Lake Peten Itza

Lake Peten Itza, a 165 m deep lake in northern Guatemala, is the deepest lake in the lowlands of Central America. Because of its great depth, it held water during full glacial periods of the Pleistocene when arid climate persisted in the region. The objective of the PISDP was to recover complete lacustrine sequences to study climate variability in lowland Central America during the late Pleistocene and Holocene on time scales ranging from decades to millennia.

Drilling was conducted by DOSECC using their Global Lake Drilling (GLAD800) drill rig, mounted on the “superbarge” R/V Kerry Kelts. Tools used to collect core included DOSECC’s Hydraulic Piston Coring (HPC) system and extended-nose bit coring tools. Core recovery was 85-95%. Between Feb 3 and March 11, 2006, we recovered 1327 m of sediment at seven sites ranging in water depth from 30 to 150 m. Multiple holes were drilled at most sites and cores were logged for density, p-wave velocity, and magnetic susceptibility using the ICDP GEOTEK core logger. Complete stratigraphic recovery was verified in near-real time using Splicer, an IODP software program that aligns features among holes using core logging data.

Smear-slide analysis of core catcher samples indicates similar lithostratigraphies among deep-water sites in the central basin. All cores show an abrupt transition from Late Glacial dense gypsum sand interbedded with silty clays, to Holocene gray clay, representing a shift from arid glacial to moist early Holocene conditions. High-frequency variations in bulk density occur throughout the last glacial period and can be correlated among sites in the deep basin. Below the gypsiferous interval is a thick sequence of diatom-rich gray clay. Radiocarbon and U/Th dating are under way and will enable temporal comparison with other proxy climate records from the region (e.g., Cariaco Basin) and high-latitude ice cores. Our aim is to decipher the history of the northern hemisphere Neotropical hydrologic cycle, its relation to changes in the position of the Atlantic Intertropical Convergence Zone (ITCZ), and linkages to climate variability in the high-latitude North Atlantic. We will test the hypothesis that changes in precipitation in the lowland Neotropics were largely related to meriodinal displacements in the mean position of the Atlantic ITCZ on orbital and suborbital time scales.

Downhole logging was done by the ICDP Operational Support Group at five sites using slimhole tools, which will permit correlation of core and downhole logs and their integration with seismic profiles. Samples from at least one hole at each site were squeezed for pore water geochemical analysis, and ephemeral properties such as alkalinity and pH were measured on site. One unexpected finding was the occurrence of elemental sulfur in several cores. An integrated program of subsurface microbiology and pore water geochemistry will be undertaken to study processes of mineral authigenesis and diagenesis.

David Hodell, Flavio Anselmetti, Daniel Ariztegui, Mark Brenner, Jason Curtis, and members of the Peten Itza Scientific Drilling Party. Additional input from David Zur, DOSECC

Download the Spanish language Lake Peten Itza project flyer here.