Bedsstratifications layers in sedimentary material o Bedding a fundamental

Bedsstratifications layers in sedimentary material o

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Beds/stratifications= layers in sedimentary material o Bedding= a fundamental characteristic of sedimentary rock Beds are >1 cm thick Laminae/laminations are <1 cm thick 20. Bounding surfaces represent: Abrupt change in composition, non-deposition, Erosional surface 21. Beds: tabular vs cross bedding o Planar/tabular bedding= internal structure are parallel to the bounding surfaces Formed by migration of large scale, straight-crested ripples and dunes o Cross bedding= internal structure are at an angle to the bounding surfaces 22. laminations, massive, graded o laminated bedding= produced by rapid change in depositional conditions (such as grain size, content organic material, mineral composition) contain parallel laminae, <1 cm thick formation: settling of fine-sized particles from suspension traction transport of sand in water at high flow velocity o massive bedding= beds that appear to be homogeneous and lacking internal structures very rapid deposition from suspension of very highly concentrated sediments
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sediment gravity flow o graded bedding= characterized by distinct vertical gradations in grain size normal grading= fining upward due to deposition from suspension or decrease in flow velocity inverse grading= coarsening upward due to change of coarse material supply, debris flow, increase in flow velocity 23. cross bedding: planar, trough, climbing ripples, herringbone, flaser/lenticular, hummocky (know the differences: how they are formed/depo env, and be able to identify in a picture) o cross bedding= internal structure are deposited at an angle to the bounding surfaces formed primarily by migration of bedforms o trough cross bedding= have bowed bounding surfaces view parallel to flow direction formed by migration of large scale, curve-crested ripples and dunes o climbing ripple cross-lamination = when sedimentation rate is really high, ripples can aggrade (build upward). They climb up the backs of the previously deposited ripples indicated waning flow conditions and rapid sediment fallout from suspension common in delta environment, also found in fluvial settings, turbidites o herringbone cross stratification= alternating layers of cross-beds dipping in opposite directions in sandstone formed in intertidal zones by tide= area that is above water at low tide and under water at high tide o flaser cross stratification= thin streaks of mud occur between sets of cross-bedding sandy sediment o lenticular cross stratification= lenses of sand in a muddy matrix incomplete sand ripples covered with mud tidal flats o hummocky cross stratification= undulating sets of swales and hummocks (circular to elliptical) in fine sandstone to coarse sandstone in cross section: gently convex-up lamination in the hummocks formed by large storm waves in shallow marine environment 24. bedform cross section terms: lee side vs stoss side o stoss side= upstream/windward face, gentle slope o lee side= downstream face, fairly steep slope 25. bedform type and flow regime 26. flow direction (paleocurrent) from the forests of cross bedding 27.
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