On the basis of mineral replacement and intergrowths, four oxide series are recognized among the sandstones – Stages of diagenesis From the type of reaction and the principal sequence of occurence three stages of diagenesis are established as follows – Among sandstones, the progress of diagenesis may be arrested at either the locomorphic or phyllomorphic […]
Stages of Diagenesis of Sandstone Read More »
Rules of substitution Terminology related to partitioned between the solid & liquid phase Distribution coefficients and Geothermometers Distribution coefficient (D) = Cs/ Cl where, Cs = the concentration of a minor element in the crystal of a mineral Cl = the concentration of that element in the liquid from which the crystal formed under equilibrium
Ionic Substitution in Minerals/ Crystals Read More »
Fick’s Law of Diffusion in Igneous Petrology Fick’s law describes the movement of elements and ions due to concentration gradients, crucial for understanding magmatic differentiation and element transport – Examples Activity-Composition relations in Igneous Petrology Roult’s Law (Ideal Solutions) Examples Henry’s Law (Dilute Solutions) Examples
Fick, Roult and Henry’s law in petrogenesis Read More »
Three major cycles of deposition have been found in the sedimentary records of the Mesozoic formations of the Spiti Basin. All other formation and beds are collectively known as Kibber Group. “The Kioto -Spiti Shale contact represents a hiatus from Late Callovian to Early Exfordian” The Spiti Shale demarkates the Jurassic age. The lowermost unit
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
Magnetostratigraphy Read More »
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.
Paleozoic of Spiti Read More »
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
Chronostratigraphy Read More »
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.
Indo Gangetic alluvium is a consequence of the Indian- Eurasian plates collision that was initiated in the Paleogene. The Ganga basin is an active foreland basin having an east-west elongated shape.
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