Abstract: Macrofauna and Microfauna of the Pensacola Bay and Perdido Bay Area, Florida and Alabama

Tanwi Gangopadhyay, Laurie C. Anderson, Megan H. Jones, Randolph A. McBride

Mollusks and foraminifera were examined to evaluate the Pensacola Bay and Perdido Bay area as a potential source for, or modern analog of, offshore subsurface Holocene facies. Grab samples were collected at 34 stations that were primarily in or near sea-grass beds or in sand substrates. Molluscan assemblages from sandy back-barrier platforms of Perdido Key and Santa Rosa Island, as well as Pensacola Pass, were readily distinguishable. Most stations behind Santa Rosa Island contained a very low diversity and abundance of mollusks. Anomalocardia auberiana was most common. Stations behind Perdido Key had a slightly higher diversity. Anomalocardia was common, but Crepidula spp., Cerithium muscarum, Nassarius vibex, Tellina spp., and vermiti gastropods characterized this area. Pensacola Pass sands contain a low abundance assemblage dominated by Ervilia nitens and small lucinids. Modern bay assemblages and those of Holocene estuarine and marine facies of the shelf share many mollusk species, although common species can differ greatly. Bay death assemblages receive bioclasts both from in situ communities and shallow-marine areas via washover.

Foraminiferal assemblages of inlet, back-barrier, and lower-bay stations are dominated by Ammonia and Elphidium, similar to assemblages of Mississippi Sound, Mobile Bay, and St. Andrew Bay. Back-barrier samples have a higher proportion of miliolid species, indicating a greater marine influence, possibly due to washover or higher salinities. Bay foraminiferal assemblages are comparable to subsurface estuarine facies on the shelf, but offshore marine death assemblages are dominated by Archaias angulatus and Peneroplis proteus.

AAPG Search and Discovery Article #90950©1996 AAPG GCAGS 46th Annual Meeting, San Antonio, Texas