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Q41. A marine organic-rich, black shale with tiny pyrite crystals shows complete absence of body or trace fossils. Which of the following statement(s) is/are TRUE?
The correct answers are The sediments were deposited in low-energy conditions., The deposition took place in dysoxic to anoxic conditions., The environment was stressful for survival of living organisms. Shale requires perfectly still, low-energy water for fine mud to settle. The black color, preserved organics, and pyrite perfectly indicate a stagnant, oxygen-starved (anoxic) environment. Because there was no oxygen and toxic hydrogen sulfide was present, it was incredibly stressful and deadly for life, explaining the total absence of fossils.
Q42. On the basis of the following schematic diagram, choose the CORRECT statement(s).
The correct answers are Mineral X grew after the development of matrix foliation (S2)., Mineral Y grew during or after the development of internal foliation (S1). In the diagram, Mineral X clearly cuts straight across the S2 foliation lines without disturbing them, proving the foliation was there first and X grew over it (postdates). Mineral Y contains internal S1 lines trapped inside it, proving S1 had to exist either right as Y was growing or before Y finished wrapping around it.
Q43. Which of the following statement(s) is/are CORRECT regarding ophitic texture?
The correct answers are Plagioclase laths are completely enclosed by large pyroxene crystals., It is a variety of poikilitic texture. When magma cools into rock, the crystals form patterns called 'textures'. 'Ophitic texture' is a specific, beautiful pattern where small, needle-like crystals of a white mineral (plagioclase) get completely swallowed up inside giant, chunky crystals of a dark mineral (pyroxene). Because smaller crystals are enclosed by a bigger one, it strictly falls under the broader category of textures known as 'poikilitic'.
Q44. The attitude of the two limbs of a fold was measured as striking 4° N, dipping 85° easterly and striking 30° N, dipping 60° easterly. Which of the following is/are TRUE for describing the geometry of the fold?
The correct answers are Synform, Antiform, Overturned, Plunging. Because both limbs are dipping in the exact same general direction (easterly), the fold is mechanically 'overturned'—one limb has been pushed past the vertical. Because their strikes are not perfectly parallel (4° N vs 30° N), the fold's hinge line must be tilting downward into the earth, making it 'plunging'. Depending on the unstated age of the rocks and closing direction, it could geometrically be classified as either a synform or an antiform.
Q45. Fossils from which of the following invertebrate classes show pentameral symmetry?
The correct answers are Echinoidea, Anthozoa. 'Pentameral symmetry' means the body is perfectly designed around a five-part star shape. Echinoidea (sea urchins and sand dollars) famously display this striking 5-fold pattern on their shells. Some specific extinct Anthozoa (like certain corals) also exhibit pentameral symmetry features (which is why the official key accepts both). Cephalopoda (squids) and Trilobita (ancient sea bugs) are strictly bilateral.
Q46. Choose the correct pair(s):
The correct answers are Paleozoic – Origin of amphibians, Cenozoic – Dominance of mammals. In the ancient, swampy Paleozoic era, fish slowly developed lungs and legs, giving rise to the very first amphibians on land. Fast forward past the dinosaur extinction, and the recent Cenozoic era became universally known as the 'Age of Mammals'. Trilobites completely dominated the Paleozoic and went extinct long before the Mesozoic even started, and flowering plants (angiosperms) didn't appear until the Mesozoic.
Q47. Under crossed polars, a mineral remains dark at all stages of rotation of the microscope stage. Which of the following statement(s) is/are NOT correct?
The correct answer is The mineral is biaxial with an optic orientation corresponding to the principal section of the indicatrix. If a crystal stays pitch black no matter how you spin the microscope stage, it is acting entirely 'isotropic'. This happens if the rock naturally lacks crystal structure (glass/garnet), or if you are staring perfectly down an 'optic axis' (a blind spot) of an anisotropic mineral, where the only vibration permitted is 'Y'. However, if you look at the 'principal section' of a biaxial mineral, light splits wildly and flashes bright colors, making statement B completely, physically impossible.
Q48. Choose the correct statement(s):
The correct answers are Skarn deposits mostly form in calcareous host rocks in contact with felsic intrusives., Gold-bearing vein deposits can form from hydrothermal solutions. Skarns are created when boiling, chemically reactive magma fluids push into reactive limestone (calcareous rock), completely transforming it and depositing ores. Hydrothermal fluids constantly carry and deposit precious gold into narrow rock cracks to form rich veins. Stratiform chromite forms deep inside cooling magma chambers, not from surface weathering. Laterites are residual crusts left by tropical rotting, not river-washed placer sands.
Q49. A northerly dipping fault (F-F) has displaced beds P, Q and R. The thickness of the beds across the fault is same. Identify the fault type(s). (Map view shows northern block beds shifted right relative to southern block)
The correct answers are Reverse fault, Sinistral fault. The map provides a top-down view of dipping rock layers that have been suddenly offset to the left across a fault line. In structural geometry, this exact visual offset pattern on a map can be mechanically produced in two completely different ways: either the entire block was horizontally shoved directly to the left (a Sinistral strike-slip fault), or the block was pushed vertically up the slanted fault ramp (a Reverse fault), which after erosion, visually shifts the slanted rock lines forward on the map.
Q50. Which of the following is/are correctly matched?
The correct answers are Dendritic drainage pattern – uniform substrate and gentle slope, Trellis drainage pattern – parallel valleys and ridges, Rectangular drainage pattern – joints and faults. Dendritic (tree-like) rivers branch naturally over smooth, evenly sloping ground. Trellis rivers flow like a grid locked into folded parallel mountain ridges. Rectangular rivers make sharp 90-degree turns forced by deep, blocky rock fractures (joints/faults). Radial patterns flow outwards from a towering central peak (like a volcano), completely disagreeing with 'flat topography'.