Aerial view of ridges lit orange by the evening sun, with a winding track below, near The Pinnacles at Arkaroola

Planetary Geology Field Week, Arkaroola 2026

Rock Wallaby 1

Trip diary, part 3 of 3: Stromatolites and the road home

Photo: RW1 team

After three days stuck in Hawker (part 1) and a big push north to Arkaroola (part 2), we had one more full day in the field before heading home.

Day 6Friday 14 August

Stromatolites, a gorge and The Pinnacles

Another day of geology with Steve Hore. First up were stromatolites in the low walls on either side of a chalky creek bed. The area has been flagged for World Heritage assessment.

Stromatolites are layered structures built up by mats of microbes, and they're some of the oldest signs of life on Earth, which is why anyone interested in looking for life on Mars pays them a lot of attention.

The team standing in a dry, stony creek bed with low rocky walls and gum trees
Starting out along the creek bed.

Then we walked through a gorge, and through many millions of years of geological history, from the Cryogenian glaciations to the carbonates of enormous barrier reefs and soft sediments from the old seabed. There were more stromatolites up on the steep gorge slopes, which were a bit precarious in places.

A wall of thinly layered pale and brown rock with a yellow measuring staff and a hammer for scale
Layer upon layer in the gorge. The staff and hammer give the scale.
Layered orange rock with a scale card
Wavy layered rock with a geology hammer
A pale boulder with swirling patterns beside a hammer
Close-up of a textured orange rock face with a scale card
Some of the close-ups from the day. Cards and hammers for scale.
A grey layered cliff topped with pink flowering plants
Looking up at steep rocky slopes with shrubs and a tree against a blue sky
Wildflowers on the cliffs, and the steep slopes of the gorge.

Steve Hobbs also ran some trials with his rover.

To end the day we headed to a lookout over The Pinnacles as the evening came on.

A walking track through red-leafed plants towards a rocky outcrop, under grey cloud
On the way to the lookout.
The Rock Wallaby 1 team posing for a group photo in front of hills
Most of the Rock Wallaby 1 crew.
Day 7Saturday 15 August

Home time

An early pack-up at the Shearers' Quarters and goodbyes to the Arkaroola staff.

On the way out we made one last stop at some stromatolites on a low hill beside the road, just as we were leaving the Arkaroola area. Then it was the long drive back to Adelaide.

A rounded rock with fine layering on red soil, with a Geological Society of Australia scale card
Four white 4WDs parked on a gravel road under a cloudy sky
One last look at the rocks beside the road, then home.
Planetary Geology Field Week logo: Mars above crossed rock hammers

Thanks

A big thank you to Steve Hore, Doug Sprigg and all the staff at Arkaroola, and to the Hawker Hotel for finding room for fifteen unexpected guests.

Diary by Thomas Windsor. Photos by Thomas Windsor, Clare Fletcher, Ryan Kupferle and other members of the team.