UPSC Combined Geo-Scientist 2026 (UPSC GSI 2026)

Physical Geology
Principle of uniformitarianism; origin, differentiation and internal structure of the Earth;
origin of atmosphere; earthquakes and volcanoes; continental drift, sea-floor spreading, isostasy,
orogeny and plate tectonics; geological action of rivers, wind, glaciers, waves; erosional and
depositional landforms; weathering processes and products.

Structural Geology
Stress, strain and rheological properties of rocks; planar and linear structures; classification
of folds and faults; Mohr’s circle and criteria for failure of rocks; ductile and brittle shear in rocks;
study of toposheets, V-rules and outcrop patterns; stereographic projections of structural elements.

Mineralogy
Elements of symmetry, notations and indices; Bravais lattices; chemical classification of
minerals; isomorphism, polymorphism, solid solution and exsolution; silicate structures; physical
and optical properties of common rock forming minerals- olivine, garnet, pyroxene, amphibole, mica,
feldspar and quartz.

Igneous Petrology
Magma types and their evolution; IUGS classification of igneous rocks; forms, structures and
textures of igneous rocks; applications of binary and ternary phase diagrams in petrogenesis;
magmatic differentiation and assimilation; petrogenesis of granites, basalts, komatiiites and alkaline
rocks (carbonatite, kimberlite, lamprophyre and nepheline syenite).

Metamorphic Petrology
Limits, types and controls of metamorphism; metamorphic structures- slate, schist and
gneiss; metamorphic textures- pre, syn and post tectonic porphyroblasts; concept of metamorphic
zone, isograd and facies; geothermal gradients, facies series and plate tectonics.

Sedimentology
Origin of sediments; sedimentary textures, grain-size scale; primary sedimentary structures;
classification of sandstone and carbonate rocks; siliciclastic depositional environments and
sedimentary facies; diagenesis of carbonate sediments.

Paleontology
Fossils and processes of fossilization; concept of species and binomial nomenclature;
morphology and classification of invertebrates (Trilobites, Brachiopods, Lamellibranchs, Gastropods
and Cephalopods); evolution in Equidae and Hominidae; microfossils-Foraminifera, Ostracoda;
Gondwana flora.
Stratigraphy
Law of superposition; stratigraphic nomenclature- lithostratigraphy, biostratigraphy and
chronostratigraphy; Archaean cratonic nucleii of Peninsular India (Dharwar, Singhbhum, and
Aravalli cratons); Proterozoic mobile belts (Central Indian Tectonic Zone, Aravalli-Delhi and Eastern
Ghats); Purana sedimentary basins (Cuddapah and Vindhyan); Phanerozoic stratigraphy of IndiaSpiti, Kashmir, Damodar valley, Kutch, Trichinopoly, Siwaliks and Indo-Gangetic alluvium.
Economic Geology
Properties of mineral deposits- form, mineral assemblage, texture, rock-ore association and
relationship; magmatic, sedimentary, metamorphic, hydrothermal, supergene and weatheringrelated processes of ore formation; processes of formation of coal, and petroleum; distribution and
geological characteristics of major mineral and hydrocarbon deposits of India.
Hydrogeology
Groundwater occurrence and aquifer characteristics, porosity, permeability, hydraulic
conductivity, transmissivity; Darcy’s Law in homogenous and heterogenous media; Bernoulli
equation, Reynold’s number; composition of groundwater; application of H and O isotopes in
groundwater studies; artificial recharge of groundwater.