Formation of a plateaubasalt series. (From the example of Iceland)
Abstract
Iceland, entirely built up by plateaubasalts, forms an ideal site to study their formation on account of the many exposures in glacial valleys and fjords. Recent and Pleistocene lava flows are, however, strongly influenced by these same glacial features. To compare with present volcanism, an area exempt from glacial influences should be chosen. The Odádahraun is northen Iceland is well suited. The normal Icelandic plateaubasalt series is predominantly built up by flows of thehelluhraun or pahoehoe type. It fromed form many volcanic centres and successive series of flows are often separated by intraformational nonconformities. The earlier plateaubasalts are not different from Recent ones; the apparent larger size of the earlier series is due only to the much longer time it has taken to build. The predominant feature of a plateaubasalt series is its quietness. This is also the main characteristic of its volcanotectonic habit. Volcanotectonics are expressed in a slight regional tilting towards the centre of the island. This is accompanied locally by the formation of dike swarms and of sills, which follow a pattern that is slightly more tilted than are the plateaubasalt flows. A different facies is found in the northwest, along Bardarströnd. This is predominantly built up by much thicker lavaflows of theapalhraun or aa type, accompanied by crystal tuffs and by tuff breccias. Moreover, fossil plant localities such as the Brjánslaekur deposits, develop in this facies. This difference between the normal Icelandic facies ofhelluhraun or pahoehoe lavas and the Bardarströnd facies ofapalhraun or aa lavas should warn us for unwarranted extrapolations from the Icelandic example to any other plateaubasalt area.
- Publication:
-
Bulletin of Volcanology
- Pub Date:
- December 1964
- DOI:
- 10.1007/BF02597514
- Bibcode:
- 1964BVol...27...93R
- Keywords:
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- Breccia;
- Lava Flow;
- Volcanic Centre;
- Fissure Eruption;
- Eruption Centre