Geological Setting
The Cape Granite Suite formed about 560-520 Ma during the Saldanian orogeny which occurred between 780 to 510 Ma (Harris & Vogelli, 2010; Villaros, Stevens & Buick, 2009). This orogeny formed as a result of the convergence of the Rio de la Plata and Kalahari cratons during the formation of Gondwanaland (Harris & Vogelli, 2010). The granitoids of the CGS were intruded into the three terranes of the metasedimentary and metavolcanic Malmesbury Group which are divided by distinct north-west trending shear zones (Scheepers, 2000). These terranes include the southwestern Tygerberg terrane, Swartland terrane at the centre and Boland terrane to the north east (Fig. 1) (Scheepers, 1995).
The Saldania mobile belt comprises of structural features that are characterised by the occurrence of ductile and dextral strike-slip shearing that preceded the orogenic event which occurred approximately 600 Ma (Scheepers, 2000). This led to the first phase of magmatism about 560-540 Ma (Scheepers & Nortje, 2000). This phase involved the syn- to post tectonic S- type granites intruding the Tygerberg terrane (Scheepers & Nortje, 2000). The second phase involved the intrusion of the I-type granites. Like the S-type granites, the strike-slip movement affected the intrusion of the I- type granitoids which occurred along the Colenso fault in the Swartland and Boland terranes about 540- 520 Ma (Scheepers, 1995; Scheepers & Nortje, 2000). The intrusion of the post-orogenic to anorogenic A- type granites occurred at approximately 520- 500 Ma, representing the third phase of magmatism (Scheepers & Nortje, 2000). They are intrusive in the Tygerberg and Swartland terranes (Scheepers & Nortje, 2000). The final phase of magmatism is often negle...
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...ircon ages of the Cape Granite Suite: implications for the magmatic evolution of the Saldania Belt.", South African Journal of Geology, vol. 105, no. 3, pp. 241-256.
Scheepers, R. & Nortjé, A. 2000, "Rhyolitic ignimbrites of the Cape Granite suite, southwestern Cape province, South Africa", Journal of African Earth Sciences, vol. 31, no. 3, pp. 647-656.
Scheepers, R. & Ozendaal, A. 1995, "Phosphorus as a typological and mineralization potential indicator: the Cape Granite Suite of the Saldania belt as a case study", Journal of African Earth Sciences, vol. 21, no. 1, pp. 127-140.
Villaros, A., Stevens, G., Moyen, J. & Buick, I.S. 2009, "The trace element compositions of S-type granites: evidence for disequilibrium melting and accessory phase entrainment in the source", Contributions to Mineralogy and Petrology, vol. 158, no. 4, pp. 543-561.
Marshak, S. (2009) Essentials of Geology, 3rd ed. New York: W.W. Norton & Company, ch. 11, p. 298-320.
Lithologically the Kimmeridge Clay Formation can be subdivided into four units (Figure 2), despite of beds at the base of the succession are poorly exposed. However, in contrast, the units from mid-eudoxus Zone to the top of the formation that are well seen in the Formation. At the base of the formation until the eudoxus Zone, the strata are made up almost entirely of bioturbated shelly clays and in between beds, horizons of oil and bituminous are present. The upper part of the Eudoxus Zone until the upper Pectinatus Zone the composition is kerogen-rich mudstones and coccolith limestone.
The shelf-edge includes carbonate-to-clastic facies transition and tectonic uplift and erosion of the carbonates followed by deposition of the clastics. The Saint Peter Sandstone is a well-sorted, almost pure quartz arenite deposited during a major mid-Ordovician low stand. Clastics spread across an exposed carbonate platform by transportation. This is shown by the well-rounded, frosted texture of the quartz grains.
The Precambrian Shield Rocks found in the Brickworks was formed in an ancient sea more than 1.4 billion years ago. Over many years, the heat and pressure from plate tectonics slowly pushed the land into a mountain chain. During the Ordovician period (around 470- 448 million years ago), the mountain chains This layer of shale and limestone is called the Georgian Bay
The third alluvial deposition consists of sand, silt and minor inter-bedded gravel, and again indicates Brimbank Park’s changing geology over time. (Geological map of Victoria, 1973). These deposits, as well as a nearby fault suggest volcanic activity 5-1.6 million years ago, which explains the olivine basalt (fig. 2) deposits which date back to to the Silurian and Tertiary period.
The site visited on this day was informally known as the Bedrock Knob (NTS grid reference: 120 342). It is in an area where patches of limestone and exposed bedrock are common. The bedrock is part of the Preca...
When standing on top of the butte, the rock that makes up a majority of the area is quartzite. Quartzite is a metamorphic rock that forms when existing rock is exposed to extreme amounts of heat and pressure (4). The quartzite that is found on Kamiak Butte was formed sometime around 1.47 to 1.4 billion years ago during the Paleozoic period of the Precambrian era. Many of the metamorphic rocks have been fractured and decayed due to physical and chemical weathering, but because quartzite consists of one of the strongest minerals quartz...
Riley, C.M. "Lahars." Geological and Mining Engineering Sciences. Michigan Tech. Web. 6 Feb. 2010. .
The coastal belt of the Franciscan Complex is composed of the youngest and least deformed units and makes up the western quarter of all Franciscan rocks. The rocks of the coastal belt are composed of arkosic sandstones, andesitic graywackes, and quartzofeldspathic graywackes interbedded with radiolarian chert (turbidite deposits) (Blake and Jones, 1981). These sedimentary rocks suggest a depositional environment of deep-sea fan systems with both oceanic and continental provenance. Parts of the belt show evidence of later metamorphism, principally due to subduction. Low-grade blueschist mineral facies are indicated by the presence of minerals such as laumonite and prehnite-pumpellyite (Blake and Jones, 1981). All rock units show evidence of thrust (imbricate) faulting due to the compressional forces of subduction. Ages of the coastal belt run from as little as 40 Ma (Eocene) to as old as 100 Ma (middle Cretaceous).
Tarbuck E., Lutgens F., Tasa D., 2014, An Introduction to Physical Geology, 5th Ed, Pearson Education, Upper Saddle River, New Jersey.
Stone Mountain rises in sharp contrast to the surrounding flat, rolling landscape creating a geomorphic monadnock. Geologists appear to have consensus of the volcanic origins and underground formation of t...
and Metamorphic rocks can be found. There are also a lot of crusted plates, and violent
Stephen .G,Malcolm.W, Guy H,(2014), GEOL20001 The Geology of Southeast Australia, School of Earth Sciences, University of Melbourne, pg. 23-25
During the Late Cretaceous a period of mountain building occurred along the west coast of North America. This is called the Laramide orogeny that started the Rocky Mountains growth about seventy-five million years ago. The Laramide orogeny was different from orogenies that had happened before hand. What caused the Laramide Orogeny is uncertain but there are many theories about what caused it. One big thing to better understand the Laramide orogeny is the theory of Uniformitarianism.
...se two tectonic plates generated intense friction and pressure that generated enough heat to melt rocks. The descent of denser oceanic Farallon Plate into the asthenosphere produced magma that was made from basalt or andesite. Which is dark colored rocks with little silica. The buoyant magma pushed through the silica-rich continental crust, partially melting the crust that it moved though, and becoming more granitic in composition. About 100 million years ago, the granitic magma pooled at depths of only 2 to 5 miles beneath the surface (United States of America). The granitic terrain that makes up the Sierra, was once thought to have only local variations but was produced from one large mass of rock. It has been discovered however that hundreds of intrusions caused the variations in the granite that is displayed in Yosemite and in the Sierra Nevada range (Huber).