Geology 2025 Paper I 50 marks Discuss

Q8

(a) Discuss the interrelationship amongst Porosity, Permeability and Hydraulic conductivity. How they are important in groundwater movement ? A sediment sample with a cross section area of 0.02 m² is tested in a permeameter with a length of 30 cm. Water flows through the sample at a rate of 0.08 m³/sec with a head difference (h₁ – h₂) 20 cm. Calculate the Hydraulic conductivity. (20 marks) (b) Describe important Lower Gondwana plant fossils with the help of neat diagrams and comment on their palaeobiogeographic significance. (15 marks) (c) Discuss the lithology, fossil content and age of palaeozoic sequence of Spiti Basin of Himachal Pradesh. (15 marks)

हिंदी में प्रश्न पढ़ें

(a) संरंधता, पारगम्यता और जलीय चालकता के अन्तर सम्बन्धों पर चर्चा कीजिये । भूजल संचलन के लिये यह किस प्रकार महत्त्वपूर्ण है ? 0.02 वर्ग मीटर अनुप्रस्थीय क्षेत्र तथा 30 से.मी. लम्बाई वाले परमीयमीटर में अवसादी नमूने को जाँचा गया । नमूने से होकर 0.08 घनमीटर प्रति सेकंड की दर से तथा शीर्षान्तर 20 से.मी. (h₁ – h₂) के साथ जल प्रवाहित होता है । नमूने की जलीय चालकता की गणना कीजिये । (20 अंक) (b) स्पष्ट चित्रों की सहायता से निम्न गोंडवाना के मुख्य वनस्पति जीवाश्मों का वर्णन कीजिये तथा उनकी पुराजीव भौगोलिक महत्ता पर टिप्पणी लिखिए । (15 अंक) (c) हिमाचल प्रदेश की स्पिति घाटी में पैलियोजोइक अनुक्रम के शैललक्षण, जीवाश्म तथा आयु पर चर्चा कीजिये । (15 अंक)

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Directive word: Discuss

This question asks you to discuss. The directive word signals the depth of analysis expected, the structure of your answer, and the weight of evidence you must bring.

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How this answer will be evaluated

Approach

Discuss demands a comprehensive treatment with critical interlinking of concepts. Structure: Part (a) – define porosity-permeability-hydraulic conductivity relationships with Darcy's law application and step-by-step calculation; Part (b) – describe Glossopteris, Gangamopteris, Vertebraria, Noeggerathiopsis with diagrams and Gondwana dispersal significance; Part (c) – trace Spiti Basin Palaeozoic sequence from Tal Group through Permian with litho-bio-chronostratigraphic integration. Conclude with unified thematic synthesis on Gondwana basin evolution.

Key points expected

  • Clear distinction between porosity (void space), permeability (flow capacity) and hydraulic conductivity (K = kρg/μ), with Darcy's law application for K calculation yielding correct value ~0.024 m/s
  • Accurate diagrams of Glossopteris, Gangamopteris, Vertebraria showing reticulate venation, and Noeggerathiopsis with fan-shaped leaves; linking to Gondwanaland reconstruction via identical flora across India-Australia-Africa-Antarctica
  • Spiti Basin Palaeozoic succession: Tal Group (Cambrian-Ordovician quartzite-shale with archaeocyathids/trilobites), Thango Group (Silurian-Devonian limestone with brachiopods/corals), and Permian (Productus limestone, Umaria marine bed)
  • Quantitative derivation showing Q = KA(h/L), proper unit conversion (cm to m), and dimensional consistency in final K value
  • Economic significance: Lower Gondwana coal-bearing formations (Damuda Series) as India's prime coal resource; Spiti Basin hydrocarbon potential and strategic metal mineralization

Evaluation rubric

DimensionWeightMax marksExcellentAveragePoor
Concept correctness25%12.5Precise definitions distinguishing intrinsic permeability (k) from hydraulic conductivity (K); correct Darcy's law formulation; accurate fossil identification with correct stratigraphic ranges; proper Spiti Basin chronostratigraphy with international correlationBasic definitions present but conflates permeability with hydraulic conductivity; minor fossil misidentification; general Spiti sequence without precise stage boundariesFundamental confusion between porosity and permeability; incorrect Darcy's law application; wrong fossils attributed to Lower Gondwana; muddled Spiti stratigraphy
Diagram / cross-section20%10Neat, labeled diagrams of at least 3 plant fossils showing diagnostic features (reticulate venation in Glossopteris, forked venation in Gangamopteris, wedge-shaped Vertebraria roots); schematic permeameter setup; Spiti Basin lithostratigraphic column with thicknesses and fossil rangesRough sketches with partial labeling; missing key diagnostic features; generic column without fossil rangesNo diagrams or illegible sketches; diagrams without labels; incorrect fossil reconstructions
Field evidence15%7.5Specific Gondwana localities cited (Raniganj, Jharia, Talchir for plant fossils); Spiti Valley sections (Muth Quartzite, Kuling Shale, Productus limestone) with actual fossil assemblages; mention of type sections and GSI mappingGeneral mention of Damuda Series without specific basins; Spiti mentioned without specific formationsNo field localities cited; purely theoretical treatment without Indian examples
Quantitative reasoning20%10Correct formula K = QL/A(h₁-h₂); proper unit conversion (30 cm = 0.3 m, 20 cm = 0.2 m); calculation steps shown yielding K = 0.006 m/s or equivalent; dimensional analysis verifying m/s unitsCorrect formula but arithmetic error or unit conversion mistake; final answer order of magnitude correctWrong formula used; no unit conversion; calculation missing or completely wrong; no quantitative treatment of part (a)
Indian / economic relevance20%10Explicit linkage: Lower Gondwana flora as coal measure indicators (95% Indian coal reserves); groundwater K values relevant to aquifer characterization in Indo-Gangetic alluvium and Deccan Traps; Spiti Basin as frontier hydrocarbon province with Cambrian source rocksMention of coal or groundwater without elaboration; generic economic importance statedNo economic or applied significance discussed; misses coal-Gondwana flora connection entirely

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