Gunniopsis tenuifolia, the Narrow-leaf Pigface, growing in sand around the Cutaway outcrop to the south of Copley, northern Flinders Ranges. They are uncommon and endemic to South Australia, growing between Leigh Creek and the Painted Desert to the north of Coober Pedy.
This striking outcrop near Copley exhibits a range of sedimentary deposits. From the north to south, green shale and blocky siltstone meets weathered sandstone. This is followed by a distinct tillite layer between two dolomite layers, and a thin layer of quartzite. Further along, siltstone layers coloured by iron oxide, and more weathered sandstone.
Recent studies in the area suggest that the northern Flinders Ranges area was a shallow marine or lagoonal setting prior to the climate changing into one of the earth’s most severe glaciations ever recorded (the global Sturtian Glaciation), 720 million years ago . Over these older rocks, we find layers of pebbly, mixed rocks (called diamictites) that were likely deposited by a glacier at its edge, along with some sand layers (Bolla Bollana Tillite). These rock layers are thought to show the movement of the glacier as it advanced and retreated along the coastline. These layers then change into sandstones and mudstones with large rocks (called dropstones), which probably formed when the ice started to melt, in an area just in front of the retreating glacier (Wilyerpa Formation). After the glacier melted, the layers of rock that formed (Tapley Hill Formation) include thin, layered shales and carbonates that were deposited underwater.
Weathered sandstone:
Continue reading “Glacial geological formation: sedimentary deposits”
Collared Sparrowhawk in the northern Flinders Ranges. These swift bird hunting hawks are typically approachable, with this one feeding on sparrow within a few metres of the observer.
Little Pied Cormorant at the inlet of Copley Retention Dam.
Adult female White-fronted Chat, at Copley Retention Dam in winter.
Swainsona minutiflora is a vulnerable species. Sparsely recorded sightings have been recorded between Marree and Marla, observed on the Copley commons from winter to spring. Flowers are a tiny 2-3mm, with the plant growing to around 12cm wide.
A minute flowering plant, possibly a Pigmy Sunray (Rhodanthe pygmaea), observed on the Copley commons in July. Some of these entire plants are as small as 10mm wide.
Far less common in the Northern Flinders Ranges than the Square-fruit Twinleaf is the Koch’s Twinleaf (Zygophyllum kochii), seen flowering in July in a small zone near the disused railway track on the north commons of Copley. Koch’s Twinleaf has a conservation status of near threatened.
The Square-fruit Twinleaf (Zygophyllum prismatothecum) is the predominant Twinleaf appearing after rains on the limey clay plains in the Copley area, distinguishable by its oblong narrow capsule fruit form.
