Saturday, July 24, 2010

Pilbara: The Second, Final Week

7/11: Woke up with the dull rumble of iron ore trains accompanying the usual bird song. Our swag out site was at most four kilometers west of the railway. It was somewhat eerie to hear engines in the night. Moreover, the rails would sing for quite a time before the train per se rolled by.

It was a good morning for a bush walk in search of spherule layers. There was a promising outcrop to the south. Only a couple kilometers of spinifex, desert pavement, gum trees, mulga, and wattles separated it from camp. I led a weaving path through the bush. It was clear, and warmed up quickly. I’m kind of glad it’s been dry; the density of spider webs has been quite low. No post-walk into the web spaz dance moves.

The outcrop disappointed. This is certainly the way of field work. From a distance, the rocks beckon. I am made hopeful of finding a spherule layer or whatever is my goal. But sometimes, no, commonly, the far view proves unreliable. Maybe there is too much talus; the outcrop is buried. Rarely, there is too much vegetation; it’s usually possible to move laterally and find an exposure. Most uncommonly, the layer I’m after simply isn’t there. Not in the sense that I can’t find it, but that it was not deposited in the first place. This is one of the fun challenges of sedimentary geology. Layers change from place to place, due to such causes depositional variations, topography, and chemistry. Understanding changes means making sense of the history, and that’s what I like to do.

The truck was out of site in the bush. A normal situation. Luckily the GPS knew where it was, at least in a straight line sense. While I don’t mind the adventure of finding my ride, I wanted to be on the road. With a dog leg to avoid some thick spinifex, we were in the Patrol and headed back up the power line road by late morning.

Food was low. Fuel was below 20%. We had less than 25 litres of water. A visit to Tom Price was in order. I drove down the railway access road. Bumpy, dusty, but by mid-afternoon we were back in my favorite Pilbara town. It was Sunday, but the Coles grocery was unexpectedly open. Wow, fresh veggies, fruit and ice.

7/12: I’ve probably written before that Tom Price is the “top town” in WA in the altitudinal sense, at 745 metres. This means potentially cold winter nights. I don’t mind chilly nights, but I dislike cold mornings, especially when the needs of nature force emergence from my swag. For this and other reasons I drove us south to Paraburdoo, in search of a lower, warmer swag out site. We found a nice site on Fortescue lavas west of town.

I’d made arrangements to look for the Paraburdoo Layer near the Paraburdoo iron mine, which is near (wait for it) Paraburdoo. Bruce and I had looked at the target section in the late 1980s. Jim Gordon, our contact at Rio Tinto, suggested that I just go look at it. But where was it, i.e., the access road to Radio Hill? I’d forgotten. I asked at the store where we bought supplies. The woman there said, ask Kerrie at the post office. I went to the post office. I didn’t see anyone named Kerrie. I asked the clerk who sold me stamps. She said, I’ll ask Kerrie. Kerrie appeared: she was the postmaster, an apparent fount of local knowledge. She said, no love, some bloke fell off the top of Radio Hill a couple years ago so now the track has a locked gate.

OK. I tried to call Jim: no answer. Did Para have internet? According to Kerrie, you bet, at the library. So at 9am Louis and I traded time online, sharing the library with a dozen Para mothers and their children. I felt large, smelly, and oddly out of place. Rio Tinto had come through for me. I had contacts at the Paraburdoo mine. I reached them on the phone. We arranged a rendezvous on Tuesday morning.

It was thus time for geotourism. With 3/4ths of a day remaining, there was adequate time to visit a pair of interesting sites west of Para. So back on the road. It’s a bitumen track all the way to Nanutarra. Relaxing to drive at 110 kph and not vibrate and bounce excessively.

I can’t resist writing the full geologic name of the first stop: the Meteorite Bore Member of the Kungarra Formation. The Meteorite Bore part has nothing to do with impacts; it’s the name of a nearby windmill; a groundwater pump. What’s cool about the Meteorite Bore is that it’s a glacial deposit. It’s composed of lithified mud and dropstones – pebbles, cobbles, and boulders – deposited on the seafloor by melting icebergs. At the time of accumulation this results a pile of mud with rocks in it. The technical name for this is diamictite. I like the way this term sounds.

