Tectonics & Tectonics & SedimentationSedimentation

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Sedimentary basinsSedimentary basins

Sedimentary basins are the subsiding areas where sediments Sedimentary basins are the subsiding areas where sediments accumulate to form stratigraphic successionsaccumulate to form stratigraphic successions

The tectonic setting is the premier criterion to distinguish The tectonic setting is the premier criterion to distinguish different types of sedimentary basinsdifferent types of sedimentary basins

• Extensional basinsExtensional basins occur within or between plates and are occur within or between plates and are associated with increased heat flow due to hot mantle plumesassociated with increased heat flow due to hot mantle plumes

• Collisional basinsCollisional basins occur where plates collide, either occur where plates collide, either characterized by subduction of an oceanic plate or continental characterized by subduction of an oceanic plate or continental collisioncollision

• Transtensional basinsTranstensional basins occur where plates move in a strike- occur where plates move in a strike-slip fashion relative to each otherslip fashion relative to each other

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I) Tectonics and SedimentationI) Tectonics and Sedimentation

A. Can explain sedimentary A. Can explain sedimentary sequence with plate tectonic sequence with plate tectonic modelsmodelsB. Cratonic sedimentationB. Cratonic sedimentation

1. craton = stable continental 1. craton = stable continental interior, positive reliefinterior, positive relief2. thin sedimentary sequences, 2. thin sedimentary sequences, unconformitiesunconformities3. positive relief leads to erosion 3. positive relief leads to erosion & unconformities& unconformities4. sedimentary sequence = ~ 1 4. sedimentary sequence = ~ 1 km of Paleozoic and Mesozoic km of Paleozoic and Mesozoic rksrks

i. l.s, s.s., sh = shallow marine, i. l.s, s.s., sh = shallow marine, fluvial-deltaicfluvial-deltaic

5. local development of basins & 5. local development of basins & archesarchesi. origin of basins = failed rifts?= i. origin of basins = failed rifts?= Michigan basinMichigan basin

Wiley.com

Alberta Geol Society

II) GeosynclinesII) Geosynclines

A. Trough that parallels continental margin = geosynclineA. Trough that parallels continental margin = geosyncline1. subdivided in miogeosyncline & eugeosyncline1. subdivided in miogeosyncline & eugeosyncline2. miogeosyncline2. miogeosyncline

i. = shallow marine ls & ss adjacent to cratoni. = shallow marine ls & ss adjacent to cratonii passes to deep water lithologiesii passes to deep water lithologies

3. eugeosyncline3. eugeosynclinei. deep marine sediments, submarine volcanics, volcaniclastic sedimentsi. deep marine sediments, submarine volcanics, volcaniclastic sedimentsii. tectonically deformedii. tectonically deformed

4. no explanation of how geosynclines formed4. no explanation of how geosynclines formed

Steven Dutch

Steven Dutch

Steven Dutch

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Sedimentary basinsSedimentary basins

ExtensionExtension

Rift basinsRift basins develop in continental crust and constitute the develop in continental crust and constitute the incipient extensional basin type; if the process continues it incipient extensional basin type; if the process continues it will ultimately lead to the development of an will ultimately lead to the development of an ocean basinocean basin flanked by flanked by passive marginspassive margins, alternatively an , alternatively an intracratonic basinintracratonic basin will form will form

Rift basins consist of a graben or half-graben separated from Rift basins consist of a graben or half-graben separated from surrounding horsts by normal faults; they can be filled with surrounding horsts by normal faults; they can be filled with both continental and marine depositsboth continental and marine deposits

Intracratonic basins develop when rifting ceases, which leads Intracratonic basins develop when rifting ceases, which leads to lithospheric cooling due to reduced heat flow; they are to lithospheric cooling due to reduced heat flow; they are commonly large but not very deepcommonly large but not very deep

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III) Plate Tectonics & III) Plate Tectonics & SedimentationSedimentation

A. Explains geosynclines (now obsolete)A. Explains geosynclines (now obsolete)1. miogeosyncline = shelf; 1. miogeosyncline = shelf; eugeosyncline = slope & riseeugeosyncline = slope & rise

B. Divergent marginsB. Divergent margins1. 2 plates separating1. 2 plates separating2. uplift = mantle plume2. uplift = mantle plume3. extension = rift valley development3. extension = rift valley development

1. normal faulting & down dropping1. normal faulting & down droppingii. eventually forms ocean basinii. eventually forms ocean basin

