Magnetic fabric of Bengal fan sediments: Holocene record of sedimentary processes and turbidite activity from the Ganges-Brahmaputra river system

Moréno, Eva; Caroir, Fabien; Fournier, Léa; Fauquembergue, Kelly; Zaragosi, Sébastien; Joussain, Ronan; Colin, Christophe; Blanc-Valleron, Marie-Madeleine; Baudin, François; Garidel‐Thoron, Thibault de; Valet, Jean Pierre; Bassinot, Franck

doi:10.1016/j.margeo.2020.106347

Cited by 8 publications

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References 63 publications

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“…Therefore, the results of experimental data here can reflect the primary sedimentary fabric characteristics of the Kelimoli Formation to a high confidence level. Previous studies have shown that magnetic fabric is a sensitive index and a useful method for the analysis of depositional patterns (Moreno et al ., 2020), which can well reflect the hydrodynamic intensity, current direction, and the preferred alignment of sedimentary grains (e.g. Hamilton & Rees, 1970; Ellwood, 1980; Lowrie & Hirt, 1987; Jackson, 1991; Schieber & Ellwood, 1993; Park et al ., 2000; Parés et al ., 2007; Felletti & Dall'Olio, 2016).…”

Section: Discussionmentioning

confidence: 99%

Middle Ordovician bottom current deposits in the western margin of the North China craton: Evidence from sedimentary and magnetic fabrics

et al. 2022

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In many modern deep‐water slope environments, deposits formed by bottom currents (contourites) are rather common. However, reports on ancient contourites in deep‐water environments are scarce and most of them remain contentious. Based on the study of high‐resolution sedimentological, sedimentary geological and magnetic fabric characteristics, this study presents the key evidence of bottom current activity in the Middle Ordovician Kelimoli Formation from the western margin of the North China craton, and reconstructs the deep‐sea circulation pattern and the direction of deep‐water bottom currents in the middle and low latitudes during the Middle Ordovician. Six typical carbonate microfacies are identified in the Kelimoli Formation, which can be grouped into three sedimentary facies types related to the main interpreted depositional processes (bottom current, undifferentiated bottom current and hemipelagic settling, and hemipelagic settling). The evidence of bottom current deposits are five‐fold. Firstly, it is possible to observe a variety of traction current structures, which mainly represent bed‐load‐dominated transport of sediments. Secondly, there are multi‐scale inverse grading and bi‐grading, as well as inversely‐graded and normally‐graded sedimentary sequences, which reflect the periodic change of bottom current activity. Thirdly, gradual or sharp contact boundaries and small internal erosional surfaces indicate omission surfaces caused by the oscillating variation of bottom current velocity. Fourthly, the continuous rhythmic change of sedimentary fabrics on the microscopic scale reflects sustained, waxing and waning current intensities. Fifthly, the anisotropy of magnetic susceptibility reveals the microscopic fabric characteristics of imbricated magnetic grains, which represent the continuous action of directional current, and the restored palaeocurrent direction indicates that the current is mainly parallel to the slope strike. After the palaeo‐north correction of the North China craton clockwise rotation of 120° to 150° since the Ordovician, anisotropy of magnetic susceptibility shows that the direction of bottom current in the study area is towards the north‐east/east. Therefore, it is speculated that there was a clockwise deep‐water circulation in the middle and low latitudes of the southern hemisphere during the Ordovician. This study not only provides sedimentological evidence for the Ordovician bottom current activity, but also contributes to a better understanding of the Ordovician palaeoceanographical environment, especially the Middle Ordovician deep‐sea circulation pattern.

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