Warning: Please do not park at the listed co-ordinates alongside the M4 motorway. These co-ordinates have been taken from the path ABOVE the road, not at street level. To access this location, please park in a safe area, and make you way to the elevated track above the road on the northern side. Parking is also available at the intersection of Old Great Western Highway and Mitchell's Pass (see child waypoint). There is an easy one kilometre walk, with stairs, to the cache's location.
A second car parking option is at the end of Knapsack St, Glenbrook, following the Lapstone Zig Zag walk (thank you to marhleet for highlighting this option).
Cache description: As you travel around area you'll see many bridges and buildings made of sandstone, This is because sandstone, and other sedimentary rocks, form a large percentage of the Sydney region.
The history of Sydney’s sedimentary history can be divided into three sections.
During the Ordovician to Carboniferous time (470 to 330 million years ago), layers of rock formed in what is known as the ‘pre-Sydney Basin’ period. Many of these rocks in the Sydney region were folded and eroded, but examples of them still to west of the Blue Mountains.
Most of the rocks in the Sydney Basin, in particular the Blue Mountains, were formed during the Permian and Triassic periods (290 to 230 million years ago). Rocks that had eroded from the pre-Sydney Basin period were once again laid down to form a new generation of sedimentary rocks.
The final period of rock building occurred during the Jurassic to Tertiary periods (205 millions years ago to today). During this time, volcanic basalt rocks formed in places where lava broke through the surface. These basalts eroded and formed into gravel, which was later layered to form gravel beds.
Also during this time, large flooding events caused the movement of pebble shaped rocks and boulders to be deposited as conglomerates – a mixture of different sized rocks, similar to a plum pudding.
The area where you are standing shows layers of sedimentary rock formed during the Triassic period.
Since its formation, the rock layers have continued to be shaped and stressed, with small folds and faults visible in the layers.
To log a find you must email me with the answer to the following questions.
- How many ‘large’ faults lines appear in the rock layers?
- Where does the ‘conglomerate layer’ appear in the cutting?
Handicaching rating: H11115
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