The Lake Petén-Itzá Scientific Drilling Project (Proyecto Paleoambiental Lago Petén-Itzá)
Mark Brenner University of Florida
Lake Petén-Itzá lies at 110 masl in the lowlands of northern Guatemala. The lake has a surface area of ~100 km2 and a maximum depth ~165 m. It was targeted for drilling because it may be the only lake in lowland Central America to have held
water and preserved a record of paleoclimate/paleoenvironment changes through the last Glacial. Plans to drill Lake Petén-Itzá were formulated in the late 1990s. A joint Swiss-US team conducted seismic-imaging campaigns in 1999 (3 kHz pinger) and 2002 (airgun) that demonstrated the basin possessed thick lacustrine deposits. The seismic images were used to identify 6 primary and 4 alternate drill sites. Preliminary coring of Holocene sections was done in 2002 using a Kullenberg gravity corer. With seismic images (Anselmetti et al. 2006) and Holocene cores in hand (Hillisheim et al. 2005), a planning workshop supported by the International Continental Scientific Drilling Program, was convened in Flores, Guatemala in 2003. Scientists from 12 countries attended the meeting.
The Lake Petén-Itzá Scientific Drilling Project (PISDP) was undertaken to achieve three major objectives:
Develop a high-resolution paleoclimate reconstruction for the lowland neotropics extending well into, and perhaps beyond the last Glacial. Explore correlations between climate changes at this tropical, low-altitude site, and marine/terrestrial paleoclimate records from tropical and extra-tropical regions (e.g. Cariaco Basin, Greenland)
Investigate shifts in vegetation that accompanied climate fluctuations in the region during glacial and interglacial times. Evaluate responses of vegetation to natural (climate) forcing and later Maya land clearance
Study sediment biogeochemistry to gain a better understanding of mineral production in the water column and sediments of the lake, in response to changing hydrologic conditions.
Figure 1 – Location of Lake Petén-Itzá, Guatemala.
Drilling was conducted by DOSECC in Lake Petén-Itzá between 3 February and 11 March, 2006 using the Global Lakes Drilling (GLAD800) rig mounted on the “superbarge” R/V Kerry Kelts. More than 60 people, including drillers, scientists, and students, participated in the field effort. Cores were retrieved at 7 sites in the lake, ranging in water depth from 30 to 150 m. A single core was collected at the shallow site (30 m), whereas three parallel holes were drilled at five sites, and five cores were taken at site PI-2 (water depth 54 m). In total, 1327 m of sediment were collected, with recovery at each site averaging between 86.3 and 94.9%.
Retrieved cores were analyzed in the field for magnetic susceptibility and gamma ray attenuation (density), using a multi-sensor core logger. Cores were ultimately shipped to the LacCore facility at the University of Minnesota for storage. Sampling parties visited Minneapolis in the summers of 2006 and 2007 to sample the cores and begin analyses. Composite Core PI-6 extended to 75.9 m below the lake floor and was chosen as the first candidate for study. The core was re-measured for magnetic susceptibility and gamma ray density at high-resolution. Next, core sections were opened, split, and imaged digitally, prior to sampling.
Core PI-6 represents ~85,000 years of continuous sediment accumulation, as determined from AMS 14C dating and tephra layers of known age. Pleistocene-age deposits possess alternating clay- and gypsum-rich sediments that reflect relatively wetter and drier conditions, respectively. Clay sections display higher magnetic susceptibility and lower density than gypsum deposits. Wetter times in lowland Central America were associated with interstadials and drier periods with stadials. Carbonate clays dominate the record from about 85 to 48 ka, suggesting relatively moist conditions. From 48 to 23 ka, the record displays wet-dry (clay-gypsum) alternations that resemble temperature inferences from Greenland ice cores and North Atlantic marine sediment cores, as well as rainfall reconstructions from the Cariaco Basin. A thick clay layer associated with the Last Glacial Maximum (LGM) chronozone (21+/-2 ka) indicates relatively moist conditions. This finding is at odds with previous inferences for arid LGM conditions in lowland Guatemala. The deglacial was marked by alternating moist and very dry conditions, with abundant gypsum precipitated from 18.0-14.7 ka, and 12.8-10.3 ka. Holocene conditions at 10.3 ka reflect increased rainfall and onset of more organic-rich sediment deposition.
Figure 2 – Drilling crew aboard the R/V Kerry Kelts (photo courtesy of ICDP).
Pollen analyses suggest 5 °C cooling at the LGM, at which time pine and oak co-existed with tropical forest elements in the region. Pollen data support geochemical analyses in pointing to times in the deglacial as the periods of greatest aridity. Changes in temperature/moisture availability throughout the deglacial (18-10.3 ka) are also being documented using stable oxygen isotope measurements on ostracod shells from the core.
Cores collected by the PISDP are providing the first well-dated, high-resolution records of Pleistocene climate and environmental change in lowland Central America. In addition to the preliminary information gleaned from core PI-6, investigation of ash layers in cores from site 7 suggest a >200 ka record was retrieved.
