Study on a mid-tertiary unconformity at Gee's Bay and in the Oamaru district
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A detailed study has been carried out on the contact relationships between the McDonald Limestone, Kokoamu Greensand, Otekaike Limestone, and Gee Greensand formations at Gee's Bay, and elsewhere in the Oamaru district.
At Gee's Bay, Otekaike Limestone (Tahatika Member) of Lower Miocene (Waitakian) age rests paraconformably on the phosphatised, corroded, and burrowed upper surface of McDonald Limestone of Lower Oligocene (Whaingaroan) age. Seesile organisms and abundant blocks and pebbles of McDonald Limestone in the Tahatika Member indicate that a hardground was developed on the top of the MoDonald Limestone during the Upper Oligocene (Duntroonian).
The upper surface of the McDonald Limestone in other sections is marked by solution breccias stylolites, algal oncolites, and widespread phosphatisation, suggesting that this hardground surface represented shallow marine conditions, and is widespread over at least 300km2 in the Oamaru district.
At Gee's Bay, Otekaike Limestone (Tahatika Member) of Lower Miocene (Waitakian) age rests paraconformably on the phosphatised, corroded, and burrowed upper surface of McDonald Limestone of Lower Oligocene (Whaingaroan) age. Seesile organisms and abundant blocks and pebbles of McDonald Limestone in the Tahatika Member indicate that a hardground was developed on the top of the MoDonald Limestone during the Upper Oligocene (Duntroonian).
The upper surface of the McDonald Limestone in other sections is marked by solution breccias stylolites, algal oncolites, and widespread phosphatisation, suggesting that this hardground surface represented shallow marine conditions, and is widespread over at least 300km2 in the Oamaru district.
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73 leaves : maps (1 in pocket), plates ; 29 1/2 cm.
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1972Watt
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POLYGON ((171.011283212158588 -44.983679660099135,170.997354425548565 -45.209700241465967,170.934034499633299 -45.209048274463626,170.788281971116987 -45.162017952868545,170.800579725090955 -44.982196275803254,170.71469614918513 -44.981461855084532,170.717164434973682 -44.927004877090283,170.820369093839417 -44.92796583111263,170.980238230890563 -44.9172947272938,171.011283212158588 -44.983679660099135))
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Watt, Daphne E., “Study on a mid-tertiary unconformity at Gee's Bay and in the Oamaru district,” Otago Geology Theses, accessed March 15, 2026, https://theses.otagogeology.org.nz/items/show/66.