7/3: quick flight to Perth, adios to Paul, hola to Louis.
7/4: Eighteen hours in town, chilly in the morning, close to zero. A late morning flight to Newman. I chatted with a gent who worked as a safety trainer for a bunch of the mining contractors. He was also in the Australian Navy Reserve, and Commander of the Sea Cadets. He had many interesting stories.
Newman and suddenly the weather was temperate again. I found the truck – vehicle number four of this trip – in the car park. It is a Nissan Patrol, which I had expected with some regret. It’s Landcruiser Lite –a powerful engine and plenty of truckness, it’s not as taut in the gearbox or suspension as the Toyotas. No worries – this will keep me from getting too far off road. It was Sunday. All of the town businesses save for the pub were closed. We sorted gear and packed the truck.
7/5: A return to the end of last year’s field season: the gate at Orebody 18. Last year, they pretended I had not been in contact. This year, Phil, a BHP geo, was there to meet us within fifteen minutes of contact. He was a young bloke, a mine geologist. He and a couple other geos had been intrigued by the project. Too bad only he was available on Monday.
Our first stop was to gather safety gear and read a safety briefing. All of the companies have gotten very serious about this, which is a good thing I suppose. It’s a bit strange to see the uniformity of all staff in safety gear all the time, even the receptionists.
I read the briefing materials after rolling my shirt sleeves down, as requested, to comply with the safety code. I signed on the appropriate line. I handed it to the safety officer. She said, you didn’t fill it out. I said – huh? It was a quiz. Oh. This wasn’t apparent, but now I’ll never forget that I should call for help on Channel 84. We put on our safety vests, hard hats, safety glasses, and stowed our gloves and ear plugs, and headed out in Phil’s truck.
I had not been to this research site for nine years; on that visit I was jet lagged so it was a haze anyway. Nonetheless, the scenery began to look familiar. We parked, and within thirty minutes I’d found the spherule layer.
It’s remarkable to me that my long term memory retains the visual map of this spot in the Pilbara, much less that I can so unerringly look at the rocks anywhere out here and find what I am after. If it were possible to quantify the last twenty-five years, I’ve spent relatively little time in the Pilbara, and even less looking at its rocks. Yet this place is ingrained in me. I don’t think I’ll ever loose the capacity and knowledge of here. I suppose this is true of places that are significant in one’s life. My time here has consistently been a catalyst in my maturation through the various stages of life. That has to help.
Anyway, Phil was delighted to see the impact layer and hear about how we think it formed. He waited patiently while Louis and I did our work. We were off-site – free of safety gear and able to take risks again – by early afternoon.
The shops in Newman were open. $450 later, we had enough chairs, ice, gas, food, water, and other random gear to last a week or two. There was still time to drive west on Rt. 95, shoot the gap north through Cathedral Gorge, and swag out off of the track to Weeli Wolli.
7/6: Oh, the pleasure of a first night under the Southern Cross, with the only noise the very distant murmur of road trains. A partially cloudy sky; the weather seemed unsettled. Louis was still asleep. I got up and stared at the back of the truck. Well, I opened it first. I’d quickly sorted and packed all of the food, water and gear the previous evening. With each new vehicle, it’s a geometric challenge to fit everything in ways that don’t rattle, abrade the truck, or cause self destruction. It’s was made a bit more challenging by the second spare tyre, which hogged a large inconvenient section of storage space. However, the current set up of the Patrol looked pretty good, although the chairs, shovel, and stove seemed ready to fall out.
After breakfast, I drove us on to Weeli Wolli. This was another return to the scene of the crime from last year, only this time I was in search of the new spherule layer. With minimal effort, we found the track we took to the research site last year. It was a rubbly and rough drive, but at least there was a track. We eventually came to a reasonable outcrop of dolomite; the main type of limestone that makes up the lower Wittenoom Formation, where the Paraburdoo Layer is located. I don’t know these rocks as well. They are poorly exposed, and when you do see them, they comprise thin layers of brown laminated rock. Yawn. Nonetheless, it was time to learn them, in order to find the Paraburdoo Layer.
Weeli Wolli is a fairly large drainage, typical of the southern Hamersley Basin. It occurs in the soft rocks – the Wittenoom – and takes advantage of the abundant folds and faults in the area. To us, this meant that the dolomite exposures we looked at were isolated hill-sized blobs. Well, time to work with what nature provided. We worked uphill. The dolomite began to show a consistent stratigraphy that we could trace from outcrop to outcrop. This was a relief. However, we couldn’t find the spherule layer.
