Terrestrial records of the Early Cretaceous paleoclimate changes in the Liupanshan Basin, NW China: Evidence from sedimentology and geochemistry

This paper reported geochemical data of the upper member of the Lower Cretaceous Liupanshan Group (Liwaxia, Madongshan and Naijiahe formations) in the Liupanshan Basin (North China) and revealed the evolution of paleoenvironment and paleoclimate recorded in the terrestrial lake. Geochemical indicators revealed a weak weathering and negligible sedimentary recycling. The provenance of the Liwaxia-Naijiahe formations were mainly felsic acidic rocks of the eastern Qilian and western Qinling areas. A series of paleoclimate proxies (such as Th/U, Rb/Sr, etc.) reveal that Liwaxia-Naijiahe formations were deposited in a semiarid- arid and anoxic paleoclimate, and the degree of aridity and paleosalinity increases from the Liwaxia to the Naijiahe period. The extensive paleoclimatic and paleosalinity changes, and organic matter enrichment recorded in northern China were caused by the regional semiarid-arid paleoclimate in the late Early Cretaceous, which was related to ocean anoxic event 1 (OAE 1) under the global hothouse climate.本论文报道了华北六盘山盆地下白垩统六盘山群上段（含李洼峡组、马东山组与乃家河组）的地球化学数据，揭示了该陆相湖泊沉积所记录的古环境与古气候演化历程。地球化学指标表明，研究层段经历了较弱的风化作用与可忽略的沉积再循环过程。李洼峡组-乃家河组的物源主要源自祁连山东部与秦岭西部的长英酸性岩石。一系列古气候代用指标（如钍铀比（Th/U）、铷锶比（Rb/Sr）等）显示，李洼峡组-乃家河组沉积于半干旱-干旱且缺氧的古环境中，且古气候干旱程度与古盐度自李洼峡期至乃家河期逐渐升高。华北地区广泛记录的古气候与古盐度变化及有机质富集现象，受控于早白垩世晚期区域性半干旱-干旱古气候，该气候背景与全球温室气候背景下的大洋缺氧事件1（OAE 1）密切相关。