© Career Avenues A 1 STRATIGRAPHY © Career Avenues A 2 Index 1. Stratigraphy – An Overview 1.1. Stratigraphy – Definition 1.2. Cratons 1.3. Fold Belts or Mobile Belts or Orogenic Belts 1.4. Phanerozoic Stratigraphy of India 2. Stratigraphic Classification and principles 2.1. Stratigraphic Classification 2.2. Principles of Stratigraphic Correlation 3. Geological Timescale 3.1. Chronostratigraphic Units 3.2. Mass Extinction events 4. Cratons (Part 1) – Aravalli and Bundelkhand Craton 4.1. Aravalli Craton 4.2. Bundelkhand Craton 5. Cratons (Part 2) – Dharwar, Bastar and Singhbhum Craton 5.1. Dharwar Craton 5.2. Bastar Craton 5.3. Singhbhum Craton 6. Mobile Belts 6.1. Central Indian Tectonic Zone (CITZ) or Satpura Mobile Belt (SMB) 6.2. Eastern Ghat Mobile Belt 6.3. Pandyan Mobile Belt 7. Proterozoic Basins 7.1. Proterozoic Basins 7.2. Vindhyan Basin 7.3. Chhattisgarh Basin 7.4. Khariar Basin 7.5. Ampani Basin 7.6. Indravati Basin 7.7. Sabari (Sukma) Basin 7.8. Pranhita – Godavari Basin 7.9. Cuddapah Basin 7.10. Kaladgi Basin 7.11. Bhima Basin 8. Phanerozoic of Extra-peninsular India 8.1. Phanerozoic Stratigraphy of Kashmir 8.2. Phanerozoic Stratigraphy of Spiti 8.3. Phanerozoic Stratigraphy of Salt Range 9. Phanerozoic of Peninsular India and Islands 9.1. Gondwana Supergroup 9.2. Mesozoic and Cenozoic Stratigraphy of Kutch © Career Avenues A 3 9.3. Cretaceous Stratigraphy of Trichinopoly 9.4. Stratigraphy of North-East India 9.5. Stratigraphy of Andaman Islands 10. Volcanic Provinces of India 10.1. Deccan Traps 10.2. Rajmahal Traps 10.3. Sylhet Traps 11. Geology of Himalaya 11.1. Himalayan Mountain Range 11.2. Subdivisions 11.3. Tectonic Evolution of Himalaya 11.4. Stratigraphy 12. Supercontinents 12.1. Supercontinents 12.2. Position of India in geological history © Career Avenues A 4 Stratigraphy is one of the most important subjects of geology. In every competitive examination, there will be at least one question from stratigraphy. This subject covers the stratigraphic principles and stratigraphy of India. The latter includes the geology of cratons, mobile belts and Proterozoic basins, Phanerozoic successions and volcanic provinces of India and Himalaya. The geological timescale is also introduced in this book. © Career Avenues A 5 Chapter 1 Stratigraphy – An Overview 1.1. Stratigraphy - Definition Stratigraphy is the branch of geology dealing with the study and description of the nature, distribution, and relations of the rocks of the earth's crust. 1.2. Cratons • Cratons are the large, coherent domain of Earth’s continental crust that has attained and maintained long term stability. These are composed of Precambrian crystalline rocks, which are poly-deformed and poly-metamorphosed. Granite-greenstone terrain typically represents cratons. • Shield → Shield is the exposed portion of a craton • Platform It is the part of craton which is covered by younger rocks • Usually, the Archean age is assigned to the cratons. But in some places, cratons are considered large crustal fragments (example: Laurentia) that were only amalgamated and attained stability during the Proterozoic. • There are around 35 large Archean cratons in the world. • Stabilization of craton is shown by, ▪ Closure of whole-rock isotopic system. ▪ Intrusions of undeformed plutons ▪ Deposition of sediments on newly created basements © Career Avenues A 6 → In India, five major cratons are occupied in peninsular India. These are, ▪ Aravalli Craton ▪ Bundelkhand Craton ▪ Dharwar Craton ▪ Bastar Craton ▪ Singhbhum Craton 1.3. Fold Belts or Mobile Belts or Orogenic Belts • Orogenic belts are elongated terrains formed when continents come together and collide with each other. These are made up of high-grade rocks and highly deformed. • There are three types of orogenic belts based on their formation, ▪ Intercontinental orogeny ▪ Intracontinental orogeny ▪ Internal or confined orogeny • Intercontinental orogenicSAMPLE belts it is formed by the collision of two or more continental blocks and closure of large oceanic basin in between. Example: Himalaya Mountain Range (formed by closure of Tethys Sea) • Intracontinental Orogenic belts it develops without closure of large ocean basin. Example: Rocky Mountain Chain. • Internal or Confined orogenic belt it develops when the splitting of a continent forms a small ocean basin that closes back on itself, thus forming a zone of oceanic subduction without bringing far-travelled blocks together. Example: Trans-Hudson Orogen. • List of Mobile Belts in India ▪ Eastern Ghat Mobile Belt (EGMB) ▪ Delhi – Aravalli Mobile Belt © Career Avenues A 7 ▪ Singhbhum Mobile Belt (SMB) ▪ Central Indian Tectonic Zone (CITZ) ▪ Kotri – Dongargarh Mobile Belt ▪ Pandyan Mobile Belt 1.4. Phanerozoic Stratigraphy of India • In the extra-peninsula, the important Phanerozoic successions are in Kashmir Valley, Spiti and Salt range. • In peninsular India, there is a large hiatus from Cambrian to Carboniferous. After that Gondwana sediments were started to deposit in some rift valleys. Also, the Mesozoic and Cenozoic successions of Kutch (Gujrat) and North-East India and Cretaceous sediments