Long-term erosion-rate calculation from the Waipiata Volcanic Field (New Zealand) based on erosion remnants of scoria cones, tuff rings and maars.

Abstract

Erosion of scoria cones, tuff rings and maars follows a general evolution. Identification of distribution patterns of preserved pyroclastic lithofacies of scoria cones, tuff rings and maars allows an estimation of "depth" of erosion since volcanism ceased. Study of the accidental lithic clast population in pyroclastic rocks of erosion remnants of basaltic maar/tuff ring volcanoes of the Miocene Waipiata Volcanic Field (WVF), New Zealand is demonstrated to be a good tool re-establish the "missing" stratigraphy and estimate the erosion since volcanism. An example from a subsequently tilted erosion remnant of the Swinburn multivent volcanic complex (WVF) demonstrates the importance of tilting as an effect of erosion rate calculations. The 3 vents of the WVF investigated from New Zealand suggest a range of erosion rates from 3.75 to 46 m/My depending on 1) the position of the remnant in comparison to uplifted fault/fold blocks; and, 2) considering or neglecting the effect of subsequent tilting on erosion rate calculations.