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

Bed geometry used to test recognition criteria of turbidites and (sandy) debrites
Bed geometry used to test recognition criteria of turbidites and (sandy) debrites
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 (Marnoso-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.
turbidity current, debris flow, bed geometry, sedimentary facies
0037-0738
163-174
Amy, L.A.
ef602b7f-ef4e-4cba-96e7-e34096eb3066
Talling, P.T.
1cbac5ec-a9f8-4868-94fe-6203f30b47cf
Peakall, J.
2351dbf6-2c4f-4250-bacf-fe1b69870f26
Wynn, R.B.
72ccd765-9240-45f8-9951-4552b497475a
Arzola Thynne, R.G.
17623e1c-0ef3-46ed-9f82-5fc5d0d54fc6
Amy, L.A.
ef602b7f-ef4e-4cba-96e7-e34096eb3066
Talling, P.T.
1cbac5ec-a9f8-4868-94fe-6203f30b47cf
Peakall, J.
2351dbf6-2c4f-4250-bacf-fe1b69870f26
Wynn, R.B.
72ccd765-9240-45f8-9951-4552b497475a
Arzola Thynne, R.G.
17623e1c-0ef3-46ed-9f82-5fc5d0d54fc6

Amy, L.A., Talling, P.T., Peakall, J., Wynn, R.B. and Arzola Thynne, R.G. (2005) Bed geometry used to test recognition criteria of turbidites and (sandy) debrites. Sedimentary Geology, 179 (1-2), 163-174. (doi:10.1016/j.sedgeo.2005.04.007).

Record type: Article

Abstract

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 (Marnoso-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.

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More information

Published date: 2005
Keywords: turbidity current, debris flow, bed geometry, sedimentary facies

Identifiers

Local EPrints ID: 17486
URI: https://eprints.soton.ac.uk/id/eprint/17486
ISSN: 0037-0738
PURE UUID: db53347c-0751-4c43-a6a4-52b159fcc0e9

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Date deposited: 10 Oct 2005
Last modified: 17 Jul 2017 16:38

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Contributors

Author: L.A. Amy
Author: P.T. Talling
Author: J. Peakall
Author: R.B. Wynn
Author: R.G. Arzola Thynne

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