Sunday, June 12, 2011

The Dinosaur Tracks of Western Australia May Go Extinct



You really have to want to visit Broome and nearby environs in the Kimberly region of Western Australia, because it’s a long ways from nearly everywhere else in the world. Even of the Australians I’ve met, relatively few have been there, despite Broome’s beautiful beaches, camel rides on those beaches, a wonderful open-air theater (the oldest In Australia), pearling history, longtime connections to Asian culture, small-town feel, and charming locals. Oh, and its dinosaur tracks, which of course was one of the reasons why I was motivated to go there with my wife Ruth in 2009.
Anyone up for some “ichnotourism”? At low tide near Broome (Western Australia), you can see some of the biggest dinosaur tracks in the world, made by sauropods about 130 million years ago. Or, you could put a gas-processing plant on top of them and build a port, which will generate absolutely no ichnotourism, stuff up the local environments, and if anything drive people away from the area. Hmm, tough choice: (A) short-term profits benefiting a few people and causing lots of collateral damage, vs. (B) preserving a world-famous natural resource, coastal environments, and cultural heritage that will continue to give back tourism dollars to the local community in perpetuity. Not to bias you, but I’m going with (B). (BTW, lovely wife Ruth for scale.)

It was May 2009 when we decided to go to Broome for a week-long vacation after field work had been completed on the Victoria coast. We had been looking for trace fossils in the Cretaceous rocks east and west of Melbourne, Victoria and had done a final field check for a paper I had just written, reporting the oldest known dinosaur burrows interpreted from the fossil record. As mentioned earlier, there were many touristic incentives for us to go to Broome, but a major factor in our decision to visit was its dinosaur tracks, which can be easily viewed by the public.
Broome had been on my list of places to visit in Australia ever since I had seen a talk in 2002 by Australian dinosaur ichnologist Tony Thulborn. Thulborn’s talk was at the International Palaeontological Congress meeting, held in Sydney that year, a meeting that gave me a great reason for the first of many visits to Australia. His presentation had the deliberately provocative title, “Giant Tracks in the Broome Sandstone (Lower Cretaceous) of Western Australia.”
The summary (abstract) of his talk also promised to provide evidence that these dinosaur tracks were the largest known, which by default made them the largest tracks made by any animals in the history of the earth. It was quite a claim, but he backed it up with photographs and careful measurements, the latter indicating tracks that were nearly 2 meters (6.6 ft) wide! At the end of his talk, he then justifiably bragged, “Mine’s the biggest!” (He assured us he was only talking about the tracks.)
I made a point of seeking out Dr. Thulborn afterwards to discuss his results, partially as an ichno-groupie, but also wanting to introduce myself as someone who was interested in coming back to Australia, perhaps to study trace fossils with him or someone else there. (The studying trace fossils part actually happened, but with other people, and it turned out just fine.) We had a nice, too-short chat about the tracks and fossil tracks in general, shook hands, and I haven't seen him since. Oh well.
Even more unfortunate, the research on the tracks seemed to halt after 2002, which I understood through the paleontological grapevine (or “bush telegraph”) was related to a large number of complicated reasons, summarized simply as “life.” A reality is that not everything in science gets done, and sometimes that includes really important, high-profile discoveries that involve the “D” word. No, not that “D” – I’m talking about dinosaurs.
In 2009, seven years after meeting Dr. Thulborn, I still remembered his talk and its photos of the spectacular dinosaur tracks near Broome, and knew I still wanted to go there. So I suggested to my faithful field companion, Ruth, that we might consider a trip to Broome after finishing field work in Victoria that year. As mentioned earlier, Broome had plenty of couple-oriented activities other than looking at more Cretaceous rocks. But I must admit that I would not have argued so persuasively about traveling across two continents and an ocean – Melbourne to Broome, then Broome to the eastern U.S. afterwards – if it had not been for the dinosaur tracks there. There really aren’t many places in Australia where you can see such tracks, and in an easily accessible (and free) public place. In contrast, Lark Quarry, the world-class tracksite near Winton in Queensland, charges admission (although it’s worth every penny), and Victoria has very few dinosaur tracks. (Well, OK, scratch that last statement. And you should buy these guys beers next time you see them.)
Naturally, we went and had a great time in Broome for the week we were there, with one of the highlights our seeing the dinosaur tracks there. The tracks are just west of town and along the coast, so we hired a rental car for the day and drove to a parking lot next to the best-known public site for the tracks, Minyirr-Gantheaume Point. You can’t just there go whenever you feel like it, though, but you need to read local tide charts ahead of time, as the tracks could be under meters of water when you arrive. And I do mean meters, because Broome and that area of Western Australia has some of the highest tide ranges of anywhere in the world, close to 10 m (or 33 feet, for you metric-phobic Yanks out there). So we had timed our visit for both low tide and sunset, which also afforded low-angle light that helped to accentuate the tracks.
Beautiful exposures of the Lower Cretaceous Broome Sandstone at Minyirr-Gantheaume Point, just west of Broome, Western Australia. Notice how the rocks above are red and white, whereas the rocks below look a little green around the gills? That’s the part submerged with every flood tide, meaning you’ll need snorkeling gear if you want to see dinosaur tracks then.
