314-6 Palaeoseasonality in the Pliocene of the North Atlantic

See more from this Division: General Discipline Sessions
See more from this Session: Paleoclimatology/Paleoceanography

Wednesday, 8 October 2008: 2:45 PM
George R. Brown Convention Center, 310BE

Tanya Knowles, Natural History Museum, London, United Kingdom, Alan Haywood, School of Earth and Environment, University of Leeds, Leeds, United Kingdom, Mark Williams, Department of Geology, University of Leicester, Leicester, United Kingdom, Paul Taylor, Department of Palaeontology, Natural History Museum, London, United Kingdom and Beth Okamura, Department of Zoology, Natural History Museum, London, United Kingdom
Abstract:
A number of previous studies have shown that there is an inverse correlation between zooid size in cheilostome bryozoans and ambient water temperature, a relationship which can provide valuable information about the seasonality experienced by fossil bryozoan colonies during their life. A total of 274 colonies of Pliocene cheilostome bryozoans from Panama, the USA (Florida, South Carolina, North Carolina, Virginia) and the UK (Suffolk) provided estimates of the mean annual range of temperature (MART) for the fossil localities. Results show a general increase in seasonality (MART) from low to mid latitudes, as expected. The small MART for Panama (4.4oC) suggests low seasonality in the Caribbean, consistent with the Central American Isthmus being either a shallow sill or nearly closed at this time (3.6-3.5 Ma). The larger than expected MART estimated for the Lower Tamiami Formation of Florida (7.4oC) is suggestive of seasonal upwelling, in agreement with studies on other faunal groups. The mean MART (8.2oC) estimated for Suffolk on the southern edge of the North Sea, combined with the presence of bryozoan genera that today inhabit warm waters, suggests warmer but less seasonal conditions than those observed in the North Sea at the present day (average MART ~12oC). Comparison of MART estimates from bryozoans with outputs from a coupled ocean-atmosphere general circulation model (HadCM3) show that, for most localities, model predicted Pliocene palaeoseasonality is consistent with estimates derived from fossil bryozoa. This is the first study to apply the MART technique to localities spanning a large latitudinal range and demonstrates that the technique is an extremely useful tool for interpreting palaeoseasonality.

See more from this Division: General Discipline Sessions
See more from this Session: Paleoclimatology/Paleoceanography