Tertiary geology of Trent Stream, Murchison Basin
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Abstract:
Fyfe (1930) in mapping the Murchieon Subdivision, W.Nelson and Nth. Westland, designated Trent Stream as the type locality for Maruia and Matiri Formations.
Re-examination of the type locality demonstrated that Maruia Formation could be subdivided into four recognizable West Coast formations, equated with Brunner, Kaiata, Omotumotu and Port Elizabeth Formations.
Matiri Formation is regarded as a unique formation, and has not been equated with any pre-existent West Coast formations. However on the interpretation of the basal conglomerate mapped by Fyfe being a large, possibly proximal turbidite in a series of dominantly distal turbidites, and additionally the fact that Matiri Formation is characterised by turbidite beds throughout, it has been decided to relocate the base of the formation as the lowest turbidite bed in the type locality. (Which happens to occur 130 cm below the base as originally defined.)
Petrographic and field investigations indicate that the history of the tertiary rocks in the type locality can be divide into two phases. Firstly, marine transgression involving Brunner, Kaiata, Omotumotu and Port Elizabeth Formations, and secondly the onset of tectonic activity producing a downwarping basin that received turbidites, and slumped material characteristic of Matiri Formation. This second phase is thought to ultimately result in the infilling of the basin by deposition of turbidite beds.
Re-examination of the type locality demonstrated that Maruia Formation could be subdivided into four recognizable West Coast formations, equated with Brunner, Kaiata, Omotumotu and Port Elizabeth Formations.
Matiri Formation is regarded as a unique formation, and has not been equated with any pre-existent West Coast formations. However on the interpretation of the basal conglomerate mapped by Fyfe being a large, possibly proximal turbidite in a series of dominantly distal turbidites, and additionally the fact that Matiri Formation is characterised by turbidite beds throughout, it has been decided to relocate the base of the formation as the lowest turbidite bed in the type locality. (Which happens to occur 130 cm below the base as originally defined.)
Petrographic and field investigations indicate that the history of the tertiary rocks in the type locality can be divide into two phases. Firstly, marine transgression involving Brunner, Kaiata, Omotumotu and Port Elizabeth Formations, and secondly the onset of tectonic activity producing a downwarping basin that received turbidites, and slumped material characteristic of Matiri Formation. This second phase is thought to ultimately result in the infilling of the basin by deposition of turbidite beds.
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57 leaves : maps (1 in pocket), plantes ; 29 cm.
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1972Crooks
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POLYGON ((172.297492847386053 -41.700621617760191,172.298866949689341 -41.644349911122134,172.355552991134573 -41.64372844559216,172.353463261183123 -41.700187539438723,172.297492847386053 -41.700621617760191))
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Citation
Crooks, Ian., “Tertiary geology of Trent Stream, Murchison Basin ,” Otago Geology Theses, accessed July 15, 2026, https://theses.otagogeology.org.nz/items/show/60.