Skip Links

USGS - science for a changing world

U.S. Geological Survey Open-File Report 2009-1228

Logs of Paleoseismic Excavations across the Central Range Fault, Trinidad

By Christopher J. Crosby, Carol S. Prentice, John Weber, and Daniel Ragona

Summary

Thumbnail of and link to plate 1 PDF (90 MB)

This publication makes available maps and trench logs associated with studies of the Central Range Fault, part of the South American-Caribbean plate boundary in Trinidad. Our studies were conducted in 2001 and 2002.

We mapped geomorphic features indicative of active faulting along the right-lateral, Central Range Fault, part of the South American-Caribbean plate boundary in Trinidad. We excavated trenches at two sites, the Samlalsingh and Tabaquite sites. At the Samlalsingh site, sediments deposited after the most recent fault movement bury the fault, and the exact location of the fault was unknown until we exposed it in our excavations. At this site, we excavated a total of eleven trenches, six of which exposed the fault. The trenches exposed fluvial sediments deposited over a strath terrace developed on Miocene bedrock units.

We cleaned the walls of the excavations, gridded the walls with either 1 m X 1 m or 1 m X 0.5 m nail and string grid, and logged the walls in detail at a scale of 1:20. Additionally, we described the different sedimentary units in the field, incorporating these descriptions into our trench logs. We mapped the locations of the trenches using a tape and compass.

Our field logs were scanned, and unit contacts were traced in Adobe Illustrator. The final drafted logs of all the trenches are presented here, along with photographs showing important relations among faults and Holocene sedimentary deposits. Logs of south walls were reversed in Illustrator, so that all logs are drafted with the view direction to the north. We collected samples of various materials exposed in the trench walls, including charcoal samples for radiocarbon dating from both faulted and unfaulted deposits. The locations of all samples collected are shown on the logs. The ages of seventeen of the charcoal samples submitted for radiocarbon analysis at the University of Arizona Accelerator Mass Spectrometry Laboratory in Tucson, Ariz., are given in Table 1. Samples found in Table 1 are shown in red on the trench logs. All radiocarbon ages are calibrated and given with 2 standard deviation age ranges.

Our studies suggest that the Central Range Fault is a Holocene fault capable of producing damaging earthquakes in Trinidad.

Last modified January 5, 2010
First posted December 22, 2009

  • This report is available only on the Web.

For additional information:
Contact Information, Earthquake Hazards Program, Northern California
U.S. Geological Survey
345 Middlefield Road, MS 977
Menlo Park, California 94025
http://quake.wr.usgs.gov/

This report is presented in Portable Document Format (PDF); the latest version of Adobe Reader or similar software is required to view it. Download the latest version of Adobe Reader, free of charge.


Suggested citation:

Crosby, Christopher J., Prentice, Carol S., Weber, John, and Ragona, Daniel, 2009, Logs of paleoseismic excavations across the Central Range Fault, Trinidad: U.S. Geological Survey Open-File Report 2009-1228, 2 plates.




Accessibility FOIA Privacy Policies and Notices

Take Pride in America logo USA.gov logo U.S. Department of the Interior | U.S. Geological Survey
URL: http:// pubs.usgs.gov /of/2009/1228/index.html
Page Contact Information: USGS Publications Team
Page Last Modified: Wednesday, 07-Dec-2016 22:13:44 EST