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