Sedimentary Basins & their Sedimentation Sedimentati on Pattern
Rajesh Singh Shekhawat MSc (Prev.) 2011 Under the guidance of Professor D. K. Pandey
INTRODUCTION Sedimentary basins are regions of prolonged subsidence of Earth's surface. Driving Mechanisms – Plate Tectonics, & other tectonic and Dynamic activities - result in isostatic adjustments, loading & unloading. Earth's crust – About 20 rigid plates, whose movement result in – Divergence, Convergence, & Strike-slip — Basin formation.
Major & Minor Plates of Earth’s Lithosphere
Tectonic Elements of Earth
Factors affecting depositional processes & resulting sedimentary facies
Wilson Cycle
5.
1.
Suturi ng
Rift Basin
2. Proto-Ocean & Ocean Basin 4. Ocean Closure
3. Arc-Trench Formation
Classification of Sedimentary Basins Many classifications given. In general, the basis of classification are – Type of Crust on which the basins rest, Position of basin with respect to plate margins, Type of plate interactions during sedimentation – for basins lying close to a plate margin.
Most Comprehensive Basin Classification by Busby & Ingersoll (1995) Divergent Settings Terrestrial rift Rifts within continental crust commonly valleys associated with bimodal volcanism. Ex– Rio Grand rift (New Mexico) Proto-oceanic rift troughs
Incipient oceanic basins floored by new oceanic crust & flanked by young rifted continental margins. Ex–Red Sea
Intraplate Settings Passive Mature rifted continental margins in intraplate Margin basin settings at O–C interfaces. Ex–East Coast of USA Continental Progradational sediment wedges constructed off embankmen edges of rifted continental margins. Ex– ts Mississippi Gulf Coast Intracratonic Broad cratonic basins floored by fossil rifts in basins axial zones. Ex–Chad Basin (Africa) Continental Stable cratons covered with thin & laterally platforms extensive sedimentary strata. Ex – Barents Sea (Asia) Active ocean At divergent plate boundaries (spreading still basins active). Ex– Pacific Ocean Oceanic Is, aseismic ridges,
Sedimentary aprons & platforms; In intraoceanic settings other than magmatic arcs. Ex–EmperorHawaii seamounts
Convergent settings Trenches Deep troughs; By subduction of oceanic lithosphere. Ex–Chile Trench Trench-slope Local depressions upper part of Trenches. Ex–Central basins America Trench Forearc basins Within arc-trench gaps. Ex–Sumatra Intraarc basins Along arc platform. Ex–Lago de Nicaragua Backarc basins Oceanic – behind intraoceanic magmatic arcs(O-O). Ex – Marianas. Continental – behind continental-margin magmatic arcs without foreland fold-thrust belts(C-C). Ex–Japan Sea. Retroarc Foreland basins on subducting plate in C-C/C-O formed foreland basins by subduction-generated compression &/or collision). Ex–Andes foothills Remnant oceanShrinking ocean basins caught b/w colliding continental basins margins &/or arc-trench systems. Ex–Bay of Bengal Peripheral Foreland basins above subducted continental margins foreland basins during C-C collisions. Ex–Persian Gulf
Transform/Strike-Slip settings Transtensio By extension along strike-slip fault systems. Ex– nal Salton Sea. Transpressio By compression. Ex–Santa Barbara Basin. nal Transrotatio By rotation of crustal blocks about vertical axes. Ex– nal Western Aleutian. Hybrid settings B/W ends ofbasins 2 sub-parallel strike-slip fault segments. Overstep Intracontinenta Diverse form due to distant collisional Ex–processes. Dead Sea Basin l wrench Ex–Qaidam Basin (China). basins Aulacogens Failed rifts at high angles to continental margins. Ex–North Sea. Impactogens Rifts at high angles to orogenic belts, without preorogenic history (in contrast with aulacogens). Ex–Baikal rift (Siberia). Successor Form in intermontane settings following cessation of local orogenic activity. Ex–S. Basin & Range basins
Strike-Slip Basins Form in a wide variety of geodynamical settings; Varied structural history, active seismicity & low heat flow. High Subsidence & Sedimentatiion rates. Relatively narrow, high syndepositional relief . Sedimentary Fill – Rapid lateral facies changes – Marginal Fans(breccias, Conglmerates) tight up against the fault; Axial lacustrine facies – mud, shale; Streamflow-dominated fans(fluviatile sandstone & conglomerate) along opposite margin;
Strike-Slip Basins Continued…. Best known intracontinental transform – San Andreas system, & 1 of the best documented pull apart basins in this system – Ridge Basin, California.
