HR: 17:00h
AN: V52G-05    [PDF]
TI: Evolution of a Large-Volume Explosive Vent-Complex at the Base of the Karoo LIP: Sterkspruit Complex, South Africa
AU: * McClintock, M K
EM: murraym@soest.hawaii.edu
AF: Department of Geology and Geophysics, SOEST, University of Hawaii, 1680 East-West Road, Honolulu, HI 96822 United States
AU: Houghton, B F
EM: bhought@soest.hawaii.edu
AF: Department of Geology and Geophysics, SOEST, University of Hawaii, 1680 East-West Road, Honolulu, HI 96822 United States
AU: Skilling, I P
EM: skilling@pitt.edu
AF: Dept of Geology and Planetary Sciences, University of Pittsburgh, 200 SRCC Building, Pittsburgh, PA 15260-3332 United States
AU: White, J D
EM: james.white@stonebow.otago.ac.nz
AF: Department of Geology, University of Otago, P.O Box 56, Dunedin, 9015 New Zealand
AB: The Sterkspruit Complex, is a well-exposed example of a recently recognized type of volcanic landform common at the base of continental flood basalt sequences. The complex is a suite of volcaniclastic rocks and lavas filling a broad crater ($>$40 km2) cut into country rock and surrounded by a blanket of distal bedded volcaniclastic rocks. The complex is a series of nested vents spaced a few hundred meters apart whose deposits may overlap. Volcaniclastic facies are rich in degassed basalt clasts and/or composite mingled basalt-sediment particles, and are intruded by rare irregular basalt dikes. Craters housing these vents grew mainly via collapse of their margins rather than by downward quarrying. Widespread pillow lavas and associated reworked sediments indicate an abrupt end to fragmental volcanism in the Sterkspruit Complex and flooding of the lowest part of the crater. A rapid transition to subaerial flood basalt flows points to rapid inundation of the landscape by lava immediately following explosive volcanism. The 50-100 m thick distal blanket of mainly bedded, fine-grained deposits records a variety of fall, flow and reworking processes. The Sterkspruit Complex seems typical of the volcaniclastic centers that form in the very earliest stages of many LIPs worldwide, and records overlapping processes of (1) explosive phreatomagmatic and strombolian eruptions seated at shallow levels in small debris-filled vents, (2) disruption of extrusive and shallowly intrusive basalt, (3) lateral growth of large craters via coalescence of many small vents by crater-margin collapse, and (3) transport of parts of this debris beyond the complex to blanket pre-eruption topography.
DE: 1749 Volcanology, geochemistry, and petrology
DE: 8400 VOLCANOLOGY
DE: 8404 Ash deposits
DE: 8414 Eruption mechanisms
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting