𝗕𝗮𝘀𝗶𝗻 𝗧𝘆𝗽𝗲𝘀

1. Divergent Basins (Extensional Basins)

Form due to crustal extension and thinning, commonly associated with rifting and continental breakup.

Examples: Rift basins, passive margin basins

a) Rift Basins

Develop along extensional fault zones where the lithosphere is stretched.

Characterized by normal faults, grabens, and half-grabens.

Common in early-stage continental breakup (e.g., East African Rift System, North Sea Rift).

Petroleum Significance: Excellent source rocks (lacustrine shales) and structural traps (fault-bounded reservoirs).

b) Passive Margin Basins

Found along continental margins after rifting stops and seafloor spreading begins.

Thick sequences of sediments accumulate due to thermal subsidence.

Examples: Gulf of Mexico, West African Margin.

Petroleum Significance: Rich in organic-rich marine shales (source rocks) and large sandstone reservoirs.

2. Convergent Basins (Compressional Basins)

Form due to plate collision and crustal shortening.

Examples: Foreland basins, forearc basins, backarc basins.

a) Foreland Basins

Develop adjacent to mountain belts due to crustal loading by orogenic (mountain-building) processes.

Examples: Western Canada Sedimentary Basin, Persian Gulf Basin.

Petroleum Significance: Thick sedimentary sequences with excellent reservoirs and traps.

b) Forearc Basins

Form between an oceanic trench and a volcanic arc in subduction zones.

Examples: Peru-Chile Forearc Basin, Japan Forearc Basin.

Petroleum Significance: Complex depositional environments with potential gas accumulations.

c) Backarc Basins

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Located behind volcanic arcs, formed due to slab rollback and extension.

Examples: Sea of Japan, South China Sea.

Petroleum Significance: Potential hydrocarbon-bearing sedimentary sequences.

3. Transform Basins (Strike-Slip Basins)

Develop along strike-slip fault zones, where crustal blocks move laterally.

Examples: San Andreas Fault Basin, Dead Sea Basin.

Petroleum Significance: Contain localized pull-apart basins with high sedimentation rates and hydrocarbon potential.

4. Intracratonic Basins

Form within stable continental interiors, often due to slow thermal subsidence.

Examples: Williston Basin (USA), Illinois Basin.

Petroleum Significance: Long-lived source rock maturation, leading to extensive hydrocarbon accumulations.

5. Cratonic Rift and Failed Rift Basins (Aulacogens)

Ancient rift basins that did not evolve into full ocean basins.

Examples: West Siberian Basin, Reelfoot Rift (USA).

Petroleum Significance: Preserve thick organic-rich sediments suitable for oil and gas generation.

Comments

Geologic and tectonic framework of the Indian shield

Major Terms and Regions Explained 1. Indian Shield The Indian Shield refers to the ancient, stable core of the Indian Plate made of hard crystalline rocks. It comprises Archean to Proterozoic rocks that have remained tectonically stable over billions of years. Important Geological Features and Regions ▪️ Ch – Chhattisgarh Basin A sedimentary basin part of the Bastar Craton . Contains rocks of Proterozoic age , mainly sedimentary. Important for understanding the evolution of central India. ▪️ CIS – Central Indian Shear Zone A major tectonic shear zone , separating the Bundelkhand and Bastar cratons . It records intense deformation and metamorphism . Acts as a suture zone , marking ancient tectonic collisions. ▪️ GR – Godavari Rift A rift valley formed due to stretching and thinning of the Earth's crust. Associated with sedimentary basins and hydrocarbon resources . ▪️ M – Madras Block An Archean crustal block in...

Geology and Tectonic. Indian Shield

1. Ch (Chattisgarh Basin): Chattisgarh Basin is a geological region in central India known for its sedimentary rock formations. It's important for its mineral resources, including coal and iron ore. 2. CIS (Central Indian Shear Zone): CIS is a tectonic boundary in central India where the Indian Plate interacts with the Eurasian Plate. It's characterized by significant faulting and seismic activity. 3. GR (Godavari Rift): The Godavari Rift is a geological feature associated with the rifting and splitting of the Indian Plate. It's located in the Godavari River basin in southeastern India. 4. M (Madras Block): The Madras Block is a stable continental block in southern India. It's part of the Indian Plate and is not associated with active tectonic processes. 5. Mk (Malanjkhand): Malanjkhand is known for its copper deposits and is one of the largest copper mines in India. 6. MR (Mahanadi Rift): The Mahanadi Rift is a geological feature related to the rifting of the Indian Pl...

Evaluation and Characteristics of Himalayas

Time Period Event / Process Geological Evidence Key Terms & Concepts Late Precambrian – Palaeozoic (>541 Ma – ~250 Ma) India part of Gondwana , north bordered by Cimmerian Superterranes, separated from Eurasia by Paleo-Tethys Ocean . Pan-African granitic intrusions (~500 Ma), unconformity between Ordovician conglomerates & Cambrian sediments. Gondwana, Paleo-Tethys Ocean, Pan-African orogeny, unconformity, granitic intrusions, Cimmerian Superterranes. Early Carboniferous – Early Permian (~359 – 272 Ma) Rifting between India & Cimmerian Superterranes → Neotethys Ocean formation. Rift-related sediments, passive margin sequences. Rifting, Neotethys Ocean, passive continental margin. Norian (210 Ma) – Callovian (160–155 Ma) Gondwana split into East & West; India part of East Gondwana with Australia & Antarctica. Rift basins, oceanic crust formation. Continental breakup, East Gondwana, West Gondwana, oceanic crust. Early Cretaceous (130–125 Ma) India broke fr...

Seismicity and Earthquakes, Isostasy and Gravity

1. Seismicity and Earthquakes in the Indian Subcontinent Key Concept: Seismicity Definition : The occurrence, frequency, and magnitude of earthquakes in a region. In India, seismicity is high due to active tectonic processes . Plate Tectonics 🌏 Indian Plate : Moves northward at about 5 cm/year. Collision with Eurasian Plate : Causes intense crustal deformation , mountain building (Himalayas), and earthquakes. This is an example of a continental-continental collision zone . Seismic Zones of India Classified into Zone II, III, IV, V (Bureau of Indian Standards, BIS). Zone V = highest hazard (e.g., Himalayas, Northeast India). Zone II = lowest hazard (e.g., parts of peninsular India). Earthquake Hazards ⚠️ Himalayas: prone to large shallow-focus earthquakes due to active thrust faulting. Northeast India: complex subduction and strike-slip faults . Examples: 1897 Shillong Earthquake (Magnitude ~8.1) 1950 Assam–Tib...

Vector geoprocessing - Clipping, Erase, identify, Union & Intersection

Think of your vector data (points, lines, polygons) like shapes drawn on a transparent sheet. Geoprocessing is just cutting, joining, or comparing those shapes to get new shapes or information. 1. Clipping ✂️ Imagine you have a big map and you only want to keep a part of it (like cutting a photo into a smaller rectangle). You use another shape (like the boundary of a district) to "clip" and keep only what is inside. Result: Only the data inside the clipping shape remains. 2. Erase 🚫 Opposite of clipping. You remove (erase) the area of one shape from another shape. Example: You have a city map and want to remove all the park areas from it. 3. Identify 🔍 This checks which features from one layer fall inside (or touch) another layer. Example: Identify all the schools inside a flood zone. 4. Union 🤝 Combines two shapes together and keeps everything from both. Works like stacking two transparent sheets and redrawing t...

Vineesh V, Geography

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