Yoredale Group (Wensleydale Group) - Essay Example

?An Essay on the Yoredale Group (Wensleydale Group) Introduction “Palaeogeography is the study of ancient geographies, using geological evidence to infer the distribution of land and sea, uplands (areas of denudation) and lowlands (sedimentary basins), the vegetational cover of the land, and the past climates that influenced them.” (Hancock and Skinner, The Oxford Companion to Earth) Depositional environments, on the other hand, may be classified as continental, marine, coastal or transitional. (Crain, Spec2000.net). Yoredale Group refers to sediments deposited and first studied in Wensleydale,North Yorkshire. Imagine a combination of layers of sedimentary rocks wherein the lowest level consists of limestone, followed by mudstone, then sandstone, seatearth, and coal. The most commonly observed is the limestone. It is not pure limestone. Instead, clay is found along with linestone in the Yoredale Group, and the impurities (like fragments of fossils) make the limestone look dark gray. But in terms of thickness of sediments, limestone makes up only a small portion of the total sedimentary rock thickness. Oftentimes, carbon is absent in the piles of sediments. Three sediment formations were identified in the Yoredale Group, namely, “the Tyne Limestone Formation, the Alston Formation, and the Stainmore Formation” starting from the bottom to the top. Waters, C.N., Dean, M.T.,, Jones, N.S., and Somerville, I.D. ([a] 1) identify Yoredale Group as the Northumberland Trough which has “facies deposits” connected “southward into the relatively deeper water”. However, the Yoredale Group “extends across the entire Solway Basin and Northumberland Trough” (3). Below it is a great limestone. It exists on the Stainmore Formation where limestone thickness is far less. It can be observed also on the upper portion of the Nomurian layer where there is much sandstone and little limestone. (Waters et. al. [b] 89) According to Smythe, D., “the Yoredale group may exhibit karstic fracture flow in the near surface” and will make a location not suitable for dumping nuclear waste. It is said to consist of “shales, limestones, and sandstones” covering a vast area and thick layer of up to 4,500 feet. Deposition of Earth Structures: Rocks, Continents, Waters Mother Earth is estimated to be nearly 4.6 billion years old. Out of that length of time, the available rock analysis technology can compute the estimated time when events took place based on the findings on rocks. Only 440 million years can be traced in the rocks themselves. Up in the north of England, one can find the “junction between two ancient continents that were once separated by a vast ocean” (Hyslop et. al. 18). It is known as the Lapetus Suture. And the ocean existed 500 million years ago covering 1000 kilometers. There was a continent (named Laurentia) wherein Scotland, Northern England, and North and West Ireland were part of the south eastern boundaries of that continent. The other parts of England came from changes in the tectonic rock formations beneath the ocean, causing the continents of Avalonia and Laurentia to collide. Geologiests identified the mountains of Caledonia as results of that collision. It took place 425 million years ago during the Paleaozoic Era. This should be seen not as an instant event but a very gradually evolutionary change in the earth’s structures. Mountains were built by the folding of the ocean floor, “cleaved and uplifted the rocks during the event termed Caledonian Oregeny” (20). New volcanoes came into existence. Another book wrote about the Paleozoic Era as having lasted for 300 million years when movements of the “Earth’s continents from the Southern Hemisphere to the Northern Hemisphere” took place (Rafferly 29). In the description of Laurentia, the author identified the greater part of that ancient continent as today’s “North America and Greenland” (33). It also describes the Caledonian Orogeny to have formed “a mountain chain stretching from present-day eastern North America through Greenland, western Scandanavia, Scotland, Ireland, and Northern England and south to the fringes of western North Africa” (223). As for the age of the Earth, scientific discoveries have proven that radioactive decay is an accurate determinant of the age of this planet. It is because anything on the earth has its radioactive life. And rocks did show how old they were. Each one has an atom with chemical elements. And an atom has electrons moving around around a nucleus. There are stable atoms. But there are also atoms with unstable isotopes. These atoms have to release particles (known as radioactivity) in order to become stable. These are true for thorium, uranium, and radium. When isotopes are released or decay, energy of the atom which held the isotope is also reduced. Disintegration takes time. Scientists have proven that the half-life of a radioactive element represents the span of time for the isotopes to be released. Thus, there is a way to calculate the time it takes for particles to decay or disintegrate or lose its weight and mass utilizing the “principal radioactive timekeepers” (Levin, 40). These are uranium, rubidium, and potassium for the very long aging process, Carbon is for telling age from 50,000 years and less. Rocks are made up of at least one mineral. There are three major classifications of rocks, namely, metamorphic, igneous, and sedimentary. Minerals in those rocks are identifiable by their chemical and physical properties, especially with the use of powerful microscopes. These are the means by which scientists are able to find stable and unstable particles. From then on, their half life can be computed accurately. The reason why these details were mentioned is to prove that the deposition of continents in time were based on scientific calculations as