Graduation Year

2015

Document Type

Thesis

Degree

M.S.

Degree Name

Master of Science (M.S.)

Department

Geology

Degree Granting Department

Geology

Major Professor

Gregory S. Herbert, Ph.D.

Committee Member

Peter J. Harries, Ph.D.

Committee Member

Pamela Hallock Muller, Ph.D.

Keywords

Foraminifera, Paleoclimatology, Paleoecology, Tamiami

Abstract

There is general agreement that a range of paleodepths and environments are represented in the individual shell units of the middle Pliocene to earliest Pleistocene Tamiami Formation of southwest Florida, but maximum depths remain poorly constrained. Here, benthic Foraminifera abundances are used as a paleoenvironmental proxy to compare the upper Tamiami from quarries in Sarasota, Florida to Recent modern coastal, bay, and reef habitats of Florida, the Grand Cayman Islands, and Puerto Rico, ranging in depth from 0 to 55 meters. I used: (1) ordination techniques, including detrended correspondence analysis (DCA) and cluster analysis, to compare upper Tamiami foraminiferal assemblages with potential modern analogs; (2) Ammonia-Elphidium (AEI) and FORAM (FI) indices to reconstruct past oxygen levels and environmental stress levels, respectively; and (3) diversity indices and rarefaction to investigate habitat-specific diversity change through time.Results indicate that the upper Tamiami units represent several distinct environments. APAC quarry, Fruitville Member Unit 4 samples group in DCA and cluster analyses with modern shallow, tropical, mangrove-proximate lagoon samples from Puerto Rico; AEI values of both Unit 4 and these lagoonal samples are consistent with high nutrients. APAC quarry, Fruitville Member Unit 3 and Pinecrest Member units 5 and 7, however, group with tropical shallow, open coast environments up to 12 m in depth and have relatively low FORAM indices suggesting stress and AEI values comparable to modern mesotophic, shelf habitats. SMR samples group with modern mangrove environments from White Water Bay at depths approximately 0 to 0.3 m, with FORAM and AEI indices indicating low oxygen and possibly high nutrients. Species richness measured by individual rarefaction in the fossil units is highest in the lowest APAC units sampled and progressively declines in younger APAC units, while SMR beds have the lowest richness of all fossil samples. The lower portion of Unit 7 contains the highest richness of all fossil and modern units, while other fossil units have either lower or comparable richness, diversity, and evenness when compared to modern habitat analogs as identified in cluster and DCA analyses. Thus, there is no clear evidence for wide-scale decline in foraminiferal biodiversity from the Plio-Pleistocene to now. Significantly, the identification of modern habitat analogs for the upper Tamiami units make it possible to compare biodiversity trends in other fauna (e.g., mollusks) thought to have experienced significant extinction.

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