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Late quaternary explosive silicic volcanism on St Lucia, West Indies

Published online by Cambridge University Press:  01 May 2009

J. V. Wright ,
M. J. Roobol ,
A. L. Smith ,
R. S. J. Sparks ,
S. A. Brazier ,
W. I. Rose Jr  and
H. Sigurdsson
J. V. Wright
Affiliation:
Sedimentology Branch, The British Petroleum Co. p.l.c., Britannic House, Moor Lane, London, England
M. J. Roobol
Affiliation:
Saudi Arabian Directorate-General of Mineral Resources, c/o W.G.M. Ltd., P.O. Box 5219, Jeddah, Saudi Arabia
A. L. Smith
Affiliation:
Department of Geology, University of Puerto Rico, Mayaguez, Puerto Rico
R. S. J. Sparks
Affiliation:
Department of Earth Sciences, University of Cambridge, Cambridge, England
S. A. Brazier
Affiliation:
Department of Earth Sciences, University of Cambridge, Cambridge, England
W. I. Rose Jr
Affiliation:
Department of Geological and Geological Engineering, Michigan Technological University, Houghton, Michigan, U.S.A.
H. Sigurdsson
Affiliation:
Graduate School of Oceanography, University of Rhode Island, Kingston, Rhode Island, U.S.A.
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Abstract

Many explosive eruptions of dacitic magmas have occurred on St Lucia during the late Quaternary. These have produced widespread aprons and fans of pumice flow and ash flow deposits radiating around the central highlands, with co-eruptive air-fall and surge layers interbedded with palaeosols and epiclastic deposits. Vents in the highlands have not been located because of the dense tropical jungle but we suspect they are now plugged by lava domes surrounded by aprons of block and ash flow deposits. Young magmatically related dacitic lava domes have been extruded in the Qualibou depression. The pumice succession can be divided into older quartz-poor deposits forming the Choiseul Pumice and younger crystal-rich deposits with abundant large quartz which are called the Belfond Pumice. The Choiseul Pumice groups together scattered remnants of the products of many eruptions of different low-silica dacitic magma types. The Belfond Pumice is the product of several eruptions of a high-silica magma type and 14C ages have dated these between 20900 to 34200 years B.P.

The pumice flow deposits occur as small-volume valley fills. A granulometric study of Belfond pumice flow deposits shows them to be strongly depleted in finer ash and vitric components. It is suggested that the narrow, winding and vegetated valleys on the island locally induced turbulence and the flows moved with large, highly fluidized and inflated heads, resulting in substantial loss of fine vitric ash. One ash flow deposit which is extremely rich in crystals and carbonized vegetation is highly depleted in fines and shows enhanced vitric losses. This flow may have been a much more violent ash hurricane or blast which surmounted topography ingesting large amounts of lush vegetation. Ignition of this released the large quantities of gas needed to elutriate most of the fines.

A model is suggested for the recent volcanic activity on St Lucia in which separate batches of silicic magma, each having a distinctive petrological and chemical character, rose into high level chambers over a large area. Eruptions of volatile-rich magma led to highly explosive pumice-forming activity from vents in the central highlands. Degassed and more crystal-rich magma was extruded later from the same vents or in the attenuated flank of the Qualibou depression to from lava dome complexes.

Type
Articles
Information
Geological Magazine , Volume 121 , Issue 1 , January 1984 , pp. 1 - 15
Copyright
Copyright © Cambridge University Press 1984

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References

Briden, J. C.Rex., D. C.Fallar, A. M. & Tomblin, J. F. 1979. K-Ar geochronology and palaeomagnetism of volcanic rocks in the Lesser Antilles island arc. Philosophical Transactions of the Royal Society of London, Series A, 291, 485–528.Google Scholar
Carey, S. N. & Sigurdsson, H. 1980. The Roseau ash: deep-sea tephra deposits from a major eruption on Dominica, Lesser Antilles arc. Journal of Volcanology and Geothermal Research 7, 67–86.Google Scholar
Gunn, B. M.Roobol, M. J. & Smith, A. L. 1974. Petrochemistry of the Pelean-type volcanoes of Martinique. Bulletin of the Geological Society of America 85, 1023–30.Google Scholar
Robson, G. R. & Tomblin, J. F. 1966. Catalogue of the Active Volcanoes of the World including Solfatara Fields. Part XX West Indies. International Association of Volcanologists; 56 pp.Google Scholar
Roobol, M. J. & Smith, A. L. 1976. Mount Pelée, Martinique: A pattern of alternating eruptive styles. Geology 4, 521–4.Google Scholar
Roobol, M. J., Wright, J. V. & Smith, A. L. 1983. Gravity slides or calderas in the Lesser Antilles island arc? Journal of Volcanology and Geothermal Research (in press).Google Scholar
Sigurdsson, H. 1972. Partly welded pyroclast flow deposits in Dominica, Lesser Antilles. Bulletin Volcanologique 36, 148–63.Google Scholar
Sigurdsson, H., Sparks, R. S. J., Carey, S. & Huang, T. C. 1980. Volcanogenic sedimentation in the Lesser Antilles arc. Journal of Geology 88, 523–40.Google Scholar
Sparks, R. S. J. 1976. Grain size variations in ignimbrites and implications for the transport of pyroclastic flows. Sedimentology 23, 147–88.CrossRefGoogle Scholar
Sparks, R. S. J. & Walker, G. P. L. 1977. The significance of vitric-enriched air-fall ashes associated with crystalenriched ignimbrites. Journal of Volcanology and Geothermal Research 2, 329–41.Google Scholar
Tomblin, J. F. 1965. The geology of the Soufriere volcanic centre, St. Lucia. Transactions of the IVth Caribbean Geological Conference Trinidad, 367–76.Google Scholar
Walker, G. P. L. 1971. Grain size characteristics of pyroclastic deposits. Journal of Geology 79, 696–714.Google Scholar
Walker, G. P. L. 1972. Crystal concentration in ignimbrites. Contributions to Mineralogy and Petrology 36, 139–46.Google Scholar
Walker, G. P. L., Heming, R. F., Sprod, T. J. & Walker, H. R. 1981. Last major eruptions of Rabaul volcano. In Cooke-Ravian Volume of Volcanological Papers (ed. Johnson, R. W.), pp. 181–93. Geological Survey of Papua New Guinea, Memoir 10.Google Scholar
Walker, G. P. L., Heming, R. F. & Wilsn, C. J. N. 1980. Low-aspect-ratio ignimbrites. Nature 283, 286–7.CrossRefGoogle Scholar
Walker, G. P. L., Wilson, C. J. N. & Froggatt, P. C. Fines-depleted ignimbrite in New Zealand – the product of a turbulent pyroclastic flow. Geology 8, 245–9.2.0.CO;2>CrossRefGoogle Scholar
Wilson, C. J. N. 1980. The role of fluidization in the emplacement of pyroclastic flows: An experimental approach. Journal of Volcanology and Geothermal Research 8, 231–49.Google Scholar
Wilson, C. J. N. & Walker, G. P. L. 1982. Ignimbrite depositional facies: The anatomy of a pyroclastic flow. Journal of the Geological Society of London 139, 581–92.Google Scholar
Wright, J. V. 1981. The Rio Caliente ignimbrite: analysis of a compound intraplinian ignimbrite from a major late Quaternary Mexican eruption. Bulletin Volcanologique 44, 198–212.CrossRefGoogle Scholar
Wright, J. V. & Walker, G. P. L. 1981. Eruption, transport and deposition of ignimbrite: A case study from Mexico. J. Volcanol. Geotherm. Res. 9, 111–31.Google Scholar
Wright, J. V., Smith, A. L. & Self, S. 1980. A working terminology of pyroclastic deposits. Journal of Volcanology and Geothermal Research 8, 315–36.Google Scholar