The Gammon Ranges are composed of folded and faulted sediments of the Adelaide Geosyncline. This very thick sedimentary sequence was deposited in a large basin during the Neoproterozoic on the passive margin of the ancient continent of Rodinia. During the Cambrian, ~540MYA, this area was part of the massive structural deformation event known as Delamerian orogeny, when this sedimentary sequence of rocks was folded and faulted into a tall mountain range. The area has undergone subsequent massive erosion resulting in the relatively low ranges seen today.
Most of the high ground and ridgetops are sequences of hard quartzites that outcrop along tips of the ranges in a cuesta (sawtooth) form. Synclines, representing the base of U folds, now form the high parts of the ranges. The high central range and plateau is surrounded by a number of smaller outlying ranges, creating the encircling pounds of low hills: Balcanoona Range encloses Illinawortina Pound to the east, Mainwater Pound is to the north, enclosed by the Yankaninna Range, and Arcoona Pound to the west.
At the listed coordinates a large carved boulder sits on a bed of quartzite rocks. The base rocks are the same hard rocks that form the ridges of the mountains around this dramatic location. Please inspect these rocks and boulder, and take some precious time to admire the view.
Earthcache Tasks. Please send your answers to the cache owner. You may log this earthcache straight away but do not forget to send your answers.
- What colour and texture are the quartzite rocks at the base of the boulder?
- What property of the quartzite rocks has reduced the rate of erosion of the mineral?
- Is the carved boulder a match for quartzite rocks? If not why is it different?