by David A. Hodell, Flavio Anselmetti, Daniel Raul Ariztegui, Mark Brenner, Jason H. Curtis, Gerald H. Haug, Gerald H. Haug, Judith Ann McKenzie

We propose to use GLAD800 to drill a series of sites in Lake Peten-Itza, northern Guatemala, to recover sedimentary sequences along a depth transect from ~30 m to near the deepest point (~150 m) in the lake. Six primary and four alternative drilling sites have been identified on the basis of two detailed seismic surveys. A sequence stratigraphic approach will be employed to constrain the vertical range of past lake level variations for glacial, interstadial, and interglacial stages during the late Pleistocene. The basal age of the sections to be drilled is not certain but we estimate that sequences should span at least the last several glacial-to-interglacial cycles. The sediment archives and pore waters recovered by drilling will be used to test hypotheses related to three broad scientific themes: 1. Paleoclimatic history of the northern lowland Neotropics on orbital to suborbital time scales emphasizing marine-terrestrial linkages (e.g., Cariaco Basin, Greenland ice cores, etc.). 2. Paleoecology and biogeography of the Maya tropical lowland forest including the history of vegetation change and disturbance by humans, climate change, and fire. 3. Biogeochemical cycling in deep lake sediments emphasizing integrated studies of microbiology, geochemistry (interstitial waters), and mineral authigenesis/diagenesis. The research proposed here will result in the first comprehensive investigation into the microbial ecology and dominant geomicrobiological mediated processes occurring in deep subsurface lacustrine sediments. Science management and drilling operation plans are proposed to successfully achieve both scientific and technical objectives of the project. An international team of research scientists has been assembled to produce a comprehensive suite of paleoenvironmental and biogeochemical measurements on the cores and pore fluids recovered from Lake Peten-Itza.

• A. Paleoclimatic history of the lowland Neotropics on orbital to suborbital time scales emphasizing marine-terrestrial linkages. Recovery of long continuous lacustrine archives from Lake Peten-Itza using GLAD800 will permit a number of hypotheses to be tested related to abrupt variability in temperature and humidity in the lowland Neotropics during the last deglaciation, glacial maximium, MIS 3, and beyond. Comparison of the lacustrine Peten-Itza record (located at 17oN) with the marine record from Cariaco Basin (located at 11oN) will help establish the geographic extent and relevance of abrupt humidity changes in the northern Neotropics. B. Paleoecology and biogeography of the Maya tropical lowland forest including the history of vegetation change and disturbance by humans, climate change, and fire. A long sequence from Peten-Itza will permit comparative study of pollen for the Holocene and older interglacial and glacial periods to assess human and climatic impacts on the tropical lowland forest. How did lowland Neotropical vegetation respond to long-term orbital forcing and abrupt climate change (e..g., Dansgaard-Oeschger cycles) during the late Pleistocene? C. Biogeochemical cycling in deep lake sediments emphasizing integrated studies of microbiology, geochemistry (interstitial waters), and mineral authigenesis/diagenesis. Geomicrobiology constitutes a strong complementary aspect to the other objectives of the Lake Peten-Itza Drilling Project and will constitute one of the first comprehensive investigations into the microbial ecology and dominant geomicrobiologically mediated processes occurring in deep subsurface lacustrine sediments. This proposed research will complement efforts to characterize the deep marine biosphere program by the Integrated Ocean Drilling Program.

Climate Change, GLAD, GLAD800, Global Environment, Guatemala, ICDP-2004/03, Lake Drilling, Maya Clay, Neotropics, Paleoclimatology, Paleoecology, PETEN-ITZA, PISDP

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