Minyirr-Gantheaume Point has a nicely done information kiosk just above the rocky marine platform containing the dinosaur tracks, with attractive signs telling visitors about both the tracks and their connections to the indigenous people of the area, the Rubibi. You see, tracks both modern and fossil, as well as their representation as iconography, comprise a key part of the spirituality and heritage of indigenous people in Australia, thus playing an integral role in the longest continuous human culture on earth. In this instance, the tracks reflect part of a Dreamtime story and songline, in which a Lawmaker named Marella (“Emu Man”) left three-toed tracks along his route. This reference to three-toed tracks is no doubt linked to those of theropod-dinosaur tracks in the area, but also may have been influenced by modern emu tracks, which closely resemble the theropod tracks in size and form. These sorts of connections between ancient legends of indigenous people and fossils are also common with in North America, but had at least 30,000 years longer to develop in Australia.
Several actual-sized molds of a typical three-toed theropod track are set in concrete at the kiosk, and part of the display states how at least nine types of dinosaur tracks have been discovered from the area. This area along the coast, much of it bearing dinosaur tracks, is also called the Lurujarri Heritage Trail, and is about 80 km (50 mi) long, reaching from just south of Broome to the north as part of an incomparably scenic area of Western Australia, sometimes simply called the Kimberley. Not coincidentally, this trail has thousands of dinosaur tracks throughout much of it, which has led some paleontologists (including Thulborn) to state that it might be one of the richest sources for dinosaur tracks in the world. Supposedly at least 16 types of dinosaur tracks (ichnospecies) have been identified from this assemblage, but they haven't been studied well enough to say exactly what dinosaurs made all of these. Astonishingly, only six dinosaur bones of any age have been found in all of Western Australia, so their presence fills in a considerable gap in the fossil record of dinosaurs in this part of the world, while also demonstrating yet again why dinosaur tracks matter.
Dinosaur “tracks” that are actually modern human traces, where the cast of a theropod dinosaur track was used to make artificial ones in concrete. I’m assuming these are based on a real track from the Broome area, but alas, further information was lacking. Shoe size: 8 1/2 (mens).
Of course, we weren’t just satisfied with an information kiosk and faux tracks, so we descended onto the rocky shoreline to look for the real things. We had read that the best ones are visible in the lowest part of the intertidal range, giving us a starting point in our search, but we also looked at what might be exposed in cross sections of the strata along the way. It was a very nice task, as the variegated sandstone beds were seemingly illuminated from within by the setting sun, making for lovely scenery.
Outcrop of the Lower Cretaceous Broome Sandstone, looking good near sunset along Minyirr-Gantheaume Point near Broome.
Sure enough, we found places where the normally flattish layers of sandstone looked like they had been punched downward and warped into unusual forms. These were likely dinosaur tracks in cross-section, very similar to ones I had seen in Jurassic and Cretaceous rocks of the western U.S. Sometimes such odd structures, when recognized as coming from dinosaurs, are nicknamed “brontosaur bulges.” The hypothesis for these features is that they were formed by compression of soft sandy layers by the feet of multi-ton dinosaurs, such as sauropods, that through their great weight deformed sediment well below where their feet actually touched the original surface.
So-called “brontosaur bulges” seen in cross-section, probably caused by sauropod dinosaurs when they stepped on soft sand about 130 million years ago, but they also could have been from large ornithopods, stegosaurs, or other weighty dinosaurs.
Further down we went, until at the water’s edge we spotted the large, three-toed tracks. Their narrow toes, sharp clawmarks, and narrower widths compared to lengths meant they were probably theropod tracks. The theropod tracks, most of which were 25-30 cm long, show this area had relatively large predatory dinosaurs in this area of Australia during the Early Cretaceous. Using a little formula for figuring out the approximate sizes of the trackmakers – 4.0 X footprint length = hip height – these theropods had hip heights of about 1.0-1.2 m (3.3-4 ft), which made them much larger than, say, Velociraptor, but smaller than Allosaurus.
Theropod tracks at low tide, preserved in the Broome Sandstone. Looks like at least one trackway is there, with the theropod heading toward Ruth, probably because she's modeling the latest in paleontological footwear.
A theropod track at low tide in the Broome Sandstone, with my left foot (25 cm long) next to it for scale. You know, there’s something about seeing the real thing that’s so much better than those phony ones by the car park.
video
 A pan of an area bearing some theropod tracks at Minyirr-Gantheaume Point and a brief paleontological explanation by Yours Truly.
More tracks were just to the north along the shoreline, but not of theropods. These were more akin to those Dr. Thulborn had mentioned in his talk seven years previously. These huge depressions were very likely sauropod tracks, some of them about a meter wide. Although these didn’t show any good definition of toes (thus they were probably undertracks), their overall size and shape were very similar to those of undoubted sauropod tracks I had seen in Late Jurassic rocks of Utah and Colorado. In some places, these depressions aligned, indicating apparent trackways, and a few showed a double–register where the rear foot (pes) overlapped the front foot (manus) as these sauropods walked slowly through this area about 130 million years ago.
Double-register or indirect register (right), where the rear foot of a sauropod stepped onto the track made by the preceding front foot of the same side. Yes, that's another probable sauropod track just to the left. Wow, sure are a lot of dinosaur tracks in this area. Reckon it and the shoreline north of Broome deserve National Heritage status?
video
This is your lucky day: yet another video explanation of the dinosaur tracks at Broome, but about the sauropod tracks. Sorry for it not having a cheery (or cheeky) soundtrack, too, but at least you get to see a brief cameo appearance by Ruth.
OK, that’s the nice, warm, fuzzy part: privileged American tourists travel far to see dinosaur tracks in Western Australia, have a good time, go home, and share their adventure with friends, students, sworn mortal enemies, and indifferent strangers. Then why the inflammatory and gloomy headline to this story?

