Mesozoic basins and associated palaeogeographic evolution in North China

In North China, the Mesozoic terrestrial basins, sedimentary palaeogeography and tectonic settings involved five evolutionary stages： （1） the Early-Middle Triassic, （2） the Late Triassic to Early-Middle Jurassic, （3） the Late Jurassic to early Early Cretaceous, （4） the middle-late Early Cretaceous and （5） the Late Cretaceous. The regional punctuated tectonic events occurred during these evolutionary stages. During the Early-Middle Triassic （stage 1）, the Xingmeng Orogenic Belt （XMOB, i.e., east- ern part of Central Asia Orogenic Belt, CAOB） of the northern North China was settled in the transition of tectonic environment from syn-orogenic compression to post-orogenic extension with intensive uplifting. It is a main provenance in the unified Ordos-North China Basin.The united continental plate of China and the Qinling-Dabie-Sulu Orogenic Belt formed due to convergence and collision between the North China Plate and the Yangtze Plate along two suture zones of the Mianlue and the Shangdan in the terminal Middle Triassic. During the Late Triassic to the Early-Middle Jurassic （stage 2）, the Late Triassic mafic or alkaline rocks and intrusions occurred on the northern and southern margins of North China Craton （NCC） and XMOB, implying that intensified extension happened all over the North China （early phase of stage 2）. Additionally, in the late phase of stage 2, the basic volcanic- filing faulted basins were widely distributed in the northeastern North China during the Early- Middle Jurassic, including a series of smalt- to medium-sized basins with coal-bearing strata and some volcanic rocks in other areas of North China, which was the result of subduction of the Palaeo-Pacific Plate during the Early-Middle Jurassic. An active continental margin with accretionary complex developed in the eastern Heilongjiang of China, Japan and the Far East of Russia at that time. However, in the end of the Early-Middle Jurassic, because of the Yan- shanian orogeny characterized by complicated thrust and fold, the previous unified Ordos- North China Basin was separated by the northeast-oriented Great Xing＇an Range and Taihang Mountain uplifted linearment. The differential evolution of basins and sedimentary palaeoge- ography between eastern and western North China was initiated, and was interpreted to result in the closure of Okhotsk Ocean and the subduction of Palaeo-Pacific Plate （late stage 2）. During the Late Jurassic （the early phase of stage 3）, a variety of faulted basins occurred in the Yanshan and Yinshan areas in the northeastern North China. In Yanshan area, basins were filled with thickened intermediate volcanic rocks and purple-red coarse-grained clastic rocks. In contrast, only thick layered sedimentary rocks with rare volcanic rocks developed in the Yinshan faulted basins, the Ordos Basin and basins in sourthern North China. XMOB wasthe main provenance of the Early Mesozoic basins in the North China, while the Ordos Basin and the Hefei Basin were partly supplied by the northern Qinling Orogenic Belt. During the Late Jurassic-early Early Cretaceous （the late phase of stage 3）, the north- ern and northeastern North China experienced extensional movement after the subduction of the Palaeo-Pacific Plate, the closure of the Mongolia-Okhotsk Ocean and the subsequent Yanshanian orogeny. At the same time, a NE-oriented, giant rift basin system （NE Asia Rift） extended from the Yanshan to the western Great Xing＇an Range, where rift basins were filled with the regional, NE-oriented, thick coarse-grained clastic rocks and a belt of volcanic rocks. In the meantime, the eastern and northeastern China and most areas of NCC were presented as highland terrains. During the middle-late Early Cretaceous （stage 4）, rift basins developed and accumulated alluvial sediments and interbedded alkaline volcanic rocks in the western and northern North China, including Yingen, Ejinaqi and Erlian regions. Basins were formed on both sides of the Tan-Lu Fault Zone under a striking-slipping force. Furthermore, faulted basins developed in the Yishu Fault Zone of Shandong （central Tan-Lu Fault Zone） as well, where dinosaur fauna flourished. Basic volcanic rocks and fluvial-lacustrine sediments were deposited in small- or medium-sized rift basins in the northeastern China. The Songliao Basin was a typical giant ba- sin that was mainly filled with late Early Cretaceous lacustrine sediments. A group of rift basins occurred in the Sanjiang area, central Heilongjiang Province, northeastern China. From the middle-late Early Cretaceous to the Late Cretaceous （stage 5）, depositional and subsiding center of the basins constantly shifted southeastwards in Heilongjiang Province. The tectonic setting changed into the Palaeo-Pacific continental margin in north and north- eastern China. Besides, during the Late Mesozoic, a huge terrestrial biota, mainly dinosaur fauna, domi- nated in North China. The Yanliao biota of the Middle-Late Jurassic and the Jehol biota of the Early Cretaceous are characterized by feathered dinosaurs, primitive birds, mammals, pterosaur, insects and plants （angiosperms）. in northeastern Asia, this Late Mesozoic tectonic background, palaeogeoraphy and palaeoecology were shared by East China, Korean Penin- sula, Japan and the Far East of Russia.