Paper No. 5
Presentation Time: 9:00 AM-6:00 PM
DISTINCTIVE CHARACTERISTICS OF BLUE HOLE FIVE, SAN SALVADOR, BAHAMAS
OSBORNE, Tashiana1, FLYNN, Elaine D.2, SPANO, Nicholas3, BERMAN, Mary Jane4, BOWLES, Rachel2, BRADY, Kristina5, GNIVECKI, Perry L.6, MICHELSON, Andrew V.7, MYRBO, Amy8 and PARK, Lisa E.9, (1)Atmospheric and Hydrologic Sciences, St. Cloud State University, 129 Robert Wick Science Building, St. Cloud, MN 56301, (2)Geography and Geology, Western Kentucky University, 1906 College Height Blvd. #31066, Bowling Green, KY 42101, (3)Geological Sciences, University of Minnesota-Duluth, 229 Heller Hall, 1114 Kirby Drive, Duluth, MN 55812, (4)Center for American and World Cultures, Miami University, Oxford, OH 45056, (5)LacCore, University of Minnesota, 500 Pillsbury Dr SE, Minneapolis, MN 55455, (6)Miami University, 571 Mosler Hall, Hamilton, OH 45011, (7)Program in Integrated Bioscience, University of Akron, Akron, OH 44325, (8)LacCore/CSDCO, Department of Earth Sciences, University of Minnesota, 500 Pillsbury Dr. SE, Minneapolis, MN 55455, (9)Geology and Environmental Science, University of Akron, University of Akron, University of Akron, Akron, OH 44325, osta0901@stcloudstate.edu
Blue Hole Five on San Salvador Island, Bahamas was examined with a focus on its hydrogeology, geologic record, and surrounding flora. Although located in a failed housing development site in the southwestern portion of the island, Blue Hole Five has no historical record of human use. This lake is ~0.1 ha and the shoreline consists of epikarsted limestone bedrock covered by surface vegetation. Algae, liver gel, mollusks, ostracodes and minnows are prevalent in the lake. The keyhole shape of Blue Hole Five can be divided into two regions: a shallow bench and a deeper hole (~6 m) with steep sides and a conduit connecting it with marine water and subjecting it to tidal fluctuations. Saline water entering the conduit explains the higher salinity (~17 ppt) and total dissolved solids (TDS) of approximately 17.8 g/L, along with the anoxic bottom conditions. Lake conditions in Blue Hole Five are brackish with a pH that varies between 7-8, and a halocline at approximately 4 m.
Lake sediment cores from three different sites in Blue Hole Five were collected in June 2012. One location was a deeper region near the conduit, another was an area of medium-depth, and the last was on the shallow bench. At each site, a dark green flocculent layer comprised the uppermost sediment, likely representing very recent human impacts such as vegetation clearance for the housing development. Sediments were composed almost exclusively of mollusk shells in some intervals, with little to no fine grained material, except towards deeper layers. Loss on ignition (LOI) results shows that the sediment is largely comprised of carbonate, with small amounts of organic material and even less inorganic material, probably deposited dust from a remote area. XRF data confirmed high levels of carbonate and strontium. SEM and smear slide observations showed an abundance of various mollusk shells and ostracodes. C. costata and A. auberiana mollusks were the most consistently dominant species throughout the first and last sites, although several other bivalve and gastropod species were present. Calcite, pyrite, diatoms, foraminifera, and iron oxides were discovered under microscopic examination. With a geologic record involving minor anthropogenic impact, Blue Hole Five will provide vital contrasting results with neighboring Bahamian blue holes in ongoing research.
