Bed geometry used to test recognition criteria of turbidites and (sandy) debrites

被引:78
作者
Amy, LA [1 ]
Talling, PJ
Peakall, J
Wynn, RB
Thynne, RGA
机构
[1] Univ Bristol, Ctr Environm & Geophys Flows, Dept Earth Sci, Bristol BS8 1RJ, Avon, England
[2] Univ Leeds, Sch Earth Sci, Leeds LS2 9JT, W Yorkshire, England
[3] Southampton Oceanog Ctr, Challenger Div, Southampton SO14 3ZH, Hants, England
基金
英国自然环境研究理事会;
关键词
turbidity current; debris flow; bed geometry; sedimentary facies;
D O I
10.1016/j.sedgeo.2005.04.007
中图分类号
P5 [地质学];
学科分类号
0709 [地质学]; 081803 [地质工程];
摘要
The origin of thick-bedded deep-water sandstones has generated much controversy in recent years. Two fundamentally different models have been proposed for beds with the same internal sedimentary characteristics: (1) progressive particle settling from the base of a turbulent flow-the "turbidity current' model and (2) en-masse freezing of a higher-concentration flow-the "sandy debris flow" model. These models predict beds with very different geometries; turbidites thin gradually whereas debrites have abrupt terminations. Previous studies have relied upon sedimentary recognition criteria (i.e., sedimentary features in small-scale outcrop or core) to interpret depositional mechanism. In this study, depositional mechanism is deduced from bed geometry gained from extensive correlations of individual sandstones preserved in a classic turbidite system (Mamoso-arenacea Formation, Italy). This approach allows recognition criteria for turbidites and submarine debrites to be independently tested. We find that tabular and tapered sandstones (turbidites) have distinctly different internal characteristics to beds with abrupt margins (debrites). Turbidites are relatively well sorted, often exhibit grading and traction structures and have relatively low matrix mud contents. They may also contain massive division, floating clasts and inverse grading. Debrites are moderate-to-poorly sorted, ungraded, structureless, contain floating clasts and have elevated matrix mud contents. These findings have implications for the assessment of submarine gravity flows deposits and reservoir rock characterization. (c) 2005 Elsevier B.V. All rights reserved.
引用
收藏
页码:163 / 174
页数:12
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