4 resultados para Cambrian

em Deakin Research Online - Australia


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Three new and a single open nomenclature species are described in this thesis which contains the first record of Erixanium from Human. Also included is the first systematic description of the carbonate platform margin slope deposits and paleogeography of the study area and a comprehensive analysis of the tribolite community features and paleoenvironments.

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Sir Frederick McCoy made a significant contribution to the foundation of stratigraphical palaeontology. He carried out extensive taxonomic work sorting, naming and describing the Palaeozoic fossils of Ireland and Britain, and also played a decisive role in the debate between Adam Sedgwick and Roderick Murchison on where to draw the boundary between the Cambrian and Silurian systems. On his arrival in the Colony of Victoria in December 1854 he found that, contrary to the expectations of most European scientists, much of the stratigraphy and palaeontology paralleled that in the Northern Hemisphere. Hence McCoy was the first to confirm that the geological column was a global phenomenon.

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The Late Caledonian to Early Hercynian North Qilian orogenic belt in northwestern China is an elongate tectonic unit situated between the North China plate in the north and the Qaidam plate in the south. North Qilian started in the latest Proterozoic to Cambrian as a rift basin on the southern margin of North China, and evolved later to an archipelagic ocean and active continental margin during the Ordovician and a foreland basin from Silurian to the Early and Middle Devonian. The Early Silurian flysch and submarine alluvial fan, the Middle to Late Silurian shallow marine to tidal flat deposits and the Early and Middle Devonian terrestrial molasse are developed along the corridor Nanshan. The shallowing-upward succession from subabyssal flysch, shallow marine, tidal flat to terrestrial molasse and its gradually narrowed regional distribution demonstrate that the foreland basin experienced the transition from flysch stage to molasse stage during the Silurian and Devonian time.

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There is no any sediments contain fossils which formed earlier than Middle Ordovician in northern Tibet yet. It is very important whether have developed the Cambrian to Early Ordovician sedimentary strata. During geological mapping of Xainza County in 2000, Tetragraptus approximatus, the typical one of graptolite belts which cosmepolitically distributed in the Arenigian of Early Ordovician, was collected from the so-call Pre-Sinian Nianqingtanggula Group. So there is developped the Early Ordovician sediments and we have established Zakang Formation and Taduo Formation which perfected the Plaeozoic sequences in northern Tibet. According to these, we can realize tectonic control, palaeogeographrc pattern as well as palaeobiogeographic distribution of the Qinghai-Tibet Plateau in the early Paleozoic and also provided the materials to the cosmepolitical biostratigraphic contrast.