Basins in Convergent Setting Compressive regime – inhomogeneous stress distribution & thermal effects produces both, Extensional & Compressional Basins.
Backarc Basin Extensional; Typically underfilled, containing mainly deep-water sediment of volcaniclastic & pelagic origin. Initially, volcaniclastics interfinger with a background of pelagic clays. As subsidence continues & outstrips sediment supply, seafloor descends below CCD – accumulates siliceous rather than calcareous clays. Clastic wedges into landward edge of basin from continent.
Back-arc Basin
Foreland Basins
Back-arc region floored by continental lithosphere – flexural subsidence coupled with major fold & thrust tectonics. Contains 4 depositional zones – Wedge top/ Piggy Back Basins Foredeep Forebulge Backbulge Foredeep & Piggy-back Basins – most common.
Foreland Basins Sediment Fill Early Stage deposits – Limestones, deep-water muds & interbedded turbidite sandstones – “ Flysch" Later Stage – Transition to coarse-grained (upward coarsening) fluvial/alluvial clastic rocks – “ Molasse".
Retro-arc foreland basins
Peripheral foreland Basin
Basins in Intraplate Settings Basins Within continental; Rift Opening stage of Wilson Cycle/continental break-up . Long, narrow, linear; No or poor connection with sea. Mechanisms Active Rifting – East African Rift Passive Rifting Sediment Fill Coarse, non-marine, alluvial, fluvial & lacustrine siliciclastics & volcaniclastics– texturally & mineralogically immature. Where periodic connection with sea(esp. in rift climax phase) – Evaporites (Jurassic of Gulf of Mexico & Texas).
East African Rift Basin
Proto Oceanic Rift Basins Post-rift phase – Basin floored with Oceanic crust. Ex – Red Sea, b/w Africa & Arabia; Southern Red Sea – young (5Ma) oceanic crust along its axial zone, with flanking shelves underlain by stretched continental lithosphere. To South, transition to continental Afar Rift; To North, Gulf of Suez Rift. Sediment Fill Subsidence outpaces sediment supply. Number of distinctive facies associations indicative of sediment starvation – Evaporites,
Red Sea – Proto Oceanic Rift Basins
Cross Section of Red Sea Rift
Passive Margin Basins Areas of high sedimentation rates — large-listric gravity-driven faults common. In areas of low clastic sediment input — Carbonate factories. Eustasy, Tectonics & other factors(Climate, etc) – control accomodation space & sediment availability, & hence sediment diistribution pattern
References OCW MIT Basin Analysis: Principles & Applications – Allen & Allen (2005) Plate Tectonics: Continental Drift & Mountain Building – Frisch, Meschede & Blakey (2011) Principles of Sedimentary Basin Analysis – A.D.Miall (2000) Sedimentary Basins: Evolution, Facies & Sediemntary Budget – Gerhard E insele (2000) Global tectonics – Kearney, Klepeis & Vine (2009) Physical Principles of Sedimentary Basins – Magnus Wangen (2010) Petroleum Geoscience – J.Gluyas & R.Swarbrick (2006) Petroleum Geoscience: From Sedimentary Environments to Rock Physics – K.Bjorlykke (2010) Petrology of Sedimentary Rocks – Sam Boggs Jr. (2009) Principles of Sedimentology & Stratigraphy – Sam Boggs Jr. (2005) Sedimentology & Stratigraphy – Gary Nichols (2009) Applied Sedimentology – Richard C. Selley (2000) Earth’s Dynamic Systems – W.K.Hamblin & E.H.Christiansen Earth Structure: An Intro to Structural geology & Tectonics – Pluijm & Marshak (2004)
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