Bannockburn Sluicings

The geology at The Bannockburn Sluicings consists of Miocene aged (24-5.3 million years old) Bannockburn and Dunstan Formations of the Manuherikia Group. This group consists of lake clay, silts, oil shales and lignite (low grade coal) seams with quartz sand and conglomerate at the base. These represent sediments deposited in a freshwater lake that extended across most of the Whakatipu region east of the Remarkables and north beyond Lindis Pass. The group is overlain by a remnant of gold-bearing Carrick Gravel, an alluvial fan gravel derived from the nearby Carrick Range and around 450,000 years in age.

Substantial quantities of alluvial gold occur in the Miocene to recent sediments all over Central Otago, eroded out from lodes or disseminated gold in the nearby schists. Recorded gold production from sluicing and dredging practices in the region from around 1890s through to 1992 total over 37,000 kilograms! Miners worked the Bannockburn Sluicings for around 50 years, from the early 1860s. To get at the gold, they blasted water at the hills (a technique called hydraulic sluicing) leaving behind the striking desert style landscape with dams, water races, rock tailings, caves and a large man-made canyon. Evidence of their settlement also remains in stone and earth houses, a blacksmith's shop, caves, rock shelters and an orchard planted in 1906.

Lignite has been mined in Central Otago since the 1860s by both underground and opencast methods. Nearly every outcrop of the Manuherikia Group has been reported as containing lignite. The lignite was mined around the Alexandra, Clyde and Cromwell areas to supply fuel for the gold dredges during the Otago Goldrush. The lignite in the Cromwell region was some of the best quality, being nearly sub-bituminous in rank, low in sulphur, moderate ash content and up to 55% moisture.

The quartz sands at Bannockburn have also been mined for their silica content, used as moulding sand, or for decorative purposes.

Buttes (see image) are erosional desert landforms characterised as an isolated hill with steep, often vertical sides and a flat top. They are a smaller version of other landforms in the same family called mesas, plateaus, and tablelands. Smaller versions again are the hoodoos - these look like chimneys. Can you identify any hoodoos on the walk? How many buttes and hoodoos can you find?

This is a great place to explore, read the info boards and imagine what it might have been like being a miner here.