THE LAKE IZABAL BASIN RESEARCH ENDEAVOR INTERNATIONAL CONTINENTAL SCIENTIFIC DRILLING PROJECT (Invited Presentation)

The Lake Izabal Basin Research Endeavor (LIBRE) International Continental Scientific Drilling Program (ICDP) project in eastern Guatemala aims at establishing a seismic observatory along the North American (NA) and Caribbean (CA) plate boundary and at obtaining long sediment cores from the deep basin. Here I will synthesize 8 years of work that allowed us to successfully establish the LIBRE ICDP project. The Lake Izabal Basin is a pull-apart depression that developed due to left-lateral displacement along the Polochic Fault, one of the four major strike-slip faults that make up the NA-CA plate boundary in Guatemala. The basin is currently bounded by the northern and southern Polochic faults, with the latter being the most seismically active of the two faults. The basin infill in the east is tectonically complex relative to the western side due to a bend along the northern Polochic Fault, resulting in faulting, folding, and uplift of some of the oldest basin deposits. Outcrop observations suggest that these sedimentary units are ~12 My old based on CA-TIMS ages from a volcanic tephra found within fluvial and lacustrine deposits. Seismic stratigraphic analysis, in combination with information from an industry well (Colorado-1), indicate that the basin is ~1.5 km deep in the east and ~5 km deep in the west and that its depocenter progressively shifted from the Miocene to the present. Well logs, in combination with X-ray fluorescence data obtained from Colorado-1 well cuttings, suggest that sediment composition is mainly influenced by local tectonics, especially along the eastern side of the basin with the uplift of the Mico Mountains. Marine incursions and hydroclimate changes appear to also influence sedimentation, with the latest major incursion occurring at ~8.3 ka. Holocene sediment cores have also provided supporting evidence for deep drilling, revealing interesting changes in biogeochemical cycles and ecosystems function in Lake Izabal. Future drilling through LIBRE will allow us to continue to learn and assess seismic risk in the region and will provide us with an unprecedented sediment record covering the last 8 million years of Earth’s history.