Holocene Climate Variability in Hispaniola: Sedimentary Alkane Evidence of Precipitation during the Terminal Classic Drought
Date of Award
Master of Science
Kelsey Ellis, Chad Lane
Laguna Saladilla (19.656 N, 71.715 W) is a large (220 ha) freshwater lake located near sea level on the north coast of Hispaniola, 2 km south of Monte Cristi National Park in the Dominican Republic, and 1 km east of the international border with Haiti. Results of prior analyses of pollen, microscopic charcoal, mollusk shells, and diatoms in an 8.5-m sediment core from the lake were interpreted to largely indicate shifts in salinity and water depth attributed to relative sea level rise over the middle and late Holocene (Caffrey et al., Paleogeography, Paleoecology, Paleoclimatology 436: 9–32, 2015). Mollusk assemblages indicated saline conditions at 7650 cal yr BP, when sediments contained abundant red mangrove pollen, but freshening over the late Holocene, with the lake becoming brackish at 3500 cal yr BP and transitioning ca. 2500 cal yr BP to its current freshwater condition. Increased charcoal abundance and higher percentages of Amaranthaceae pollen after 2500 cal yr BP indicate increased fires and generally dry climate in coastal north Hispaniola, but detailed climate reconstruction was not possible from the proxies examined. To develop a precipitation record for north coastal Hispaniola, I examined compound-specific hydrogen isotopes in 39 samples covering the last ca. 1700 years at Laguna Saladilla. I also analyzed hydrogen isotopes in samples of bulk sediment covering this same period. Results provided evidence of increased aridity and evapotranspiration/precipitation ratios during the time known as the Terminal Classic Drought. Results complement and extend prior proxy analyses, illustrating the benefits of hydrogen isotopes in the reconstruction of paleoenvironments. My research also tested the correlation of sedimentary bulk hydrogen to compound-specific hydrogen isotopes, showing that bulk hydrogen isotopes did not respond the same controls as the compound-specific record at this site. The correlation of bulk hydrogen isotopes to other proxies at Laguna Saladilla, however, suggest v that it is still a useful proxy for understanding past environments. This research extends upon the work of multiple studies to reconstruct climate changes during the Terminal Classic Drought in the circum-Caribbean region
MacLennan, Elizabeth, "Holocene Climate Variability in Hispaniola: Sedimentary Alkane Evidence of Precipitation during the Terminal Classic Drought. " Master's Thesis, University of Tennessee, 2019.