Meteorite Bore Member

Since the glaciation that froze the water to make the culprit icebergs took place over 2.3 billion years ago, the Meteorite Bore Member rocks are not in the best shape. They’ve been metamorphosed. This compression squeezed the mud into low grade metamorphic rock. Since the forces involved were largely horizontal, the Member has a pronounced vertical fabric. The outcrops look like giant decks of poorly shuffled red-orange cards: big piles of rocks staked up end on. The dropstones are harder than the surrounding muds; they don’t deform, so they stick out of the rocks, similar to nuts in bread dough. Even neater, fins of metamorphosed mud have fused to each dropstone. When I picked one up, the hard rock – a piece of iron formation – was surrounded by a halo of compressed mud. I’ve never seen anything like this.

After contemplating the Meteorite Bore rocks for a bit, it was time to proceed to Woongara Pool. While only about eight kilometers from Meteorite Bore, it’s a thirty kilometer drive. Time was a bit short. I did not want to be on the road too late and up the odds of a road kill encounter with a roo or a cow. But hey, we were there. The track looked good. I didn’t see the sign at the gate that said “Cheela Springs Station – No Entry”.

Woongara Pool sits along the south edge of the Hamersley Basin, where deformation is greatest. The sedimentary rocks of the Hamersley Group at Woongara have thus been folded to vertical orientations. This makes a dramatic landscape. Woongara Pool sits in the fairly narrow Woongara Gorge. I hoped Louis would like it. The Patrol rounded the corner into the dramatic opening of the Gorge. The pool was mostly dry. Damn. There were dead and dying cows around it. Ugh. Well, the Gorge was still pretty in the afternoon light.

Woongara Pool, no dead cows in sight

7/13: I was sore after swagging out on a rubbly surface of Fortescue Group lavas. I’d sort of hollowed out a rock-free spot for my swag, but something poky still had conversation with by back during the night. Nonetheless, the rocks were interesting; very different from the usual Hamersley Group debris. Sandstone, lava, and white quartz – some sort of vein fill I suspect – instead of the usual chert, iron formation, and carbonate.

By the time we got to the security gate at the Paraburdoo Iron Mine, at 9 am sharp, I was alert. Time to chat up new geos and go look for the Paraburdoo Layer at a site I had not visited for twenty-three years. No worries. I called the geology office, and Jacqui arrived in about five minutes. She led us through Rio Tinto’s safety induction: a straightforward quiz this time. We both passed.

We waited while Jacqui fetched a truck. She returned with a graduate geo – a student – in the shotgun seat. Denzyl was on a break from Curtin Institute of Technology in Perth. This uni produces a lot of mining geos. Like Phil at Orebody 18, he was curious and avid to learn what we were about. We followed their Rio Tinto Landcruiser to the locked gate. I was pleased and touched at the preparations made for our visit. I’d anticipated searching for the drainage where I’d worked in the past, hoping that my vague memories would be triggered by the landscape. Bruce had sent me a couple of aerial photographs of our old sites, which I’d forwarded to Paraburdoo. The Rio Tinto geos had already reconnoitered the area; they knew just where to go. How nice.

As we left the track to Radio Hill and turned up an old route, the landscape did begin to look familiar. I recognized the hill I’d been on in 1986 when I’d watched a man and a woman load a trailer with slabs of rock. That was a weekend day; I presume the rocks ended up in a wall or patio in Para. The track degraded. We parked. I gave a brief spiel about what we were looking for. Both Denzyl and Jacqui looked shocked when I said that the Paraburdoo Layer was two centimeters thick. Sure, it was hard to imagine finding such a thin bed amidst the steep ridges of dolomite, spinifex, spider webs, and loose rock where I planned to look. There was to be a blast in the mine at 12:30. For safety, we had to exit this area by noon. I looked forward to a long day of up and down scrambles.

We started climbing. The dolomite exposures were pretty good, though badly folded and faulted. This was becoming normal. We climbed a ridge. The outcrop died. The next ridge to the east looked good. I led a short march over there. The dolomite bedding matched where we’d been, but I could tell that there was more continuous exposure here. I went up the drainage. I sent Louis over the ridge top. Denzyl and Jacqui followed me. I’d made Louis go the hard way. We chatted about life in Para, geology work in North America, and the Rio Tinto work culture. The drainage got steeper. I wondered how long we could all stand to look for the Paraburdoo Layer.

