SEDIMENTARY ARCHITECTURE OF TAMPA BAY, FL: A COMPLEX INFILLING HISTORY

A suite of sediment cores collected in Tampa Bay, FL indicates that the estuary has experienced a complex depositional history. Seven sedimentary facies have been identified representing a variety of depositional environments. The basal unit, the Blue-Green Clay facies, consists of sand and clay, in varying proportions, occasionally with cobble size material, and is interpreted to represent reworking of the underlying carbonate platform. The Shelly Sand/Gravel facies consists mainly of sand with an abundance of shells and shell fragments, some gravel size. It is interpreted as Open Marine, and stratigraphically lies immediately above the Blue-Green Clay facies. It may exist as the basal unit in some cores, or near the surface of cores collected near the bay mouth. The Muddy Sand/Sand facies contains little to no shell material, and is interpreted to represent fluvial deposition. It is often found near the bases of cores collected near the bay head. The Organic Mud facies consists of freshwater shells, mostly gastropods, and is intercalated within the Muddy Sand/Sand and Carbonate Organic Mud/Sand facies. It is interpreted to represent deposition in freshwater marsh environments. The Carbonate Organic Mud/Sand facies contains fresh to brackish water sand-size gastropod shells, and is interpreted to represent lacustrine deposition. The Organic Sandy Shelly Mud facies represents deposition in a paralic environment. This facies is often interpreted to represent the initial flooding surface of the Holocene sea-level transgression and almost always underlays the Muddy Shelly Sand/Gravel facies. The Muddy Shelly Sand/Gravel facies consists of muddy quartz sand with an abundance of shells and shell fragments, and represents modern estuarine conditions. It occupies the surface of all but the most seaward cores collected in Tampa Bay.

Although most facies are found throughout the 6 main regions of Tampa Bay (Safety Harbor, upper Tampa Bay, Hillsborough Bay, south McDill, middle-lower Tampa Bay, and Lower Tampa Bay) the facies architecture varies considerably from region to region. Each region has a unique facies architecture showing that Tampa Bay as a whole has had a complex sedimentological history with different regions developing as independent basins.