Sequence stratigraphic and petrological analyses of the Cambrian oncoids exposed in the Liaoning Province, North China Platform

Author(s):  
E. Z. Xiao ◽  
S. Jiang ◽  
T. Zafar ◽  
M. Riaz ◽  
K. Latif ◽  
...  
2014 ◽  
Vol 88 (2) ◽  
pp. 359-366 ◽  
Author(s):  
Guoxiang Li ◽  
Zhifei Zhang ◽  
Hong Hua ◽  
Huining Yang

The early Cambrian calcareous skeletal fossilApistoconchaConway Morris is characterized by its two valves having posterior teeth and internal umbonal cavities. It has been reported from lower Cambrian Botomian-equivalent carbonate rocks in Australia, Mongolia, and Greenland. Here we report a new occurrence ofApistoconchain the lower Cambrian Xinji Formation of Luonan, southeast Shaanxi Province, North China Platform. Based on material (five ventral and four dorsal valves) from the Xinji Formation,Apistoconchacf.aphelesis systematically described and the taxonomic affinity ofApistoconchais discussed. The shell ofApistoconchapossesses an ‘antero-posterior’ plane of bilateral symmetry, and its two valves apparently articulated in life, although the tooth-like structures and pits show little resemblance to the teeth and sockets, respectively, of bivalved shells of rhynchonelliform brachiopods or pelecypods.Apistoconchacannot be assigned to the crown groups of either brachiopods or mollusks, even though functional morphological analysis indicates thatApistoconchamay be a ‘stem-group brachiopod’. UnlikeApistoconcha, the morphologically similarTianzhushanellaLiu is known only from a single type of valve lacking posterior teeth and pits.Tianzhushanellamay represent either a univalved animal or a bivalved animal, the other valve of which has not yet been identified. Even though bothApistoconchaandTianzhushanellamay represent stem-group brachiopods, they probably correspond to different stages of brachiopod evolution. Thus assignment ofApistoconchaandTianzhushanellato the same family (Tianzhushanellidae) may obscure their phylogenic implications.


2013 ◽  
Vol 318 ◽  
pp. 447-452
Author(s):  
Shun She Luo ◽  
Zhen Zhong Gao ◽  
You Bin He ◽  
Qi Qi Lv ◽  
Ying Meng

The middle Ordovician of Pingliang area on the west margin of North-China platform is represented by a succession of deep-water sediments in which contourites are well-developed. Contour current deposits are well-developed. The contourites can be classified into:calcarenitic contourite, calcisiltitic contourite and calcilutitic contourite. Three typical contourite successions are recognized: complete contourite succession, incomplete contourite succession and contourite successions consisting only of calcarenitic contourites. According to the palaeocorrent and the palaeogeographic format analyse,carbonate contourite drift in the study area is unfolded crossing northwest-southeast, forwarding from southeast to northwest along the slope, and compared with other contourite drifts, it has some characteristics of coarser-grained sediment, thicker individual layers, and highly developed calcarenitic contourites and so on.


1991 ◽  
Vol 55 (379) ◽  
pp. 263-276 ◽  
Author(s):  
Sang Longkang

AbstractBased on geological studies, 141 rock analyses and 5 trace element analyses of metabasites, the present paper deals with the rock association, chemical features, protolith formation and the original tectonic settings upwards through the Lower Proterozoic metamorphic strata in the Dabieshan-Lianyungang area, in the south-east of the North China Platform. The results of the study indicate that the lower and middle parts of the metamorphic strata comprise terrigenous clastics, phosphoritic and aluminous sedimentary formations which formed under stable continental margin conditions. In the middle-upper part a calc-alkaline volcano-sedimentary formation under the active continental margin was developed. The Lower Proterozoic meta-strata of sedimentary-volcanosedimentary origin from bottom upwards suggest that the tectonic evolution of the south-eastern margin of the North China Platform is a process from stabilization to mobilization. This process suggests a northward subduction of the Yangtze Plate under the North China Plate during the later part of the early Proterozoic.


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