Cromwell Gorge
The Cromwell Gorge is a steep gorge cut by the former Clutha River in the Central Otago region of New Zealand's South Island. It winds between the Dunstan and Cairnmuir Mountains, linking the townships of Cromwell and Clyde. It is one of three substantial river gorges in Central Otago, the others being the Kawarau Gorge to the west of Cromwell, and the Roxburgh Gorge south of Alexandra.
Long-associated with gold mining, orchards and the production of stone fruit, the gorge was flooded in the early 1990s to form Lake Dunstan behind the hydroelectric Clyde Dam. The former Otago Central Railway which traced the river through the gorge from Clyde was removed, while State Highway 8 was realigned above the newly formed lake.
The Dunstan Trail, a major new cycle route, was opened on the lake's right bank in 2021.
Geography
The Cromwell Gorge formed in response to the uplift of the Dunstan and Cairnmuir Mountains and simultaneous antecedent incision by the Clutha River. At the northern entrance to the gorge lies the township of Cromwell, while the township of Clyde lies to the south. To the east, the gorge is bound by the Dunstan Mountains and to the west, the Cairnmuir Mountains. The overall relief from the highest point of the gorge and the floor of the gorge is.The Cromwell Gorge is the entrance to the Upper Clutha Valley and was historically an important thoroughfare for early Māori moa hunters, and later pastoralists and gold miners in the late nineteenth century. It remains an important access route into Central Otago's interior via State Highway 8.
Geology
The Cromwell Gorge is dominated by the characteristic rocky tors and craggy outcrops of the Haast Schist Group; grey quartzofeldspathic metagreywacke interlayered with micaceous meta-argillite and greenschist formed during the Rangitata Orogeny. The schist in Central Otago has a well-defined pervasive schistosity, with shallow dips defining the broad regional-scale warps in schistosity caused during Miocene deformation. The warped geometries are antiformal over mountain ranges and synformal under the intervening basins. Associated reverse faulting along the south-eastern flanks of many Central Otago mountain ranges gives rise to the basin and range topography of parallel ridges and basins with steep south-eastern limbs and gently-dipping north-western flanks.The Cromwell Gorge exits the Dunstan and Cairnmuir Mountains immediately to the north of Clyde. Both mountain ranges are controlled to the south-east by large reverse faults; the Dunstan Fault and Earnscleugh Fault, respectively. Investigations have found that geologically-recent deformation associated with the Dunstan Fault has extended south-west towards Clyde, rather than being translated along the southern margin of the Cairnmuir Mountains. This is important as it suggests that there is no recent activity on the transfer zone between the Dunstan and Earnscleugh Faults. This transfer zone is controlled by the well-documented River Channel Fault, a steeply dipping fault mapped as running down the centre of the gorge and directly beneath the Clyde Dam. The former Clutha River followed several of these faults as it coursed through the Cromwell Gorge.
Vegetation
Vegetation in the Cromwell Gorge has seen considerable change, as has the wider Central Otago region, since at least the Holocene. The arrival of humans in Central Otago resulted in particularly extensive changes in vegetation as Māori hunter-gatherers used clearance fires improvidently. Early Māori firing of woody cover from about the thirteenth century resulted in a vastly different vegetation in the Cromwell Gorge. Initial woody cover included totara and beech forest over what is now a treeless Central Otago.Grassland and scrub now cover most of Central Otago. On the former valley floor of the Cromwell Gorge, low tussock grassland of several varieties dominated, while manuka, kānuka and matagouri scrub patched the lower slopes. Uncontrolled burn-offs, over-grazing, and the introduction of the rabbit in the mid-1800s, have heavily modified the vegetation cover since European settlement. This is further worsened by Central Otago being the driest region in New Zealand. Those areas of the gorge which are the driest are dominated by cushions of scabweed, sweet briar rosehip, and thyme, all of which flourish. The introduction of thyme to Central Otago is most-often attributed to Jean Desire Feraud, a French goldminer and orchardist who was part of the Otago gold rush.
There is evidence of native plant regeneration in areas where conservation has been put in place, though its reestablishment in the Cromwell Gorge is not nearly as extensive as the nearby Roxburgh Gorge. Forests of kōwhai have recently been postulated to have also been present in the Cromwell Gorge, upon which moa grazed.
Today in spring and summer the gorge blossoms with wild flowers: the purple of thyme, the blue of Vipers bugloss, the red of Spur valerian, and the yellows of Californian poppy and stone crop.
