Cascade Fieldwork Jan 26-Feb 1

I was in Dunedin just long enough to do laundry, catch up on emails, and say hello to flatmates less they forget who I am. With a healthy weather outlook for the West Coast at a time which suited both my and my advisor's schedules, we were off.

Our pilot was notably young but also obviously inexperienced in that he actually gave us a safety briefing, the first pilot in NZ I have had do this. We had a pleasant helicopter flight following the Fault from Haast to our camp next to the middle reach of the Cascade River. Here several slices of a wide assortment of fault-bounded rocks intersect the Alpine Fault with the result that there are in fact several strands of the Fault. Because of the varied basement rocks, the Cascade River has the most diverse range of rock types in all of New Zealand.

Because of the great weather and long days we were able to be very productive, checking all creeks, but one, along a 5km stretch of the Cascade. The creeks varied significantly- some had great outcrops, some had waterfalls to climb or bypass, some were drowned in fresh slip detritus or downed trees, some had unpleasantries like stinging nettles or overabundant spider webs, some were wholly devoid of outcrop. The Cascade River was lower than I had ever seen it which prompted us to cross it and spend half a day checking out McKay Creek. McKay was impressively gorged right from the start so we did not make it very far upstream despite some fun bouldering traverses I did.

Each morning we awoke to the dawn chorus of New Zealand bird song along with the delicate pitter-patter of sandflies on our tents. The sandflies were noteworthy, rarely giving us a break, especially when engaged in tasks like cooking. Only one day did we awake to poor weather and suffer some rain, but it pleasantly broke for a pleasant afternoon. Our food rations fared spectacularly, but my aluminum foil was gone the first day as many of the samples I took have little structural integrity.

Fieldwork has been going well. Despite there being much left to do, gaps are starting to be filled and targeted studies are starting to be realized. The last day was spent at the Martyr River with more geologists in tow. The Martyr Alpine Fault outcrop has changed dramatically sometime in the last two months. I have more work to do there before the outcrop deteriorates further. Thanks to Virginia.

Above: A recently active trace of the Alpine Fault in Saddle Creek showing NW-side up displacement. Cataclastic fault rocks are juxtaposed against river gravels.

Alpine Fault geomorphology in the lower Cascade

Cascade Camp

Southern counterpart of the Red Hills near Nelson (see previous posts), offset 480km by the Alpine Fault.