MITCHELL-TAPPING, HUGH J., Edison Community College, Fort Myers, FL; JOEL BELLUCCI, GRAHAM WOODY, THOMAS J. LEE, Estero Bay Marine Laboratory, Fort Myers Beach, FL

Abstract: Mud Hole: A Unique Warm-Water Submarine Spring Located Offshore Southwestern Florida

Mud Hole Submarine Spring is an unusual warm-water submarine discharge of water offshore of the southwestern Gulf Coast of Florida. The general location of the spring is Lat. 26° 15' 48" Long. 82° 01' 06". This warm-water submarine spring discharges water from many vents in a sinkhole depression, about 61 m in diameter at about 20 m deep. The bottom sediment consists of gray silt and mud atop sand and limestone gravel, which, when disturbed, causes clouds of mud to be thrown into suspension, giving the spring the name "Mud Hole." This study mapped the spring and measured physical water quality hourly during the period May 5 through June 17,1998. Warm water flowing from several orifices has a constant temperature of 35.31°C, 7.25 pH, and 34.6 ppt salinity. The warm plume extends about 1.5 m above the main orifice (1 m long by 0.3 m wide) and has a velocity estimated at 0.6 m/s with a discharge of about 0.17 m³/s (4 million gallons/day). The whole depression total discharge is however considerably larger. This study concludes that the discharge is fault-related and sourced from the east coast Straits of Florida via the Floridan aquifer, based on the geology. The water temperature indicates that the water comes from considerable depth (surrounding seawater only averages 21°C while local onshore deep Upper Floridan water ranges from 26.6°C to 29.4°C). A temperature profile from the oil-exploration well, SL #224B-1, located offshore north of Sanibel Island, indicates that this temperature exists only at a depth greater than 460 m in the Boulder Zone of the Floridan aquifer. Therefore, it is thought that the artesian Floridan Aquifer is the source of the water migrating through a fault zone to the spring, and not the surficial aquifer as has been reported in the literature.

AAPG Search and Discovery Article #90924©1999 GCAGS Annual Meeting Lafayette, Louisiana