Blinman diapir is an area of igneous intrusion, including this unusual Gneiss outcrop on the roadside of Glass Gorge, 200m past the grid heading west from Blinman.
The Nuccaleena Formation is a narrow pink dolomite layer that is frequently found in outcrops across the Flinders Ranges, and is described as being a good ‘geological marker horizon’.
This Nuccaleena Formation outcrop, just 5m wide, is seen in Parachilna Gorge, between the Brachina Formation siltstones and the older calcereous Elatina and Trezona Formations.Continue reading “Pink Dolomite: the Nuccaleena Formation”
An example of weathered Balcanoona Formation of flaggy dolomite progressing to massive dolomite with limestone conglomerate layers.
Limestone conglomerate beneath interesting dolomite formation.
For more information about the Balcanoona Formation, see The Legacy of Time.
Published by the Geological Society of Australia, South Australian Division.
One of the best records in the world of sedimentary deposition in the period of geological time between about 800 million and 500 million years ago is exposed in the Flinders Ranges, Mount Lofty Ranges and the Olary region in South Australia. Sandy and silty sediments derived from erosion of older rocks of the Gawler Craton in the hinterland to the west, and island masses of this basement rock rising from an undersea ridge over 200 km to the east, were deposited into an extensive marine basin called the Adelaide Geosyncline in which the seafloor was slowly subsiding along a series of elongated north-south step or graben faults.
During the 300 million years of continuing but intermittent subsidence of the basin floor, a thick pile of sediment accumulated in the geosyncline. This sequence was then compressed and hardened by deep burial and later folded into a high mountain range by a new regime of earth movements.
Subsequent erosion has reduced these highlands to their present form and deposited huge amounts of sediment to the east into younger sedimentary basins formed by later crustal down warping. Continue reading “Brachina Gorge Geological Trail”
An outcrop of blocks of sandstone and beds of crystalline calcite in the vicinity of a copper deposit.
This iron rich formation spanned approximately 70 metres, exposed in various states. The most prominent outcrop was silicified, with breccia and broken veins of hematite and quartz, indicating hydrothermal deposition and fault disturbance.
Step 1. Grind up mineral-rich rocks found in the area, including Hematite, Galena and earthy Malachite and Azurite.
Step 2. Smelting. To smelt iron oxide, charcoal was used to covert the oxygen into carbon dioxide, leaving iron. To smelt galena, lead sulphide, heat alone released the sulphur, leaving lead (seen below).
Leigh Creek Library has an excellent range of field guides including the following titles.