Frontispiece: Triumphant and exhausted after carefully removing a block of very tacky blue clay gouge. It absorbs the shock from a hammer blow so perfectly, that you end up expending more effort sampling it than you would with a very hard rock. 99.9% of Alpine Fault movement probably occurs in a 1.5m wide zone of this stuff. Extracting an intact sample allows us to determine the coefficient of friction, permeability, and other important properties that will affect the types of earthquakes generated. Photo by Lara.As far as fieldwork goes, I can safely say it was the best of times and the worst of times...
We awoke to a frosty winter wonderland at Homer Hut well before dawn, carefully packed our tramping gear, field gear and food and carefully drove through to Milford Sound. After a Bowen Falls detour, we met our pilot Shaun and loaded up for another beautiful flight out of Milford. Shaun said he wanted to get some video footage so he flew us past the Age Glacier and across the Donne Glacier on the flanks of Mt Tutoko (2723m), definitely not the shortest route but arguably the most scenic possible route to Big Bay. To clear the saddle we actually had to spiral upward to gain altitude. The tide being low, we safely landed on the north end of Three Mile Beach and Shaun kindly taxied us as far south on the beach as he could, saving us probably 30 minutes of walking with heavy packs.
Mt Tutoko
After a few minutes enjoying the sun and letting the surrealism of the Cessna flight wear off, we slung our rather heavy packs on our backs and set off for McKenzie Creek as the plane shrank into the distance. With a sunny day and prospect for dry feet for a day or so, I fought the inevitable and removed my boots for the McKenzie Creek crossings. We took a rather ambitious "short cut" through the bush, and another to skirt the lower McKenzie Creek gorge. At the main fork in the creek we headed south towards the Alpine Fault. Much of the creek was steep boulder hopping with few downed trees, which made for surprisingly good travel. From the top of this creek we had a commanding view of Big Bay far below and in the distance.We dropped packs and searched a few hundred meters for a suitable campsite, which looked grim for awhile. We were incredibly lucky to find a dry site just big enough for a tent and with a bit of engineering were able to carve it into a very comfortable camp, our home for the next 4 nights (and shelter in times of persistent rain). No sandflies either!
Going up McKenzie Creek
Big Bay in the distance
Camp McKenzie
The fieldwork was amazing! We explored 6 unnamed creeks never before visited by geologists. From maps and aerial photos I could tell they had the right ingredients to have good exposures (evidence of slips, steep, narrow, and running perpendicular to the trace of the fault), but the quality and continuity of the outcrop far exceeded my hopes. These creeks have some of the best exposures anywhere on the Alpine Fault, and allow for a much better view of the inner workings of the most important fault in New Zealand. It is the sort of place I really need to spend a long week of good weather in the summer to fully document. Despite great outcrop, I still had the usual head-scratching that goes with doing fieldwork in my field area. There seems to be an endless supply of things I have never seen before and do not quite understand yet! The samples and descriptions from this fieldwork will probably become an important part of my PhD.
Friday in particular was probably the best single day of PhD fieldwork I have done- sunny and relatively warm, we followed the Alpine Fault trace for over a kilometer with 5 superb exposures of the fault to document and sample. Unfortunately the day was too short, but if we had another hour or so we would have scrambled up to the saddle near Mt Pyke, the highest point on the Alpine Fault at 680m, which potentially has never been visited before. We bush-bashed back in the failing light, making it back just in time to do without using a headlamp.
Some of the other days were not quite as pleasant with persistent light rain. Some of the rains we stuck out, others we retreated to the tent for a cup of soup and dry clothes. Once the rain soaks through the canopy of the trees, it does not take long for every bush and fern to have the capacity to drench any miserable soul brushing against it. At one point it became too wet to write in my waterproof notebook, which I took as a sign to call it a day.
Pacific Plate at top and center. Alpine Fault core at lower right.
A wet and cold (but still smiling) field assistant
We also felt two local earthquakes of M4.7 and M4.9 which was exciting.
The first we felt from our tent (150m from the Alpine Fault) at 7:30am, the second we felt a mere 10m away from the fault! For the second one the shaking lasted a couple seconds and the trees, heavily laden with water from the rain, release all their water in one instantaneous downpour. Halfway through the quake a distant boom was heard to the SW. After both earthquakes I remember being left with an uneasy feeling of "now what!?" We hoped they were not foreshocks...10m away from the fault would probably be a pretty horrible place to be in a M8 earthquake!
Another important and unexpected find was perfectly-preserved marine shells in a glacial silt deposit at 400m elevation! The shells still have their mother-of-pearl and look to be really young. Dating these shells will give me an uplift rate due to the Alpine Fault in this area.