Then, like at the Governor last year, I just looked down. There was the layer. I said something to the effect of, I hate to make this look easy, but here it is. We’d been working for seventy-five minutes. I called Louis over, and we got to work, quickly measuring a section and taking samples. We were able to exit the area well in advance of the blast. That was easy.

Denzyl invited us back to the Geology office, where we met the rest of the geo team. Like Denzyl, they were curious and avid to hear about the project. I’d prepared a short talk for just this situation, so I gave it to them. Such a pleasure to have an intelligent and interested audience. I think they also appreciated a break from the routine of mine work. We said our goodbyes and left by early afternoon.

Back to Tom Price. We needed more supplies. It was time to ship rocks to the States. I dealt with rocks and gave Louis a shopping list. He came back quickly; unbelievably, the store was out of produce. Bugger, so much for Chernobyl potatoes! We eventually found enough palatable food for finish out the trip, and sent 12 kilos of rocks to the Northern Hemisphere.

My next goal was to get a shower. The closest hot water was in Karijini National Park. The sun was setting; no way to get there before dark. We ended up swagging out along the same track as last year’s rainy camp. Louis was pleased to see that the remnants of his rain shelter were still in place. This night, it was clear, the usual lovely shifting panorama of the planets and the Milky Way, punctuated by meteors.

7/14: I was dangerously close to having dreadlocks and flies were avoiding me, in spite of clothing changes and spit baths. I suggested that we camp at the Eco Lodge in Karijini. It had solar showers. Last year the Eco Lodge was the least appealing place I slept; the campsite was dirty, the neighbors noisy, the staff surly, and the showers cool. As we turned into the Lodge access road, I thought, how can they improve this year? This question was quickly addressed; the campground had burned. As learned later, a bush fire threatened the complex, so the staff preemptively ignited the grounds. The recent burn made the camping loops absurdly stark: a loose arrangement of caravans, tents, and vans on the brown and black earth. I thought, ugh, but maybe the water is hot.

In the spirit of being curious or optimistic, I booked a campsite. The young Aussie woman behind the counter gave me a site near the upscale part of the Lodge (canvas tents with raised floors and other amenities). This area had not burned off. OK, plus one. I checked out the showers. They were decently warm. Plus two.
It was late morning. After setting up camp, there was abundant day light left for exploring Karijini again. I’ve been here so many times in winter, what to do? I looked at the Park map, and found a few hikes I did not remember taking. Louis was amenable, so we headed first to Knox Gorge.

I’ve written extensively about the Hamersley Range gorges: deep clefts cut into the iron formation, up to several hundred feet deep. Each gorge differs, depending on the rocks making up its floor. If the base is iron formation, the gorge trends narrow and deep; if it’s a softer rock such as shale, it can be a broader valley. Knox was one of the broad ones. I think that the softer substrate also encourages plants; Knox was choked with gum trees, rock figs, bunch grasses, and wattles. The hike was a gentle walk among the vegetation, gradually opening out into pools with small waterfalls. Eventually I felt the urge to sit and take pictures, leaving Louis to continue through a large pool that required wading. He had been looking forward to this.

Knox Gorge

After lunch, we tackled Weano Gorge. I don’t know why it’s called Weano. This was a wholly different place than Knox. A steep descent and scramble down a talus pile led to the narrow gorge floor. There was no chance of getting lost here; the gorge was narrow, and all of its short side drainages quickly ended in chutes or cliffs.
Down and further down. Weano eventually reached a point where it was a couple meters wide, with an extreme drop off. This point was blocked by a whole gum tree trunk, which was jammed in the declivity. The flood that brought these remains here – stripped of small branches and bark- must have been epic. This was as far as we could go without technical equipment. The sun shone on the cliffs through the cleft; this produced a vertical ribbon of orange light framed by the horizontal layering of iron formation. It was good that I had carried my tripod.

Weano Gorge

A shower, finally. I enjoyed removing a layer of grime from my skin, and was surprised to discover a bit of tan underneath it, in spite of all of the sunscreen and dust I was also wearing.

A good dinner led to a short hike, an epic search for the camper’s dishwashing station. Harder to find in the burned off area in the dark: no paths. The relative abundance of civilization suggested that it was a good night to indulge a tad. I went to the lodge to buy a couple drinks. The guy helping me was the only other American I met on the trip. He was easily the rudest person I met. Maybe this was in contrast to the average gregarious and helpful Aussie, or maybe it was his personality. I hope people thought he was Canadian.

