On this excursion we will examine some interesting and unusual Adelaidean and early Cambrian rocks near the eastern margin of the Adelaide Fold Belt. We will spend Day 1 in the region around Truro, starting with a scenic walk to observe Kanmantoo sediments exposed in the gorge of Middle Hut Creek. We will drive along the Truro-to-Eudunda road to examine outcrops of Appila Tillite (the local equivalent of Sturt Tillite), and Truro Volcanics, for which Truro is (geologically) famous. These volcanic rocks are important as they are one of the few formations in the Adelaidean sequence that can be dated radiometrically, thus providing an absolute (numerical) age. “Hands-on” activities will include fossicking around the old Wheal Barton copper mine, identifying a lamprophyre dyke and examining a diatreme - a volcanic pipe which has brought up some interesting minerals – another fossicking opportunity!
Day 2 will be spent exploring Red Creek, about 14 km southeast of Truro as the crow flies – and a very scenic 26 km drive from Nuriootpa where we will overnight. This creek is a hidden geological treasure. Firstly, it contains some of the best exposures to be found of Truro Volcanics. These are interbedded with early Cambrian sediments (Heatherdale Shale, of the Normanville Group) in the form of thin ash bands and basalt flows. Some of the basalts exhibit “pillow” structures, indicating that the lavas cooled rapidly as they poured into a sea or lake. Further up the creek the shales grade into fine sandstone in which the tracks of giant Cambrian worm-like creatures can be seen crossing a rippled sea floor. We have permission from the landowners to access this very special and rarely visited locality. Note that it involves walking along a rough path alongside and occasionally within the creek – and a steep scramble up the hillside if you wish to see the pillow lavas close up (it is worth it!).
Ideally we would prefer participants to attend for the whole weekend in order to enjoy the whole geological experience, but there is the option of attending for one or other of the days. Please indicate when you sign up for the trip whether you will attend for the whole weekend, or Day 1 or 2 only. For those attending for the whole weekend we will overnight at Nuriootpa, recommended accommodation the Vine Inn. Please make your own booking: Phone: 08 8562 2133 or online via email@example.com.
We will have dinner together on Saturday night at the Vine Inn.
Sign up at the May or June FGC meeting, or contact Frances (firstname.lastname@example.org)