List of top Geology Questions

In a sedimentary succession shown in the figure, the last occurrence of the fossil species Q (dated 50 Ma) and the first occurrence of the fossil species R (dated 30 Ma) are recorded at Y and X, respectively. The estimated rate of sedimentation is (assume constant rate of sedimentation).

Age of granitic rocks can be determined using Rb-Sr whole rock radioactive dating method and the following age equation, \[ \left( \frac{^{87}Sr}{^{86}Sr} \right) = \left( \frac{^{87}Sr}{^{86}Sr} \right)_i + \left( \frac{^{87}Rb}{^{86}Sr} \right) \left( e^{\lambda t} - 1 \right) \] For a suite of representative co-magmatic granitic rocks, the Rb-Sr whole rock isochron plot and relevant data are shown in the diagram. The age of granite is calculated at ....... Ga (1 Ga = \( 10^9 \) yrs, give answer in one decimal place).

Considering garnet chemical formula in 12 oxygen basis, the number of Mg cations in a garnet of chemical composition P (as shown in the figure) is ........ (give answer in two decimal places).

The schematic map given below shows intersecting strike lines of the same lithological contact. In the map, AB and CD are 5 cm and 3.5 cm, respectively. The scale of the map is 1 cm = 100 m. The plunge of the fold axis is ....... degrees (give answer in one decimal place).

Shown below is an isobaric binary temperature-composition phase diagram in the system X-Y with complete miscibility between X and Y.

Match the earth layers (Group I) with corresponding approximate thicknesses (Group II).
Group I Group II
P. Lithosphere 1. 2900 km
Q. Mantle 2. 2250 km
R. Outer Core 3. 1200 km
S. Inner Core 4. 100 km

Match the igneous bodies in Group I with their ages in Group II.
Group I Group II
P. Singhbhum granite 1. Neoproterozoic
Q. Malani rhyolite 2. Cretaceous
R. Deccan volcanics 3. Permian
S. Panjal Traps 4. Archaean

Which one of the following sequences of silicate structures indicates an increasing degree of sharing of corners of (\text{SiO}_4)^{4-} tetrahedra?

Match the geological processes (Group I) with their examples in Indian stratigraphy (Group II).
Group I Group II
P. Permo-Carboniferous glaciation 1. Ariyalur Group
Q. Cretaceous marine transgression 2. Siwalik Group
R. Neogene fluvial sedimentation 3. Talchir Formation
S. Cretaceous inter-trappean sedimentation 4. Lameta Formation

Match the sedimentary features in Group I with the corresponding sedimentary environments of their formation in Group II.
Group I Group II
P. Point Bar 1. Tidal
Q. Barchan 2. Meandering fluvial channel
R. Dropstone 3. Aeolian
S. Herring-bone cross stratification 4. Glacial

In the given map, the X-Y surface has the same orientation as in the Palaeozoic sequence. X-Y represents

Match the mineral deposits in Group I with their Indian occurrences in Group II.
Group I Group II
P. Chromite 1. Jhamarkotra, Rajasthan
Q. Magnesite 2. Gudur, Andhra Pradesh
R. Mica 3. Byrapur, Karnataka
S. Phosphorite 4. Chalk Hills, Tamil Nadu

Consider a granulite facies metamorphic rock with peak metamorphic condition at 9 kbar, 850°C. Assume a single layer crust of \(\rho = 3000 \, \text{kg/m}^3\) and \(g = 10 \, \text{m/sec}^2\) during metamorphism. The depth of burial during peak metamorphism is (give answer in kilometers).

A horizontal cylindrical ore body (diameter = 20 m, length = 200 m) has 5% metal content and a density of 3500 kg/m\(^3\). The reserve of the ore body is ........ million ton(s) (give answer in two decimal places).

A drainage basin of fourth order covers an area of 40 sq. km. Within the basin, total length of 1st order drainage is 12.5 km, 2nd order drainage is 8.8 km, 3rd order drainage is 4.7 km and 4th order drainage is 4.0 km. The drainage density of the basin is ........ km\(^{-1}\) (give answer in two decimal places).

Consider four minerals P, Q, R and S in a three-component chemical system (A-B-C) as shown in the figure. For a crossing tie-line relationship, the variance (degrees of freedom) of the equilibrium mineral assemblage at X is .........
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The refractive indices of four minerals (P, Q, R, S) are as follows:
P (\( \alpha = 1.712 \), \( \beta = 1.721 \), \( \gamma = 1.727 \)),
Q (\( \epsilon = 1.553 \), \( \omega = 1.544 \)),
R (\( \alpha = 1.664 \), \( \beta = 1.672 \), \( \gamma = 1.694 \)),
S (\( \omega = 1.658 \), \( \epsilon = 1.486 \)).
The value of maximum birefringence among all the minerals is ......... (give answer in three decimal places).

The top surface of a coal seam is exposed at 150 m contour level on a hill top at location A. The same surface of the seam is also exposed on a river bed at location B at the 50 m contour level. The aerial distance A-B is 1 km. The amount of dip of the coal seam along A-B is (degree). (Give answer in one decimal place).

Aluminium (Al) can occur in both tetrahedral and octahedral co-ordinations in silicates. The amount of octahedral Al in a pyroxene crystal of composition Mg\(_1\)Fe\(_0.4\)Al\(_1\)Si\(_1.8\)O\(_6\) is ........... (give answer in one decimal place).

The birefringence of a mineral of thickness 30 μm and retardation 0.27 μm is (give answer in three decimal places).

The core-rim compositions of a normally zoned plagioclase crystal are as follows:
Core: Ca₀.₆Na₀.₄Al₁.₆Si₂.₄O₈
Rim: Ca₀.₄Na₀.₆Al₁.₄Si₂.₆O₈
The amount of increase of Na atom from core to rim per formula unit of plagioclase is (give answer in one decimal place).

A fault surface in an outcrop has slickenside lineation whose pitch is 30°. The horizontal slip on the fault is 1.25 m, as determined from displaced vein. The net slip on the fault is ........ meter (give answer in two decimal places).