Origin and age of upland schist tors in Central Otago, New Zealand

Abstract

From field observations, and analyses conducted on samples collected on the summit and flanks of the Old Man and Pisa Ranges, it is proposed that past periods of chemical weathering have been instrumental in the development of upland schist tors in Central Otago. Tor surfaces are cavernously weathered, and weathering pits up to 1 m in diameter can be found on detached blocks around the base of many tors. Oxidation beneath the current zone of weathering was observed in some profiles developing on regolith below the summits. Small amounts of kaolinite believed to have formed under more temperate weathering conditions in the past were detected in the C and D horizons of the higher profiles forming on regolith. It is concluded that many of the upland tors may be polygenetic forms that predate the Otiran Glacial Stage.

Keywords:

• tors
• weathering
• Central Otago
• schist