← Back to Sessions

Age Dating and Sedimentology of a Pre-Colombian Tsunami Deposit, Northwest Puerto Rico

Description: 

Written and geologic evidence show that within the last 500 years most tsunamis impacting Puerto Rico have been generated by local intraplate earthquakes or by earthquakes in the far field across the Atlantic, yet it is unclear whether the Puerto Rico Trench has produced great earthquakes and tsunamis in the Holocene. Multiple prehistoric tsunami deposits have been found along the northern islands within the lesser Antilles arc with ages suggesting a pre-Colombian event 500 to 800 years ago. This study extends evidence of this possible pre-Colombian event farther west along the Puerto Rico Trench, to East Bajura, a coastal mangrove pond in northwest Puerto Rico. At East Bajura pond, we observed a distinct sandy deposit at more than 30 coring locations. We used a Rotating X-Ray Computed Tomography (RXCT) system to scan 19 sediment cores at 130-micron resolution. We utilized the 3D imagery to interpret relative sediment grain size, identify subtle differences between sedimentological units, examine sedimentary structures, and look for sections with minimal bioturbation. Based on the density analysis, we selected a representative core with distinct stratigraphy and abundant organic content for radiocarbon analysis. To constrain the timing of sand deposition, we selected seven samples of semi-translucent mangrove rootlets and wood taken from above and below the deposit for radiocarbon analysis. The deposit age is determined using an event-free Bayesian age-depth model in Oxcal, which indicates deposition of the deposit in East Bajura occurred between 1470 and 1530 CE, which is consistent with ages of tsunami deposits in the lesser Antilles. Further analysis will focus on developing the age-depth model and applying similar age dating and lithostratigraphic analyses on a deeper and thicker sand deposit observed in the East Bajura stratigraphic archive. Ultimately, this work aims to extend the pre-historic record of tsunami events along the northern coast of Puerto Rico.

Session: Active Faults in the Caribbean and Central America [Poster]

Type: Poster

Date: 4/20/2023

Presentation Time: 08:00 AM (local time)

Presenting Author: Bruce Jaffe

Student Presenter: No

Invited Presentation: 

Authors