Larapinta Trail, Tjoritja / West MacDonnell National Park, central Australia – a potential geotrail

Weisheit, Anett1

1 Northern Territory Geological Survey, Department of Industry, Tourism and Trade, Alice Springs, Australia

The Larapinta Trail extends from Alice Springs Telegraph Station in the east along the West MacDonnell Ranges to the summit of Mount Sonder / Rwetyepme 230km to the west. This renowned hiking trail is divided into 12 sections (graded moderate to very hard); each section takes one or two days to walk. The Larapinta Trail is managed by the Northern Territory Government Parks and Wildlife, who provide detailed access and hiking information, and maps. General information about flora, fauna, landscape, geology, and culture is also available through various published guidebooks and trail maps.

The rocks comprising the spectacular scenery along the trail are well exposed and easily accessible. They include orthogneisses, metasedimentary rocks, and igneous rocks of two Palaeoproterozoic basement provinces (Aileron and Warumpi), and sedimentary rocks of the Neoproterozoic–Devonian Amadeus Basin. Cenozoic consolidated and non-consolidated sediments occur as colluvial and alluvial regolith. Rock types and textures exposed along the trail are therefore varied with occurrences of interesting minerals (eg garnet, staurolite) and fossils (stromatolite). There are also excellent exposures of rock relationships such as intrusive and tectonic contacts, unconformities, bedding and layering, and alteration and brecciation zones. Additionally, many of the rocks preserve evidence for ductile and brittle deformation; for instance, mylonitic shear zones, faulting, fracturing, and centimetre- to 100 metre-scale folding.

This variability of lithologies and rock structures profoundly influenced the morphology of the West MacDonnell Ranges. Deep valleys formed by shear zones, alternating ridges and valleys of sedimentary layers 10s of km long, and rolling hills of granitic rocks are some of the characteristic geomorphological features that can be seen along the trail. The rocks and their associated landscape developed over ca 1.8 billion years, including episodes of metamorphism and magmatism, terrestrial and marine sedimentation, mountain building, and erosion. They also span the time of emergence and development of early life, and preserve impact structures and palaeosurfaces.

Central Australia’s unique geology and climate support a multitude of fauna and flora, of which some can be seen along the trail. Climate in particular, but also flora, fire, and termites have in turn affected the exposed rocks leading to distinctive weathering and regolith.

The West MacDonnell Ranges are home to the Arrente People, whose ancestors lived in this country for at least 35 000 years. Some evidence of this cultural heritage, as well as remains of early European settlement can be visited along the trail, and there are excellent museums and heritage sites in Alice Springs.

A geological trail guide available in a convenient format — a small printed book, booklets, or digital data — would greatly enhance the hiker’s experience of the West MacDonnell Ranges. It would provide many benefits of geotrails outlined by the Australian Geoscience Council Inc, and others. These include, but are not limited to, ease of access along an established tourism track, provision of visitor engagement, learning and enjoyment, and promotion of conservation.


Biography

Anett studied geology at the University of Tuebingen, Germany, and worked as a mapping geologist with the Northern Territory Geological Survey in Alice Springs since 2014. She worked on a geological guide for the Larapinta Trail in her spare time.

About the GSA

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