Identifier

etd-11062014-103552

Degree

Master of Science (MS)

Department

Oceanography and Coastal Sciences

Document Type

Thesis

Abstract

This study is focused on a paleoenvironmental history of a backbarrier coastal lagoon situated on the seaward margin of the Lafourche delta lobe in coastal Louisiana. A 2.2 meter long sediment core (Core BC 53) was collected from a mangrove-covered land strip on the northern margin of Bay Champagne, and was studied using pollen analysis, Loss-on-ignition (LOI), X-ray Fluorescence (XRF) analysis, and Cesium-137 and radiocarbon dating techniques to establish sediment stratigraphy and core chronology. Bay Champagne, a backbarrier lagoon formed during the evolution of Bayou Lafourche, has shown to be highly sensitive to geomorphological and vegetation changes induced by sea-level rise as noted by palynological, paleotempestological, and sedimentological records. In addition to capturing the rise and fall of the Lafourche delta lobe, Core BC 53 also preserved hurricane-induced sedimentary record. Pollen data revealed that Bay Champagne is mainly characterized by coastal marsh taxa. Freshwater marsh was dominant during the active period of the Lafourche delta about 1600 years ago. This was followed by a shift to salt marsh during its deterioration phase around 300 years ago. Avicennia germinans (black mangrove) emerged within the stratigraphy around 1880 A.D., which shows a direct correlation to relative sea-level rise. LOI and XRF data uncovered the presence of four hurricanes. Storm layers were not overwashed from the beach barrier due to its far distance from the coring site; however, these sedimentary signatures originated from the center of Bay Champagne and fluvial regions north of the lagoon. The distinct increase in charcoal concentration and decrease in arboreal pollen following Layer B implies the occurrence of wildfires induced by the hurricane. This is comparable to the results in Liu et al. (2008), which recorded three hurricane-induced fire linkages in coastal Alabama. Geological changes caused by Hurricane Isaac (September 2012) are found in the upper 3 cm of the core. This storm produced extensive fluvial flooding to the area as shown by LOI and XRF. These findings from Hurricane Isaac may provide a modern analog for interpreting the impacts of prehistoric hurricanes in sediment stratigraphic studies from this coastal region.

Date

2014

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Liu, Kam-biu

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