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Late Cenozoic Erosion in New Zealand

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thesis
posted on 09.11.2021, 00:04 by Adams, John Edward

Uplift and erosion are roughly equal in the Southern Alps of New Zealand and the following rates have been determined: tectonic uplift 620 +/- 20 Mt y^-1, river load 700 +/- 200 Mt y^-1, offshore deposition 580 +/- 110 Mt y^-1. The tectonic uplift is the result of oblique collision between the Indian and Pacific plates, with the edge of the Pacific plate being upturned and uplifted as the Southern Alps, crustal narrowing of 22 mm y^-1 being converted to uplift along a curved fault plane. Almost all rock eroded from the Southern Alps is carried as suspended load by rivers. River bedload is of minor importance, and its abrasion adds to the suspended load. The estimated suspended load amounts to 265 Mt y^-1, but with a single exception only normal load have been sampled, and the additional abnormal load from earthquake-caused landslips is estimated to double the normal load. The river load estimate is confirmed in part by spot checks from sediment accumulated in onshore traps. A model proposed for the growth of the Southern Alps from a peneplain shows that the range attained steady state about 1.5 My after uplift started. With uplift initial non steady state, flat topped mountains like those that remain in Otago, become steady state spiky mountains. The range as a whole is in steady state, though the individual mountains change. The offshore deposition rates agree with the river load and tectonic uplift estimates and thus provide substantial confirmation for the steady state model.

History

Copyright Date

01/01/1978

Date of Award

01/01/1978

Publisher

Te Herenga Waka—Victoria University of Wellington

Rights License

Author Retains Copyright

Degree Discipline

Geology

Degree Grantor

Te Herenga Waka—Victoria University of Wellington

Degree Level

Doctoral

Degree Name

Doctor of Philosophy

Victoria University of Wellington Item Type

Awarded Doctoral Thesis

Language

en_NZ

Victoria University of Wellington School

School of Geography, Environment and Earth Sciences

Advisors

Wellman, Harold; Barrett, Peter