The mountainous Reydarfjordur area of Eastern Iceland is composed of at least 25,000 ft, of gently dipping Tertiary lavas. A part of this westerly dipping succession, averaging 2,000 ft, in thickness, and containing a considerable portion of acid. rocks, has been studied. in detail and mapped for 25 miles North/South along the strike, It has been shown that volcanicity during the eruption of this 2,000 ft. unit The Reydarfjordur Acid Volcanic Succession — was rhythmic and six separate phases of volcanicity have been recognised. Each phase reaches its maximum development in or near the Reydarfjordur Acid Centre where there were usually eruptions of acid lavas often preceded by large scale pyroclastic eruptions initiating each phase. Contemporaneously, basic and intermediate lavas were extruded from north—south fissures to form the Flank Succession. In the Reydarfjordur/Faskrudsfjordur area acid—intermediate, rhyolitic andesite lavas form a considerable proportion of the succession, but in the peripheral regions tholeiite and, basaltic andesite lavas predominate, and in regions distant from the centre the lavas erupted at this time were normal flood basalts. The significance of this is discussed and comparisons are drawn between the Reydarfjordur area and. other areas of acid volcanicity in Eastern Iceland. A detailed description is given of four rhyolite basalt composite lavas (the previously undescribed extrusive products of composite dykes) while the Appendix contains petrographic and some chemical data on the commonly occurring lava types and some notes on flow structure in acid lavas.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:602200 |
| Date | January 1963 |
| Creators | Gibson, Ian Lethbridge |
| Publisher | Imperial College London |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/10044/1/13260 |
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