Slide 1

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

Slide 2

RUDITE CLASSIFICATION EES 450: Sedimentary Geology Rudites (Conglomerates, Breccias, & Diamictites) Extraformational Intraformational (Edgewise or solution breccias and conglomerates) Orthoconglomerate Paraconglomerate (Diamictite) OligomictPolymict Matrix bedded or laminated Matrix not bedded or laminated TilliteTilloid

Slide 3

RUDITE CLASSIFICATION Terms: - Extraformational = Clasts from older rocks than the formation in which found. - Intraformational = Clasts from 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.). EES 450: Sedimentary Geology

Slide 4

RUDITE CLASSIFICATION Epiclastic conglomerates and breccias or rudites: - Epiclastic = Formed at Earths 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 EES 450: Sedimentary Geology

Slide 5

RUDITE CLASSIFICATION Epiclastic conglomerates and breccias or rudites: - Epiclastic rudites = 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. EES 450: Sedimentary Geology Fissile or non-fissile?

Slide 6

RUDITE CLASSIFICATION EES 450: Sedimentary Geology Rudites (Conglomerates, Breccias, & Diamictites) Extraformational Intraformational (Edgewise or solution breccias and conglomerates) Orthoconglomerate Paraconglomerate (Diamictite) OligomictPolymict Matrix bedded or laminated Matrix not bedded or laminated TilliteTilloid

Slide 7

RUDITE CLASSIFICATION EES 450: Sedimentary Geology Extraformational Intraformational (Edgewise or solution breccias and conglomerates) Clasts derived from older rocks than the formation in which they are found Clasts derived from the same formation in which they are found

Slide 8

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 intrabasinal rudites include: Evaporite solution. Karst solution. Paleosols. EES 450: Sedimentary Geology

Slide 9

RUDITE CLASSIFICATION EES 450: Sedimentary Geology Rudites (Conglomerates, Breccias, & Diamictites) Extraformational Intraformational (Edgewise or solution breccias and conglomerates) Orthoconglomerate Paraconglomerate (Diamictite) OligomictPolymict Matrix bedded or laminated Matrix not bedded or laminated TilliteTilloid

Slide 10

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

Slide 11

RUDITE CLASSIFICATION EES 450: Sedimentary Geology Rudites (Conglomerates, Breccias, & Diamictites) Extraformational Intraformational (Edgewise or solution breccias and conglomerates) Orthoconglomerate Paraconglomerate (Diamictite) OligomictPolymict Matrix bedded or laminated Matrix not bedded or laminated TilliteTilloid

Slide 12

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). EES 450: Sedimentary Geology Volcanic pebbles Quartz pebbles

Slide 13

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. EES 450: Sedimentary Geology

Slide 14

RUDITE CLASSIFICATION Interpretive terms for conglomerates: - Fanglomerates: Conglomerates deposited in an alluvial fan environment. EES 450: Sedimentary Geology

Slide 15

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. EES 450: Sedimentary Geology Caliche brecciaCollapse breccia You breccia

Slide 16

RUDITE CLASSIFICATION EES 450: Sedimentary Geology Rudites (Conglomerates, Breccias, & Diamictites) Extraformational Intraformational (Edgewise or solution breccias and conglomerates) Orthoconglomerate Paraconglomerate (Diamictite) OligomictPolymict Matrix bedded or laminated Matrix not bedded or laminated TilliteTilloid

Slide 17

RUDITE CLASSIFICATION Paraconglomerate (diamictite): Poorly-sorted, matrix-supported rudites large clasts in a muddy matrix generally 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. EES 450: Sedimentary Geology

Slide 18

Laminated diamictite Tilloid or debrite Paraconglomerates (diamictites)

Slide 19

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

Slide 20

RUDITE CLASSIFICATION Olistostrome: Large-scale diamictite deposits formed by debris flows and submarine landslides, commonly in continental slope and trench environments. - Common at subduction zones in accretionary wedges. EES 450: Sedimentary Geology Olistolith