Otago Region - Geography

Geography

Beginning in the west, the geography of Otago consists of high alpine mountains. The highest peak in Otago is Mount Aspiring/Tititea, which is on the Main Divide. From the high mountains the rivers discharge into large glacial lakes. In this part of Otago glacial activity - both recent and very old - dominates the landscape, with large 'U' shaped valleys and rivers which have high sediment loads. River flows also vary dramatically, with large flood flows occurring after heavy rain. Lakes Wakatipu, Wanaka and Hawea form the sources of the Clutha, the largest river (by discharge) in New Zealand. The Clutha flows through Otago and discharges near Balclutha.

Travelling east from the mountains, the Central Otago drylands predominate. These are Canterbury-Otago tussock grasslands dominated by the block mountains, upthrust schist mountains. In contrast to Canterbury, where the Northwest winds blow across the plains without interruption, in Otago the block mountains impede and dilute the effects of the Nor'wester.

The main Central Otago centres, such as Alexandra and Cromwell, are found in the intermontane basins between the block mountains. The schist bedrock influence extends to the eastern part of Otago, where remnant volcanics mark its edge. The remains of the most spectacular of these are the Miocene volcanics centred on Otago Harbour. Elsewhere, basalt outcrops can be found along the coast and at other sites.

In the southeastern corner of Otago lies The Catlins, an area of rough hill country which geologically forms part of the Murihiku terrane, an accretion which extends inland through the Hokonui Hills in the Southland Region. This itself forms part of a larger system known as the Southland Syncline, which links to similar formations in Nelson (offset by the Alpine Fault) and even in New Caledonia, 3,500 km (2,200 mi) away. The Catlins ranges are strike ridges composed of Triassic and Jurassic sandstones, mudstones and other related sedimentary rocks, often with a high incidence of feldspar. Fossils of the late and middle Triassic Warepan and Kaihikuan stages are found in the area.