of Trichinopoly (Tamil Nadu) are important. • In the Cenozoic, the collision of the northward drifting Indian plate and Eurasian plate resulted in the formationSAMPLE of Himalayan Mountain Range. This mountain range possesses very important structural elements like thrusts. • Mantle plume related volcanism resulted in the formation of Volcanic provinces in India. Deccan Trap is most important of all. • The movement of continental blocks resulted in the formation of supercontinents at various geological times. Study of cratons, mobile belts, rift valleys and stratigraphic correlation and age determining methods are used to establish the configuration of the Supercontinent at its time. © Career Avenues A 8 Practice Questions Level: Easy 1. Match the following Group I Group II a. Principle of Superposition 1. James Hutton b. Principle of Uniformitarianism 2. William Smith c. Principle of Faunal Succession 3. Nicolas Steno a. a-2, b-1, c-3 b. a-2, b-3, c-1 c. a-3, b-2, c -1 d. a-3, b-1, c-2 2. The geochronologic equivalent of ‘series’ a. system b. epoch c. formation d. period 3. the assemblage of fossils of organisms that lived and buried in the same place, where it is found a. Biocoenosis b. Thanatocoenosis c. Barren interval d. Biozone 4. A ‘complex’ can be consistSAMPLE of, a. Only sedimentary rocks b. Igneous and sedimentary rocks c. Igneous and metamorphic rocks d. Igneous, metamorphic and sedimentary rocks Level: Medium 5. Match the following Group I Group II a. Lithostratigraphy 1. Range zone b. Magnetostratigraphy 2. System c. Biostratigraphy 3. Formation d. Chronostratigraphy 4. Polarity zone a. a-4, b-2, c-3, d-1 b. a-3, b-4, c-1, d-2 c. a-3, b-4, c-2, d-1 d. a-2, b-4, c-1, d-3 6. Find out the biozone represented by the following figure © Career Avenues A 9 a. Assemblage Zone b. Consecutive Zone c. Taxon Range Zone d. Concurrent Range Zone 7. Choose the option showing CORRECT order of hierarchy. a. Stage < system < series < erathem b. Erathem < stage < series < system c. Erathem < stage < system < series d. Stage < series < system < erathem 8. A range zone that is definedSAMPLE by the overlapping of two taxa is called, a. Partial range zone b. Acme zone c. Taxon range zone d. Concurrent range zone Level: Difficult 9. Find out the CORRECT sequence of events, from older to younger. (A, B and C → deposition of beds, D1 and D2 dyke intrusions) a. A – B – C – D1 – D2 b. C – B – A – D1 – D2 c. C – D2 – B – A – D1 d. D2 – C – B – A – D1 10. Find out the CORRECT statement(s). I. Lithostratigraphic classification accounts the thickness of strata. II. Lithostratigraphic classification accounts lithology. III. Lithostratigraphic classification accounts the stratigraphic position of beds. a. I only © Career Avenues A 10 b. I and II c. II and III d. All of the above Multiple Select Questions 11. Which of the following is(are) the unit(s) of Lithostratigraphy? a. Group b. Epoch c. Member d. Zone 12. Which of the following statement(s)about lithostratigraphic classification is(are) CORRECT? a. A Group is the primary formal unit of lithostratigraphic classification. b. Units of lithostratigraphic classification are defined by lithology. c. Units of lithostratigraphic classification are defined by lithology and age. d. Member is the smallest formal unit of lithostratigraphic classification. 13. Which of the following statement(s)about biostratigraphic classification is(are) CORRECT? a. Interval zones are defined by the first and last appearance of fossils. b. Consecutive range zones are defined by the lineage of species. c. Assemblage zones are defined by the first appearance of two taxa. d. Acme zones are definedSAMPLE by the abundance of species. 14. Choose the CORRECT magnetostratigraphic polarity subzone and zones from the following pairs. a. Jaramillo - Brunhes b. Olduvai - Matuyama c. Reunion - Gilbert d. Mammoth - Gauss 15. Choose the CORRECT chronostratigraphic – geochronologic equivalents from the following pairs. a. System - Epoch b. Stage - Age c. Series - Period d. Era - Erathem 16. Stratigraphic principals that are proposed by Nicolas Steno a. Principle of superposition b. Principle of lateral continuity c. Principle of cross-cutting relationship d. Principle of faunal succession 17. A stratigraphic horizon will abruptly end _________. a. When it meets a fault b. When it meets an erosional surface c. In cross beddings d. If there is not enough sediment supply © Career Avenues A 11 Answers 1. d 2. b 3. a 4. d 5. b 6. d 7. d 8. d 9. c 10. c 11. a, c 12. b 13. a, b, d 14. b, d 15. b, d 16. a, b 17. a, b © Career Avenues A 12 JAM 2020 In an undeformed and normal stratigraphic succession, a dolerite dyke was emplaced before deposition of sandstone B. The difference between the maximum ages (in Myr) of deposition of sandstone A and sandstone B is ____ Mark: 2 Ans: 57 Explanation: the possible age of Sandstone A is 132 to 75 Ma (because it can’t be more than the age of Volcanic ash bed 1 and less than the age of dolerite dyke) and Sandstone B is 75 to 62 Ma (because it can’t be more than the age of dolerite dyke and less than the age of Volcanic ash bed 2).