Stephen Hack explored the range in 1856 and in 1857 the first pastoral lease was taken up in the area,[5]Yardea, which was set up on the site of a former Aboriginal camp and included a freshwater spring later used as the station's water source. More sheep stations were soon established, including Hiltaba and Paney Station.[2] Two good seasons followed in 1857 and 1858, with pastoralists reporting permanent freshwater lakes on their runs. Stations were required to stock 50 sheep per square mile (19 per square kilometre) but soon properties such as Nonning were shearing flocks of 90,000.[5]
The first mail service from Port Augusta to Yardea commenced in 1876, with the telegraph service to Western Australia that passes through the range commencing in 1903[5]
Geology
Pink granite at Hiltaba Nature ReserveAcraman Salt Lake with Gawler Range in backgroundConical Hill Track in the Gawler Range
The rocks within the ranges were formed by volcanic activity between ~1595-1592 Ma, when the Gawler Range Volcanics (GRV) were erupted.[6] Approximately 30 000km3 of dominantly rhyolitic and daciticlava were rapidly extruded, and their eroded remnants preserve one of the most voluminous felsic magmatic events preserved on earth. Basaltic and basaltic-andesite comprise a remarkably minor component of the magmatism (<1%). The Gawler Ranges Volcanics were also erupted at remarkably high temperatures (~950-1100°C) for felsic magmas, and this, coupled with their very high halogen (particularly F and Cl) compositions resulted in low viscosity (runny) magmas when compared to typical rhyolites and dacites which are generally several hundred degrees cooler. This low viscosity resulted in emplacement as a series of lobate flows with a stacked pancake-like morphology which cooled rapidly resulting in porphyritic textures and widespread columnar jointing. The ranges are a small part of the Gawler Craton which is a craton rich in mineral resources, although many are only recently discovered and not yet fully exploited.[citation needed]
At approximately 580Ma the Gawler Ranges were impacted by a large meteorite which excavated the Acraman impact crater, in which the modern Lake Acraman now sits. The original crater was possibly as large as 90km in diameter and flung fist-sized debris several hundred kilometres to the east, where it has been preserved in sediments which now comprise the Flinders Ranges.[citation needed]
Geomorphology
The highest point is Nukey Bluff at 465 metres (1,526ft) above sea level. Bornhardts dominate the landscape.[8] Soils are invariably dominated by the weathering products of the volcanics, and are typically red in colour due to abundant oxidised iron weathering in the arid environment. No major rivers drain the ranges, however several internal catchments feed the modern playa lakes Gairdner, Acraman, Everard, McFarlane, Harry and Island Lagoon.
↑ Pankhurst et al., 2011 A Mesoproterozoic continental flood rhyolite province, the Gawler Ranges, Australia: the end member example of the Large Igneous Province clan
↑ Deborah Furbank (2010): Briefing note on the Southern Hairy-nosed Wombat. Yorke Peninsula Natural Resource Management Group PDFArchived 2012-03-25 at the Wayback Machine
In geology, felsic is a modifier describing igneous rocks that are relatively rich in elements that form feldspar and quartz. It is contrasted with mafic rocks, which are relatively richer in magnesium and iron. Felsic refers to silicate minerals, magma, and rocks which are enriched in the lighter elements such as silicon, oxygen, aluminium, sodium, and potassium. Felsic magma or lava is higher in viscosity than mafic magma/lava, and have low temperatures to keep the felsic minerals molten.
Magma is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natural satellites. Besides molten rock, magma may also contain suspended crystals and gas bubbles.
Rhyolite is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained groundmass. The mineral assemblage is predominantly quartz, sanidine, and plagioclase. It is the extrusive equivalent of granite.
Dacite is a volcanic rock formed by rapid solidification of lava that is high in silica and low in alkali metal oxides. It has a fine-grained (aphanitic) to porphyritic texture and is intermediate in composition between andesite and rhyolite. It is composed predominantly of plagioclase feldspar and quartz.
A large igneous province (LIP) is an extremely large accumulation of igneous rocks, including intrusive and extrusive, arising when magma travels through the crust towards the surface. The formation of LIPs is variously attributed to mantle plumes or to processes associated with divergent plate tectonics. The formation of some of the LIPs in the past 500 million years coincide in time with mass extinctions and rapid climatic changes, which has led to numerous hypotheses about causal relationships. LIPs are fundamentally different from any other currently active volcanoes or volcanic systems.
The rock cycle is a basic concept in geology that describes transitions through geologic time among the three main rock types: sedimentary, metamorphic, and igneous. Each rock type is altered when it is forced out of its equilibrium conditions. For example, an igneous rock such as basalt may break down and dissolve when exposed to the atmosphere, or melt as it is subducted under a continent. Due to the driving forces of the rock cycle, plate tectonics and the water cycle, rocks do not remain in equilibrium and change as they encounter new environments. The rock cycle explains how the three rock types are related to each other, and how processes change from one type to another over time. This cyclical aspect makes rock change a geologic cycle and, on planets containing life, a biogeochemical cycle.
In geology, igneous differentiation, or magmatic differentiation, is an umbrella term for the various processes by which magmas undergo bulk chemical change during the partial melting process, cooling, emplacement, or eruption. The sequence of magmas produced by igneous differentiation is known as a magma series.
