The geology of part of the Okuku survey district, North Canterbury, New Zealand (1955)
AuthorsWarren, Guyonshow all
The area under consideration occupies approximately forty square miles in the Okuku Survey District, 35 to 45 miles NNW of Christchurch; it is situated in hilly country five to ten miles inland from the south-western extension of the Culverden depression. In the west and south-west, it is drained by the Okuku River flowing south to its junction with the Ashley; in the north-west by tributaries of the Waitohi River, a branch of the Huruni; and in the east by the North, Middle and South Branches of the Waipara River. Access to the northern part is gained by the road to the ‘Virginia country’, ending at ‘Mt. Whitnow’ station twenty miles by road west of the township of Hawarden. A circuitous and little used road joining Whiterock and the north end of Lees Valley by way of Okuku and Lees Passes, affords access to the southern part of the area during dry weather. Two permanent homesteads are situated in the district, those of ‘Haydon Downs’ and ‘Melrose’ on the Virginia road in the extreme north-east; ‘The Brothers’ Station, on the South Branch of the Waipara near Lees Pass, is occupied intermittently during the summer. Three outlying musterers huts have been used during fieldwork. The country lies between 1500 and 4300 feet above sea level, ridge heights and steepness of slope generally increasing westwards. Sheep are carried over the whole area during the summer, but the higher country cannot safely be stocked during the winter months. A good cover of white tussock, native and exotic grasses is supported over the majority of the country below 3500 feet, but slopes are too steep, and the soil veneer generally too shallow to permit cultivation. Beech forest occurs in strands of up to 800 acres in extent, and becomes increasingly frequent westward; it is continuous over the country about the higher reaches of the Ashley River immediately west of the present area. The forest association is dominated by Mountain beech, with relatively rare strands of broadleaf, totara, houhere, kowhai, and red beech. The present rate of regeneration is inadequate to maintain the forest in all but a few isolated localities, but it is clear that here as elsewhere over the forested areas of Canterbury, decadence has been accelerated rather than originated by the depredations of introduced animals, by burning, and by other processes directly or indirectly associated with colonization.