I could tell that the dolomite continued downhill and across the creek from where the truck sat. Near the northern edge of the drainage, there was a nice ravine with good outcrop on both sides. This seemed like a good target. After lunch we set out.
Back to walking on rubbly stumbly outcrops, through and around spinifex, and scrambling down cliffs. My route hit the main Weeli Wolli drainage. It showed evidence of recent flooding; large gum trees lay horizontal in the channels, their roots and branches packed with debris. The bare dolomite outcrops were polished and scoured. Large bars of gravel and cobbles partially covered them, and made walking tricky.
We made it across, and got to my target ravine. I left Louis there to look for the spherule layer, while I walked uphill to tie us into the stratigraphy we’d looked at earlier in the day. Of course, I went slowly so I could look for the spherule layer. This means staring at every visible bed, a slow process.
I performed my once-a-field season fall into the spinifex. A couple dozen punctures in the left hand and arm, oh well. I’d climbed high enough, it was time to turn around and find Louis. I figured, we’d looked hard, but no layer, no regrets.
When I got back to the ravine, he waved something at me and mumbled indistinctly (a trend). Eventually I understood that he’d found the layer! A few very minimal outcrops at the top of the cliff on the south side of the ravine. I was suddenly happy, and forgot the allergy-induced fatigue I had been suffering. We had a look. Definitely spherules. I was bemused to have a new spherule section. I’d essentially assumed we would not find it at Weeli Wolli. I was happy to be surprised. It reinforced my faith in serendipity. If I had not gone on walkabout, and Louis weren’t so thorough and inclined to scramble up cliffs, we would have never found the one centimeter of spherules at Weeli Wolli.
7/7: The morning entertainment was a several hour drive from Weeli Wolli to my next site, Range Gorge. More time north on Rt. 95, then west towards Wittenoom from Auski. Range Gorge is one of the series of steep valleys that cuts the north side of the Hamersley Range. There are no tracks into it, nor does it have access from Karijini National Park. However, an exploration company drilled a research core here in the late 1980s. I’ll look at that in Perth next week. I wanted to come here to look at the above ground part of the section, in the hopes of finding the Paraburdoo Layer.
The first challenge was to find the twenty four year old track to the drill site. A new berm on the site of the road made this tricky, but with some high torque from the Patrol, we succeeded. I was pleased to see that the drill site, the outcrops of dolomite behind it, and several hundred acres of the surrounding bush had recently burned. Bare rock, burnt bushes and trees, and the ashes of spinifex – what’s not to like? It was dramatic. The bare rock of the plain ended right at the first cliff of dolomite; a xeriscape without the plants (currently).
More dolomite, only this time a straightforward bottom to top section to see and learn. I again put Louis to work at bed by bed examination, and went climbing to get perspective on the overall stratigraphy. My coordination was a bit dicey from my allergies, but I looked, climbed, and eventually got oriented. I’d managed to climb an isolated knob. In the 180 degree view in front of me the Hamersley Range continued to rise. There were a series of intriguing rock overhangs in the cliffs right below me. I immediately thought: Aboriginal sites? To the right (west), Range Gorge cut into the cliffs, its incision making a broad alluvium- and gum tree-filled valley. It was a big drainage. I wanted to walk up it and see what was there. Maybe very long day hike In the future? The Fortescue River plain filled the scene behind me. Broad, flat, and mostly burned off from my vantage. The Chichester Ranges were barely visible on the horizon. I loved this view.
Louis had not found the layer. We worked it over together. It wasn’t there, or was hiding really well. Actually, there were a number of thick landside beds in the dolomite, which is unusual. Their presence meant that the Paraburdoo Layer had to be deeper underground. I hope we can find it in the core when we get back to Perth.
Our work done, I suggested a walk to look at the overhangs I’d seen. We scrambled up the burned over drainage. There was still plenty of loose rock. The overhangs were all at the top of steep talus piles. They turned out to be kangaroo hostels, based on the tracks and droppings covering the area. If the Aboriginals used these sites, they did not leave any evidence.
Time to explore was good. This is one beneficial aspect of this research project. The rock unit we are looking for is so specific that I can definitely say we’ve looked hard for it, time to cease. Projects covering a broader areas require more self-control. It’s thus a luxury to have energy and time for a post-work stroll in the bush.