Findings of the PISDP of interest to a broad range of scientists, including paleoclimatologists, climate modelers, palynologists, biogeographers, sedimentologists, microbiologists, paleoecologists, and others. The public should also take interest, as the high-resolution paleoclimate records from the PISDP will provide information on the range of natural climate variability in the lowland neotropics prior to human impact.
Anselmetti, F.S., D. Ariztegui, D.A. Hodell, A. Gilli, M.B. Hillesheim, M. Brenner, and J.A. McKenzie. 2006. Late Quaternary climate-induced lake level variations in Lake Petén Itzá, Guatemala, inferred from seismic stratigraphic analysis. Palaeogeography, Palaeoclimatology, Palaeoecology 230:52-69.
Bush, M.B., Correa-Metrio, A., Hodell, D.A., Brenner, M., Anselmetti, F.S., Ariztegui, D., Mueller, A.D., Curtis, J.H., Grzesik, D., Burton, C., and Gilli, A. In press. The Last Glacial Maximum in lowland Central America. In: F. Vimeux, F. Sylvestre, and M. Khodri (Eds.), Past Climate Variability from the Last Glacial Maximum to the Holocene in South America and Surrounding Regions. Developments in Paleoenvironmental Research (DPER) Series. Springer, Dordrecht, Berlin, Heidelberg, New York.
Escobar, J., D.A. Hodell, M. Brenner, J.H. Curtis. In prep. Climate change in the northern neotropics during the last deglaciation. Geology.
Hillesheim, M.B., D.A. Hodell, B.W. Leyden, M. Brenner, J.H. Curtis, F.S. Anselmetti, D. Ariztegui, D.G. Buck, T.P. Guilderson, M.F. Rosenmeier, and D.W. Schnurrenberger. 2005. Lowland neotropical climate change during the late deglacial and early Holocene. Journal of Quaternary Science 20:363-376.
Hodell, D.A., Anselmetti, F.S., Ariztegui, D., Brenner, M., Curtis, J.H., Gilli, A., Grzesik, D.A., Guilderson, T.J., Muller, A.D., Bush, M.B., Correa-Metrio, Y.A., Escobar, J., and Kutterolf, S. 2008. An 85-ka Record of climate change in lowland Central America. Quaternary Science Reviews. 27:1152-1165.
Hodell, D., Anselmetti, F., Brenner, M., Ariztegui, D., and the PISDP Scientific Party. 2006. The Lake Petén-Itzá Scientific Drilling Project (PISDP). Scientific Drilling 3: 25-29.
Hodell, D., Anselmetti, F.S., Ariztegui, D. Brenner, M., Curtis. J., and the PISDP Scientific Party. 2006. Preliminary results of the Lake Petén-Itzá Scientific Drilling Project. DOSECC News 4:5-6.
Hodell, D., Anselmetti, F.S., Ariztegui, D. Brenner, M., Curtis. J., and the PISDP Scientific Party. 2006. 1.3 km of sediment recovered by the Lake Petén-Itzá Scientific Drilling Project. DOSECC News 4:1-2.
Mueller, Andreas D.. 2009. Late Quaternary Environmental Change in the Lowland Neotropics: The Petén-Itzá Scientific Drilling Project, Guatemala. PhD Dissertation ETH No. 18349.
Anselmetti, F.; Hodell, D.; Ariztegui, D.; Brenner, M.; Curtis, J.; Escobar, J.; Gilli, A.; Grzesik, D.; Kutterolf, S.; Mueller, A.D. 2008. The Peten Itza Scientific Drilling Project: A 200-ka record of climate change in lowland Central America. International Geological Congress. Oslo, Norway. August 2008.
Brenner, M., Hodell, D.A., Curtis, J.H., Escobar, J., Anselmetti, F.S., Ariztegui, D., Muller, A.D., Grzesik, D.A. 2008. Proyecto Paleoambiental Lago Petén-Itzá: nuevas perspectivas sobre el paleoambiente y paleoclima de Centroamerica. I Congreso Nacional de Cienagas y Lagunas. Medellin, Colombia. Sept 2008.
Escobar, J., Hodell, D.A., Anselmetti, F.S., Ariztegui, D., Brenner, M., Curtis, J.H., Gilli, A., Grzesik, D.A., Guilderson, T.J., Muller, A.D., Bush, M.B., Correa-Metrio, Y.A., Kutterolf, S. 2008. An 85-ka paleoclimate record from lowland Central America. Joint Assembly of the American Geophysical Union (AGU). Fort Lauderdale, Florida. May 2008.
Escobar, J., Hodell, D.A., Brenner, M., Curtis, J.H., Gilli, A., Anselmetti, F.S., Ariztegui, D., Grzesik, D.A., Mueller, A.D. 2008. Paleoclimate of lowland Central America during the last deglaciation. European Geophysical Union (EGU). Vienna, Austria. April 2008.
Hodell, D., Anselmetti, F., Ariztegui, D., Brenner, M., Curtis, J., Escobar, J., Gilli, A., Grzesik, D., Kutterolf, S., Mueller, A.D. 2008. The Petén-Itzá Scientific Drilling Project: A 200-ka record of climate change in lowland Central America. European Geophysical Union (EGU). Vienna, Austria. April 2008.