characteristics of this period has paid less attention.Herein,we reconstruct the late Jurassic and early Cretaceous paleoclimate and paleoelevation in the north THM and Ordos basin,based on clumped isotope thermometer.The clumped isotope thermometer is a new method that can estimate the formation temperature[T(?₄₇)]of carbonate.Then,we use the temperature contrast between the contemporaneous low elevation site and studied basin to estimate paleo-elevation by applying suitable temperature-elevation lapse rate.Furthermore,in combined with the study of thermochronology analyses and structure deformation,we discuss the evolution of topography in the north THM.In this study,we collect paleosol carbonate nodules from the late Jurassic to early Cretaceous in the Datong-Hunyuan Basin;calcareous concretions from the late Jurassic in the Ningwu-Jingle Basin;paleosol carbonate nodules and marl from the late Jurassic in the Ordos Basin.We successfully obtain the original surface temperature in the Datong-Hunyuan Basin.Combined with reconstructed paleosol water?¹⁸O,major and minor components of paleosol,the mean annual temperature was also reconstructed.The results show cold-dry climate with modest seasonal temperature variation at 160Ma.The mean annual temperature ranges from 7-12?,with warm season ground temperature of 20±2?.During the late Aptian-Albian,the North China experienced significant warming with strong seasonal fluctuation,coincident with global warming trend during greenhouse condition.Our estimation suggests that the paleoelevation of north THM was 2.5 km at 160Ma,2.6 km at 113 Ma and 1-1.5 km at ca.105 Ma.The result supported that the initial uplift of north THM occurred at middle Jurassic.According to thermochronology analyses and structure deformation,the north THM may experience exhumation and prolonged cooling during the late Jurassic-earliest Cretaceous(155-135 Ma),thus,the paleoelevation of north THM should be much higher than 2.5 km after 160 Ma.When placed in the context of collapsed of easter NC carton,the maintained high topography at 113 Ma demonstrated that the present topographic feature of THM highland in NC may established since early Cretaceous time.At last,our study suggests a ca.1.5±0.5km elevation decrease at the end of Early Cretaceous,which is possibly related to the isostatic adjustment caused by asthenosphere upwelling and partial crustal thinning in the central NC carton.This work is a new attempt to reconstruct the paleo-elevation of the interior NC during the late Mesozoic by clumped isotope thermometer.For the first time,the paleo-elevation of the Taihangshan orogenic belt in the NC was reconstructed,which provides a reference for studying the Mesozoic geomorphological evolution of the NC.