7/15: My morning walk was through the burned bush. It was barren but moving. All of the burned trees, shrubs, and grasses were resprouting. The way of an ecology of fire.

One gorge left: Kalamina. An early start guaranteed some quiet time in the gorge. This was rare. It’s school holiday time in Australia. The Eco Lodge had been rich in families as well as the usual travelers: twentysomethings, adventurers, pensioners, and the odd geologist or two. Interacting with Australian families is interesting. In every instance I can remember, only the father/husband talked to us. The women would smile, but rarely converse. Was this because we were guys, or does it reflect some Aussie family dynamic? Most families also consisted of two parents and three children. This grew to be uncanny. I could consistently predict whether a family was Australian or foreign (mostly Europeans) based on the number of kids. This pattern was consistent in the NT and Kimberley. Kalamina Gorge attracted lots of families. I talked to fathers from Port Hedland, Perth, Drobbo, Tom Price, and Brisbane. It takes valor to drive across Aus in a campervan with three small children, that’s for sure.

Kalamina Gorge

 More Kalamina Gorge

7/16: Time to go back to work. I’d spent the afternoon at Fortescue Falls in Dales Gorge, writing this blog. Louis went walkabout. I generated many surprised stares as I sat typing, with my feet dangling over the big pool. Cognitive dissonance, my pleasure.

Australia Fifteen had taken me to the western, eastern, and northern margins of the Hamersley Basin. Only one direction was left. Luckily, there were mapped outcrops of Wittenoom Formation available in the far south. Another remote area of the Basin, which I’d never penetrated. The rocks at the southern margin have crumpled into tight folds, courtesy of the same mountain building event, the Capricorn Orogeny, that I’ve mentioned before. The peaks are higher here, well over one thousand meters. I needed no more rationales to go for a look see.

The most promising area was southeast of Mt. Hilditch, named for Len Hilditch, the prospector who discovered the ore deposit at Newman. An adjacent peak is Mt. Ella, named for his wife. Why not Mt. Len? The Hilditch’s old prospecting vehicle is displayed at the Newman Visitor Centre. It’s a 1950s 4WD; a raw piece of machinery. I admire the courage, individual and relationship stamina, and hope it must have taken to poke around the Hamersley Basin in the fifty years ago. This was before quality maps existed. Bad tracks, hard living, and unknown territory. Running up hills to see their rocks. Hmmm, that actually has a certain appeal.

Anyway, the direct route to Mt. Hilditch was blocked by the West Angelas iron mine. I outlined a dog leg route around this via Giles Point – named for Ernest Giles, the first European explorer to travel the Pilbara. I fully trusted Louis to navigate us in while I focused on the road. The Giles Point track is another old route like the Pannawonica-Millstream road. It was in surprisingly good shape, courtesy of many recent exploration tracks that slashed off it across the bush.

We cut across Wanna Munna Flats. The bull dust was thick in places, making the Patrol fishtail a tad and leaving a suspended cloud of fine red dust in our wake. After an hour, Mt. Ella came into view. The track remained good. We took a short pass to the north, and turned west towards Mt. Hilditch, only to see the tailings pile from the West Angelas mine. Tailings had been spread further south beyond any reasonable expectation. I wanted to avoid active mine areas at all costs. What to do. Well, the Patrol looked official, so I turned on the beacon light, lit the headlights, and drove on.

The track turned south, and abruptly climbed. I was able to downshift rapidly, avoiding any traumatic need to use the low range gears, or roll off the hill. The track wound into the valley I’d targeted. I could see promising outcrops to the north. After some prospecting, we found an old track that wandered the right direction. Lunch and a hike. I set off quickly. The landscape was pretty rugged and spinifex-laden. This was no place to swag out, so a mid-afternoon departure was indicated.

I came to the first outcrop. Crap. It was a blue-black, fractured, and badly ferruginized chert. Not a good sign. This lithology often indicates poor exposures and bad preservation of the sort of information I am interested in. Pressing on, the next exposure was no better. It was a thick accumulation of surface weathering deposits. From the truck, it had looked tantalizingly like a dolomite outcrop. No Paraburdoo Layer here. Well, the cliffs still looked promising for the Bee Gorge Layer. The hills were a challenging climb, even for the Hamersley Basin. Steep and treacherously covered with loose rock, just enough to make balancing difficult. The outcrop improved. I began to hope. I passed through the last good marker bed below the Bee Gorge Layer. The outcrop died. Bugger. We poked around for a couple hours. No joy.

