A fossil carbonate contourite drift on the Lower Ordovician palaeocontinental margin of the middle Yangtze Terrane, Jiuxi, northern Hunan, southern China

Taizhong Duan, Zhenzhong Gao, Yunfu Zeng, Dorrik Stow

Research output: Contribution to journalArticle

Abstract

The Early Ordovician (Tremadocian) in part of Jiuxi, northern Hunan Province, comprises a succession of deep-water carbonate sediments deposited on a palaeocontinental margin at the southern edge of the Yangtze Platform. A distinctive elongate mound-like form, some 350–450 m thick, can be recognized lying between shallow-water platform carbonates and deeper-water mudstones. This elongate body, here called the Jiuxi drift, is made up dominantly of sediments interpreted as contourites on the basis of their mid to base-of-slope location, alongslope current indicators, features of traction flow processes coupled with intense bioturbation, and distinctive contourite sequences (typically 30–80 cm thick). Five contourite facies are recognized: calcilutites, calcisiltites, calcarenites, calcirudites (possibly contourite lag deposits), and bioclastic contourites. Hemipelagites and turbidites make up only a small proportion of the drift, which accumulated at an average sedimentation rate of 38 m/m.y. Large-scale cross-stratified units found in parts of the calcilutitic contourite section are believed to result from seafloor development of mudwaves and/or erosional furrows under the influence of a semipermanent bottom-current regime.
Original languageEnglish
Pages (from-to)271-284
Number of pages14
JournalSedimentary Geology
Volume82
Issue number1-4
DOIs
Publication statusPublished - Jan 1993

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