Sedimentology of pakaha group, late Cretaceous-Paleocene, Kaitangata sub-basin, great south basin, New Zealand

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Lindqvist, Jon K.

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Abstract:

Late Cretaceous-Paleocene nonmarine and shallow marine sediments of Pakaha Group in Kaitangata Sub-basin, 80 km south of Dunedin, provide a useful reference for exploration of the mainly-offshore Great South Basin. Deposition occurred in adjacent passive and actively subsiding zones west and east of Castle Hill Fault. Castle Hill Fault, a southern coalescence of Titri and Tuapeka Faults, has a northerly trend within the study area and extends offshore to the southeast. East of Castle Hill Fault, a lower 500+ m thick coal-bearing interval of Taratu Formation is overlain by a ~ 180 m thick interfingering assemblage of Latest Cretaceous-Paleocene paralic sediments; informally referred to as 'Golf Club succession' (GCs). GCs comprises a series of eastward-prograding, tide-influenced sandy pebble conglomerate units (included in upper Taratu Formation) and westward-onlapping transgressive sandstone bodies (included in Golf Club Member ofWangaloa Formation). Shoreface sandstones are locally cemented with calcite, dolomite, magnesian siderite, framboidal pyrite, and alkali feldspar. Clear authigenic overgrowths on detrital potassium feldspar grains are found throughout Wangaloa Formation. Evidence of syndepositional sulphide diagenesis related to meteoric groundwater seepage in the shoreface zone (massive pyrite cement, chimney structures, and pyrite-cemented walls of Rhizocorallium trace fossils) is present in one transgressive sand body. Tidal influence during deposition of granule and pebble conglomerate units interbedded with shoreface sands is indicated by abundant examples of paired mud drapes, tidal bundles, and Teredolites in transported wood. Mud-draped straight-crested conglomerate megaripples of ~ 1 m wavelength preserved in the upper part of GCs exposed near W angaloa Domain provide evidence of increasing activity of ocean swell waves approaching from the east. Overlying GCs, the upper 45 m of Wangaloa Formation assigned to Mitchells Rocks Member (MRM), consists of fine-grained sandstone and shell beds composed mainly of turritelline gastropods. Hummocky and swaley cross-stratification, megaripple bed-forms, and abundant Ophiomorpha burrows in MRM are consistent with deposition in a storm-influenced shoreface setting. Early Paleocene shoreline transgression and deposition of MRM across Castle Hill Fault zone in the Benhar area reflects a cessation in growth faulting, reduction in local coarse-grained sediment supply, and relative sea level rise. Anomalously high gamma radiation emitted by MRM is associated with monazite-bearing heavy mineral concentrations composed mainly of degraded ilmenite (pseudorutile) and zircon sand. Heavy minerals are interpreted to have been concentrated in the foreshore and

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viii, 277 leaves : ill. (some col.) ; 30 cm.

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2009Lindqvist

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POLYGON ((169.738090972414852 -46.240028488223061,169.731951973512139 -46.239376701380095,169.736605080254066 -46.160922857891016,169.7771581430423 -46.11206443198342,169.834443968677476 -46.068419460907364,169.927605428075537 -46.054294019344447,170.029819354121116 -46.061761265952839,170.118025922487902 -46.075928466755748,170.18882585191264 -46.096744451599562,170.241866803869982 -46.131377271353429,170.275741826883376 -46.20839444619039,170.247596232854278 -46.29106733588312,170.151753844637994 -46.350633127436744,170.027089642645137 -46.366508081138228,169.917040529035688 -46.365972779065721,169.832964974345089 -46.332715142906238,169.770413576528739 -46.285717403689979,169.738090972414852 -46.240028488223061))

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http://download.otagogeology.org.nz/temp/Abstracts/2009Lindqvist.pdf

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Citation

Lindqvist, Jon K., “Sedimentology of pakaha group, late Cretaceous-Paleocene, Kaitangata sub-basin, great south basin, New Zealand ,” Otago Geology Theses, accessed February 13, 2025, https://theses.otagogeology.org.nz/items/show/509.

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