Nan Peng

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., eastern 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 volcanicfilling faulted basins were widely distributed in the northeastern North China during the Early–Middle Jurassic, including a series of small- 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 Yanshanian 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 palaeogeography 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 was the 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 northern 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 basin 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 northeastern China. Besides, during the Late Mesozoic, a huge terrestrial biota, mainly dinosaur fauna, dominated 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 Peninsula, Japan and the Far East of Russia.

Sedimentary response to the intracontinental orogenic process: insight from the anatomy of a small Mesozoic basin in western Yanshan, northern North China

ABSTRACT The intra-continental orogeny and tectonic evolution of the Mesozoic Yanshan fold-thrust belt (YFTB) in the northern North China Craton (NCC) have been strongly debated. Here, we focus on the Shangyi basin, located in the centre of the YFTB. An integrated analysis of sedimentary facies, palaeocurrents, clast compositions, and detrital zircon dating of sediments was adopted to determine the palaeogeography, provenance, basin evolution, and intra-continental orogenic process. The Shangyi basin comprises the well-exposed Early–early Middle Jurassic Xiahuayuan Formation and the Longmen Formation, and the Late Jurassic–Early Cretaceous Tuchengzi Formation. Based on the 18 measured sections, five facies associations – including alluvial fan, fluvial, delta, lacustrine, and eolian facies – have been identified and described in detail. The onset of the Shangyi basin was filled with fluvial, deltaic, and lacustrine deposits controlled by the normal fault bounding the northern basin, corresponding to the pre-orogeny. In the Middle Jurassic, the cobble–boulder conglomerates of alluvial fan, as molasse deposits, were compatible with the syn-orogeny of the Yanshan movement, which played a critical role in northern North China and even East Asia. After the depositional break in the Middle–Late Jurassic, the Shangyi basin, controlled by the normal fault present in the north of the basin, re-subsided and quickly expanded southward with thick sedimentation, which is correlative with the post-orogeny. Combined with A-type granites, metamorphic core complexes, mafic dikes, and rift basins of the Late Jurassic–early Early Cretaceous present in the northern NCC and Mongolia, significant extension was widespread in the northern NCC and even in northeast Asia. Moreover, vertical changes of provenance indicate that the Taihang Mountain and the Inner Mongolia palaeo-uplift (IMPU) present at the west and north of the basin, respectively, experienced uplift twice in the Middle–Late Jurassic and Early Cretaceous, resulting in a regional depositional break.

Sedimentary characteristics and provenance of the basal conglomerate of the Late Jurassic-Early Cretaceous Jiaolai Basin, eastern China and their implications for the uplift of the Sulu Orogenic Belt

ABSTRACT The basal conglomerates (‘Linsishan Conglomerate’, LC, herein) are exposed discontinuously along the northern part of the Sulu Orogenic Belt (SOB) and the southern part of the Jiaobei Terrane. Studying these conglomerates can offer key constrains for the formation age of the Jiaolai Basin and improve our understanding of the uplift and erosional histories of the SOB and Jiaobei Terrane, which are still in great controversy. In Huangyadi section, the LC is characterized as debris-flow deposits, channel deposits, and sheet-flow deposits. However, in Shanjiao section, the LC is changed to sheet-flow and sieve deposits, as well as debris-flow and channel deposits. These deposit characteristics indicate an unstable tectonic setting during initial opening stage of the basin. Based on the data of conglomerate component, palaeocurrent, and debris zircons ages, it can be inferred that the sediments in the Laiyang region were sourced from the Jiaobei Terrane and Northern Sulu Orogenic Belt (NSOB), and the sediments in the Zhucheng and Wulian regions were derived from the Jiaobei Terrane and the Southern Sulu Orogenic Belt (SSOB). Besides, the sediments in the Haiyang and Jimo regions were provided by the NSOB and SSOB, respectively. The significant SHRIMP U–Pb ages of a tuff developing in the LC has been obtained, indicating that 149 ± 2.5 Ma is the oldest age constraint for the Jiaolai Basin. In addition, our result shows that the Latest Jurassic (ca. 149 Ma) may be a critical time; before this time, the Jiaobei Terrane and the SOB experienced a rapid uplift with minimal uplift velocity (~0.9 km/Ma); since then, the Orogen began to collapse and a series of basins formed rapidly in its core, which indicate the tectonic stress regime of the Dabie-Sulu Orogen varied from compressional stress to tensile stress.

The 144–140 Ma Mafic Dykes in North China and Northeast China Indicating Regional Extensional Tectonic Setting

Previous studies indicate that the North China Craton (NCC) had undergone the loss of thickened lithosphere and fundamental change of physical and chemical property of lithospheric mantle (the destruction of NCC) during the Mesozoic. The peak period of the destruction of NCC is estimated to be 130 Ma, accompanied by widespread metamorphic core complex, rift basins, A-type granites and mafic dykes. However, it remains greatly controversial on the tectonic setting of NCC in the pre130Ma, especially the Late Jurassic–Early Cretaceous, which is also related with the initiation of the destruction of NCC. In recent years, we have found lots of Late Jurassic-Early Cretaceous mafic dykes in western Liaoning, northern Hebei, western Shandong and Heilongjiang (Fig. 1). Geochronological studies of the mafic dykes indicate that it was formed in the early period of Early Cretaceous (144–140Ma). Therefore, these mafic dykes could provide great insights into the tectonic setting and dynamic mechanism of NCC and adjacent region during the Late Jurassic–Early Cretaceous.