scholarly journals Occurrence ofMicrodictyonfrom the lower Cambrian Xinji Formation along the southern margin of the North China Platform

2017 ◽  
Vol 92 (1) ◽  
pp. 59-70 ◽  
Author(s):  
Bing Pan ◽  
Timothy P. Topper ◽  
Christian B. Skovsted ◽  
Lanyun Miao ◽  
Guoxiang Li
Keyword(s):  
Lower Cambrian ◽  
North China ◽  
Ontogenetic Variation ◽  
Early Cambrian ◽  
North China Platform ◽  
Middle Cambrian ◽  
The North ◽  
Formation Stage ◽  
Inadequate Knowledge ◽  
Stage 4

AbstractDisarticulated net-like plates of the lobopodMicrodictyonhad a near cosmopolitan distribution from the early to middle Cambrian but are yet to be documented from the North China Platform. Here we report isolated plates ofMicrodictyonfrom the lower Cambrian Xinji Formation (Stage 4, Series 2) of the North China Platform, extending the paleogeographic distribution ofMicrodictyonin the early Cambrian. The plates ofMicrodictyonfrom the Xinji Formation are similar to those of other species established on the basis of isolated plates but do bear some new characters, such as mushroom-shaped nodes with a single inclined platform-like apex and an upper surface that displays radial lines. However, the plates documented here are left under open nomenclature due to inadequate knowledge of intraspecific and ontogenetic variation and low specimen numbers. Through comparison of the node shapes of the isolated plates of differentMicrodictyonspecies, we consider that low mushroom-shaped nodes could be a primitive and conservative character ofMicrodictyonwhile tall mushroom-shaped nodes may be a derived character. Subtle differences in shape and number of node apices may also represent intraspecific or ontogenetic variation.

scholarly journals Diversified calcimicrobes in dendrolites of the Zhangxia Formation, Miaolingian Series (Middle Cambrian) of the North China craton

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Ming-Xiang Mei ◽  
Muhammad Riaz ◽  
Zhen-Wu Zhang ◽  
Qing-Fen Meng ◽  
Yuan Hu
Keyword(s):  
North China ◽  
Cyanobacterial Mats ◽  
Third Order ◽  
Depositional Sequence ◽  
Middle Cambrian ◽  
Forming Mechanism ◽  
The North ◽  
Biological Affinity ◽  
History Of ◽  
Group 3

AbstractAs a type of non-laminated microbial carbonates, dendrolites are dominated by isolated dendritic clusters of calcimicrobes and are distinct from stromatolites and thrombolites. The dendrolites in the upper part of the Miaolingian Zhangxia Formation at Anjiazhuang section in Feicheng city of Shandong Province, China, provide an excellent example for further understanding of both growth pattern and forming mechanism of dendrolites. These dendrolites are featured by sedimentary fabrics and composition of calcified microbes as follows. (1) The strata of massive limestones, composed of dendrolites with thickness of more than one hundred meters, intergrade with thick-bedded to massive leiolites, formimg the upper part of a third-order depositional sequence that constitutes a forced regressive systems tract. (2) A centimeter-sized bush-like fabric (shrub) typically produced by calcified microbes is similar to the mesoclot in thrombolites but distinctive from clotted fabrics of thrombolites. This bush-like fabric is actually constituted by diversified calcified microbes like the modern shrub as a result of gliding mobility of filamentous cyanobacteria. Such forms traditionally include: the Epiphyton group (which actually has uncertain biological affinity), the Hedstroemia group which closely resembles modern rivulariacean cyanobacteria, and the possible calcified cyanobacteria of the Lithocodium–Bacinella group. (3) Significantly, dense micrite of leiolite is associated with sponge fossils and burrows, and is covered by microstromatolite. The Lithocodium–Bacinella group is a controversial group of interpreted calcified cyanobacteria in the Cambrian that has also been widely observed and described in the Mesozoic. Therefore, dendrolites with symbiosis of leiolites in the studied section provide an extraordinary example for further understanding of growing style of bush-like fabrics (shrubs) of the dendrolites dominated by cyanobacterial mats. Furthermore, the present research provides some useful thinking approaches for better understanding of the history of the Early Paleozoic skeletal reefs and the microbe–metazoan transitions of the Cambrian.

Occurrence of the Enigmatic Bivalved FossilApistoconchain the Lower Cambrian of Southeast Shaanxi, North China Platform

2014 ◽  
Vol 88 (2) ◽  
pp. 359-366 ◽  
Author(s):  
Guoxiang Li ◽  
Zhifei Zhang ◽  
Hong Hua ◽  
Huining Yang
Keyword(s):  
Carbonate Rocks ◽  
Lower Cambrian ◽  
Morphological Analysis ◽  
North China ◽  
Bilateral Symmetry ◽  
Shaanxi Province ◽  
Single Type ◽  
Posterior Teeth ◽  
North China Platform ◽  
Stem Group

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.

The petrochemistry of the Lower Proterozoic metamorphic rocks from the Dabieshan-Lianyungang area, the southeastern margin of the North China Platform

1991 ◽  
Vol 55 (379) ◽  
pp. 263-276 ◽  
Author(s):  
Sang Longkang
Keyword(s):  
Continental Margin ◽  
North China ◽  
Active Continental Margin ◽  
The South ◽  
North China Platform ◽  
The North ◽  
Lower Proterozoic ◽  
Southeastern Margin ◽  
Tectonic Settings ◽  
North China Plate

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.

Lower Cambrian (Branchian) trilobites and biostratigraphy of the Hanford Brook Formation, southern New Brunswick

2000 ◽  
Vol 74 (5) ◽  
pp. 858-878 ◽  
Author(s):  
Stephen R. Westrop ◽  
Ed Landing
Keyword(s):  
New Species ◽  
Nova Scotia ◽  
North America ◽  
New Brunswick ◽  
Lower Cambrian ◽  
Early Cambrian ◽  
The West ◽  
Middle Cambrian ◽  
Sequence Stratigraphic ◽  
Two New Species

The Hanford Brook Formation, one of the classic Cambrian units of Avalonian North America, contains at least eight species of endemic trilobites, including Berabichia milleri Westrop n. sp., that are assigned to seven genera. The vertical succession of faunas is far more complex than has been recognized previously, with each member containing a lithofacies-specific assemblage. These are, in ascending order: a bradoriid-linguloid Association without trilobites in the nearshore St. Martin's Member, a Protolenus Association in dysaerobic siltstones and sandstones of the Somerset Street Member, and a Kingaspidoides-Berabichia Association in hummocky cross-stratified sandstones of the Long Island Member that overlie a parasequence boundary at Hanford Brook. Due to the breakdown of biogeographic barriers in the late Early Cambrian, two new species-based zones, the Protolenus elegans and Kingaspidoides cf. obliquoculatus zones, share trilobite genera with the Tissafinian Stage of Morocco. This generic similarity has been the basis for correlation of this upper Lower Cambrian interval on the Avalon continent with the West Gondwanan lowest Middle Cambrian. However, the clear facies control on the occurrence of genera in the Hanford Brook Formation and the presence of an abrupt faunal break and unconformity at the base of the Tissafinian in Morocco makes this correlation questionable. The Hanford Brook Formation may represent a late Early Cambrian interval unknown in Gondwana. Sequence-stratigraphic criteria even raise the possibility that the Protolenus Association is the biofacies equivalent of Callavia broeggeri Zone faunas of the Brigus Formation of Newfoundland, Nova Scotia and Massachusetts.

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