PALYNOFACIES ANALYSIS AND PALEOENVIRONMENTAL RECONSTRUCTION OF HOLOCENE LACUSTRINE SEDIMENTS, LAKE IZABAL, EASTERN GUATEMALA

Lake sediments provide long and detailed records of climate and environmental changes in the recent past. A 5 m-long core was obtained from the southern shores of Lake Izabal, eastern Guatemala to investigate the climatic and environmental changes in the area through the study of the palynological record. The core contains a sedimentation record of ~ 1,000 years based on extrapolation of five ¹⁴C dates obtained from organic matter throughout the core. The sediments appear to be homogeneous with laminated sandy and silty mud facies that are rich in organic matter, and they have moderate to excellent recovery and good preservation of palynomorphs. Density and magnetic susceptibility scanning and x-radiographs, however, suggest that the core is highly variable with respect to its organic matter content and mineral composition. Eight significant particulate organic matter categories (pollen, spores, amorphous organic matter [AOM], opaques, fungi, algae, structured phytoclasts and degraded phytoclasts) have been identified from 12 kerogen slides and used for palynofacies evaluation. Preliminary results reveal a high ratio of translucent structured and degraded phytoclasts to opaques in the samples. Large structured phytoclast debris dominate the samples from 66 cm to 200 cm while smaller sized degraded phytoclasts are dominant from 233 cm to 500 cm, with the highest level of degradation occurring in the sample at 366 cm. Meanwhile, palynomorph distribution appears to be more uniform. The masking effects of phytoclasts result in lower numbers for palynomorphs throughout the core. Pilot AOM, phytoclasts and palynomorph (APP) ternary plots suggest prevalence of proximal facies, high terrestrial influx, high sedimentation rates, and oxic conditions in the lake. This preliminary interpretation is supported by the dominance of bisaccates in the pollen assemblage, typical of deposition adjacent to land areas with coniferous vegetation. Thus, this study provides insights into past environmental conditions within a modern lacustrine basin in eastern Guatemala.