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.
| Identifer | oai:union.ndltd.org:USF/oai:scholarcommons.usf.edu:etd-4862 |
| Date | 17 August 2010 |
| Creators | Sliko, Jennifer Leigh |
| Publisher | Scholar Commons |
| Source Sets | University of South Flordia |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Graduate Theses and Dissertations |
| Rights | default |
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