Magnetostratigraphy is based on the polarity of the earth’s magnetic field as it is preserved in the sediments at the time when they were deposited. The magnetic minerals in the sediments orient themself in the direction of earth’s magnetic field and preserved. The earth’s magnetic poles have switched their position periodically in the geological past […]
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Biostratigraphy deals with the classification and correlation of rock strata based on their fossil contents. Fossils help in assigning relative ages to stratigraphic units can be correlated with different parts of the world. The biostratigraphy is based on the concept that there is evolutionary changes in the flora and fauna which if unidirectional. These animals
The Continuous Paleozoic succession is beautifully exposed in the area of Spiti valley. A rich collection of fossils reported from the region has made Spiti valley a standard sections for correlation of Phanerozoic rocks of Indian and adjoining regions of the sub-continent. There are three more groups naming Sanugba Group, Kanawar Group and Kuling Group.
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Any natural phenomena that obey a definite law of flow rate can be used to mark off certain intervals of time that can serve as a ‘clock’. The basic unit of time is second which. The other method that is commonly used by geologists is the subdividing time according to non-equal time intervals determined by
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We can classify the layered rock sequences primarily on the basis of their lithological characters. This scheme of classification is known as Lithostratigraphic Classification. “A bed or lamina represents a uniform condition of deposition in a basin.” A formation may comprise a single predominant rock type or an association of two or more rock types.
The North Singhbhum Mobile Belt (NSMB) is a multiple folded, low to medium grade meta-sedimentary and meta-igneous rocks of Proterozoic age (1.0–2.4 Ga) sandwiched between the Archaean (>2.4 Ga) Singhbhum Craton in the south, and the Meso/Neo-Proterozoic (0.9–1.7 Ga) Chotanagpur Gneissic Complex (CGC) in the north by north-dipping ductile shear zones. Clastic sediments with minor volcanics comprising the
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“A Stratotype or type Section is a geological term that names the physical location or outcrop of a particular reference exposure of a stratigraphic sequence or stratigraphic boundary.” Classification of Stratotypes : GSSP (Global Boundary Stratotype Sections and Point) A GSSP is an internationally agreed upon stratigraphic section which serves as the reference section of
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The Outer or Sub-Himalaya is the main zone of the Cenozoic sedimentation. The Paleogene-Neogene sequences of the Sub-Himalaya occurs in the northern states of India. The Subathu, Murree and Dharamshala are the main Paleogene groups of rocks where Siwalik is a major Neogene group of Cenozoic sequences of the Sub-Himalaya. Other deposits belongs to the
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An unconformity is a plane of discontinuity that separates two rocks, which differs in age. The younger of these rocks are nearly always of sedimentary origin and must have been deposited on the surface of the older rock, which is a surface of erosion. Formation of unconformity : The formation of unconformity may be defined
The structure of the Dharwar Craton is interpreted in terms of a foreland in the west and an accretionary complex in the east. The older sequence that shows a relatively higher degree of metamorphism and intrusive contact with the granitic and gneisses has been named as Sargur Group. The granitic gneisses that show intrusive contact
