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.

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