Middle to Late Holocene Evolution of Weedon Island and NW Tampa Bay, Florida

Weedon Island, a peninsula extending into the western margin of Tampa Bay, Florida, is a complex of well-known mid- to late-Holocene archaeological sites. The lack of modern development on the peninsula, in an otherwise densely populated area, makes Weedon Island an ideal place to reconstruct the Holocene evolution of northwestern Tampa Bay and its relationship with pre-historic human occupation. The lack of significant topography in the Tampa Bay region allows minor changes in sea level to significantly affect the coastal geomorphology. In addition, extensive archaeological shell middens may have influenced, or been influenced by, the position of the paleo-shoreline(s).

In an effort to identify how rising Holocene sea level, coupled with pre-historic structures, affected the morphology of Weedon Island, 40 cores were collected across the Weedon Island peninsula. Sedimentological and radiocarbon analyses of the cores identified a transgressive sequence, capped by eolian sands and archaeological middens, showing that the northern part of Tampa Bay had been inundated by seawater prior to ca. 4000 years ago. Several additional cores were recently collected from the nearshore marine environment in Old Tampa Bay adjacent to Weedon Island. The new cores, coupled with an additional radiocarbon age estimate, extend the marine inundation of the northwestern part of Tampa Bay to ca. 5000 years ago. Lithological analysis of the entire suite of cores from Weedon Island shows an apparent relict beach face, highlighting a seemingly gradual, rather than abrupt, flooding of Tampa Bay.