Yoredale Group (Wensleydale Group) Essay Example | Topics and Well Written Essays - 2000 words

Yoredale Group (Wensleydale Group) - Essay Example (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, â€Å"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 Trou gh which has â€Å"facies deposits† connected â€Å"southward into the relatively deeper water†. However, the Yoredale Group â€Å"extends across the entire Solway Basin and Northumberland Trough† (3). ... 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 â€Å"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 ver y gradually evolutionary change in the earth’s structures. Mountains were built by the folding of the ocean floor, â€Å"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 â€Å"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 â€Å"North America and Greenland† (33). It also describes the Caledonian Orogeny to have formed â€Å"a mountain chain stretching from present-day eastern North America