by Jonathan Obrist-Farner, Andreas Eckert, Peter M.J. Douglas, Mark Brenner, Jason H. Curtis, Caroline (Cara) Burberry, Liseth Carolina Pérez Alvarado, Carlos A. Jaramillo, Isabelle Domaizon, Alexander Correa Metrio, Nigel J. Wattrus, Paul Mann, Stephen Shangxi Gao, Francisca E. Oboh-Ikuenobe, Tripti Bhattacharya, Susan Zimmerman, Emanuele Lodolo

We seek funding to organize a workshop to discuss the scientific importance and societal significance of drilling and coring the Lake Izabal Basin (LIB), eastern lowland Guatemala. The LIB is an active pull-apart basin that developed along the Polochic Fault (PF), the northern left-lateral fault of the Polochic-Motagua Fault System (PMFS). The PMFS represents the western, onland extension of the North American (NA) and Caribbean (CA) plate boundary. Preliminary analysis of an industry well, reflection seismic profiles, and outcrops indicate that the basin fill is thick and asymmetric, with more than 4 km of sedimentary rocks that started to accumulate in the early Miocene. The proposal has two components. First, we plan to drill and core the PF to a depth ~ 2 km and establish a fault observatory at depth that will result in a better understanding of the loading state of the fault, seismogenic depth, the spatial and temporal evolution of the state of stress, and the fault’s relation to the proposed fault switch activity with the Motagua Fault. Such information is necessary for long term seismic hazard assessment. Presently, seismic hazard assessment has been focused on the Cocos subduction zone. However, the most destructive earthquakes in Guatemalan history occurred along the PMFS. Second, we plan to drill and core five locations along the depocenter migration axis of the LIB, targeting the progradational infill of the basin. Drilling and obtaining overlapping cores along the progradational infill can provide a record spanning more than 1 My (could be as old as 10 My). With such information, we can 1) produce climate records over multiple glacial-interglacial cycles, and potentially into the Pliocene, making LIB a very attractive target for improving our understanding of climate and its changes in the Neotropics; 2) provide a Quaternary record that will allow the estimation of rates of origination, extinction, and migration of species that gave rise to the main vegetation types that occupy the area today; and 3) provide a long record to understand volcanic activity along the Central American volcanic arc.

• The scientific objectives are twofold. The first objective is to drill, log, and core the Polochic Fault at the northern side of the Lake Izabal Basin. The borehole is targeted to a depth of at least 2 km to establish a fault observatory at depth. The borehole and core will enable us to:
• 1) measure the contemporary state of stress,
• 2) measure rock physical properties and,
• 3) install low-noise high-resolution seismometers to determine seismicity and seismogenic depth. The information gained will be used to determine the loading state of the fault and the associated seismic hazard. The second objective is to drill several boreholes to a depth of approximately 500 m targeting the progradational infill of the Lake Izabal Basin. We aim to recover overlapping cores that can provide a temporal record spanning at least 1 My, possibly 5-10 My. The cores will provide information related to:
• 1) climate in the Neotropics over multiple glacial-interglacial cycles,
• 2) the origination, extinction, and migration of species in the area and,
• 3) volcanic activity along the Central American volcanic arc.

Central America, Geohazards, Guatemala, Lake Drilling, Lake Izabal, Libre, Miocene, Paleoclimate, Tectonics

Latitude: 15.5, Longitude: -89.1667