This page explores how the land in the Bannockburn region evolved over time. Each evolutionary period or activity made its impact, so what we see today is the combined result of many layers of landform change or use.
New Zealand is geologically a young country. It is still moving and shaking along the major fault lines which give us the Southern Alps and the spectacular mountain ranges that surround us. From a site in Bannockburn with clear views to the north, look beyond Lake Dunstan and imagine a giant glacier sliding towards you and carving out the Upper Clutha valley. To the west of Bannockburn the glaciers of the Wakiatipu Basin flowed into the Gibston Valley, coming to a halt at the Nevis Bluff.
When the glaciers melted the water they released formed giant rivers which further carved the landscape. In the Wakatipu region the meltwater flowed south over Kingston, through a choke-point at Garston and over Athol and Mid-Dome onto the Southland Plains. As that meltwater flow reduced an alternative route diverted the water flow near Mid Dome to where the Mataura River now flows through the Slate Range mountains below Nokomai Station and southwards on its current route past Gore to the sea.
Another metwater flow came from Wakatipu through the Kawarua Valley forming the present-day Kawarau River and its rugged gorge. The Shotover River also joins the Kawarau River near Frankton/Hawea and is the cause of any discolouration noticeable where the Kawarau River merges with the Mata-Au/Clutha at the Cromwell Junction. While the Shotover River is the prime source of silt buildup in the Kawau Arm of Lake Dunstan, it also originates near Mt Aurum - the source of much aluvial (river-borne) gold found in Central Otago.
Before the forming of the Southern Alps a giant lake covered Otago some 16 - 18 million years ago. A last active remnant of Lake Manuherikia is the Manuherikia River that flows into the Mata Au/Clutha River at Alexandra. Lake Manuherikia was giant in size but relatively shallow and was responsible for much sedimentary deposit, some of which is visible in white clay cliffs just above the Galloway Bridge north of Alexandra and in the Blue Lakes at St Bathans.
In the Bannockburn area it can be accepted that Lake Manuherikia helped form the clay cliff remnants of the local heritage sites at the Bannockburn Sluicings, the Bannockburn Antimony Mines, and the coal seams noticeable in Lake Dunstan's Bannockburn Arm at the New Cairnmuir Coal Mine site.
A stuff.co.nz article 'Otago's lost lake of wonders' by Bob Brokie offers a fascinating insight about Lake Manuherikia.
At NZgeo.com Trevor Worthy investigates exciting New Zealand snakes and crocodiles remnants from the lake.
Look here for Jill Hamel's research on the archaeology of Otago which is to be respected.