A Multiproxy Record of Late Holocene Environmental Change in Arancibia, Costa Rica

Authors: Sally P. Horn*, University Of Tennessee, Erik N Johanson, Florida Atlantic University , Mauricio Murillo Herrera, University of Costa Rica , Chad S Lane, University of North Carolina Wilmington, Taber Friedel, Florida Atlantic University , Morgan Steckler , University of Tennessee, Mathew S Boehm, University of Tennessee , Qiusheng Wu, University of Tennessee
Topics: Paleoenvironmental Change
Keywords: Central America, lake sediments, climate change, landslides, human-environment interactions
Session Type: Virtual Paper
Day: 4/7/2021
Start / End Time: 9:35 AM / 10:50 AM
Room: Virtual 40
Presentation File: No File Uploaded

Laguna Arancibia is a small (1.5 ha), moderately deep (6.2 m) lake located at ca. 1250 meters elevation on the Pacific slope of the Cordillera de Tilarán in Costa Rica. The lake occupies a closed basin in an area of frequent landslides and probably formed from a slide or slump. In 2019, we recovered parallel cores from the deepest part of the basin for paleoenvironmental analyses. Radiocarbon dates indicate the profile extends to 1400 cal yr BP. Shifts in mineral content, magnetic susceptibility, and stable carbon isotope ratios indicate changes in watershed conditions that likely reflect both agricultural land use and repeated landslides near the lake. Three intervals of more positive δ13C values suggest enhanced agricultural activity from 1410–1310 cal yr BP, 825–790 cal yr BP, and 550–515 cal yr BP. These first two intervals bracket the Terminal Classic Drought between 1200 and 850 cal yr BP. This interval of regional drought in the circum-Caribbean may have been dry at Laguna Arancibia, leading to a reduction in agricultural activity. The Spanish Conquest of Costa Rica may have reduced or eliminated agriculture in the basin around 500 years ago. Ongoing analyses of pollen grains, diatoms, charcoal fragments, and hydrogen isotopes in leaf waxes will test these interpretations. We also plan additional sediment coring closer to the edge of the lake, where we may be able to recover deeper lake sediments, if present, and archaeological investigations at the lake, to enable comparison of trajectories of social and environmental change.

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