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Q51. Find out the correct statement(s).
The correct answers are Authigenic minerals form during diagenesis of sandstone., Heavy minerals in sandstone are good indicators of provenance., Matrix in sandstone may form by post-depositional infiltration and/or authigenic filling. 'Authigenic' minerals are crystals that chemically grow right in place while sand turns to stone (diagenesis). Tough 'heavy minerals' survive transport and act like a chemical fingerprint pointing back to the original mountain they eroded from (provenance). Clay matrix can easily wash in later. Arkose is rich in weak feldspar, making it highly immature compared to pure, tough quartz arenite.
Q52. Which of the following statements in relation to the solar system is/are correct?
The correct answers are The most abundant elements are H and He., The abundances of elements with atomic numbers 1-50 show an overall decreasing trend. The universe is overwhelmingly made of its first two simplest, lightest ingredients: Hydrogen and Helium. As elements get heavier and more complex (atomic numbers 1-50), they generally become much rarer because they can only be forged inside dying stars, creating a steady downward trend in abundance. Heavy elements are exceptionally rare, and odd-numbered elements are typically less abundant than their even-numbered counterparts.
Q53. Select the correct statement(s).
The correct answers are Phenocrysts are found in igneous rocks whereas porphyroblasts are found in metamorphic rocks, Phenocrysts are indicators of crystallization history whereas porphyroblasts indicate metamorphic history. A 'phenocryst' is a giant crystal that grew freely in a cooling pool of liquid magma (igneous). A 'porphyroblast' is a giant crystal that forcibly grew by eating surrounding minerals while locked inside solid, hot, pressurized rock (metamorphic). Option C is wrong because porphyroblasts are brand-new growths, not leftover relict grains. Option D reverses the poikilitic definitions.
Q54. Select the correct statement(s).
The correct answers are Laccoliths are convex upward whereas lopoliths are convex downward bodies, Laccoliths can form from any type of magma whereas lopoliths form only from basaltic magma, Laccoliths are smaller in dimensions than lopoliths. A 'laccolith' is a blister-like pocket of magma that pushes the rocks above it into a dome (convex upward), is typically small, and forms from viscous magmas. A 'lopolith' is an unfathomably massive, bowl-shaped depression (convex downward) formed when unbelievably heavy, dense basaltic magma sinks and sags the Earth's crust beneath its sheer weight. Both can absolutely show internal layering, making option C incorrect.
Q55. Choose the reaction(s) indicating metamorphism of pelites at T> 600 °C and P< 8 kbar.
The correct answers are muscovite + quartz -> sillimanite + K-feldspar + H2O, muscovite + biotite + quartz + H2O -> sillimanite + melt. A 'pelite' is a metamorphosed shale/mudstone. At temperatures exceeding 600°C, the rock becomes blisteringly hot. Under these conditions, the water-bearing mineral muscovite violently breaks down, reacting with quartz to form the high-temperature indicator mineral 'sillimanite', K-feldspar, and occasionally prompting the entire rock to begin melting. Option A describes low-grade mafic rocks, and Option D describes ultra-high-pressure conditions (jadeite).
Q56. Select the pair(s) that is/are correctly matched.
The correct answers are Lathi Formation – Jurassic wood fossils, Panchet Formation – Triassic reptile fossils. In Indian stratigraphy, the Lathi Formation in Rajasthan is famously known for hosting massive, petrified Jurassic tree trunks (Akal Wood Fossil Park). The Panchet Formation is correctly recognized for yielding significant Triassic reptile and amphibian remains. The Pinjor Formation is much younger (Pleistocene), and the Kota Formation is Jurassic, making the other chronological pairings wildly incorrect.
Q57. Which of the following is/are mode(s) of preservation of fossils?
The correct answers are Small organisms get trapped on viscous resins secreted by trees, Leaves preserved as thin films of carbon, Negative impressions of hard parts of organisms. Fossils form in several genuine ways: insects get permanently encased in tree resin (amber), ancient leaves get compressed into dark carbon imprints (carbonization), and buried shells dissolve away to leave behind a hollow 3D mold (negative impression). Option D describes 'dendrites', which are just manganese crystals growing in rock cracks that deceptively look like fern fossils, making them fake 'pseudofossils'.
Q58. Which of the following gastropods has/have siphonal canal?
The correct answers are Cerithium, Cypraea, Fusus, Murex. In marine biology, many predatory sea snails (gastropods) have a fleshy tube called a siphon to taste the water. Their shells evolved a notch or an elongated tube at the base to protect this organ, known as a siphonal canal. Cerithium, Cypraea (cowries), Fusus, and Murex all possess this anatomical shell feature to accommodate their siphons.
Q59. Which of the following geomorphic features indicate(s) the presence of a fault?
The correct answers are Triangular facets, Sudden topographic jump. When a fault violently breaks and thrusts a block of rock upward, it creates a steep, sheer cliff (a sudden topographic jump). As rivers slice down through this exposed cliff face, they carve it into a series of jagged, flat-iron shaped mountain faces known as 'triangular facets'. Conversely, ox-bow lakes and point bars are gentle river features completely unrelated to tectonic faults.
Q60. Which of the following statements is/are correct with reference to subsurface water?
The correct answers are Vadose water occurs in the zone of aeration, For significant groundwater underflow, the medium must be highly permeable, Intersection of the water table with the land surface can result in the formation of a spring. Vadose water is the moisture trapped in the dry dirt above the water table (zone of aeration). To flow effectively underground, water absolutely requires a highly permeable rock. A spring naturally forms whenever the underground water table physically intersects the sloping surface of the ground. Option A is incorrect because a 'perched' water table sits high up above the main, regional water table.