The best place to see glacial rocks in Arkaroola is Tillite Gorge, where walkers can explore several kilometres of colourful tillite / puddingstone.

Logging Requirements

In order to claim a find on this EarthCache, complete the following tasks and message the answers:

1. At the posted coordinates, there are several rocks/clasts embedded within the rock. Are they the same rock type (what are their colours)? Does this fit the description of tillite - Why?

2. Based on the rocks/clasts' angular/blocky nature, do you think it was a low energy deposition immediately before the Sturtian glaciation, or high energy deposition? Note that highly blocky and bigger sized rocks/clasts would likely indicate a low energy deposition.

3. At Waypoint 2, you will note several cores taken from the rock. How many cores can you count? Why do you think they were coring?

4. Take a photograph of your favourite trillite sample within the gorge, and upload with your log.

Introduction

Access to Tillite Gorge involves a four-wheel drive journey through spectacular Arkaroola scenery to a parking area and road terminus. A return walk of approximately two hours from the car park along Arkaroola Creek to“Lorraine’s Bar” takes you through extended deposits of Sturtian tillites in a stunningly scenic creek valley setting bounded by abrupt low cliffs of solid and unmodified glacial deposits.

Tillite

Tillite is a conglomerate rock, formed by glacial origin. The inclusions are more ancient rocks eroded from old mountains, and transported into sediments, which then were cemented together. They are also named puddingstone or plum pudding rock. These distinctive rocks may have formed when glaciers, upon reaching the sea, calved off as icebergs and dropped their rocky burden.

Deposition

The continuous sedimentary sequence from the Sturtian tillites to Arkaroola Reef is an area of research significance described here, including the early geological research, insights to ancient environments, climate change, early life, and radical theories such as “Snowball Earth”.

Precambrian evidence of glaciation and glacial tillites may be found in the Flinders Ranges, the Kimberley Region of northern Western Australia, western New South Wales and in Central Australia (Preiss, 1987 adapted from Worboys and Hore, 2013). Preiss states (1987):

“The Adelaide Geosyncline contains one of the most complete, best preserved and best documented late Proterozoic glacial sequences in the world, especially for the Sturtian glaciation.”

References

• Government of South Australia (1993) - The Geology of South Australia: Volume 1, The Precambrian; Bulletin 54.
• Wallace, M.W., Hood, A., Woon, E.M.S., Giddings, J.A., and Fromhold, T.A. (2015) - The Cryogenian Balcanoona reef complexes of the Northern Flinders Ranges: Implications for Neoproterozoic ocean chemistry, https://doi.org/10.1016/j.palaeo.2014.09.028.
• Worboys, G.L. and Hore, S.B. (2013) - Arkaroola Protection Area: A field guide to selected geological features, Arkaroola Wilderness Sanctuary and Department of Environment, Water and Natural Resources, Adelaide.