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29 Cards in this Set
- Front
- Back
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2 methods for describing the form of a grain.
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Krumbein's spericity method and Zingg's classification
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fabric where the grains overlap like shingles on a roof
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Imbrication
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reverse grading
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grains are stacked from fine to course
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lowest velocity to highest velocity bedforms
dunes, chutes and pools, planar bedding, antidunes, ripples |
ripples, dunes, planar bedding, antidunes, chutes and pools
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structures common to a meandering river
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ripples, trough cross bedding, laminations
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association of trace fossils that are recurrent in time and space and reflect environmental conditions such as water depth, salinity and nature of the substrate
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ichnofacies
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thrombolite
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build up of algal mats without distinct laminations
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most common accessory mineral in sandstones
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feldspar
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arkose sandstones must contain what mineral?
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potassium feldspar
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next to silica, what is the most common cement within sandstones?
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calcite
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What properties would a texturally mature sandstone have?
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more matrix, rounded, well sorted
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3 main deatures to look for when identifying a paleosol
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root traces, soil horizons, soil structures
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irregular network of planes surrounded by more stable aggregates of soil
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cutans and peds
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two most important properties of a fluid to determine how they will transport a mineral?
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viscocity and density
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entrainment
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beginning of transport when material is picked up by flow
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what assumptions does the Hjulstrom diagram make?
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plane bed, 1 m wide, only quartz
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washload
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material transported through suspension but the material isn't coming from the bed but upstream
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autosuspension
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with enough movement, as the particle moves downstream it picks up more material, gaining more weight and density which causes more turbulant water
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ideal turbidite sequence
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bouma sequence
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dispersive force for grain flows
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grain to grain interaction
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grain size from smallest to largest.
1 phi, 2mm, 64 microns, -8 phi |
64 microns, 1 phi, 2mm, -8 phi
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skewness
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degree of symmetry or assymetry of the grain size distribution
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contains a large portion of unstable or metastable clasts
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petromict
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almost exclusively fluvial or littorial (beach) origin
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quartzose
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composed of a single type of clast
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oligomict
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formed from teh breakdown of older rocks via weathering and erosion
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epiclastic
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most commonly composed of rip-up clasts
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intraformational
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soil horizons
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O - almost completely organic
A - Mineral matter mixed with some humus E - light colored mineral particles Zone of leaching B - Accumulation of clay from above C - partially altered parent material |
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9 common ichnofacies
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Nereites, Zoophycos, Cruziana, Skolithos, Psilonichnus,
Scoyenia, Glossifungites, Trypanites, Teredolites |