The Gawler Craton covers approximately 440,000 square kilometres of central South Australia. Its Precambrian crystalline basement crustal block was cratonised ca. 1550–1450 Ma. Prior to 1550 Ma the craton comprised a number of active Proterozoic orogenic belts extending back in time to at least 2450 Ma.
Silicic is an adjective to describe magma or igneous rock rich in silica. The amount of silica that constitutes a silicic rock is usually defined as at least 63 percent. Granite and rhyolite are the most common silicic rocks.
In geology, an igneous intrusion is a body of intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth. Intrusions have a wide variety of forms and compositions, illustrated by examples like the Palisades Sill of New York and New Jersey; the Henry Mountains of Utah; the Bushveld Igneous Complex of South Africa; Shiprock in New Mexico; the Ardnamurchan intrusion in Scotland; and the Sierra Nevada Batholith of California.
The Mount Pleasant Caldera is a large eroded Late Devonian volcanic caldera complex, located in the northern Appalachian Mountains of southwestern New Brunswick, Canada. It is one of few noticeable pre-Cenozoic calderas, and its formation is associated to a period of crustal thinning that followed the Acadian orogeny in the northern Appalachian Mountains. It sits relatively near to the coastline.
Minnipa is a small town serving the local grain growing community located on South Australia's Eyre Peninsula.
Magmatic water, also known as juvenile water, is an aqueous phase in equilibrium with minerals that have been dissolved by magma deep within the Earth's crust and is released to the atmosphere during a volcanic eruption. It plays a key role in assessing the crystallization of igneous rocks, particularly silicates, as well as the rheology and evolution of magma chambers. Magma is composed of minerals, crystals and volatiles in varying relative natural abundance. Magmatic differentiation varies significantly based on various factors, most notably the presence of water. An abundance of volatiles within magma chambers decreases viscosity and leads to the formation of minerals bearing halogens, including chloride and hydroxide groups. In addition, the relative abundance of volatiles varies within basaltic, andesitic, and rhyolitic magma chambers, leading to some volcanoes being exceedingly more explosive than others. Magmatic water is practically insoluble in silicate melts but has demonstrated the highest solubility within rhyolitic melts. An abundance of magmatic water has been shown to lead to high-grade deformation, altering the amount of δ18O and δ2H within host rocks.
Igneous rock, or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rocks are formed through the cooling and solidification of magma or lava.
South Australia is an Australian state, situated in the southern central part of the country, and featuring some low-lying mountain ranges, the most significant being the Mount Lofty Ranges, which extend into the state's capital city, Adelaide, which comprises most of the state's population. Adelaide is situated on the eastern shores of Gulf St Vincent, on the Adelaide Plains, north of the Fleurieu Peninsula, between Gulf St Vincent and the low-lying Mount Lofty Ranges. The state of South Australia, which stretches along the coast of the continent and has boundaries with every other state in Australia, with the exception of the Australian Capital Territory and Tasmania. The Western Australia border has a history with South Australia, involving the South Australian Government Astronomer, Dodwell and the Western Australian Government Astronomer, Curlewis in the 1920s to mark the border on the ground.
Yardea Station is a pastoral lease in the Australian state of South Australia that operates as a sheep station, now within the Gawler Ranges National Park. Paney Station became part of Yardea Station in 1904.
The Southern Oklahoma Aulacogen is a failed rift, or failed rift arm (aulacogen), of the triple junction that became the Iapetus Ocean spreading ridges. It is a significant geological feature in the Western and Southern United States. It formed sometime in the early to mid Cambrian Period and spans the Wichita Mountains, Taovayan Valley, Anadarko Basin, and Hardeman Basin in Southwestern Oklahoma. The Southern Oklahoma Aulacogen is primarily composed of basaltic dikes, gabbros, and units of granitic rock.
Archean felsic volcanic rocks are felsic volcanic rocks that were formed in the Archean Eon. The term "felsic" means that the rocks have silica content of 62–78%. Given that the Earth formed at ~4.5 billion year ago, Archean felsic volcanic rocks provide clues on the Earth's first volcanic activities on the Earth's surface started 500 million years after the Earth's formation.
The Sleaford orogeny was an event in the assembly of the Gawler Craton, which now underlies the Eyre Peninsula in South Australia. Between 2.46 and 2.41 billion years ago in the Proterozoic, the Sleaford and Mulgathing complexes emplaced among the older 3.15 billion year old Archean Cooyerdoo Granite 2.82 billion year old Coolanie Gneiss with sedimentary, felsic and ultramafic igneous rocks. The overlapping Sleaford orogeny caused deformation and greenschist and granulite-grade metamorphism on the sequence of metamorphic facies.
Hiltaba Nature Reserve is located in the north of the Eyre Peninsula on the western edge of the Gawler Ranges, South Australia. It is situated on a former pastoral lease known as Hiltaba, or Hiltaba Station, that had operated as a sheep station. It is owned by the Nature Foundation, which purchased the property in 2012.
This page is based on this Wikipedia article Text is available under the CC BY-SA 4.0 license; additional terms may apply. Images, videos and audio are available under their respective licenses.
