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The Qinghai-Tibetan Plateau and its surrounding areas have a long and complex tectonic evolutionary history. Cratons and blocks, such as northern India, Lhasa, Qiangtang, Qaidam and Central Qilian, and their in-between orogenic belts constitute the main part of the Qinghai-Tibetan Plateau. During the Cambrian Period, most of these cratons and blocks were on the northwestern periphery of Gondwana, and were associated with the surrounding blocks, e.g. Arabian, Central Iran, Afghanistan, Tarim, Alxa, North China, South China and Sibumasu through the Proto-Tethys Ocean. The Cambrian stratigraphic sequences on these stable blocks are composed of mixed siliciclastic and carbonate rocks deposited in the shallow-water marine environments, and contain the trilobite assemblages of shelf facies. The Cambrian stratigraphic sequences in the Qilian tectonic belts, however, are characterized by the intermediate-basic igneous rocks and silicates formed in the Proto-Tethys Ocean, and contain the trilobite assemblages of deep-water slope facies. Combining with previous data, field observations and newly discovered fossils through funding by the Second Tibetan Plateau Scientific Expedition and Research, the general characteristics of the Cambrian strata in different tectonic units of the Qinghai-Tibetan Plateau and its surrounding areas have been summarized in this paper. Furthermore, efforts have been made to subdivide and correlate the Cambrian strata across these areas by utilizing available biostratigraphic and geochronological data. As a result, a comprehensive litho- and biostratigraphy chart has been compiled. Finally, from the biogeographic perspective, this paper also provides a brief overview of the Cambrian paleogeographical reconstruction of the major tectonic blocks, and discusses the problems associated with the evolution of the Proto-Tethys tectonic belt. [ABSTRACT FROM AUTHOR]

Abstract: Eggs, embryos, and hatchlings of olivooids are common and distinctive components of the earliest Cambrian small shelly fossil assemblage (Anabarites trisulcatus–Protohertzina anabarica Zone) at the northern and northwestern edge of the Yangtze Platform. Embryos are preserved in 3D as phosphatized permineralizations with superficial cellular structures. Nanofocus X-ray computed tomography reveals that diagenetic structures characterize the interior of most phosphatized eggs and embryos. The Olivooidae fam. nov. is herein distinguished from the possibly related hexaconulariids. Statistical size investigations and morphological studies indicate that at least three, but possibly five or more species of olivooids occur in the early Cambrian of South China. Fossilized smooth egg stages reflect a high biodiversity, encompassing 8–10 or more biological species. Eggs and embryos of Olivooides multisulcatus, Olivooides mirabilis and Quadrapyrgites quadratacris are represented by distinct and characteristic size clusters. The size ranges of embryonic parts of hatchlings roughly correspond to the size clusters of the embryos. From reconstruction of the developmental series of Olivooides multisulcatus it appears that the cleavage mode of olivooids was transitional between superficial and total cleavage. Late embryos and hatchlings of Olivooides multisulcatus and Olivooides mirabilis are characterized by pentaradial symmetry, whereas tubes of Quadrapyrgites quadratacris exhibit tetraradial symmetry. Tubular hatchlings of olivooids may represent larval or adult stages, or perhaps, nonfeeding larvae. Although the biological affinity of olivooids is weakely constrained, we hypothesize that they belong within an extinct clade of the Cycloneuralia. Their assignment to the Cnidaria is considered unlikely. [Copyright &y& Elsevier]

The diversification of animals during the Cambrian Period is one of the most significant evolutionary events in Earth's history. However, the sequence of events leading to the origin of 'modern' ecosystems and the exact temporal relationship between Ediacaran and Cambrian faunas are uncertain, as identification of the Ediacaran–Cambrian boundary and global correlation through this interval remains problematic. Here we review the controversies surrounding global correlation of the base of the Cambrian and present new high-resolution biostratigraphic, lithostratigraphic and δ13C chemostratigraphic data for terminal Ediacaran to basal Cambrian strata in the Zavkhan Basin of Mongolia. This predominantly carbonate sequence, through the Zuun-Arts and Bayangol formations in southwestern Mongolia, captures a distinct, negative δ13C excursion close to the top of the Zuun-Arts Formation recognized as the BAsal Cambrian carbon isotope Excursion (BACE). In this location, the nadir of the BACE closely coincides with first occurrence of the characteristic early Cambrian protoconodont Protohertzina anabarica. Despite recent suggestions that there is an evolutionary continuum of biomineralizing animals across the Ediacaran–Cambrian transition, we suggest that this continuum is restricted to tubular forms, and that skeletal taxa such as Protohertzina depict 'true' Cambrian representatives that are restricted entirely to the Cambrian. Employing the first appearance of the trace fossil Treptichnus pedum to define the base of the Cambrian suffers significant drawbacks, particularly in carbonate settings where it is not commonly preserved. As T. pedum is the only proxy available to correlate the Cambrian Global boundary Stratotype Section and Point (GSSP) defined at Fortune Head, Newfoundland, we suggest that the GSSP be redefined elsewhere, in a new stratigraphic section that contains secondary markers that permit global correlation. We propose the nadir of the BACE as the favored candidate to define the base of the Cambrian. However, it is essential that the BACE be complemented with secondary markers. In many global sections the nadir of the BACE and the first occurrence of the genus Protohertzina are closely juxtaposed, as are the BACE and T. pedum. Hence these taxa provide essential biostratigraphic control on the BACE and increase potential for effective global correlation. We also recommend that an Auxiliary boundary Stratotype Section and Point (ASSP) be simultaneously established in order to incorporate additional markers that will aid global correlation of the Ediacaran–Cambrian boundary. The BAY4/5 section through the upper Zuun-Arts and Bayangol formations yields key shelly fossils and δ13C values and is therefore an ideal candidate for consideration as the GSSP for the Ediacaran–Cambrian boundary. [ABSTRACT FROM AUTHOR]

Chengjiang-type fossil brachiopods with preservation of non-mineralized tissues are reported for the first time from the Lower Cambrian Shipai Formation of the Three Gorges area, western Hubei Province, China. Recent excavation in the Wangjiaping and Aijiahe sections resulted in the new discovery of some linguloid brachiopods, showing strong similarity in preservation with those occurring in the well-known Chengjiang fauna (Yu’anshan Formation of eastern Yunnan, China). The brachiopods can be referred to Palaeobolus liantuoensis , Lingulellotreta malongensis and Eoobolus . sp. The new material of Palaeobolus exhibits a flattened impression of proximal pedicle, which also represents the first report of pedicle known from this cosmopolitan linguloid taxon. The occurrence of Lingulellotreta in the Shipai Formation ( Redlichia meitanensis and Palaeolenus lantenoisi zones) represents an important geological extension of this genus to upper Tsanglangpuan Stage (Series 2, Stage 4) in the Yangtze Platform, and signifying that the FAD of Lingulellotreta in the regional Lower Cambrian of the Yangtze Platform seems not synchronous. [ABSTRACT FROM AUTHOR]