4. coarse immature sediments 4. coarse immature sediments deposited; alluvial, fluvial, lacustrinedeposited; alluvial, fluvial, lacustrine5. aulacogens may develop & fill5. aulacogens may develop & fill

i. fluvial & deltaic deposits fill basini. fluvial & deltaic deposits fill basin

6. junction coalesce to form ocean 6. junction coalesce to form ocean basinbasin

i. evaporites, marine sedimentsi. evaporites, marine sediments

7. seafloor spreading develops & 7. seafloor spreading develops & pelagic oozespelagic oozes

Mississippi & Connecticut-Hudson Mississippi & Connecticut-Hudson Valleys--InactiveValleys--Inactive

Rio Grande Rift--ActiveRio Grande Rift--Active

Properties of crust and upper mantle beneath the Rio Grande. Pure shear model is probable explanation, with a "taffy-like" thinning of the lower crust and the upper crust faulting in many places to produce the rift valley. This contrasts to "simple shear" model wherein a single, large detachment fault controls continental rifting.

Nicolle Rager, NSF

Red Sea-Ocean BeginningRed Sea-Ocean Beginning

Deep axial trough, broad Deep axial trough, broad shallow shelfshallow shelf

Miocene (5-25mya) evaporites Miocene (5-25mya) evaporites (over 4km thick) below shelf(over 4km thick) below shelfEvaporties probably overlie Evaporties probably overlie thin, stretched continental crustthin, stretched continental crustEvaporite deposition end 5 Evaporite deposition end 5 mya- connection to Indian sea mya- connection to Indian sea establishedestablishedOpen ocean water led to Open ocean water led to flourishing planktonflourishing planktonBiogenic seds give way laterally Biogenic seds give way laterally to thin terrigenous clays, sands, to thin terrigenous clays, sands, gravels from eroding flanksgravels from eroding flanks

Stephen A. Nelson

III) Plate Tectonics & III) Plate Tectonics & SedimentationSedimentation

C. Convergent marginsC. Convergent margins1. cont-cont collision = uplift & coarse clastic debris, 1. cont-cont collision = uplift & coarse clastic debris,

fluvial depositsfluvial deposits

2. oceanic-oceanic collision = island arc2. oceanic-oceanic collision = island arci. submarine volcanism & turbidites, shales, pelagic i. submarine volcanism & turbidites, shales, pelagic

oozesoozes

3. ocean-continent collision = continental margin arc3. ocean-continent collision = continental margin arci. felsic batholiths, silicic volcanicsi. felsic batholiths, silicic volcanics

ii. immature seds = alluvial & fluvial ssii. immature seds = alluvial & fluvial ss

ii. accretionary wedge, melangeii. accretionary wedge, melange

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Sedimentary basinsSedimentary basins

CollisionCollision

Forearc basins form between the accretionary prism and the Forearc basins form between the accretionary prism and the volcanic arc and subside entirely due to sediment loading; volcanic arc and subside entirely due to sediment loading; like trench basins, their fill depends strongly on whether like trench basins, their fill depends strongly on whether they are intra-oceanic or proximal to a continentthey are intra-oceanic or proximal to a continent

Backarc basins are extensional basins that may form on the Backarc basins are extensional basins that may form on the overriding plate, behind the volcanic arcoverriding plate, behind the volcanic arc

Retroarc foreland basins form as a result of lithospheric Retroarc foreland basins form as a result of lithospheric loading behind a mountainous arc under a compressional loading behind a mountainous arc under a compressional regime; they are commonly filled with continental depositsregime; they are commonly filled with continental deposits

ARC Morphology/TerminologyARC Morphology/Terminology

ForearcsForearcs

Trenches and Accretionary Trenches and Accretionary WedgesWedges

III) Plate Tectonics & III) Plate Tectonics & SedimentationSedimentation

D. Transform MarginD. Transform Margin1. strike slip motion1. strike slip motion

2. irregularities produce local extension & 2. irregularities produce local extension & compressioncompression

3. typical of southern California3. typical of southern Californiai. may develop sediment-starved basini. may develop sediment-starved basin

ii. eventually infilledii. eventually infilled

San Andreas TransformSan Andreas Transform

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Sedimentary basinsSedimentary basins

TranstensionTranstension

Strike-slip basinsStrike-slip basins form in transtensional regimes and are form in transtensional regimes and are usually relatively small but also deep; they are commonly usually relatively small but also deep; they are commonly filled with coarse facies (e.g., alluvial fans) adjacent to filled with coarse facies (e.g., alluvial fans) adjacent to lacustrine or marine depositslacustrine or marine deposits

Woods Hole

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