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EES 450: Sedimentary Geology

Breccia Conglomerate Diamictite Sandstone Siltstone Shale. Rudites. Mechanical Weathering. Clastic or Detrital. EES 450: Sedimentary Geology. New Clay Minerals. Shale. Source Rocks. Limestone Chert Diatomite. Biochemical. Solution. Evaporites Chert Limestone Ironstone.

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EES 450: Sedimentary Geology

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  1. Breccia Conglomerate Diamictite Sandstone Siltstone Shale Rudites Mechanical Weathering Clastic or Detrital EES 450: Sedimentary Geology New Clay Minerals Shale Source Rocks Limestone Chert Diatomite Biochemical Solution Evaporites Chert Limestone Ironstone Clastic, siliciclastic or detrital rocks 70% - 80% of all sedimentary rocks Chemical Weathering Chemical Rudite- Rocks composed of rounded or angular detrital grains, which are coarser than sand in size. Peat Coal Bitumen Resins Plant Extraction Organic Crustal, upper mantle melts Explosive Eruption Tuff, Bentonite Agglomerate Volcaniclastic

  2. Rudites (Conglomerates, Breccias, & Diamictites) EES 450: Sedimentary Geology Extraformational Intraformational (Edgewise or solution breccias and conglomerates) Rudite classification Orthoconglomerate Paraconglomerate(Diamictite) Oligomict Polymict Matrix bedded or laminated Matrix not bedded or laminated Tillite Tilloid

  3. EES 450: Sedimentary Geology rudite classification ●Terms: - Extraformational= Clastsfrom older rocks than the formation in which found. - Intraformational= Clastsfrom the same formation in which found. - Orthoconglomerate= Clast-supported rock with < 15% matrix (sand-sized or finer). - Paraconglomerate= Matrix-supported rock with at least 15% sand-sized or finer. - Oligomict = Clasts of only a few different lithologies. - Polymict = Clasts of many different lithologies. - Tillite= Poorly sorted, matrix-supported conglomerate of glacial origin. - Tilloid= General term for matrix-supported rock of ? origin (landslide, mudflow, etc.).

  4. EES 450: Sedimentary Geology rudite classification ●Epiclastic conglomerates and breccias or rudites: - Epiclastic= Formed at Earth’s surface by consolidation of fragments of pre-existing rocks. - Cataclastic= Often a metamorphic rock formed by the fracturing and communition (crushing) of existing rock (mainly found associated with fault zones). - Textural classification

  5. EES 450: Sedimentary Geology rudite classification ●Epiclastic conglomerates and breccias or rudites: - Epiclasticrudites= Sedimentary rocks whose fragments are derived from weathering and erosion. - If the rock contains > 30% clasts and is clast- or matrix-supported with a matrix of sand or mud, then the rock is a conglomerate (or breccia). - If the rock contains < 30% clasts and is mud- supported (mud with no fissility), the rock is a diamictite. Fissile or non-fissile?

  6. Rudites (Conglomerates, Breccias, & Diamictites) EES 450: Sedimentary Geology Extraformational Intraformational (Edgewise or solution breccias and conglomerates) Rudite classification Orthoconglomerate Paraconglomerate(Diamictite) Oligomict Polymict Matrix bedded or laminated Matrix not bedded or laminated Tillite Tilloid

  7. Extraformational Intraformational (Edgewise or solution breccias and conglomerates) EES 450: Sedimentary Geology Clastsderived from the same formation in which they are found rudite classification Clastsderived from older rocks than the formation in which they are found

  8. EES 450: Sedimentary Geology rudite classification ●Flat-pebble or edgewise conglomerate: Conglomerates (usually carbonate- or mud-rich) formed by the penecontemporaneous breakup and re-working of semi-consolidated, usually laminated sediment. - These are almost always intrabasinal in origin. - Other settings for intrabasinalruditesinclude: Evaporite solution.  Karst solution. Paleosols.

  9. Rudites (Conglomerates, Breccias, & Diamictites) EES 450: Sedimentary Geology Extraformational Intraformational (Edgewise or solution breccias and conglomerates) Rudite classification Orthoconglomerate Paraconglomerate(Diamictite) Oligomict Polymict Matrix bedded or laminated Matrix not bedded or laminated Tillite Tilloid

  10. Ortho- (correct, normal) conglomerate Para- (almost, nearly) conglomerate EES 450: Sedimentary Geology rudite classification - Generally clast-supported. - Generally matrix-supported. - Generally < 15% matrix. - Generally > 15% matrix. - Generally deposited in aquatic basins. - Generally more matrix than clasts. - Often stratified. - Typically deposited by viscous fluids. - Generally unstratified.

  11. Rudites (Conglomerates, Breccias, & Diamictites) EES 450: Sedimentary Geology Extraformational Intraformational (Edgewise or solution breccias and conglomerates) Rudite classification Orthoconglomerate Paraconglomerate(Diamictite) Oligomict Polymict Matrix bedded or laminated Matrix not bedded or laminated Tillite Tilloid

  12. EES 450: Sedimentary Geology rudite classification ●Orthoconglomerate: Clast-supported rudites with rounded clasts containing < 15% matrix; generally deposited in aquatic basins. - Oligomict conglomerates: Conglomerates containing rounded clasts of only one or two compositions (often quartz or chert). Quartz pebbles Volcanic pebbles

  13. EES 450: Sedimentary Geology rudite classification ●Orthoconglomerate: Clast-supported rudites with rounded clasts containing < 15% matrix; generally deposited in aquatic basins. - Polymict conglomerates: Conglomerates containing rounded clasts of several different compositions.

  14. EES 450: Sedimentary Geology rudite classification ●Interpretive terms for conglomerates: - Fanglomerates: Conglomerates deposited in an alluvial fan environment.

  15. EES 450: Sedimentary Geology rudite classification ●Interpretive terms for conglomerates: - Breccia: Rudites containing > 30% angular clasts, which are produced by brittle failure. Same classification terms (ortho-, para-, oligomict, polymict) are used for breccia. Care needs to be taken to distinguish these from igneous, metamorphic and hydrothermal breccia. Caliche breccia Collapse breccia You breccia

  16. Rudites (Conglomerates, Breccias, & Diamictites) EES 450: Sedimentary Geology Extraformational Intraformational (Edgewise or solution breccias and conglomerates) Rudite classification Orthoconglomerate Paraconglomerate(Diamictite) Oligomict Polymict Matrix bedded or laminated Matrix not bedded or laminated Tillite Tilloid

  17. EES 450: Sedimentary Geology rudite classification ●Paraconglomerate(diamictite): Poorly-sorted, matrix-supported rudites– large clasts in a muddy matrix – generally < 30% clasts present, but > 15% matrix – often deposited in viscous fluids (ice, debris flows) – common in aquatic basin. - May include genetic terms: Tillite– glacial. Tilloid – uncertain (mass movement). Debrite – mass movement.

  18. Paraconglomerates (diamictites) EES 450: Sedimentary Geology Laminated diamictite Tilloid or debrite

  19. Paraconglomerates (diamictites) EES 450: Sedimentary Geology Thinning and overlap Laminated diamictite Pebble dent Tilloid or debrite

  20. EES 450: Sedimentary Geology rudite classification ●Olistostrome: Large-scale diamictitedeposits formed by debris flows and submarine landslides, commonly in continental slope and trench environments. - Common at subduction zones in accretionary wedges. Olistolith

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