With Fiordland fieldwork a success, we drove on to our West Coast targets with the quickest grocery stop possible at the burgeoning cesspool of Queenstown. The Martyr River outcrop was quite different than previous configurations and portions of the outcrop had clearly eroded back tens of meters since I last visited. The exposure along the river was now eroded back such that the fault plane was right at river level, not much help for excavating. Fortunately the rest of the outcrop further up the slope was much more amendable and included a 6m by 12m exposure of a largely already exposed fault plane that was the subject of much of our work. Happily here too we found plenty of curved slickenlines to document. Despite the dramatically different outcrops my previous observations and interpretations largely held up, always appreciated! Sandflies were very tolerable. I enjoyed showing the others around including the view of Monkey Puzzle Gorge, the Cascade lookout at the end of the road, and Jackson Bay (even though The Cray Pot was closed). We settled in to the nightly routine of going to the only bar and restaurant in town, the Hard Antler, which fortunately did great meals.
We had one day where we ended up going through the effort of driving to the Martyr River but the rain was sufficiently strong that we deemed it unsafe to work beneath the precarious outcrop, and so retreated back to Haast. I decided to use the opportunity to go for a wet bush bash to explore some of the karst on Jackson Head. I struggled upward through some strongly woven kiekie/supplejack combos to eventually reach the hanging valley above. I documented numerous sinkholes, submergences, and resurgences but the most promising sink would have been a bit too dangerous to enter alone. The foggy bush was beautiful and the serenity was top notch, even if I was thoroughly soaking wet the whole time. Mysteriously near the top of the hill I found an apartment-sized chunk of high-grade schist, a hard thing to explain.
With our Martyr fieldwork successfully complete, we shifted to our last and most uncertain field area, the Haast-Paringa Cattle Track. This area probably had not been visited by geologists in decades (perhaps 40 years) but had a number of steep creeks that might give us the outcrop we wanted and at least one creek that had a good exposure in the past. After quite a lot of unneeded confusion, we eventually found the right place to meet the helicopter pilot at the half-pipe in the bush next to the Whakapohai River. In two shifts we shuttled us and our gear around the low clouds into a drizzly Maori Saddle Hut. Unlike Hokuri Hut, we would have this hut to ourselves the whole time. It was a surprisingly unique and tidy wooden tongue-and-groove hut built in 1980 and notably featuring a triple-decker bunk bed. I did not know what to expect but travel on the Haast-Paringa Cattle Track was excellent once we tossed and cut some of the windfall- wide, well-graded, and cliff-hugging. There were a few slippery creeks to cross. Chasm Creek had one of the more impressive swingbridges I have seen anywhere in New Zealand and could not have been much older than a year or two.
Between our time and the weather forecast finally closing in on us, we really only had two days to explore before being pulled out on the cusp of a large storm. We spent the first day looking in Summit Creek where there was an outcrop decades before but found little of what we hoped. We found a sequence of glacial silts tens of meters thick, a bizarre occurrence given the terrain and our height on the range but nevertheless unhelpful. For our last day we came up with a new strategy and decided to explore the southwestern tributaries of Chasm Creek. Here we did find a fault exposure, albeit one with weird kinematics and recorded it for posterity. On a further gamble Russ and I ventured up the steep and intimidating Chasm Creek, eventually finding one of the very best bedrock-on-bedrock exposures of the Alpine Fault anywhere (frontispiece; left side Australian Plate, right side Pacific Plate). We all worked on the various outcrops in this area for a good amount of time. Though the exposure was spectacular, the outcrop was not really amenable to large exposures of the fault plane itself. Though we were unable to record any curved slickenlines, we all were a little jazzed to find a new exposure of the plate boundary.
The flight out from Maori Saddle Hut was on the cusp of the approaching storm and one of the rougher flights I have ever had. We stopped for a meal in Fox and found Whataroa had fallen on hard times- their pub and main hotel being closed. We drove on to Greymouth, effectively getting me there a day earlier than planned. We all had a nice last celebratory meal at the Monteith's Brewery. And now of course the rest of the work begins, compiling field notes, photos, and forming our interpretations. A huge thanks to Russ, Tim, and Jesse. It was some of the most enjoyable fieldwork I have done and I am looking forward to working on the results with them.
No comments:
Post a Comment