HR: 0800h
AN: V31B-0497    [Abstracts]
TI: Stratigraphy of the Grande Savane Ignimbrite Sequence, Dominica, Lesser Antilles
AU: * Schneider, S
EM: jssiv@charter.net
AF: Department of Geological Sciences, California State University, San Bernardino, CA 92407, United States
AU: Smith, A L
EM: alsmith@csusb.edu
AF: Department of Geological Sciences, California State University, San Bernardino, CA 92407, United States
AU: Deuerling, K
EM: kdeuer@ufl.edu
AF: Department of Geological Sciences, University of Florida, Gainesville, FL 32611, United States
AU: Killingsworth, N
EM: nlkillingswo@ualr.edu
AF: Department of Earth Sciences, University of Arkansas Little Rock, Little Rock, AR 72204, United States
AU: Daly, G
EM: gedaly@prodigy.net
AF: Department of Geological Sciences, California State University, San Bernardino, CA 92407, United States
AB: The island of Dominica, located in the central part of the Lesser Antilles island arc has eight potentially active volcanoes. One of these, Morne Diablotins, is a composite stratovolcano with several superimposed stratigraphic sequences ranging in age from Pliocene (4-2 Ma) to "Younger" Pleistocene (<1.8 Ma). The most recent major eruptive activity from this volcano was a series of Plinian eruptions that produced ignimbrites that gave dates of >22,000 and >40,000 years B.P. The ignimbrite sequences form four flow fans that reached both the east and west coasts of the island. One of these flow fans, the Grande Savane, on the west coast of the island, also extends off-shore for a distance of at least 14 km as a distinctive submarine fan. Stratigraphical studies of the on- shore deposits that make up this fan indicate an older sequence of block and ash flow deposits, within which occurs a distinctive vulcanian fall deposit. These are overlain, with no evidence of an intervening paleosol, by a sequence of ignimbrites containing welded horizons (ranging in thickness from around 4 m to 16m). The lack of fall deposits beneath the ignimbrites suggest they may have been formed by instantaneous continuous collapse of the eruption column. This whole succession is overlain by a series of planar and dune bedded pumiceous surge deposits with interbedded pumiceous lapilli fall and ash fall deposits, that extend laterally outside of the main area of ignimbrite deposition. Beds within this upper sequence often contain accretionary lapilli and gas cavities suggesting magma-water interaction. The youngest deposits from Morne Diablotins appear to be valley- fill deposits of both ignimbrite and block and ash flow. A comparison of the of the Grande Savane pyroclastic sequence with the Pointe Ronde (west coast) and Londonderry (east coast) pyroclastic flow fans will provide information on the eruptive history of this major Plinian episode.
DE: 8404 Volcanoclastic deposits
DE: 8414 Eruption mechanisms and flow emplacement
DE: 8428 Explosive volcanism
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting