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The stratigraphy of a proximal late Hercynian pyroclastic sequence: the Vilancós region of the Pyrenees

Published online by Cambridge University Press:  01 May 2009

J. S. Gilbert
J. S. Gilbert
Affiliation:
Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, U.K.
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Abstract

Volcanic activity, the result of crustal differentiation during the Hercynian orogeny, generated eight explosive eruptions in the Vilancós region of the Spanish Pyrenees. The volcanic products comprise the Erill Castell Volcanic Formation of Stephanian age, which crops out as a 20 km long, WNW-trending strip < 2 km wide dipping steeply to the south.The Vilancós region represents a small fragment of an originally extensive regional terrain of silicic centres.

The explosive eruptions mainly generated strongly peraluminous and phenocrystal garnet-bearing subaerial ignimbrite facies. Proximal intra-formational breccias represent a substantial volume of the preserved erupted product and one phreatoplinian deposit is exposed. Mass-flow deposits are common, and small-volume basalt, andesite and rhyolite lava flows, minor tuffs and palaesols also occur.

Electron microprobe data show that each garnet-bearing member of the Vilancós region has a distinct garnet composition. This is used as geochemical fingerprinting tool to aid mapping and correlation between proximal intra-formational breccias and ignimbrite of the same eruption. Within one debris-flow deposit (the Vilancós Breccia Member) at least three garnet populations occur. Two of these are derived from pyroclastic members within the mapped region, the other comes from an unexposed rhyolite lava source.

Type
Articles
Information
Geological Magazine , Volume 128 , Issue 2 , March 1991 , pp. 111 - 128
Copyright
Copyright © Cambridge University Press 1991

