DYNAMICS OF PACIFIC PLATE CRUST IN THE SOUTH ISLAND (NEW-ZEALAND) ZONE OF OBLIQUE CONTINENT-CONTINENT CONVERGENCE

Here we analyze topographic and fission track data to quantify the res ponse of the surface of the Pacific plate in South Island, New Zealand , to late Cenozoic oblique continental convergence across the Alpine f ault. Over the central 350 km length of the Southern Alps mountain cha in we derive and map the rates of mean surface uplift, the rates of wo rking associated with mean surface uplift during the late Cenozoic mou ntain building, the amounts and rates of denudation and consequent iso static rebound, and the tectonic component of rock uplift. The rate of mean surface uplift ranges from <0.1 mm/yr adjacent to the Alpine fau lt to >0.3 mm/yr over most of the area east of the Main Divide. The hi ghest rates of mean surface uplift occur to the southeast of the regio ns of highest mean elevation and relief. The rate of working against g ravity during uplift of the mean surface ranges from approximately 2.5 mW m-2 in the southwest to approximately 10 mW m-2 in the central eas tern parts of the Alps. Areas of lower mean elevation uplifted most re cently have received rates of energy input similar to that of areas of higher mean elevation where uplift started earlier. The amount of den udation is large compared with the mean surface uplift and ranges from approximately 18 km adjacent to the Alpine fault to approximately 2 k m along the southeast margin of the Southern Alps. The rate of denudat ion ranges from approximately 2.5 to approximately 0.5 mm/yr with incr easing distance from the Alpine fault across the Alps to the southeast . The amount of isostatic uplift ranges from a maximum of 14 km adjace nt to the Alpine fault to approximately 2 km along the southeast margi n of the Alps. The tectonic component of uplift varies from approximat ely 4 km along the Alpine fault to approximately 1 km along the easter n margin of the Alps.