Title

Benthic foraminifera as indicators of recent mixed turbidite-contourite sediment transport system in the Eastern Mediterranean upper continental slope, offshore Israel

Document Type

Journal Article

Publication Title

Marine Geology

Volume

445

Publisher

Elsevier

School

School of Science / Centre for Marine Ecosystems Research

Funders

Israel Science Foundation (grant No. 954/15 to OK),

Chief Scientist office of the Ministry of Energy, Israel (grant No. 76/17 to OK and OHK),

Mediterranean Sea Research Center of Israel (MERCI),

Australian Research Council LIEF Project (LE170100219).

Grant Number

LE170100219

Comments

Ashkenazi, L., Katz, O., Abramovich, S., Almogi-Labin, A., Makovsky, Y., Gadol, O., ... & Hyams-Kaphzan, O. (2022). Benthic foraminifera as indicators of recent mixed turbidite-contourite sediment transport system in the Eastern Mediterranean upper continental slope, offshore Israel. Marine Geology, 106756.

https://doi.org/10.1016/j.margeo.2022.106756

Abstract

Nile derived siliciclastic sediments are the main source of sedimentation along the Levant continental margins of the Mediterranean Sea. These sediments are transported along the southeastern Mediterranean coast via well-documented longshore currents, mainly operating along the shelf. However, the cross shelf component of sediment transport, responsible for conveying sediments toward the upper slope, is less known. To better understand the cross-shelf vs. the longshore component of sediment transport we studied a ~6 m long piston core (DOR280) sampled on the upper continental slope (280 m water depth) and analyzed benthic foraminiferal assemblages and their shell taphonomy alongside the particle size distribution and mineralogy of bulk sediments, to document both the source and the transport mechanism of those upper continental-slope sediments. The radiocarbon dating at the core-base is ~650 Cal. Yrs BP, indicating an exceptionally high average sedimentation rate of ~800 cm/kyr. DOR280 consists of two alternating distinct sedimentary facies: (1) laminated (L) intervals up to ~40 cm thick each and showing a high ratio of allochthonous vs. autochthonous (allo/auto) benthic foraminiferal species and a high percentage of broken shells, indicating contribution of transported sediments originating from mid-shelf habitats; (2) non-laminated (NL) intervals up to ~200 cm thick each and showing a low allo/auto ratio and low percentages of broken shells, indicating mostly in-situ hemipelagic deposition. The L intervals are interpreted here as turbidites. The sedimentation rates calculated only for the NL intervals are still exceptionally high, thus excluding hemipelagic sedimentation as the sole mechanism for the NL deposition. Therefore, a contour bottom current transported component is suggested here as a source of the NL sedimentation. We conclude that a mixed contourite-turbidite system actively prevails along the upper continental slope of the Levant coast, offshore Israel. The mid-shelf to upper slope sediment transport is nearly continuous and presents occasional turbidite events of average decadal reoccurrence time.

DOI

10.1016/j.margeo.2022.106756

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