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Title: Investigations into the structure of South-Eastern Iceland
Author: Helgi, Torfason
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 1979
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The lava pile in south-eastern Iceland is gently inclined to'l-:ards north-west, having the regional dip of 6-8°. Its age ranges from approximately 12-13 m.y. at sea-level at Austurhorn in the east to approximately 3.2-3.4 m.y. at the margin of the Vatnajokull ice sheet to the west. At least six central volcanoes are encountered in the lava pile represented in the Sections I, II and III. Abundant occurrences of acid rocks are related to these centres, and to exposed and unexposed major intrusions. Thick units of basic and mixed acid/basic breccias which are related to these centres thin rapidly when traced along strike. There are at least three major horizons of breccias and/or hyaloclastites to the east of the Vatnajokull ice sheet; the green breccias in Kalfafellsdalur are not related to any known central volcano, but formed under subaqueous conditions. The Kolumuli central volcano was active for approximately O.9-1.3 m.y. and volcanism was renewed in Mulatindar after 3-5 m.y. time interval of no eruptions in the area. The core of the volcano is very altered, and a chlorite-epidote aureole is a result of intense geothernal activity on the volcano. The central part of the volcano subsided to form a caldera in the latter half of the activity in the volcano, preceded and followed by intensive injection of acid cone sheets; a swarm of basic cone sheets was not positively identified. The major intrusions in south-eastern Iceland were emplaced some 40-60km outside the Neovolcanic zone at 1-1.5 km depth. Minor intrusions which accompanied this intrusive activity, inclined sheets and dykes, were emplaced at the same and even later time. This intrusive activity resulted in crustal uplift to the east and the formation of a prominent flexure, approximately 250km long. The intrusive activity and the formation of the flexure took place betHeen 1.5 and 2.5 m.y. and was earlier in Fljotsdalur in the north growing southwards in the course of time. This is believed to be related to the southward growth of the eastern Neaovolcanic zone, which is still in progress. The lava pile was subjected to horizontal compressive stress,normal to the Neovolcanic zone,at the time.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available