Tectonics & Sedimentation

EaES Sedimentary basins Sedimentary basins are the subsiding areas where sediments accumulate to form stratigraphic successions The tectonic setting is the premier criterion to distinguish different types of sedimentary basins Extensional basins occur within or between plates and are associated with increased heat flow due to hot mantle plumes Extensional basins occur within or between plates and are associated with increased heat flow due to hot mantle plumes Collisional basins occur where plates collide, either characterized by subduction of an oceanic plate or continental collision Collisional basins occur where plates collide, either characterized by subduction of an oceanic plate or continental collision Transtensional basins occur where plates move in a strike-slip fashion relative to each other Transtensional basins occur where plates move in a strike-slip fashion relative to each other

EaES

I) Tectonics and Sedimentation A. Can explain sedimentary sequence with plate tectonic models B. Cratonic sedimentation 1. craton = stable continental interior, positive relief 2. thin sedimentary sequences, unconformities 3. positive relief leads to erosion & unconformities 4. sedimentary sequence = ~ 1 km of Paleozoic and Mesozoic rks i. l.s, s.s., sh = shallow marine, fluvial-deltaic 5. local development of basins & arches i. origin of basins = failed rifts?= Michigan basin Wiley.com Alberta Geol Society

II) Geosynclines A. Trough that parallels continental margin = geosyncline 1. subdivided in miogeosyncline & eugeosyncline 2. miogeosyncline i. = shallow marine ls & ss adjacent to craton ii passes to deep water lithologies 3. eugeosyncline i. deep marine sediments, submarine volcanics, volcaniclastic sediments ii. tectonically deformed 4. no explanation of how geosynclines formed Steven Dutch

EaES Sedimentary basins Extension Rift basins develop in continental crust and constitute the incipient extensional basin type; if the process continues it will ultimately lead to the development of an ocean basin flanked by passive margins, alternatively an intracratonic basin will form Rift basins consist of a graben or half-graben separated from surrounding horsts by normal faults; they can be filled with both continental and marine deposits Intracratonic basins develop when rifting ceases, which leads to lithospheric cooling due to reduced heat flow; they are commonly large but not very deep

EaES

III) Plate Tectonics & Sedimentation A. Explains geosynclines (now obsolete) 1. miogeosyncline = shelf; eugeosyncline = slope & rise B. Divergent margins 1. 2 plates separating 2. uplift = mantle plume 3. extension = rift valley development 1. normal faulting & down dropping ii. eventually forms ocean basin 4. coarse immature sediments deposited; alluvial, fluvial, lacustrine 5. aulacogens may develop & fill i. fluvial & deltaic deposits fill basin 6. junction coalesce to form ocean basin i. evaporites, marine sediments 7. seafloor spreading develops & pelagic oozes

Mississippi & Connecticut-Hudson Valleys--Inactive

Rio 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 Beginning Deep axial trough, broad shallow shelf Miocene (5-25mya) evaporites (over 4km thick) below shelf Evaporties probably overlie thin, stretched continental crust Evaporite deposition end 5 mya- connection to Indian sea established Open ocean water led to flourishing plankton Biogenic seds give way laterally to thin terrigenous clays, sands, gravels from eroding flanks Stephen A. Nelson

III) Plate Tectonics & Sedimentation C. Convergent margins 1. cont-cont collision = uplift & coarse clastic debris, fluvial deposits 2. oceanic-oceanic collision = island arc i. submarine volcanism & turbidites, shales, pelagic oozes 3. ocean-continent collision = continental margin arc i. felsic batholiths, silicic volcanics ii. immature seds = alluvial & fluvial ss ii. accretionary wedge, melange

EaES Sedimentary basins Collision Forearc basins form between the accretionary prism and the volcanic arc and subside entirely due to sediment loading; like trench basins, their fill depends strongly on whether they are intra-oceanic or proximal to a continent Backarc basins are extensional basins that may form on the overriding plate, behind the volcanic arc Retroarc foreland basins form as a result of lithospheric loading behind a mountainous arc under a compressional regime; they are commonly filled with continental deposits

ARC Morphology/Terminology

Forearcs

Trenches and Accretionary Wedges

III) Plate Tectonics & Sedimentation D. Transform Margin 1. strike slip motion 2. irregularities produce local extension & compression 3. typical of southern California i. may develop sediment-starved basin ii. eventually infilled

San Andreas Transform

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

Woods Hole

EaES