Jurassic-Cretaceous Transition Terrestrial Red Beds In Northern North China And Their Regional Paleogeography, Paleoecology, And Tectonic Evolution

The Jurassic-Cretaceous transition red beds, represented by the Tuchengzi, Houcheng and Daqingshan formations, are widespread in northern North China and adjacent regions. It is associated with a number of major geological issues that remain controvercial, and has great significance in the study of the destruction of North China Craton, biotic transition and regional tectonic setting. Based on previous studies, this paper focuses on stratigraphy, filling sequences, sedimentology, paleocurrent, detrital composition and intruded mafic dykes and analyzed the age of the srata, terrestrial J/K boundary in China, sedimentary system, provenance, paleogeography, paleoecology, paleoenvironment, basin evolution and tectonic setting, and offers some new perspectives.We obtained three new zircon U-Pb ages from the tuff beds in the uppermost of the Tuchengzi Formation in western Liaoning, basal Houcheng Foramtion in northern Hebei and Yanqing, Beijing. These ages are 137 Ma,154 Ma and 153 Ma. Combined with previous published dating data in recent years, we constrained the age of Tuchengzi/Houcheng Formation to be 154-137 Ma, which is in agreement with the Jurassic-Cretaceous transitional time. The newly results of the international J/K boundary indicate that the terrestrial Jurassic-Cretaceous boundary in China exists in the Tuchengzi/Houcheng Formation.According to the 22 measured sections of the Tuchengzi Formation in the Chaoyang-Beipiao Basin in western Liaoning, Houcheng Formation in the Shangyi Basin in northwestern Hebei, and Daqingshan Formation in the Shiguaizi Basin in Yinshan-Daqingshan, five sedimentary system including alluvial fan, fluvial, delta, lacustrine and eolian have been recognized and described in detail. Provenance analysis indicate that the Jurassic-Cretaceous transition red beds were derived from local source instead of the Xingmeng Orogenic Belt.Paleocurrent features in different regions show characteristics of a localized convergent fluvial system, suggesting that a series of relatively independent small-to mid-scale basins developed in northern North China. The east-west-trending Yinshan-Yanshan orogenic belt, formed in the late Middle Jurassic, uplifted successively and constituted a paleogeographic highland in northern North China during the Jurassic-Cretaceous transition time. The Taihang Mountain experienced twice extensive uplite in the late Middle Jurassic and Late Jurassic-Early Cretaceous, especially for the second time, which constituted the NNE trending mountain system in the central of North China Craton. The presence of regional Late Jurassic-Early Cretaceous eolian sandstone was coupling with the Eastern China Plateau. Severe paleogeography, paleoecology and paleoenvironment restricted the biotic evolution and transition.A great number of mafic dykes intruded in the Late Jurassic-Early Cretaceous strata in northern and eastern North China Craton and Northeast China have been found and yielded the ages of 144-134 Ma. Combined with widespread coeval rift basins, A-type granites, bimodal volcanic rocks and metamorphic core complexes, we propose that the Jurassic-Cretaceous trantision basins formed in extensitonal tectonic setting controlled by the post-orogenic collapse of the Mongol-Okhotsk orogenic belt.