16 Undergraduate Research (Posters)

Thursday, 20 March 2008
8:00 AM - 12:00 PM

ORIGIN OF A VOLCANIC MEGABRECCIA ON THE EASTERN COAST OF THE ISLAND OF DOMINICA

Paper number: 16-17
Program: THEME SESSIONS
Time: 8:00 AM – 12:00 PM

Authors

  • R.V. Garcia Presenting Author
    New Mexico State University, Las Cruces, NM
  • A.L. Smith
    California State Univ, San Bernardino, CA
  • Joan Fryxell
    California State Univ - San Bernardino Dept Geological Sciences, San Bernardino, CA
  • G.E. Daly
    California State Univ, San Bernardino, CA
  • K.M. Deuerling
    University of Florida, Gainesville, FL

Abstract

Classifying the type of volcanic megabreccia that is present on the east coast of the island of Dominica is a difficult task due to the limited exposures of bedrock. The most visible exposures can be found at the sea cliffs. However, they are highly inaccessible due to strong surf, limited beaches and steep topography. Therefore, the majority of the data is taken from one section of the sea cliffs that was accessible by foot. Photographs taken by another student this past summer have also been useful in understanding the magnitude of the megabreccia.

There are various megabreccias on the island, ranging from lahars to block and ash flows. The characteristics of the outcrop in question differ from those of the other megabreccias on the island. The clast sizes are much larger, averaging from 60cm to 600cm. The thin sections of the samples taken provide evidence of a drier flow. There are also distinctive jigsaw cracks in some of the larger clasts that are not seen in the other megabreccias. After comparing the different types of megabreccias, the most analogous is a debris avalanche. Geochemical data from the samples was also compared to that of the Grande Soufriere Hills volcanic center with the intention of pinpointing a source for this deposit. Initial findings suggest that the megabreccia can be classified as a debris avalanche possibly originating from the Grande Soufriere Hills volcanic center.