ASSESSMENT OF LAKE IZABAL BASIN'S SEDIMENTARY SEQUENCES USING SEISMIC STRATIGRAPHY AND PETROGRAPHIC ANALYSIS: INSIGHTS INTO PROVENANCE, PALEOCLIMATE AND TECTONIC CHANGE

The Lake Izabal Basin (LIB) in eastern Guatemala, located along the North American and Caribbean plate boundary, was initiated by strike-slip tectonics in the mid-Miocene and contains one of the longest continental records to date from the northern Neotropics. We provide an assessment of the sedimentary sequences of the basin using seismic stratigraphic analysis of 10 seismic lines and X-ray fluorescence data from 278 well cutting samples from an industry well that drilled 1400 m of the basin’s infill. We used source discriminant diagrams, elemental composition, elemental ratios, and principal component analysis (PCA) to infer provenance, and changes in erosion, lake water chemistry and lake productivity. Seismic stratigraphic analysis indicates that the basin opened as a half graben structure, with progressive westward migration of the basin’s depocenter in response to left-lateral displacement of the Polochic Fault. We correlate two major seismic surfaces on the eastern side of the basin with stratigraphic information from the Colorado-1 well. These surfaces record lateral changes in depositional characteristics, most likely related to lake level drawdown or tectonic changes in the basin (source uplift). Source discriminant diagrams suggest that sediments were likely derived from a quartz-rich sedimentary source. Results from PCA analysis suggest that elements associated with erosion increase from the mid-Miocene to the mid-Pliocene and then decrease to the present, likely linked to regional tectonics influence on sediment supply through time. On the other hand, higher variability is observed in elements and elemental ratios related to lake water chemistry and productivity changes, which may reflect either marine incursions or hydroclimatic changes through time. These results provide insights on provenance, paleoenvironmental, tectonic, and paleoclimatic changes in the basin and their potential links to long-term changes in sea-level, regional hydroclimate, and tectonics along a major tectonic plate boundary.

Keywords: Basin evolution, Provenance, Paleoclimate, Paleoenvironment, Hydroclimate