Micro-erosion meter (MEM) erosion data for Peninsula South Island New Zealand
Description
This data contains measurements of rock surface lowering rates and swelling obtained using the MEM on a tectonically active coastal landform. Erosion monitoring profiles installed in 1973 at Kaikōura Peninsula to record erosion rates of limestone and mudstone shore platforms were also used to monitor rock erosion after a tectonic uplift at the same site in 2016 caused ~1 m of uplift and changed the coastal morphology. Following tectonic uplift, we assumed that, except for lithological trends, the erosion patterns identified exhibited before the uplift by previous authors (Kirk, 1977; Stephenson and Kirk, 1998; Inkpen et al., 2010) have disappeared. Four years after the uplift, surface lowering rates increased to 2.25 mm/yr from a pre-uplift rate of 1.10 mm/yr, 104% increase. Higher post-uplift erosion data measured with the MEM revealed that mudstone lithologies respond faster to uplift events due to the softer bedrock while limestone lithologies are slower to react to the changing process-events due to being harder. Similar to pre-uplift erosion rates, erosion is still higher on mudstone platforms compared to the limestone platforms. Significant changes in erosion rates with faster rates on the mudstones compared to the limestone platforms suggested geological properties continue to play a significant role after uplift events. Previously reported seasonal trends in erosion rates have disappeared because algae are no longer able to colonize the large areas of platform surfaces during winter months. Significant differences in lowering rates now exist across rock lithology and elevation.
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Steps to reproduce
Micro-erosion meter (MEM) sites are measured quarterly to capture seasonal and yearly rock surface variations. The MEM used in this study consists of an equilateral triangular frame with legs and an engineering dial gauge. It records three readings by rotating the frame 60° when placed on three stainless steel bolts permanently fixed into the rock surface. Typically, the bolts are 15 cm apart to measure within an area of 97.5 cm2 (Kirk, 1977). The exact relocation of the frame on three bolts is via the Kelvin Clamp principle thus ensuring a time-series of surface elevation change, both positive and negative (Stephenson and Finlayson, 2009). Surface topographic readings from the three different positions at each MEM bolt site were obtained from both mudstone and limestone sites in the study site but this may differ according to the type of MEM used.