Title :

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

Author(s) :

Moreno, Eva [Auteur]
Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques [LOCEAN]
Caroir, Fabien [Auteur]
Laboratoire d’Océanologie et de Géosciences (LOG) - UMR 8187 [LOG]
Fournier, Léa [Auteur]
Environnements et Paléoenvironnements OCéaniques [EPOC]
Fauquembergue, Kelly [Auteur]
Environnements et Paléoenvironnements OCéaniques [EPOC]
Zaragosi, Sébastien [Auteur]
Environnements et Paléoenvironnements OCéaniques [EPOC]
Joussain, Ronan [Auteur]
Géosciences Paris Saclay [GEOPS]
Colin, Christophe [Auteur]
Géosciences Paris Saclay [GEOPS]
Blanc-Valleron, Marie-Madeleine [Auteur]
Centre de Recherche en Paléontologie - Paris [CR2P]
Baudin, François [Auteur]
Institut des Sciences de la Terre de Paris [iSTeP]
de Garidel-Thoron, Thibault [Auteur]
Centre Européen de Recherche et d'Enseignement des Géosciences de l'Environnement [CEREGE]
Valet, Jean-Pierre [Auteur]
Institut de Physique du Globe de Paris [IPGP (UMR_7154)]
Bassinot, Franck [Auteur]
Paléocéanographie [PALEOCEAN]

Journal title :

Marine Geology

Pages :

106347

Publisher :

Elsevier

Publication date :

2020-12

ISSN :

0025-3227

English keyword(s) :

Bengal fan
Holocene
turbidite activity
magnetic fabric
magnetic mineralogy

HAL domain(s) :

Planète et Univers [physics]/Océan, Atmosphère
Planète et Univers [physics]/Interfaces continentales, environnement

English abstract : [en]

We present here a study based on the Anisotropy of Magnetic Susceptibility (AMS) and magnetic mineralogy carried out on the composite core MD17&18taken from the eastern levee of the active channel of the middle Bengal Fan ...
Show more >We present here a study based on the Anisotropy of Magnetic Susceptibility (AMS) and magnetic mineralogy carried out on the composite core MD17&18taken from the eastern levee of the active channel of the middle Bengal Fan in the Indian Ocean. Based on C-14 dating, the sedimentary sequence covers 9.8 ka in 39 m of sediment. It therefore records at very high resolution the variations in continental material exported to the ocean by the Ganges-Brahmaputra river system during the Holocene.This sequence was divided into two units according to turbidite activity: Unit 1 from 9.8 to 9.2 ka cal. BP representing 39 m of coarse-grained turbidite sequences (coarse silts to fine sands) and extremely high sedimentation rates. Unit 2 of 9.2 ka cal. BP to the present characterized by a sharp decrease in the sedimentation rate, the presence of fine-grained turbidites characterized by strong decrease in the ln(Ti/Ca) ratio.Our AMS results indicate that the magnetic fabric is highly sensitive to the mode of deposition. The turbidite sequences are clearly characterized by very high F and Pj values, not only of the coarse-grained turbidite levels in unit 1, but also of the fine turbidites in unit 2. We suggest that this strong degree of anisotropy is the result of the strong and rapid deposition during the turbidite sequences which induces an additional compaction effect.Furthermore, low temperature SIRM measurements revealed that the magnetic minerals representative of the Ganges and Brahmaputra drainage area are magnetite, hematite and goethite. A higher supply in fine-grained magnetite was observed during the turbidite sequences in phase with an increase in sediment grain size.Show less >

Language :

Anglais

Peer reviewed article :

Oui

Audience :

Internationale

Popular science :

Non

ANR Project :

Paléo-variabilité de la mousson indienne

Collections :

• Laboratoire d'Océanologie et de Géosciences (LOG) - UMR 8187

Source :

Harvested from HAL