Ordovician carbonate contourite drifts in Hunan and Gansu Provinces, China
Published:January 01, 2002
Shunshe Luo, Zhenzhong Gao, Youbin He, Dorrik A. V. Stow, 2002. "Ordovician carbonate contourite drifts in Hunan and Gansu Provinces, China", Deep-Water Contourite Systems: Modern Drifts and Ancient Series, Seismic and Sedimentary Characteristics, D. A. V. Stow, C. J. Pudsey, J. A. Howe, J.-C. Faugères, A. R. Viana
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The Early Ordovician continental margin at the southern edge of the Yangtze Platform, China, is represented by a succession of deep-water carbonate sediments near Jiuxi. A distinctive elongate mound-like form, some 120 km long, 25 km wide and 350–450 m thick, has been identified between shallow-water platform carbonates and deeper-water mudstones, and interpreted as the Jiuxi drift. The principal facies include calcilutites, calcisiltites, calcarenites, calcirudites, and bioclas-tic contourites, interpreted as contourites on the basis of their slope location, alongslope palaeocurrent indicators, features of traction flow processes coupled with intense bioturbation, and distinctive contourite sequences. During the Middle Ordovician, along the western slope of the Ordos Platform, Gansu Province, a narrow deep gateway (here called the Pingliang gateway) opened up between two deep-water basins. An elongate, mounded, carbonate body (70 km × 15 km × 150 m thick), developed along the eastern slope of this gateway, has been interpreted as the Pingliang contourite drift. A similar suite of contourite facies and sequences is found as at Jiuxi, although there is a greater abundance of calcarenitic contourites in the Pingliang drift, as well as other evidence that suggests a more active bottom current regime in this Ordovician gateway region
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Deep-Water Contourite Systems: Modern Drifts and Ancient Series, Seismic and Sedimentary Characteristics
Countourites are a widespread but poorly known group of sediments linked to the action of powerful bottom currents in deep water. Although we know they are especially common along continental margins and through oceanic gateways, they have been surrounded by contoversy since they were first recognized in the early 1960s. Where correctly recognized and decoded they can provide one of the keys to our better understanding of bottom water circulation and of the ocean–climate link. They are part of the spectrum of deposits that confronts the oil industry as exploration moves into progressively greater water depths.
This memoir is an important outcome of the International Geological Correlation Project 432 on Bottom Currents, Contourites and Palaeocirculation. It includes 30 papers involving over 75 key scientists from around the world. Following an introductory state–of–the–art paper by the editors, there are 25 separate case studies on modern drifts and four on ancient contourite series. Each contribution highlights the specific geological and oceanographic setting, bathymetry, physiographic and stratigraphic context, seismic attributes and sedimentary characteristics of that drift. Case studies range from some of the well-documented North Atlantic drifts to those much less known from the Mediterrenean, from important syntheses of the Gulf of Cadiz and Vema Channel Gateway, to completely new data on South Atlantic, Pacific and Antartic margin systems. The four papers on ancient series from Japan, China and Cyprus serve to emphasise the complex nature and subtle characteristics of contourites, which make their identification a scientific challenge.
This volume is dedicated to the memory of Charlie Hollister (1936–1999), one of the founding fathers and pioneers of countourite research.