well. It was not just a comparison of rocks and their appearance in various places, but also a comparison of the age of those rocks. Stratigraphy is another way of providing dates and events for a study of geological history. It is actually an old yet very useful method of super-imposing layers of rocks and sedimentations to identify younger rocks versus the older rocks. The younger rocks will show some deformation, which means something happened to change the form of a layer. Correlation of the layers “requires an interdisciplinary approach combining biostratigraphy, radiometric dating, volcanic ho9rizons, facies analysis, well-log interpretation, seismic stratigraphy and chemostratigraphy.” (Woodcock and Strachan 234) Deposition of Yoredale or Wensleydale Group was studied using the Millstone Grit which can be inspected in Northern England. A clear picture of this is shown in Figure 4. As can be best described by Table 3.1 below, the Wensleydale Group was depositioned under the Millstone Grit Group. Note that the method applied was by defining the “Lithostratigraphy” of subsystems and the Carboniferous System. And the Wensleydale Group is right on top of the Carboneiferous Limestone. People will come to wonder how the Wensleydale Group otherwise known as the older name Yoredale Group which is made of “shales, limestones, and sandstones” went under the Millstone Grit Group, when the same group is in Yorkshire Dales National Park which is a valley (Smythe). Furthermore, the Millstone Grit “is estimated to be up to 2100 m thick in Landashire and 1800m thick in West Yorkshire, but thins southwards to less than 200 m in the East Midlands and north Wales” (Science Group of BGS & EA 5). In Figure 3, Yoredale Group is on top where it is correlated with the other layers. The explanation was given to be the deposition of parts of the earth which must have happened over a long period of time that is, millions of years ago. This analysis is consistent with the geological studies of rocks and layers of sedimentation, the radioactive time of minerals found in rocks, and the other scientific ways of understanding the earth. (Source: Science Group of BGS & EA. Baseline Report Series: 18. The Millstone Grit of Northern England. UK: Groundwater Systems and Water Quality Commissioned Report CR/05/015N; Science Group: Air, Land & Water Technical Report NC/99/74/18. 2005. PDF p.5) Conclusion Present models of the Yoredale Group were presented in this essay. One group is on the upper Nomurian layer. The Wensleydale valley serves as the example. The other goes under heavy rock formations like the Millstone Grit Rocks. Therefore, there was a need to find the explanation for the difference. The geological history of the earth holds some scientific explanations. Figure 1 shows how the continents and oceans looked like millions of years ago. They are far from how the present continents appear at present. And the scientific proof was determined through verifiable and quantifiable means. In simplest terms, there were changes in the positions of the earth’s rocks, land, volcanic, and water formation which is called geological deposition. But it took very gradual movements over hundreds of millions of years for all these changes to take place. Yoredale was one of those groups wherein parts were depositioned. Figure 1. Picture of Earth 500 Million Years Ago Figure 2. Geological Eras and Periods of Major Changes (Source: Hyslop, E.K., Clarke, S.M., Everest, J.D., Lawrence, D.J.D., Arkley, S.L.B., Everest, J.D., Millward, D., Thompson, G.L., and Young, B. Geodiversity Audit and Action Plan: Northumberland National Park. UK: Potts Printers. 2007 p.19) Figure 3. Yoredale Group on the Upper Layer (Source: Benchley, P.J. and Rawson, P.F.. The Geology of England and Wales 2nd Edition. UK: Geological Society of London, 2006. Print. p. 194.) Figure 4. Millstone Grit in Northern England (Source: Science Group of BGS & EA. Baseline Report Series: 18. The Millstone Grit of Northern England. UK: Groundwater Systems and Water Quality Commissioned Report CR/05/015N; Science Group: Air, Land & Water Technical Report NC/99/74/18. 2005. PDF Print.) Works Cited Benchley, P.J. and Rawson, P.F.. The Geology of England and Wales 2nd Edition. UK: Geological Society of London, 2006. Print Crain, P. “Depositional Environment Basics”. Crain’s Petrophysical Handbook. Spec2000.net. Web. July 28, 2012. Hancock, Paul and Skinner, Brian J. “Paleogeography”. The Oxford Companion to the Earth 2000. Encyclopedia.com Web. July 28, 2012. Hyslop, E.K., Clarke, S.M., Everest, J.D., Lawrence, D.J.D., Arkley, S.L.B., Everest, J.D., Millward, D., Thompson, G.L., and Young, B. Geodiversity Audit and Action Plan: Northumberland National Park. UK: Potts Printers. 2007 Print. Levin, Harld L. The Earth Through Time 9th Edition. USA: John Wiley & Sons. October 6, 2009. Print Rafferly, John P. The Paleozoic Era: Diversification of Plant and Animal Life. NY,USA: Britannica Educational Publishing. 2011. Print Science Group of BGS & EA. Baseline Report Series: 18. The Millstone Grit of Northern England. UK: Groundwater Systems and Water Quality Commissioned Report CR/05/015N; Science Group: Air, Land & Water Technical Report NC/99/74/18. 2005. PDF Print. Smythe, David. Why the Whole of West Cumbria is Unsuitable for a Nuclear Waste Repository. PDF File November 2010. Web. July 30, 2012. Waters, C.N., Dean, M.T. ,, Jones, N.S., and Somerville, I.D.[a]. Chapter 13 Northumberland Trough and Solway Basin. PDF File. March 13, 2012. Web. July 30, 2012.. Waters, C.N., et.al.[b]. A Revised Correlation of Carboniferous Rocks in the British Isles. Special Report No. 26. London, UK: The Geological Society. 2011. Woodcock, Nigel H. and Strachan, Rob. Geological History of Britain and Ireland 2nd Edition. West Sussex, UK: John Wiley and Sons. April 12, 2012. Print. Read More