Research Interests     My research focuses on using sediment cores collected from lake and ocean bottoms to reconstruct past changes in Earth's climate, oceans, and environment.  Although I use many techniques to date and extract paleoenvironmental information from sediment cores, my specialty is the application of stable isotopes  (oxygen, carbon, nitrogen, strontium) to study a broad spectrum of geologic problems including paleoclimatology, paleoceanography, paleolimnology, geochemical cycling, stratigraphy, and diagenesis. Our stable isotope laboratory is well equipped to make most isotopic measurements. Current projects include: Lake Sediment Cores Lake cores are retrieved by our paleolimnology group as part of the FLorida Institute of PaleoEnvironmental Research (FLIPER).  The FLIPER laboratory is part of a new interdisciplinary program at the University of Florida called LUECI (Land Use Environmental Change Institute) whose aim is to study human-climate-environment interactions on a variety of time scales.  FLIPER provides an historical perspective to study how humans interact with their environment, and encompasses a broad range of basic and applied research questions including: human impacts on aquatic ecosystems; deforestation and soil erosion in tropical environments; paleoclimate change including the frequency of extreme events; the role of climate change in the evolution of ancient civilizations; and paleorecords of global change. Current projects include: Climate and Ecologic Change in Mesoamerica during the late Holocene: Implications for Maya Cultural Evolution For an example of this work, see the article entitled "Mayan Meltdown" highlighting our research in Florida Explore magazine.     Paleoenvironmental reconstruction at Angkor Wat, Cambodia The Khmer Civilization occupied the Angkor Wat area between ~800 and 1431 A.D.  This project is a collaborative effort with archaeologist Alan Kolata from the University of Chicago, and seeks to understand the complex interactions among the Khmer and climate-environmental change. For more info, see article in the U. Chicago Chronicle.     Scientific Drilling in Lake Peten-Itza (Guatemala) to reconstruct late Pleistocene climate change during the glacial-to-interglacial cycles in the lowland Neotropics For more information on this work see the Peten-Itza Drilling Project web site.     Speleothems Holocene Paleoclimatology of the Yucatan Peninsula using stalagmites collected from caves. This is a pilot project in collaboration with researchers at the Universidad Autonoma de Yucatan (UADY) and Instituto Nacional de AntropologÌa e Historia (INAH) to produce paleoclimate records by measurement of various proxy indicators (oxygen isotopes, color, lumninescence, etc.) in subaerial and submersed speleothems in Yucatec caves.  The objective is to test some of the paleoclimate inferences based on our lake sediment cores with results obtained from speleothems.          Marine Sediment Cores Most of the marine sediment cores I study are collected by the scientific drilling vessel JOIDES Resolution, operated by the Ocean Drilling Program.  I have sailed on Leg 162 to the high-latitude North Atlantic Ocean and Legs 114, 177, and 208 to the South Atlantic sector of the Southern Ocean.  My recent research has focused on using Leg 177 sediments to reconstruct past climate and oceanographic changes in the Southern Ocean on orbital and suborbital timescales during the late Pleistocene (see Leg 177 synthesis).  In March-April, 2003, sailed on ODP Leg 208 to the Walvis Ridge, South Atlantic. Distribution, timing, and origin of ice rafted detritus events in the South Atlantic sector of the Southern Ocean, and their potential significance for global millennial-scale climate variability.  For more information on this work, see article in Science.       ODP Leg 208 Late Miocene-early Pliocene paleoceanography from ODP Sites 1262 and 1264, Walvis Ridge, South Atlantic.  Strontium, lead, and neodymium isotopes to test the origin of kaolinite at the Paleocene/Eocene .      IODP Expedition 303 From September 25 to November 16, 2004, I sailed as stratigraphic correlator on IODP Expedition 303. In collaboration with J. Channell and J. Stoner, post-cruise research will focus on developing global millennial-scale chronostratigraphic template for the Pleistocene using paleointensity and oxygen isotopes.  In collaboration with O. Romero and U. Roehl, a pilot study will be conducted using the XRF core scanner to measure elemental  concentrations and ratios and assess their use in identifying millennial-to-submillennial lithologic variability.   For more information on this work, see Exp 303 Preliminary Report.       Geoarchaeology I am also interested in geoarchaeological research and have an active project in: Strontium and oxygen isotopes as a tool to trace migrational patterns of ancient humans (Maya) and animals in Mesoamerica.   For more information on this work see article in Journal of Archaeological Science.