Between June 8th and 11th we will be camping along the Paralana escarpment, a tectonically active area in the middle of the Indo-Australian plate, thousands of kilometres away from the nearest plate boundary. Over the course of the three days we will have the opportunity to visit sites along the escarpment which preserve evdience of the mild tectonism currently shaping the region- see Figure 1 for a locality map. In the next few pages I detail a number of exposures I described as part of my B.Sc (Hons) under the supervision of Mike Sandiford in 2002. We will probably not have time to visit all the localities, but I hope that the localities we do visit will serve to dispel the notion that Australia is in a geological coma!
The trip so far has dealt with the ancient geological history of the region, so, before describing the field localities we will visit, I begin by briefly outlining the Phanerozoic geology of the region.
Following the Delamerian orogeny, tectonic reactivation during the Devonian and Carboniferous 'Alice Springs' events is indicated by a number of low-temperature thermochronometric studies (Gibson and Stuwe, 2000; McLaren et al., 2002a). The Mt Painter region is then understood to have undergone an extended period of tectonic quiescence. During this time, topography developed during the Cambrian and Devonian/Carboniferous tectonic episodes was eroded to a peneplain (Coats and Blissett, 1971a). Coats and Blissett (1971a) argue that this planation surface- The Freeling Heights Surface, is preserved as erosional remnants atop peaks in the area.
Crucial in understanding the nature and timing of recent activity along the Paralana escarpment, are the sediments to the east of the range front, within the Frome Embayment. Descriptions of these sediments and their significance have been made by Callen (1974) and by Callen and Tedford. (1976).
The Frome embayment is a closed draining system which receives surface run-off from the Flinders Ranges to the west, the Olary Ranges to the south and the Barrier Ranges to the east. During the Palaeocene to Eocene fine to very coarse-grained, sub-mature to mature sands with characteristic basal pebble beds of the Eyre Formation were deposited within the Frome Embayment. (Callen, 1974) shows that deposition of the Eyre Formation ceased during the Upper Eocene leaving a widespread sand blanket. Following deposition of the Eyre Formation, stable conditions prevailed throughout the Oligocene to Early Miocene, during which time silcrete was developed as a cap on many of the Eyre Formation outcrops.
Sedimentation re-commenced within the Frome Embayment during the Lower Middle
Miocene with the deposition of alternating fine to medium grained sand, silts and clay as well as thin dolomite beds. These low-energy fluviatile and lacustrine sediments of the Namba Formation (Callen, 1974) are overlain by the Upper Miocene to Pliocene, possibly Lower Pleistocene Willawortina Formation. Callen and Tedford. (1976) argued that the transition from low-energy sediments of the Namba Formation, to the extremely poorly sorted, wedge shaped deposits of bouldery to pebbly sediments of the Willawortina Formation represents the initiation of Late Cainozoic uplift of the Flinders Ranges.