Details

Autor(en) / Beteiligte

• Sliko, Jennifer Leigh

Titel

Nearshore marine paleoenvironmental reconstruction of southwest Florida during the Pliocene and Pleistocene

Ort / Verlag

ProQuest Dissertations Publishing

Erscheinungsjahr

2010

Link zum Volltext

• ProQuest

Quelle

ProQuest Dissertations & Theses A&I

Beschreibungen/Notizen

• Future climate change has been the subject of considerable speculation with scientists called upon to predict timing, magnitude, and impact of these changes. The Pliocene Warm Period serves as the best-available, pre-modern analog to predicted climate changes, and Pliocene climate anomalies are examined as possible scenarios for future climate change. Comparing modern conditions to the mean climate state of the Pliocene is essential for better constrained predictions of future climate change, and seasonal paleoenvironmental records provide a data set more analogous to instrumental observations and thereby reducing the uncertainty in modeled climate changes. This study first examines the potential of large gastropod shells as a paleoclimate proxy. Specimens of Busycon sinistrum, active in winter, and Fasciolaria tulipa, active in the summer, were collected alive from Tampa Bay and St. Joseph Bay in the hope of establishing a multi-year record of seasonality. The δ18O time series of each shell were compared with predicted δ18O, based on local marine temperature variations, and both species cease shell growth during the winter months, despite opposing seasons of feeding activity. As none of the profiles provide information on winter environmental parameters, this sclerochronological system was replaced by work on pristine specimens of the scleractinian coral Siderastrea spp. Seasonal δ18O and Sr/Ca time series from two Pliocene corals, collected from the Lower Pinecrest Member of the Tamiami Formation in southwest Florida, were used to calculate seawater δ18O variations. Inferred salinity in the Pliocene has a reversed seasonal pattern from that of modern annual salinity variations, and is interpreted to be a response to an increase in winter precipitation, a teleconnection of the Pliocene “Super El Niño.” Concentrations of variance in the typical ENSO frequency band are not apparent above the 95% confidence interval, suggesting that the Pliocene was dominated by a perennial, rather than an intermittent, El Niño-like state. Further geochemical analyses from both Pliocene and Pleistocene Siderastrea spp. corals indicate a high nutrient nearshore marine environment in south Florida. Marine phosphates, inferred from P/Ca analyses, were significantly higher in the Pliocene Tamiami Fm. than in the Early Pleistocene Caloosahatchee and Bermont Fms, and the decline in nutrients preceded local extinction by >0.5 Ma. Additionally, high-resolution P/Ca analyses of an individual coral reveal no evidence of seasonality required by a previously hypothesized upwelling-based nutrient delivery mechanism. The Pliocene nearshore marine environment in southwest Florida was characterized by higher nutrients than in the Pleistocene and precipitation patterns similar to modern El Niño teleconnections.