D. Clay Kelly
Micropaleontology and Paleoceanography
Office: A462 Weeks Hall
Attributes such as relatively complete fossil record, occurrences in statistically abundant numbers, and readily quantifiable shell shapes uniquely qualify planktonic foraminifera for a spate of evolutionary and paleoceanographic studies. In addition, the geochemical info encoded within their calcite shells has transformed these microscopic, marine protists into standard paleoceanographic tools. I am building a diverse reasearch program designed to capitalize on the many advantages offered by fossil and living foraminifera. To this end, I have been an active participant in the Ocean Drilling Program and am employing such investigative techniques as faunal studies, stable isotopes, and morphometric analysis to better understand the interplay between ocean/climate change and biotic evolution. Some of our current research interests are: (1) Response of Marine Microbiota to Past Global Warming: The Paleocene/Eocene Thermal Maximum (PETM) was a shortlived pulse of global warming that occurred 55.5 Ma. It is characterized by sudden warming of oceanic deepwaters and high-latitude sea surface temperatures, a mass extinction among cosmopolitan deep-sea benthic foraminifera, and a transient perturbation to the global carbon cycle. (2) Microbiotic Evolution/Extinction in the Pelagic Realm: Several clades of Cenozoic planktonic foraminifera suffered a marked decrease in shell size prior to extinction. Hence, relict populations of these lineages consist of diminutive species. Recognition of this stress-induced "terminal dwarfing" has major implications for reconstructing foram phylogenies, clade longevity, and relating biotic extinction to ocean/climate change. (3) Oligocene Braarudosphaera Deposits: We are researching recurrent blooms of nearshore nannoplankton in open, blue-water environments of the South Atlantic. The recurrence of these exotic nannofossil deposits is suggestive of orbital forcing. (4) Quaternary History of Blake Ridge (N. Atlantic) and the Possible Role of Methane Hydrate Dissociation: This ongoing collaboration with the U.S.G.S. is evaluating the hypothesis that a large depression (38 X 18 km) on the seafloor was formed by a massive release of methane gas. (5) Late Miocene Carbon Isotope Shift (~6.1 Ma): This event represents a fundamental change in global carbon cycling. It is evidenced by carbon isotopic increases in terrestrial materials (e.g., mammal teeth, pedogenic carbonates) and carbon isotopic decreases in marine carbonates. We are using deep-sea cores from the Tasman Sea to investigate the timing of this event, as well as documenting the sedimentological and microbiotic responses.
I teach courses that range from the introductory to graduate levels. These classes include: Survey of Oceanography, Geobiology, Micropaleontology, and Paleoceanography.