Application of Fourier transform infrared (FTIR) spectroscopy in quantitative mineralogy of the South China Sea: Example of core MD01-2393. Diqiu Kexue – Zhongguo Dishi Daxue Xuebao - CNRS - Centre national de la recherche scientifique Accéder directement au contenu
Article Dans Une Revue Marine Geology Année : 2004

Application of Fourier transform infrared (FTIR) spectroscopy in quantitative mineralogy of the South China Sea: Example of core MD01-2393. Diqiu Kexue – Zhongguo Dishi Daxue Xuebao

Résumé

The expression of tide- and wind-driven processes in the internal architecture and external morphology of very large submarine dunes is investigated at a dune field located in the central part of the Dover Strait (Southern North Sea). Current measurements and sediment transport calculations enable quantification of the dominant tide- and wind-driven processes, and very high resolution seismic recordings are used to analyse internal structure and external morphology of dunes. In the study area, moderate to storm winds induce temporary currents that can lead to the reversal of sediment transport direction and induced erosive processes on the seabed. Dune master-bedding consists of extended erosive surfaces with 9–118 slopes that bound storm-generated sets of cross-beds, 1.5–4.85 m thick (2.65 m on average). Three types of architectures are observed within the dune field, and occasionally within single dunes. These types, which display a strong linkage between internal structure and external morphology, consist of: (1) asymmetric dunes with cosets, which dip in the direction of the marked external asymmetry of the dunes; (2) dunes with a complex external morphology composed of mega-herringbone structures, each displaying an opposing progradation direction; and (3) dunes with a symmetric megaripple bedding unit at their summit. The diversity of the internal architecture and external morphology results from the variable combinations of tide- and wind-driven processes occurring in the study area. The asymmetry of tidal peak current velocity and the relative strength of wind-driven currents are the parameters that have the most important influence on dune architecture. Asymmetric dunes with cosets result from a strong asymmetry in tidal peak current velocity, which is reversed only slightly during storms. Dunes with mega-herringbone structures and dunes with symmetric megaripple units at their summit are observed in areas where the asymmetry of the tidal peak current velocity is negligible, allowing reversal of the sediment transport and dune migration directions each time moderate winds blow. The latter architectural type is specific to sand-rich areas. The different dune architecture types display strong geometrical similarities to structures observed in dunes from other shelf environments where driving processes are different. This implies that a study based only on a geometric description of internal structures will not enable the reconstitution of ancient depositional environments. A better discriminant criteria seems to be the thickness of the second-order sets of cross-beds which is correlated with specific hydro-sedimentary processes. Dune height also probably has an important influence on the thickness of second-order sets of cross-beds, as dune height and set thickness display a clear relationship in the present study.

Dates et versions

hal-04220928 , version 1 (28-09-2023)

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Citer

Sophie Le Bot, Alain Trentesaux. Application of Fourier transform infrared (FTIR) spectroscopy in quantitative mineralogy of the South China Sea: Example of core MD01-2393. Diqiu Kexue – Zhongguo Dishi Daxue Xuebao. Marine Geology, 2004, 211 (1-2), pp.143-168. ⟨10.1016/j.margeo.2004.07.002⟩. ⟨hal-04220928⟩
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