Bladensburg National Park has a monsoonal climate like Townsville so we expected it to be quite dry when we visited in late September. There had been winter rain, though, and it was actually greener than the Charters Towers area.
We saw storms in the distance as we drove towards the park, and again on our first night, while puddles and small waterholes in the gullies testified to recent rain. The camping area is on Surprise Creek, and the waterhole it is named for was perhaps a hundred metres long and fifteen across, although quite shallow.
The vegetation is a mosaic, all tolerant of dry conditions but critically dependent on the soil (or lack of it). Spinifex, Mitchell grass, shrubs and fair-sized trees alternate with bare rock and gravel.
With lots of beautiful scenery to show off, I have uploaded more and bigger pictures than usual. Scroll through them in the lightbox to see them at full size.
Deep history
The whole of Western Queensland was under water in the time of the dinosaurs, depositing layer upon layer of sedimentary rocks (and a fair few dinosaurs, now fossils) over millions of years. Since it dried out, it has all been eroded by rivers and wind, and parts of it have been capped by volcanic lava, to leave us the landforms we see today.
Up around Porcupine Gorge the high ground is volcanic, as it is around Carnarvon Gorge. In both areas, cracks in the basalt have been eroded to form gorges, then valleys, then wide open plains. But White Mountains and Bladensburg missed out on the volcanoes, so what formed Sawpit Gorge and the mesas around Winton?
The answer is a natural concrete formed by mineral-rich water soaking through soft sandstones and mudstones to form a ‘duricrust‘. It may be called silcrete or ferricrete according to its chemistry, but the important thing is that it’s hard enough to act as a cap like the basalt. My ‘diving board’ at Sawpit Gorge (scroll down) is a tiny but dramatic example.
Geology is destiny
The pictures above should now make more sense.
The bed of Surprise Creek is duricrust, as is the flat ground around Skull Hole. The Logan’s Falls landscape is mostly duricrust, too, some of it breaking down into rubble and pebbles, while Skull Hole itself and the gorge below Logan’s Falls formed from cracks in that rock.
Most of the land around the Bough Shed Waterhole is sandy soil dropped by Surprise Creek as its course has varied over thousands of years, and the banks beside the creek crossing suggest that the soil is probably only a metre or two deep.
Plants generally establish quickly on any loose soil, so bare patches are silt and sand recently dropped by run-off, or rock. If you’re as curious as I was, the Geological Service has great maps and you can download their Winton map via this page.
• Introduction and index to Bladensburg (Paluma – White Mountains) blog posts late 2022.
We learned during our visit that ‘Skull Hole’ was so called because it was a massacre site. That’s all we learned, though. According to the Colonial Frontier Massacres Project a settler party attacked local people in 1877, killing about 200 of them in response to the death of one of the settlers’ stockmen (more details).