sedimentary structure
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Sedimentary Structure
Primary Features :Formed during the rock formation
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Sedimentary Layers
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Sedimentary structures
Bedding is most important
feature of a Sed. Rocks
Beds are usually > 1 cm
Laminae < 1 cm
Orientation of bedding helpsin knowing the paleo-currentdirection of the old rivers
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GRADED BEDDING
Top
Bottom
T
B
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Fine gravelly litho-unit
Medium-coarse sandy
litho-unit (cross stratified)
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Laminated layers of fine silt and clay
Cross-stratified sst.Paleo-flow from
right to left
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Typical cross stratification
in
Sand Dunes
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pp e
marks
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Foot
prints
Biogenic structures
Snake Trails
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Mud cracks
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Sedimentary Structure
Unconformity : A substantial break or
gap in geologic record where a rockunit is overlain by another that is not
next in stratigraphic succession
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Unconformities
Angular unconformity = Tilted or folded
sedimentary rocks are overlain by other
more flat-lying strata.
Disconformity = An unconformity in whichthe bedding planes above and below the
break are parallel
Nonconformity = An unconformity developed
between sedimentary rocks and loder rocks(Plutonic igneous rocks or massive
metamorphic rocks) that had been exposedto erosion.