History
Māori
The first settlers in the region were the Māori as they travelled through Central Otago en route to the West Coast on pounamu expeditions, as well as in search of seasonal food resources. Although the Lindis Pass was the usual route for early Māori to access their summer camps at Lake Hāwea and Lake Wānaka, there is sufficient evidence the Cromwell Gorge was used as an important thoroughfare. Early Māori archaeological sites are concentrated through the gorge, particularly on the true left of the former Clutha River, and include small moa hunter camps with associated moa bones. Four sites have been identified at Rockfall I and II, Italian Creek, Muttontown Gully and Clyde West.Evidence for Māori occupation of specific sites in the Cromwell Gorge was well-documented during the Clutha Valley Archaeological Project resulting from the decision to build the Clyde Dam. Despite the limited number of samples available, rock shelters and adjacent sites showed the following finds to be culturally significant:
Italian Creek
- Eel net which may have been abandoned in transit, or left with the expectation of returning for it
- Cooked remains of a Kākā
- Moa bone and egg shell fragments
Rockfall I & II
- Two prehistoric occupations
- Oven-charcoal identifications
- Tuatara bone fragments
- Moa bone and egg shell fragments
Muttontown Gully
- A slab of flint from which about one dozen flakes lying beside it had been chipped
European settlement
The first European to set eyes on the Cromwell Gorge was Nathanael Chalmers who first traversed the valley in 1853, accompanied by two Māori guides: Reko, a Ngāi Tahu chief from Tuturau, and Kaikōura, a man who had run away from the Kaikōura ranges.Chalmers made his trip into Central Otago's interior when no roads or tracks existed, hoping to retrace the steps that his guide, Reko, had made from the Waitaki some twenty years earlier. The trek from the Mataura River in Southland to Waitaki was some distance, climbing mountain passes in excess of something Chalmers was blissfully ignorant of ahead of his expedition. Unfortunately for Chalmers, he contracted a bout of chronic diarrhoea early into his trip and suffered with it for many weeks. Having eventually made it as far as Lakes Wakatipu, Hāwea and Wānaka, his illness got the better of him and he realised he would not be able to make it to Waitaki.
In a letter to historian Herries Beattie, Chalmers recorded his account of the journey stating that the shortest way back to Southland would be to build a flax fibre mokihi or raft and ride it all the way down the Clutha River. As they set off from Lake Hāwea and entered the Clutha Rive, Chalmers wrote that they:
Within half a day, they came to the Clutha's junction with the Kawarau River, leading Chalmers to write:
When they emerged from the gorge at the site of the present-day Clyde Dam, he wrote "then our troubles were over".
Chalmers' early foray into Central Otago was closely followed in the mid 1850s by early pastoralists and runholders searching for sheep grazing land in the vast, trackless interior. It was only after surveyor John Turnbull Thomson and Alexander Garvie lead a reconnaissance survey of the region in 1857-58, that pastoralists moved into the area in earnest; within a year of Turnbull's survey some had been applied for.
Gold
The Cromwell Gorge was the site of Central Otago's first gold rush into the region's interior and followed soon after the discovery of gold at Gabriel's Gully near Lawrence. The initial rush to the gorge, referred to as the Dunstan goldfield, began on 16 August 1862 following an announcement in the Otago Daily Times that two men, Hartley and Reilly, had discovered 87 lb of gold.The winter of 1862 was exceptionally severe and resulted in unseasonably low-levels of the Clutha River. Horatio Hartley and Christopher Reilly worked the sides of the Cromwell Gorge for three months until they were forced to take the huge hoard of gold they had secretly amassed to the Chief Gold Receiver in Dunedin in August 1862. Hartley and Reilly's discovery caused great excitement as they deposited some of gold, sparking a gold rush to what would become known as Hartley's Beach. Hartley and Reilly, in divulging the location of their rich finds, were rewarded with £2000 from the Otago Provincial Government. On 23 September 1862 the Dunstan goldfield was proclaimed, the selection of this name in preference to Hartley's being largely in deference to Reilly, who was 'jealous of the pre-eminence' accorded Hartley as the discoverer.
Within days of the announcement of Hartley and Reilly's discovery, 2000 miners had descended on the Dunstan goldfield with the first gold export to leave the goldfield on 6 October 1862 carrying some 6030 t oz of gold. Between 1 September 1862 and 1 April 1863, 120,886 t oz of gold were recovered from Otago, with most of this coming from the Dunstan goldfield. By the end of 1864 the easily won gold had been mined and many had moved off to other more lucrative fields.