Sediment Infilling of Louisiana Continental-Shelf Dredge Pits: A Record of Sedimentary Processes in the Northern Gulf of Mexico

Identifier

etd-04032017-122054

Author

Meg Cathlin O'Connor, Louisiana State University and Agricultural and Mechanical CollegeFollow

Degree

Master of Science (MS)

Department

Geology and Geophysics

Document Type

Thesis

Abstract

Sediment cores were collected at continental-shelf sites of the Northern Gulf of Mexico off the coast of Louisiana to develop a better understanding of post-dredging evolution of mud-capped dredge pits. The two pits studied were Sandy Point (SP) and Raccoon Island (RI) (both with water depths of ~10m and dredged to ~ 15-20 m below water surface), which were dredged in 2012 and 2013 respectively. Vibracores and multicores were collected in 2015. Preliminary radiochemistry analyses identified Beryllium-7 distribution in multicore samples from both sites. SP1, the northwestern site in the Sandy Point dredge pit, showed 26 cm of 7Be penetration. In the Raccoon Island multicores, 7Be penetration depths varied from 36 cm in the center of the dredge pit (RI3) to throughout the entire length of a 50 cm core from the northern-most site (RI1), indicating that 7Be occurred deeper than the 50 cm multicore. Because rivers are a major source of 7Be in coastal marine sediments (concentrated from the atmosphere), 26-50 cm of 7Be activity indicates rapid and long-distance transport of sediment from likely fluvial sources (here the Atchafalaya and Mississippi Rivers) and suggests that the pits are efficient sediment traps.

Date

2017

Document Availability at the Time of Submission

Secure the entire work for patent and/or proprietary purposes for a period of one year. Student has submitted appropriate documentation which states: During this period the copyright owner also agrees not to exercise her/his ownership rights, including public use in works, without prior authorization from LSU. At the end of the one year period, either we or LSU may request an automatic extension for one additional year. At the end of the one year secure period (or its extension, if such is requested), the work will be released for access worldwide.

Recommended Citation

O'Connor, Meg Cathlin, "Sediment Infilling of Louisiana Continental-Shelf Dredge Pits: A Record of Sedimentary Processes in the Northern Gulf of Mexico" (2017). LSU Master's Theses. 4432.
https://repository.lsu.edu/gradschool_theses/4432

Committee Chair

Bentley, Sam

DOI

10.31390/gradschool_theses.4432