Chapter 4 Flashcards
To understand the various types of sedimentary process
What are the 3 main groups of sedimentary structures?
Stratification structure and Bedforms
Bedding plane Markings
Other Structures
What are the 4 fundamental types of sedimentary rocks?
Deposition Structures
Erosional Structures
Deformation Structures
Biogenic structures
What is a bed?
Tabular or lenticular layers of sedimentary rock that have lithological, textural, or structural unity that distinguishes it from the layers above and below it.
What is a bedding plane?
The upper and lower surfaces of a bed
What is a sedimentation unit?
A thickness of sediment deposited in near constant physical conditions
What is Strata?
Beds thicker than 1 cm
What is laminae?
Beds thinner than 1 cm
What is a subdivision as it relates to bedding?
A division within a single bed marked by distinct associations with a sedimentary structure.
What is an amalgamation surface?
A marked discontinuity between two beds of similar composition
what is an amalgamation bed?
Beds separated by an amalgamation surface
What is a bedset?
Groups of similar beds or crossbeds
What are cross strata?
Layer/Laminae that are deposited at an angle to the bounding surface
What is a single bedset?
2 or more superimposed beds characterized by similar composition, texture, and internal structures
What are composite Bedsets?
A group of beds differing in composition, texture, and internal structure but deposited in a similar way
What are the types of planar bedding?
Laminated, Graded, and Massive
What is a planar bed?
Beds that do not contain internal dipping laminae
How are laminated beds produced?
through less severe or short lived fluctuations in sedimentation
How is a laminated bed formed?
Through the settling of fine particles from suspension and traction transport of sand in water
What is Graded bedding?
Beds characterized by distinct gradations in size
What is normal grading?
Going from coarse to fine in an upwards sequences
What is reverse grading?
Going from fine to coarse in an upward sequence
How does reverse grading happen?
Through dispersive pressures and kinetic sieving
What is kinetic sieving?
Agitation of rock causing finer particles to move down.
What is massive bedding?
A bed that lacks internal structure
How is a massive bed formed?
Can be formed through liquefaction of sediments due to sudden shock.
What are current ripples?
Asymmetrical ripples that develop in reaction to unidirectional flow and face downstream
What are oscillation ripples?
Ripples that form by reaction
How is cross bedding formed?
Through migration of ripples/dunes in water or air
What is a trough cross bed?
A cross bedded unit in which 1 or more of the bounding surfaces are curved.
What is a Flaser Bedding?
A type of ripple bedding in which thin streaks of mud occur between cross rippled laminated sediment.
What is lenticular bedding?
inter-bedded mud and cross laminated sand in which the ripples are laterally and vertically discontinuous.
What is a flame structure?
Wavy/flame shaped tounge of mud that projects upward into the overlying layer
What are sole markings?
positive relief casts made at the base of a bed
What is a groove cast?
elongated, nearly straight ridges resulting from infilling of erosional relief
What is a flute cast?
elongated welts or ridges with a bulbous end and a flared end that merges with the bed plane