Redemption occurred during egress. I’d spotted another promising exposure right by the track, within distant sight of the mine tailings pile. A five minute hike and we were on the Bee Gorge Layer. A good continuous exposure. Easy. This simplicity raises a question of geologic philosophy. I had driven past this outcrop en route to the futile site at Mt. Hilditch. Was it necessary to struggle first before this easy find? There are many answers to this, take your choice from karma to the Protestant worldview to my own stubbornness.

A final swag out in the Pilbara. Where to have it? Not near Mt. Hilditch. In addition to the spinifex issue, there was certain to be the constant rumble of the West Angelas mine. We returned to the east, eventually finding a good clear spot on the flats. I regret last nights in the Pilbara. A good camp, a decent meal, the standard fantastic sunset, and a night of stars help, but also make the ache worse.

7/17: The last field day dawned as normal. Incipient light in the east. The stillness of bush night giving way to bird song and the rush of a slight breeze. The first sunlight touching tops of hills and trees, golden and brightening. Spotty clouds drifting down from the northwest. It was decently warm. I wiggled out of my swag to enjoy this beginning.

Australia Fifteen had successfully reached all of my target areas. My planning had included leeway for the unexpected. This day looked like one of these times, only the unanticipated part was – what to do rather than go to Newman and begin the civilization reinsertion process? Eagle Rock Falls sounded interesting and photogenic, and it was on the way.

We packed, buried the fire pit, found the track, and headed east past Giles Point. When I’m driving in the Pilbara I always track the stratigraphy in the hills around me. It’s become second nature. The mountain east of Giles Point looked very intriguing. Louis sensed it too. I took another glance through the trees. Whoa, there might even be dolomite over there. Eagle Rock Falls suddenly seemed much less interesting.

Park, gear up, boot up, hike out. There was certainly lots of dolomite exposed. I began to hope that we might find the Paraburdoo Layer. I found a drainage that seemed to have the thickest dolomite exposure, i.e., the most rocks visible, and started looking. Typical scratchy deeply weathered cryptically layered stuff. I examined every bed. Louis did the same. Moving upwards, I recognized some of the marker beds I’d found in the Paraburdoo. The Layer should be below them. I worked back downhill. The outcrop remained tantalizingly promising. We couldn’t find the bloody thing. Time to move uphill, searching for the Bee Gorge Layer. That should certainly be exposed… But a repeat of Mt. Hilditch ensued. The outcrop died, inconveniently. We searched until exhaustion, hunger, and the need for a shower overruled the hope of success.

It was interesting to examine such a promising site and not find either of the spherule layers. There are plenty of good reasons for such non-success:
  1. The layers may have been buried.
  2. They might have been locally removed or rendered unrecognizable by deformation.
  3. They might have been visible but simply different in appearance.
  4. Louis and I might have been too tired and just missed them.
  5. They might not have been deposited here.
I’ve listed these hypotheses in order of decreasing likelihood. So was the time at Mt. Giles failure? I usually feel tense at a new site until I find what I’m after. Did I pick a bad place to search? Am I wasting my time and resources? Am I not good at what I’m doing? I felt these anxieties and others many times during the work of Australia Fifteen. I’ve had similar and stronger feelings during my past field seasons. This year, they mattered less. Oh well, I didn’t find the damn layers, but I could not have looked any harder for them. Wherever I went, I learned more about the Paraburdoo Member of the Wittenoom Formation; building this mental map was both fun and satisfying. It was just fun to be out there trying.

I haven’t answered the failure question. It’s not a binary choice. I’m sure on some grant report the work at Giles Point will reduce to a dot on a map indicating no spherule layers were found: non-success. But on the larger scale, I’ve have the satisfaction of poking into a new place and examining it with my best effort. The process is a sufficient result.

I didn’t worry this too much on the drive back to Newman.

7/18: Goodbye to the Pilbara via an early afternoon flight. Hello to Perth: chilly, strikingly humid, and suddenly full of the diverse rush of human activity.

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