7/8: A cloudy morning, especially in the west. That was our direction of travel. I thought, a good day for driving; my plan was to commute to the west edge of the Hamersley Basin, where there was a potential Paraburdoo Layer exposure. Escaping from Range Gorge, I pointed the truck west on the Wittenoom-Pannawonica road. Time to sit and drive, racing over the Fortescue River floodplain at maximum safe speed. A landscape covered with mulga and gum trees; frequent cattle sightings too. We passed the Mt. Florance Station turnoff. Coolawanyah Station was next. Coolawanyah had done a particularly nice job marking their turnoff, using a pair of nicely painted tractor tyres.
A pause at the Rio Tinto railway to watch an ore train roll by, headed north. A bit more than a kilometer long. I lost count of the number of ore cars. All that rock, going to China, Japan, Taiwan, and Korea. I wonder how many of my home appliances are made with Pilbara iron ore?
The sky was darker. I could see rain bands in the west. Oh crap. Nothing to do but drive onwards. A light sprinkle began at lunch time. Good, the Patrol windshield wipers were in decent shape. The rain got heavier. I was relieved we were on a main track. It was unsealed, but the surface was well-compacted so it wasn’t immediately going to turn into a sea of red mud.
I had to put the wipers on high and slow down. Water began to puddle on the road. About forty kilometers from Pannawonica, the sky lightened. The rain stopped. The wet track was doing just fine. I slowed for the numerous muddy patches. Splash! Oops, that big puddle was more of a pool. The white Patrol was now largely red, up to about mid-window height. No worries, we did not loose traction.
Stopping in Pannawonica seemed like a good idea. I wanted a tarp for weather security. Panna is another mining town. It was founded in the early 1960s like Tom Price and Newman. Its independent operation was absorbed by Rio Tinto in the 1990s. It’s a small place. Luckily the store had a tarp, bread, and the other few things that we needed.
OK, the clouds seemed to have dissipated, but where to go? I saw a sign that said Bungaroo Project, pointing south down a wide track. Hmm, Bungaroo Creek was pretty close to where I wanted to look the Paraburdoo Layer. The track was good, built by Rio Tinto. Definitely for exploration; roads cut off from it at intervals to drill sites. We eventually found a old, unused side track and swagged out.
The clouds gradually returned. We were at a relatively low elevation at 360 meters. It was warm and after the rain, strangely humid with a strong smell of damp rocks. We swagged close to the Patrol, and prepared for a quick evacuation. I fell asleep right away.
Only to wake up with rain falling on my face at 12:30 am. Time to bolt. We threw our stuff in the Patrol and headed back to the main road, stopping just at the berm. Slow, somewhat anxious driving through a heavy downpour. Parked, we sat in the truck. The downpour stopped. Louis bravely set up his tent. I went to sleep again, in the driver’s seat. No worse that economy class on a Qantas 747.
7/9: I woke up at 4 am. The stars were out. I spread out my swag and got a bit more rest. Dawn and the weather looked a bit more settled. Still partially cloudy: numerous blue patches. The brief storms had soaked the ground to a depth of six centimeters at most.
We went in search of the old Pannawonica to Millstream road. When I came to the Pilbara in 1985, this was the main route from Wittenoom to Panna and beyond to the coast road. The Bungaroo Project road had bisected it somewhere. I’d missed it the night before in haste to make a wet swag out.
This trip has been much more about hunt and find than Australia Fourteen. We’ve done all the easy sites. The project has pushed into the peripheries of the Hamersley Basin: more remote, old, and less traveled tracks. Finding the old Millstream Road is a good example. It was on my Pilbara Tourist map (1:1000000 scale) and on my topographic map (1:100000 scale). My GPS, which includes the topo database, showed us where we were: not on the Millstream Road. However, this was useless. We could tell the geographic direction to go, but which route to take to get to it? All of the new mining tracks weren’t on any map or the GPS. Finally, I decided, let’s just try this one: a straight track, probably a mining survey line, plowed through the bush. It cut the Millstream Road in about 2 kilometers. The GPS confirmed our location. Easy continued.
I’d wanted to find the Millstream Road in order to get to the Jimmawurranda Creek area. I’d been there in 1985 with Bruce, and subsequently for some of my Ph. D work. It had dolomite. Thirty kilometers of damp dirt track, and a couple road encounters (see a future post) later, wee found a good site. It was mid-morning. The sky was clear enough to seriously boost my morale.
This project requires optimism. As I wrote in the introduction, the Paraburdoo Layer is at most a couple of centimeters thick: fingernail-scale. Imagine trying to find this amidst discontinuous outcrops, talus, spinifex, faults, fold, streams, and other complexifiers and the need for hope should be clear. One helpful bit is that the spherule layer weathers to a grey-green color, which is unlike the usual brown dolomite, black to grey to ochre to red cherts, tan shales, and green volcanic rocks. Unless of course, any or all of the above are covered by an orange-red iron stain, whitish caliche, or purple-black desert varnish.
