The Red Centre has “the best rocks in Australia.”
So says current Geological Society of Australia president Amber Jarrett, speaking at historic Alice Springs Telegraph Station.
Living and working in the region, Jarrett is likely a tad biased.
But then so were almost 100 geology enthusiasts, many of them locals, who had gathered for the launch of a new book of geology and geotourism, Behind the landscape of the Central Ranges: A Geological Guide to the Larapinta Trail and Tjoritja/West MacDonnell National Park.
An estimated 5000 visitors each year pull on a backpack and sturdy boots to tread the Larapinta Trail, an internationally renowned wilderness trek for hikers (and more recently cross-country runners).
First opened in 1989 the trail was completed to full length in 2002 and winds 223km west along the West MacDonnell Ranges from the Old Telegraph Station near the town of Alice Springs (also called Mparntwe) to Mt Sonder (or Rwetyepme), the fourth highest mountain in the Northern Territory (1380m).
Along the route, walkers encounter a unique desert flora and fauna, as well as numerous gorges, peaks, and waterholes set among some of the Red Centre’s most spectacular scenery and geology, which, thanks to the arid conditions is on full display to the passerby.
The launch presentations were held in the shade of a river red gum adjacent to the normally dry Todd River and included speeches from sponsors and supporters of the book project, displays by other STEM specialists, and a presentation of the guidebook by author and NT Geological Survey geologist Anett Weisheit, who fielded questions from an inquisitive audience.
Weisheit says the book features some 60 educational stops along the route for the reader/walker, and is divided according to the 12 sections of the trail, each section colour-coded to provide a self-guided and first-hand experience of the region’s varied geology.
The book also boasts maps and presents information about Aboriginal people and the history of the region over 150 years.
Several speakers thought the book suitable for readers of all ages, from school children to university students, as well as the interested general reader.
Weisheit says her choice for the book’s structure was inspired by her education and ready accessibility to the geology of the Centre’s arid environment.
“I studied geology in Germany, that’s how I started my education”, she says. “We studied the topic, say granite or igneous rocks, and we went through them step by step with an outcrop or a rock display in the scenery.
“I thought here I could do the same because you see the rocks step by step along the trail.”
Section 2 of the trail for example, features sandstone and gneisses, she says, so these geological characteristics became the topic for that section of the book, and so on for each section of the trail.
“As you walk you have the topics; it works really well along the trail, but less so if you [were to] go to, say, the south-west coast [of Australia] where there is so much vegetation over the rocks and the landscape is [consequently] rather subdued.
“It would be less accessible to the lay person, but here [in the Centre] it is so much in your eye.”
The book guides the reader on a veritable tour de force of Australia’s oldest visible landscapes, embracing locations “aged from the Quaternary (a few thousand years) to the Palaeoproterozoic (thousands of millions of years) and spanning some 40% of Earth’s history.”
Geotourism adds considerable value to traditional nature-based tourism because it brings together landscape and geology, flora and fauna, Aboriginal cultural and post-European settlement considerations.
Australian Geosciences Council spokesman Angus Robinson
As Weisheit writes to introduce the regional geology, most of the rocks of Central Australia are “very much older than those of the Rocky Mountains or the Alps of central Asia”, their story evident from at least four mountain ranges formed over time, then eroded.
The oldest rocks seen along the trail are from the Sadadeen Range gneiss, which “formed from molten rock (magma) about 1800 million years ago (Ma).”
The rocks of Sections 1-6 are visible in the rolling hills so characteristic of the eastern parts of the trail, remnants of an earth surface of long ago, now partly erased after movements in the earth’s crust, mountain building processes, and widespread erosion.
Ranges that had formed some 1730, 1630 and 1570 Ma eroded, their sediments accumulating in an ancient shallow sea between 1000 and 800 Ma.
These sediments ultimately turned into sandstones and mudstones, sedimentary rocks that make up the layers of the Amadeus Basin—a feature that dominates the region’s geology and which can be up to 11 km deep—which was still forming up until about 360 Ma when complex life forms first began to appear.
Sections 7 to 12 cross the two oldest units of the Amadeus basin, the Heavitree Formation and carbonate rocks of the Bitter Springs Group, aged 1050 to 1000 Ma and 637 to 897 Ma respectively.
A new mountain range was formed between about 450 and 300 Ma around the time the first dinosaurs appeared.
As the dinosaurs died out this older land surface was dissected into the ranges and valleys seen today, where the past nonetheless remains clearly visible in the present.
Spokesman for the Australian Geosciences Council Angus Robinson told the gathering of the value of the red Centre to a fledgling Australian geotourism.
“Two years ago, the Australian Geoscience Council launched what is known as the National Geotourism Strategy,” Robinson says, “implemented to support the development of major geotourism projects in line with what has been happening overseas.
“Its goals include geo-trail development—of which the Larapinta Trail is one—and enhancing the quality of interpretation of the natural environment, which Anett has done most splendidly.
“Geotourism adds considerable value to traditional nature-based tourism because it brings together landscape and geology, flora and fauna, Aboriginal cultural and post-European settlement considerations.”
Geotourism, he says, can be defined as sustainable tourism focussed on the geology and landscape as a basis for providing visitor enjoyment, engagement and learning.