Surprise find! Young marine fossils in glacial silt at 400m elevation!
We were thoroughly wet by the time we packed up so we opted to follow the river down the gorge this time. The going was remarkably easy and it was obvious the nastiness of the gorge has been drowned out in surplus sediment. The rain just would not quit though! We saw lots of double rainbows that seemed cruelly ironic as the rain continued to fall. We made it to Big Bay at a comfortable hour, happy to have a large place to spread out wet gear but not as happy to be back in the realm of persistent sandflies. We found the firewood supply hopelessly wet, but we hung our gear around the stove to psychologically dry anyway.
After a while the rainbows seemed cruelly ironic as the rain continued to fall...
We were scheduled for a 2pm pick-up on the beach (5 minutes from the hut), so I had a lazy morning of listening to music and reading some old National Geographic magazines in the hut. The weather was patchy but we were pretty certain of a pick-up. At 1:45pm we walked out to the beach where I walked in circles to avoid sandflies and keep warm. The wind and rain came in gusts and sheets with some nice fine spells between. The waves had a horrible way of sounding like a motor whenever my back was turned to the sea. As the chance of a pickup decreased, my brain fluctuated between confronting our increasingly grim situation and really random irrelevant thoughts...I remember thinking about the phrase "It's a bird! It's a plane!..."- who the hell gets that excited about a bird!? A plane on the other hand...
After 3 hours of waiting for the plane to whisk us back to Milford (my boot prints littering the beach in all directions at this point), the sun began to set and we unpacked our packs back at the hut for an uneasy night's sleep. All of a sudden we were 3 days walk from the nearest road end, without a means of communication, and with only a day's worth of food. Part of our predicament is the weather did not exactly match the forecast and we had no way of knowing when it would improve enough to fly and that there were also concerns that the pilot may have forgotten about us. We explored the option of breaking into private huts to use a radio, but ultimately decided our best option would be to hike along the coast for 5 hours to Martins Bay where we knew there would be an airstrip (which would be easier for the pilot to land at) and we might be able to find a radio...and as a worse case scenario this would also put us about a two days run from the nearest road end should we be desperate enough. We left intentions in the Big Bay Hut book for the pilot to check should they land at Big Bay and not find us, and we had a personal locator beacon as a last resort.
High spirits
3 hours later...
June 15, D-Day, the Day of Desperation. This day perhaps deserves its own post but I would rather not overly reminisce on the misery. We awoke well before dawn and started hiking with our stupidly heavy backpacks (rock samples) by headlamp south along the beach. There was a light persistent rain associated with gale force headwinds. The winds were northwest and we hiked into them almost the whole way. The sea was also rough and the winds carried the spray from the breaking waves directly into our faces. Every hundred meters or so we would have to hide behind a rock to recover. Looking back was completely demoralizing- we never seemed to travel as far as it felt like in the strong winds. The plane would definitely not be flying in this wind so we had to hope for a sudden change in the weather. My memory has already begun repressing, but the weather combined with our predicament left me truly and utterly miserable. I did not take a single photo the whole time as it was not something I particularly wanted to remember.
Once at Martins Bay we checked all the huts and I found one with a radio I could almost break into if i could reach through a narrow slot and undo the window latch. I made a contraption out of a steel rod, a stick, a colander and some number 8 wire that very nearly almost worked. It was a frustrating puzzle that I felt so close to solving, but ultimately had to give up in the interest of time.
We walked onward toward the airstrip- I was feeling very dejected and despondent knowing that we might have to run out the Hollyford on an empty stomach. A hundred meters short of the clearing I heard a motor running and instinctively ran to the clearing and waved my arms as frantically as I could just missing the plane flying overhead. My heart sank thinking I had been a few seconds away from being seen. Then I saw the plane reappear and land in front of me! I can't tell you how happy I was to see that airplane and our pilot Jennie climb out. It turned out they had not forgotten about us and the weather was worse at Milford than it was at Big Bay and she took off as soon as traffic control gave her clearance.
We had a nice flight over the Kaipo coast (everywhere inland was socked in) where I spotted some enticing cave entrances in the limestone. Back at Milford we were surprised to see a clear crisp day with waterfalls everywhere after the rains and fresh snow on the peaks. The fieldwork was very productive and in retrospect it was a healthy dose of suffering to keep things in perspective. It could have been so much worse.
Hollyford skyline
Thanks to National Geographic for funding, pilots Shaun and Jennie at Fly Fiordland and a special thanks to my great field assistant Lara.
