The Sacred Canyon is located 12 kilometers off Flinders Ranges Way and about 60 kilometers north from Hawker. The road in is subject to flooding with many creek crossings and can be quite muddy at times.
The sacred canyon is a significant site for the Adnyamathanha people. The age of the engravings here are of a date unknown but the Adnyamathanha people believe that the engravings were not made by people but were created for them by ancestral beings during dreamtime.
Aboriginal Engravings
The Adelaide Rift Complex (also known as Adelaide Geosyncline) is a major geological province in central South Australia. It stretches from the northernmost parts of the Flinders Ranges, narrowing at the Fleurieu Peninsula and extending into Kangaroo Island, and composes the two major mountain ranges of the State: the Flinders Ranges and the Mount Lofty Ranges. The sediments in the rift complex were deposited between about 870 Ma (the middle Neoproterozoic) to ~500 Ma (the end of the Cambrian). They consist of a thick pile of sedimentary rocks and minor volcanic rocks that were deposited on the eastern margin of Australia during the time of breakup of the supercontinent Rodinia. A number of authors have noted the similarity in these sedimentary rocks with rocks found in western North America and have suggested that they were formerly adjacent to each other in Rodinia.
Flinders Ranges from the Cazneaux Tree
Sandstone is a clastic sedimentary rock composed mainly of sand-sized minerals or rock grains. Most sandstone is composed of quartz or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any color, but the most common colors are tan, brown, yellow, red, grey, pink, white, and black. Since sandstone beds often form highly visible cliffs and other topographic features, certain colors of sandstone have been strongly identified with certain regions. Rock formations that are primarily composed of sandstone usually allow percolation of water and other fluids and are porous enough to store large quantities, making them valuable aquifers and petroleum reservoirs. Fine-grained aquifers, such as sandstones, are better able to filter out pollutants from the surface than are rocks with cracks and crevices, such as limestone or other rocks fractured by seismic activity.
Cement is what binds the siliciclastic framework grains together. Cement is a secondary mineral that forms after deposition and during burial of the sandstone. These cementing materials may be either silicate minerals or non-silicate minerals, such as calcite. Silica cement can consist of either quartz or opal minerals. Quartz is the most common silicate mineral that acts as cement.
Cementation involves ions carried in groundwater chemically precipitating to form new crystalline material between sedimentary grains. The new pore-filling minerals form "bridges" between original sediment grains, thereby binding them together. In this way sand becomes "sandstone", and gravel becomes "conglomerate" or "breccia". Cementation occurs as part of the diagenesis or lithification of sediments. Cementation occurs primarily below the water table regardless of sedimentary grain sizes present. Large volumes of pore water must pass through sediment pores for new mineral cements to crystallize and so millions of years are generally required to complete the cementation process. Common mineral cements include calcite, quartz or silica phases like cristobalite, iron oxides, and clay minerals, but other mineral cements also occur.
Cementation
These questions can be answered when you reach the rock pool / rock shelter.
Questions
Q1 While standing on the river pebbles, describe the rock in colour and texture on either side of the gorge. Is the rock different on each side?
Q2 Describe the river pebbles in colour and texture that you are standing on. Are they different from the walls around you?
Q3 Cement is a secondary.....?
(Optional) Q4 How many rock engravings can you see? Without touching them, what do the look like up close.
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References ~ SA government info sign, Wikipedia