A 9200-YEAR PALYNOLOGICAL RECORD FROM HOLOCENE SEDIMENTS IN LAKE IZABAL, EASTERN GUATEMALA

A 7.6-m long core from Lake Izabal in eastern Guatemala contains well-preserved palynomorphs that can be used to reconstruct vegetation changes in Neotropical areas. Thirty-nine palynomorph samples spanning approximately 9.2 ka BP, based on extrapolation of six AMS ¹⁴C dates of woody fragments, were analyzed for pollen and spores, which are widely considered good proxies for paleoecological reconstruction. The preservation potential, abundance, and diversity of these palynomorphs in sediments are controlled by factors such as vegetation, climate, transporting agent, and depositional and burial history. Initial analysis reveals that the total palynomorph assemblage is dominated by different types of the gymnospermous bisaccate pollen (mostly Pinus; >40%), followed by forest taxa (Quercus, Myricaceae, Palmae, Malvaceae, etc.). The forest taxa are abundant and diverse at 5.0-7.6 m depth, suggesting that warm and humid conditions probably favored forest expansion 4500-9200 years BP. This depth interval is also characterized by abundant and well-preserved spores that are indicative of proximity to provenance. The interval from 3.6-5.0 m (3000-4500 years BP) is considered transitional due to a mixed assemblage of forest and disturbance vegetation taxa. From 0-3.5 m (<3000 years BP), disturbance taxa represented mostly by Poaceae and Asteraceae are abundant and diverse in the sediment. It is possible that these disturbance taxa record either drier conditions or pervasive cultivation by humans. Inferences from this paleoecological study will be compared with other proxy records and climate models in the northern Neotropics to reconstruct past vegetation patterns relative to paleoenvironmental variations that impacted Guatemala and other parts of the region.

Keywords: Lake Izabal, Guatemala, pollen, paleoecology, Neotropics