Does this mean I’m an optimist? Well, at minimum I’m persistent. I like the feeling of success. There is also the hope of finding something new, unusual, and exciting. This is also a great excuse to be outdoors, in Aus, and looking at rocks.
We went south of the road. Lots of dolomite exposures, along with abundant folds and faults. Déjà vu for the Weeli Wolli sections. However, just like that site, my observations began to crystallize quickly into stratigraphic patterns. Ok, these two black chert/golden carbonate sequences are here, above the think dolomite beds… Intensely creative and useful as long as I wrote it down.
Lunch and time to work to the north. It seemed a good idea to pick a campsite first. The bush was thick and unburned throughout the area. I think it always has been. This meant that best bet for swag out was a stream drainage. Drainages always have plenty of wood stacked up from past floods, a reasonable sky view for star patrol, and the stream sediments are often softer than typical Pilbara soils. So how do you find a good place to swag out in a stream? Bruce and I evolved the following technique in the late 1980s:
1) Aim the truck along a fairly wide drainage: one that’s pretty open, where there’s potential to get far of the road.
2) If tyre tracks exist, follow them. They usually mean some one has successfully followed the drainage, and returned (hopefully).
3) Bounce along as far as you can stand, trying to control the truck as it groans in 4WD over bars of sand, gravel and small boulders.
4) Back up frequently to avoid drop offs that would bog the truck.
5) Get tired.
6) See the right place to stop: room for swags, a fire pit, a kitchen, and the truck.
7) Park, fall out of the truck and recover.
Louis and I did this. He’s initiated now.
The rocks to the north called. We walked several kilometers and looked at a dozen outcrops. The rocks showed the same sequence as south of the road. Interesting but disappointing; we were not getting any deeper in the stratigraphic section, meaning that the Paraburdoo Layer was buried. Just like Range Gorge
.
7/10: I’d driven at least 760 kilometers since July 4th, mostly on unsealed roads. A good night’s sleep in the Jimmawurranda Creek drainage had helped, but I was still tired after the rainy night. Louis was developing a cold. My allergies were fading but still taxing. Another long drive was next on the agenda. It seemed like a good time for a break. We followed the Millstream Road to Millstream.
Millstream is a part of national park. It’s historical; Millstream Station opened in the late 19th century as a cattle station and sheep station. The sheep didn’t last, at minimum because dingoes find lambs to be delectable. The cattle station persisted into the 1980s, when the government took over the lease, i.e., no more cows. Well, this is the colonial history of Millstream. The station site was a in a logical site because it is where a major aquifer breaches to the Earth’s surface. This has formed fairly permanent spring-fed pools. Of course, the Aboriginals knew this was an important place a good 20,000 years ago. New signs at the station indicated that Millstream has been an important gathering site for a number of different groups for at least that long.
I was happy to be someplace that was verdant and wet. We had enough energy for a couple of short walks among the pools. It was quite strange to hear and see running water: well, water running on the ground, not falling from clouds. Millstream had a real feeling of oasis. This was most poignant at the lily pond; a pool full of flowers, seeded there by one of the station women over one hundred years ago. I’ve never seen wild water lilies before.
Most of the large Millstream pools follow old channels of the Fortescue River, creating long curved water bodies. A swim in one of these was indicated as a pre-lunch activity. I jumped in, and happily floated in the cloud of dust, sweat, and grime dissolved from my skin as I paddled about.
Back to work. More dolomite called to the south, along the Hamersley Front. Back to hunt and find. Ok, Millstream was on the maps, so we knew where we were starting from. How about this track? Damn, a “Pastoral Lease – No Passage” sign, hand lettered in green paint on a sheet of corrugated iron. It didn’t say which station this was: no one to call about access. OK, let’s go seventeen kilometers and try this one. A locked gate, another hand lettered sign. This trend continued monotonically. I was annoyed and somewhat frustrated; the day was passing, it was time to find a swag out spot.
The road intersected the Pilbara Iron railway line (Karratha-Tom Price-Paraburdoo). I’d gotten an access permit, so we headed south along the tracks. More locked gates. Finally, the power line road, following the same trend as the railway, but here cutting across the bush – pretty close to a dolomite exposure. We took it. We swagged out close to the Front, in hopeful site a good outcrop for the next morning’s work.
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