Usefulness of fossils Fossils are useful for the following purposes: i) Determining the relative geological age of rocks ii) Interpreting the palaeo depositional environment of the sediments iii) Correlating sedimentary sequences and help in the search for economic minerals in sedimentary rocks iv) Studying evolution i) Determining the relative geological age of rocks Different fossils are found in the sedimentary strata of differing ages in the earth. The older fossils are found beneath the younger ones in a normal (ie. not overturned) sedimentary sequence. Trilobites, for example, are only found in Palaeozoic rocks of Cambrian to Permian age and have not been found together with dinosaurs which are confined to the younger Mesozoic rocks of Triassic to Cretaceous age above . Fossils can therefore be used to date or give the relative geological age of the rocks they are trapped in. The fossils used must not be reworked from some older deposit. Fossil assemblages rather than individual fossils are more useful as their overlapping ranges provide a more precise dating of the rocks. ii) Interpreting the palaeo depositional environments of the enclosing sediments By applying the uniformitarian principle that the present is the key to the past, fossils can be used to interpret the palaeoenvironment of the sedimentary deposit in which the fossils are found. Coral reefs are only found in shallow warm clear tropical waters of the oceans today. The presence of fossil corals can be used to interpret that at a particular time in the distant geological past, the area where the fossil is found was in a similar paleo depositional environment although it might be very different now (eg. corals found on top of high mountains or tropical plant fossils found in very cold places). The fossils used must be in site and not transported in from some other place. iii) Correlating sedimentary sequences and help in the search for economic minerals in sedimentary rocks If the same fossils are found in two or more separate places at present (eg. in South America and Africa), we can deduce that they were connected in the distant past and are separated now because of erosion and removal of the rocks between them or continental drift. This is useful in aiding the search for economic minerals associated with sedimentary rocks such as oil, gas, coal and alluvial deposits of diamonds, gold, tin and others. iv) Studying evolution Fossils are the frozen records of how animals and plants have been changing from the past to the present in response to changes in the physical and biological environments. Fossils enable us to track these changes and work out how these organisms have evolved through time.
Posted on: Fri, 15 Nov 2013 16:49:28 +0000
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