Swinburn volcanic body.
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Abstract:
This field-mapping project concerns the area ofLonglands Station and the volcanics around Swinburn Peak. The area has been tectonically active since the Cretaceous with normal faulting, folding and reverse faulting accompanied by volcanism. The basement consists of Otago schist forming the core of a NE-trending anticline surrounded by Tertiary sediments. The schist is block-faulted, bordered to the east and south by faults. During the Tertiary a transgressive-regressive sequence deposited sediment nonconformably on the schist below the Tertiary units. After the peak transgression, tectonic activity set in consisting of three stages. During the pre-transgressive event the Hogburn Formation was deposited. Valley erosion caused then the forming of topography. During the Miocene continental basaltic volcanism was active unconformably covering the Tertiary sediments with tuffs and flows. Prior to and after the volcanism occurred the first post-transgressive uplift event resulting in the deposition of the Dunstan Formation. The volcanics belong to the Waipiata Volcanic Formation predating the Dunedin Volcano Complex. It was not clear from previously published work whether the volcanics are eruptives or intrusives. This study has revealed that there is no evidence for intrusion and good evidence that the Swinburn body is a flow. The geochemical data on the volcanics indicate that they are part of the alkali basalt - hawaiite lineage (Coombs & Wilkinson 1969). The volcanics are overlain by quartzites and quartz pebble conglomerates ofDunstan Formation found as sarsens all over the area. The deformation in the area continued. A second uplift event caused the uplift of the NWtrending ranges providing the source for newly eroded basement greywacke found in the Wedderburn Formation and especially in the Maniototo Conglomerate. The Quaternary phase of uplift is still continuing as deformation within the Pliocene Maniototo Conglomerate shows. Three post-transgressive phases of uplift were recognised in the area compatible with observations in nearby areas (Youngson, 1996). An additional uplift event occurred prior to the transgression.
Thesis description:
59 leaves : ill. (some col.), folded col. map ; 30 cm.
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OU geology Identifier:
2002Zieger
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POLYGON ((170.313197692423188 -45.130658364246578,170.360727572103485 -45.130576566459894,170.361320928863051 -45.181499342083782,170.311674178240963 -45.180936126389255,170.313197692423188 -45.130658364246578))
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Citation
Zieger, Matthaeus., “Swinburn volcanic body.,” Otago Geology Theses, accessed February 8, 2025, https://theses.otagogeology.org.nz/items/show/400.