18 Sep (GEOL) Jonathan Obrist-Farner, Paleolimnology

Jonathan Obrist-Farner, Missouri Science and Technology University

Title: Lessons from the past that inform our future: A sedimentologist perspective on tectonics, climate and paleoenvironmental change

Time: Thu, 18 Sep, 4:30pm

Location: Exploratory 1309 and via Zoom (for link, email lhinnov@gmu.edu)

Host: Linda Hinnov

ABSTRACT: As Earth’s atmosphere warms and human populations grow, more people are becoming vulnerable to both natural and human-induced disasters. This is especially true in Central America, where a rapidly expanding population faces climate extremes and a wide range of geological hazards. In this talk, I will synthesize nine years of sedimentological and paleolimnological research in western Central America that has helped us address some of these challenges. In the first part, I will show how the recent sedimentological record of lakes has been used to reconstruct past tectonic activity along the North American and Caribbean plate boundary. We will examine six lakes situated along this boundary and explore how the catastrophic 1976 Mw 7.5 Motagua earthquake impacted them. By combining documentation of destruction with sedimentary evidence, we were able to understand how the asymmetric distribution of seismic energy during the event influenced not only the lakes but also the broader pattern of destruction. This work provides crucial insight into how lakes respond to recent earthquakes, enabling us to calibrate their records and use them to investigate the paleoseismic history of the region, including how often the boundary ruptures in large earthquakes. The second part of the talk will focus on how our work laid the foundation for the Lake Izabal Basin Research Endeavor (LIBRE) International Continental Scientific Drilling Program. The project aims to establish a seismic observatory along the North American and Caribbean plate boundary and to recover long sediment cores from the deep basin. Analyses of seismicity near the Lake Izabal Basin, combined with industry seismic data, well logs, outcrops, and Holocene sediment cores, have allowed us to reconstruct the basin’s infill history and its tectonic evolution. Outcrop observations and seismic interpretations suggest the basin preserves a sedimentary record spanning several million years. Radiocarbon-dated sediment cores from Lake Izabal, which lies on the basin’s eastern side, provide a first glimpse into this record, revealing evidence of Holocene hydroclimate change, sea-level shifts, and ecosystem dynamics in the northern Neotropics. Future drilling through LIBRE will extend this record back eight million years, offering unprecedented insight into Earth’s history while also improving our ability to assess seismic risk in the region.