Abstract The stratigraphy, palynofacies, palaeotemperatures (spore coloration, vitrinite reflectance), illite crystallinity, and carbonate stable isotope patterns (δ18O, δ13C) of the Triassic sediments exposed on the south-east Otago coast between Pilot Point and Roaring Bay are discussed in relation to the Hillfoot Fault and the differentiation of the Dun Mountain-Maitai and Murihiku Terranes. Detailed sections, spore-pollen biostratigraphy, and palaeotemperatures are described from the Etalian Tilson Siltstone and Bates Siltstone at Kaka Point and from an undescribed upper Etalian-lower Kaihikuan succession at Campbell Point. New stable isotope analysis of diagenetic carbonates from the Triassic sediments of Campbell Point and Roaring Bay are included. Differences in the Triassic sediments to the north and south of the Hillfoot Fault are related to minor variations in their tectonic history and not to fundamental differences in depositional setting, lithofacies, and metamorphism. Higher palaeotemperatures and greater mineral alteration to the south of the Hillfoot Fault are interpreted as the effects of localised fluid flow along this structure when it acted as a zone of décollement in a fore-arc basinal setting under low or very low geothermal gradients.
Keywords stratigraphy; palynofacies; palaeotemperatures; spore coloration; vitrinite reflectance; illite crystallinity; stable isotopes; tectonics; biostratigraphy; palynology; sedimentology; Early-Middle Triassic; Kaka Point Structural Belt; south-east Otago; Hillfoot Fault; Dun Mountain-Maitai Terrane; Murihiku Terrane
R02032 Received 20 August 2002; accepted 13 December 2002; published 30
April 2003
© Journal of the Royal Society of New Zealand, Volume 33, Number
1, March 2003, pp 57-84
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