This page explores how today's amazing semi-arid landscape in the Bannockburn region evolved over the ages. 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.
Picture: Hamish Campbell,
Te Ara - The Encyclopedia of New Zealand
From the days of 'Zealandia' 16 - 19 million years before New Zealand had its present shape or mountains, a 'flatish' Central Otago was covered by giant Lake Manuherikia which extended from Bannockburn to Ranfurly and from Alexandra into the Waitaki Valley region. A last active remnant of this flat landscape lake 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 Bannockburn Sluicings, the Bannockburn Antimony Mines, and the coal seams in Lake Dunstan's Bannockburn Arm at the New Cairnmuir Coal Mine site.
Otago's lost lake of wonders
A stuff.co.nz article by Bob Brokie offers fascinating insights about Lake Manuherikia.
Deep Secrets - Discovering New Zealand's Tropical Past
At New Zealand Geographic, Trevor Worthy investigates exciting fossil finds of New Zealand snake and crocodile remnants from Lake Manuherikia.
Mountain Forming and Ice Ages
New Zealand is geologically a young country. Although the schist rocks are greater than 250 million years old, they have only been pushed to the surface beginning about 8 million years ago. The Southern Alps formed about 5 million years ago and local mountain ranges raised Lake Manuherikia's silted bottom, some remains being noted in current mountain-top fossil finds.
Around 2.6 million years ago the world cooled and much of New Zealand became covered by sheets of ice. Sea levels dropped, so for a period New Zealand's three main islands were all joined as one land. The ice-retreat began about 12,000 years ago, so it was in this timeframe that ice carved valleys, glaciers melted and raging rivers of meltwater carved gorges.
From a site in Bannockburn with clear views to the north, look beyond Lake Dunstan and imagine a series of giant glaciers sliding towards you one after the other, not quite reaching Lowburn or Cromwell. See them and their meltwater steadly carving and eroding out the Upper Clutha valley and their meltwater forming Lakes Wanaka, Hawea and the Clutha/Mata-Au River.
In the Wakatipu region glacier meltwater originally flowed south over Kingston, through a choke-point at Garston, over Athol and Mid-Dome onto the Southland Plains. As that flow reduced, an alternative route diverted the water at Mid Dome through the Slate Range mountains. The Mataura River now flows through the valleys by Nokomai Station and southwards on its current route past Gore to the sea.
To the west of Bannockburn glaciers of the Wakiatipu Basin also flowed into the Gibston Valley, coming to a halt near the Nevis Bluff. The Shotover River also joins the Kawarau River near Frankton/Queenstown Airport and is the cause of any discolouration noticeable where the Kawarau River merges with the Clutha at the Cromwell junction. While the Shotover River is the prime source of silt buildup in the Kawarau Arm of Lake Dunstan, it also originates near Mt Aurum - the source of much aluvial (river-borne) gold found in Central Otago.
To the east of Bannockburn the flows of the Clutha and Kawara rivers merged at Cromwell and carved out the rugged Cromwell Gorge, now somewhat tamed by Lake Dunstan.
The Human Arrival
While globally there were various forms of human ancestor (ape, chimpanzee, etc) going back millions of years, Homo sapiens have been recorded from 300,000 years ago, with modern man (homo sapiens sapiens) appearing about 70,000 years ago. From an Otago perspective, the first Polynesian settlers probably arrived in southern New Zealand in the 12th century. Their clearing of Otago open forests by fire aided hunting of moa and contributed to the extinction of eight moa and eleven small bird species. In the 16th and 17th centuries family groups were small and highly mobile, while from about 1750 familes moved into coastal villages and permanent housing, with planned gardens and storeage of food predominating.
The first Europeans living in Otago were whalers at shore stations between 1831 and 1848. Organised settlement began in 1848 with the Free Church of Scotland settlement being formed at Dunedin. This was followed by an influx of runholders establishing large farming stations in the interior. The stations had a comparatively small impact on the land compared to that caused by miners arriving in the gold rushes from 1861.
The Archaeology of Otago
Look here for Jill Hamel's Department of Conservation research paper on the archaeology of Otago. Jill is highly respected in Otago archaeology circles, for her footprints have been on probably every hill you can see from Bannockburn, and on many more beyond those.