Pliocene marine climates in southwest Florida: Just as seasonal but cooler than today

Conference · Mon Mar 01 00:00:00 EST 1993 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:6119536

Jones, D S ^[1]

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1. Univ. of Florida, Gainesville, FL (United States). Florida Museum of Natural History

Despite climatic models for the northern hemisphere which suggests a warm Middle Pliocene with reduced polar ice volumes, oxygen isotopic analyses of mollusks from shallow-marine strata of the Pliocene Pinecrest Beds near Sarasota, FL yield paleotemperatures cooler than those which characterize the region today. Shells from well-preserved, infaunal (Mercenaria campechiensis (Mc)) and epifaunal (Carolinapecten eboreus) bivalves as well as one gastropod (Turritella apicalis) were sampled in detail by high-resolution, sequential, micro-sampling techniques. Specimens were collected from the central portion of Unit 7, the main shell bed at both the APAC and Quality Aggregates shell pits, dated at 3.0 [+-] 0.5 Ma. Modern shells of Mc from two localities on the FL coast, Charlotte Harbor to the south and Suwannee Reef to the north, were also sampled for comparison with temperature data collected at monthly intervals throughout the year. [delta][sup 18]O cycles in all specimens of Mc correspond with documented annual shell growth increments, providing a temporal framework for sample interpretation. In modern shells, the [delta][sup 18]O records faithfully track the annual pattern of measured marine temperature change. In Pliocene shells, the amplitudes of [delta][sup 18]O cycles in Mc indicate a comparable degree of seasonality (ca. 8-9 C); however, calculations suggest paleotemperatures were cooler than present in both summer and winter by several C. Results from T. apicalis are similar whereas those from the pectinid, C. eboreus, suggest seasonal migratory behavior may complicate interpretation of the isotopic signature. [delta][sup 18]O values from all the fossil mollusks also indicate slightly cooler paleotemperatures than estimated from ostracode faunal studies of the same bed. Conventional views which attribute the tremendous species richness and abundance of these Pliocene shell beds to warm, equable climates apparently need reevaluation.

• OSTI ID: 6119536
• Report Number(s): CONF-9304188-; CODEN: GAAPBC
• Journal Information: Geological Society of America, Abstracts with Programs; (United States), Vol. 25:4; Conference: 42. annual Geological Society of America (GSA) Southeastern Section meeting, Tallahassee, FL (United States), 1-2 Apr 1993; ISSN 0016-7592
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
FLORIDA
PALEOTEMPERATURE
PLIOCENE EPOCH
MOLLUSCS
OXYGEN 18
PALEOCLIMATOLOGY
PALEONTOLOGY
SEASONAL VARIATIONS
SEDIMENTARY BASINS
ANIMALS
AQUATIC ORGANISMS
CENOZOIC ERA
DEVELOPED COUNTRIES
EVEN-EVEN NUCLEI
GEOLOGIC AGES
GEOLOGIC STRUCTURES
INVERTEBRATES
ISOTOPES
LIGHT NUCLEI
NORTH AMERICA
NUCLEI
OXYGEN ISOTOPES
STABLE ISOTOPES
TERTIARY PERIOD
USA
VARIATIONS
580000* - Geosciences