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References

Bjerrum, L. 1971. Subaqueous slope failures in Norwegian fjords. Norwegian Geotechnical Institute Publication 88, 1–8.Google Scholar
Booth, B., Croasdale, R. & Walker, G. P. L. 1978. A quantitative study of five thousand years of volcanism on São Miguel, Azores. Philosophical Transactions of the Royal Society of London A, 288, 271–319.Google Scholar
Cas, R. A. F. & Wright, J. V. 1987. Volcanic Successions Modern and Ancient. London: Allen & Unwin, 528 pp.Google Scholar
Druitt, T. H. 1985. Vent evolution and lag breccia formation during the Cape Riva eruption of Santorini, Greece. Journal of Geology 93, 439–54.CrossRefGoogle Scholar
Druitt, T. H. & Bacon, C. R. 1986. Lithic breccia and ignimbrite erupted during the collapse of Crater Lake Caldera, Oregon. Journal of Volcanology and Geothermal Research 29, 1–32.Google Scholar
Driutt, T. H. & Sparks, R. S. J. 1982. A proximal ignimbrite breccia facies on Santorini, Greece. Journal of Volcanology and Geothermal Research 13, 147–71.CrossRefGoogle Scholar
Gilbert, J. S. & Rogers, N. W. 1989. The significance of garnet in the Permo-Carboniferous volcanic rocks of the Pyrenees. Journal of the Geological Society of London 146, 477–90.CrossRefGoogle Scholar
Hartevelt, J. J. A. 1970. Geology of the Upper Segre and Valira Valleys, central Pyrenees, Andorra/Spain. Leidse Geologische Mededelingen 45, 167–236.Google Scholar
Lowe, D. R. 1976. Grain flow and grain flow deposits. Journal of Sedimentary Petrology 46, 188–99.Google Scholar
Mey, P. H. W. 1967. The geology of the Upper Ribagorzana and Baliera Valleys, central Pyrenees, Spain. Leidse Geologische Mededelingen 41, 153–220.Google Scholar
Mey, P. H. W. 1968 a. The geology of the Upper Ribagorzana and Tor Valleys, central Pyrenees, Spain. Leidse Geologische Mededelingen 41, 229–92.Google Scholar
Mey, P. H. W. 1968 b. Geological map of the central Pyrenees, sheet 8. Geological Institute, Leiden University.Google Scholar
Nagtegaal, P. J. C. 1969. Sedimentology, palaeoclimatology and diagenesis of post-Hercynian continental deposits in the south-central Pyrenees, Spain. Leidse Geologische Mededelingen 42, 143–238.Google Scholar
Nicolas, A. 1972. Was the Hercynian orogenic belt of Europe of Andean type? Nature 236, 221–3.Google Scholar
Pierson, T. C. & Scott, K. M. 1985. Downstream dilution of a lahar: transition from debris flow to hyper-concentrated streamflow. Water Resources Research 21, 1511–24.CrossRefGoogle Scholar
Rickwood, P. C. 1968. On recasting analyses of garnet into end-member molecules. Contributions to Mineralogy and Petrology 18, 175–98.CrossRefGoogle Scholar
Roberti, K. J. 1970. Geological Map of the Flamisell and Manyanet Valleys, central Pyrenees. Geological Institute, Leiden University.Google Scholar
Roger, P. H. 1965. Etude stratigraphique et structurale de la zone des Nogueras entre l'Esera et l'Isabena (Huesca-Espagne). Acta Linneenne Bordeaux 102, 3–27.Google Scholar
Scott, K. M. & Dinehart, R. L. 1985. Sediment transport and deposit characteristics of hyperconcentrated streamflow evolved from lahars at Mount St Helens, Washington. In International Workship on Flow at Hyperconcentrations of Sediment, China, pp. 1–33.Google Scholar
Self, S. & Sparks, R. S. J. 1978. Characteristics of widespread pyroclastic deposits formed by the interaction of silicic magma and water. Bulletin of Volcanology 41, 196–212.Google Scholar
Smith, G. A. 1986. Coarse-grained non-marine volcaniclastic sediment. Geological Society of America Bulletin 97, 1–10.Google Scholar
Sparks, R. S. J., Self, S. & Walker, G. P. L. 1973. Products of ignimbrite eruptions. Geology 1, 115–8.Google Scholar
Walker, G. P. L. 1981. Characteristics of two phreatoplinian ashes, and their water flushed origin. Journal of Volcanology and Geothermal Research 9, 395–407.Google Scholar
Walker, G. P. L. 1985. Origin of coarse lithic breccias near ignimbrite source vents. Journal of Volcanology and Geothermal Research 25, 157–71.CrossRefGoogle Scholar
Walker, G. P. L., Self, S. & Froggatt, P. C. 1981. The ground layer of the Taupo Ignimbrite: a striking example of sedimentation from a pyroclastic flow. Journal of Volcanology and Geothermal Research 10, 1–11.CrossRefGoogle Scholar
Wickham, S. M. & Oxburgh, E. R. O. 1986. A rifted tectonic setting for the Hercynian high-thermal gradient metamorphism in the Pyrenees. Tectonophysics 129, 53–69.Google Scholar
Wickham, S. M. & Oxburgh, E. R. O. 1987. Low pressure regional metamorphism in the Pyrenees and its implications for the thermal evolution of rifted continental crust. Philosophical Transactions of the Royal Society of London A, 321, 219–43.Google Scholar
Wright, J. V. & Walker, G. P. L. 1977. The ignimbrite source problem: significance of a co-ignimbrite lag-fall deposit. Geology 5, 729–32.Google Scholar
Zandvliet, J. 1960. The geology of the Upper Salat and Pallaresa valleys, central Pyrenees, France/Spain. Leidse Geologische Mededelingen 25, 1–127.Google Scholar
Ziegler, P. A. 1984. Caledonian and Hercynian crustal consolidation of Western and central Europe – A working hypothesis. Geologie en Mijnbouw 63, 93–108.Google Scholar
Zwart, H. J. 1979. The geology of the central Pyrenees. Leidse Geologische Mededelingen 50, 1–74.Google Scholar
Zwart, H. J. & Roberti, K. F. 1976. Geological Map of the Central Pyrenees, sheet 9. Geological Institute, Leiden University.Google Scholar