Well it turns out that a liquefied-natural-gas (LNG) processing plant, accompanied by a port and other major development, is being planned for James Price Point, about 60 km (35 mi) north of Broome and part of the 80-km long coastline holding the dinosaur tracks. The plant would be the joint effort of a number of energy companies, including Shell and BP. (Gee, what's the worst that could happen?) Anyway, the plan has recently received a lot of attention from environmental and indigenous-rights activists (see links at the end of this post), and seems that most people are not very happy about it. Also, according to Tony Thulborn (remember him?) in a long, detailed online comment to a recent news story in Nature, this is probably the worst place possible to put the plant because of how it will adversely affect (that’s lawyer-speak for “destroy”) the dinosaur tracks in that area.
But this isn’t just a matter of direct destruction of the tracks, which will certainly happen in the immediate vicinity of the plant. Scientifically invaluable trace fossils north and south of the plant also could be buried under thick layers of sand, meaning that paleontologists won’t be able to study them. You mean, the people behind the gas-processing plant are actually going to hire trucks to carry in heaps of sand and dump them onto the dinosaur tracks, just to tick off those crazy scientists and environmentalists? (Cue Mr. Burns laughing diabolically in the background.)
No, it’s a matter of shoreline dynamics at play, and how we humans can alter these factors once we change a shoreline, however little or big. The port will host large tankers, which in turn will require breakwaters, groins, and other modifications to the shoreline. How the sand will be moved by longshore drift, tides, or storms then comprise a big question mark. Although, on the plus side, more sand in some places along the shore might hide the tracks and thus better preserve them. But there’s no way to know which ones will win the “longshore lottery,” so to speak.
So what can you do to help make sure these 130 million-year-old tracks are around a few more years so that scientists can study them, tourists can see them, and an important part of indigenous cultural history is kept alive? Write to the following bloke and tell him (politely, using the word “please” as much as possible) that you would like this area to have National Heritage status. Then it will be less vulnerable to development, and more likely to change in a slower and more geologically appropriate way.
The Honourable Tony Burke, MP
Minister for the Environment
PO Box 6022
House of Representatives
Parliament House
Canberra ACT 2600

The decision about whether this area will get National Heritage status will be made by June 30, so do your best to make your voice heard before then. As one of the signs said at Minyirr-Gantheaume Point: “Please look after our country. If you do, this country will look after you.”

Sunset on Cable Beach near Broome, Western Australia. Is the sun setting on the dinosaur tracks of Western Australia, too? Yes, but let's hope it does literally, and not metaphorically.



And today's appropriate song for ending this post is Return to Country, by Kerrianne Cox, who is from Western Australia and working with other activists to oppose the LNG plant at James Price Point. The reverie interrupting the song and slide show doesn't quite work for me, although I agree with the sentiment, especially the exquisite Cretaceous rocks in that part of Australia.

Pertinent Links

Gas hub 'would destroy dinosaur prints

PRI story, “Dinosaurs Walked Here,” including audio interview (MP3) with Dr. Steve Salibsury, paleontologist at University of Queensland:
Pindanpost (blog) with lots of links about the story

2 comments:

  1. Great blog... didn't even realise about those giant sauropod footprints.

    ReplyDelete
  2. I like this web site very much, Its a rattling nice position to read and get information.


    Gas Training

    ReplyDelete