Reconstructing the MIS 2 Pascagoula-Biloxi Paleovalley and Associated
Valley-Fill in the Northern Gulf of Mexico
Abstract
Systemic modification of coastal systems in the northern Gulf of Mexico
is generated by rapid geomorphic change due to storms, relative sea
level rise, significant reduction in sediment supply, and anthropogenic
alteration. Policy makers, engineers, and scientists must understand the
overall geologic evolution as well as small scale processes associated
with past sea level cycles to make informed decisions when addressing
current and future sea level rise. After the Last Glacial Maximum, sea
level rose rapidly during marine isotope stage (MIS) 2 (approximately
29-14 ka) leading to a transgressive reworking of lithosomes. As sea
level continued to rise, Holocene sediments underwent significant
reworking and backstepping resulting in drowned paleovalley
architecture. Coastal geomorphic evolution is partially preserved within
the geologic record specifically within incised valleys and shelf
deposits. This study synthesizes ~700 km of boomer
geophysical data collected in 2021, 19 sediment cores, microfossil
analyses, and radiocarbon dates to create a geomorphic evolutionary
framework of the Pascagoula-Biloxi paleovalley and associated fill along
the innershelf of the northern Gulf of Mexico. Sediment cores described
within the footprint of the Pascagoula-Biloxi paleovalley consist of
muddy bedding overlying muddy sand and sandy mud with Pleistocene clay
around 450-500 cm downcore. One such core contained large wood chunks
dated to ~11 ka cal yr BP resting on a Pleistocene clay
basal facies. Preserved wood indicates either rapid burial or an anoxic
system, in this case - likely a swamp. Along the edge of the
Pascagoula-Biloxi paleovalley, a sediment core exhibits well preserved
interbedded clay and peat layers also dated to ~11 ka
cal yr BP. These similar ages indicate terrestrial/shoreline deposition,
and these data provide constraints to reconstruct the immature paleo
shoreline and associated features of the early Holocene.