Temporal Scales of Mass Wasting Sedimentation across the Mississippi River Delta Front Delineated by 210Pb/137Cs Geochronology-Reference-Cited by-同舟云学术

Temporal Scales of Mass Wasting Sedimentation across the Mississippi River Delta Front Delineated by 210Pb/137Cs Geochronology

Published:2024-09-13 Issue:9 Volume:12 Page:1644
ISSN:2077-1312
Container-title:Journal of Marine Science and Engineering
language:en
Short-container-title:JMSE

Author:

Duxbury Jeffrey¹²,Bentley Samuel J.¹²^ORCID,Xu Kehui²³^ORCID,Jafari Navid H.²⁴

Affiliation:

1. Department of Geology and Geophysics, Louisiana State University, Baton Rouge, LA 70803, USA

2. Coastal Studies Institute, Louisiana State University, Baton Rouge, LA 70803, USA

3. Department of Oceanography and Coastal Studies, Louisiana State University, Baton Rouge, LA 70803, USA

4. Department of Civil and Environmental Engineering, Louisiana State University, Baton Rouge, LA 70803, USA

Abstract

The Mississippi River Delta Front (MRDF) is a subaqueous apron of rapidly deposited and weakly consolidated sediment extending from the subaerial portions of the Birdsfoot Delta of the Mississippi River, long characterized by mass-wasting sediment transport. Four (4) depositional environments dominate regionally (an undisturbed topset apron, mudflow gully, mudflow lobe, and prodelta), centering around mudflow distribution initiated by a variety of factors (hurricanes, storms, and fluid pressure). To better understand the spatiotemporal scales of the events as well as the controlling processes, eight cores (5.8–8.0 m long) taken offshore from the South Pass (SP) and the Southwest Pass (SWP) were analyzed for gamma density, grain size, sediment fabric (X-radiography), and geochronology (210Pb/137Cs radionuclides). Previous work has focused on the deposition of individual passes and has been restricted to <3 m core penetration, limiting its geochronologic completeness. Building on other recent studies, within the mudflow gully and lobe cores, the homogeneous stepped profiles of 210Pb activities and the corresponding decreased gamma density indicate the presence of gravity-driven mass failures. 210Pb/137Cs indicates that gully sedimentary sediment accumulation since 1953 is greater than 580 cm (sediment accumulation rate [SAR] of 12.8 cm/y) in the southwest pass site, and a lower SAR of the South Pass gully sites (2.6 cm/y). This study shows that (1) recent dated mudflow deposits are identifiable in both the SWP and SP; (2) SWP mudflows have return periods of 10.7 y, six times more frequent than at the SP (66.7 y); (3) 210Pb inventories display higher levels in the SWP area, with the highest focusing factors in proximal/gully sedimentation, and (4) submarine landslides in both study areas remain important for sediment transport despite the differences in sediment delivery and discharge source proximity.

Funder

Department of Interior Bureau of Ocean Energy Management

Publisher

MDPI AG

Link

https://www.mdpi.com/2077-1312/12/9/1644/pdf

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