Print this pageGeochemical and Sediment Diversity of Mobile Bay, Alabama
Wayne C. Isphording1, Jane Ashley Cordi2, and Ricky A. Schaeffer3
1University of South Alabama, P. O. Box 2031, Mobile, Alabama 36688
2U.S. Coast Guard Academy, 15 Mohegan Ave., New London, Connecticut 06320
3Well Data Services, P.O. Box 867, Milton, Florida 32572
ABSTRACT
Mobile Bay is the largest estuary located adjacent to the Gulf of Mexico and the second largest in the United States (exceeded only by the Chesapeake Bay system). As with other estuaries in the Gulf Coast, it owes its existence to flooding of a river valley that took place following sea level rise during the late Quaternary. It now serves as the primary depositional basin for the nation’s sixth largest river system which drains over two-thirds of the State of Alabama and portions of Mississippi, Tennessee, and Georgia, as well. In terms of riverine discharge volume, the quantity of water entering the bay from its contributory rivers is exceeded only by quantities associated with the Mississippi, Columbia, and Yukon rivers.
Detailed investigations carried out during the past half century, and especially two recent studies, have shown that the bay continues to undergo dynamic changes that are controlled by both natural and anthropogenic activities. Because of the large discharge that enters the bay, it is not surprising that it has been more impacted by contaminants than any other bay in the northern Gulf. Sorption of both heavy metals and other contaminants has been further facilitated by several characteristics of the bay’s sediments. These include: (1) the ion site partitioning behavior of the sediments, (2) an elevated organic carbon content, (3) a clay mineralogy dominated by smectite and mixed-layer clays, and (4) a preponderance of silt- and clay-sized sediment arising from the high sand trap efficiency of the bay head delta. Natural events, nevertheless, have acted in part to slow, or reverse, the actions of man. Significant chemical and textural changes in the bay’s bottom sediments seen over the past 30 years can be traced largely to a single hurricane event that occurred in 1979.
Isphording, W. C., J. A. Cordi, and R. A. Schaeffer, 2009, Geochemical and sediment diversity of Mobile Bay, Alabama: Gulf Coast Association of Geological Societies Transactions, v. 59, p. 363-381.
TemplateEndEditableAAPG Search and Discover Article #90093 © 2009 GCAGS 59th Annual Meeting, Shreveport, Louisiana