Sedimentary Textures

Question 1

Is Genetic classification of sedimentary rocks accurate?

Answer 1

NO

Question 2

T or F: Sed structures may be classified on the basis of their morphological or descriptive characteristics

Answer 2

True

Question 3

These are tabular or lenticular sedimentary rocks having characteristics that distinguish them from strata above and below

Answer 3

Beds

Question 4

Beds ( > 1cm)
Laminae (< 1cm)

Answer 4

True

Question 5

A distinct discontinuity, such as erosional surface, that is present between two beds of similar composition.

Answer 5

Amalgamation Surface

Question 6

T or F: Bedding planes are syn-depositional features created by processes such as intensive burrowing of some layers by organisms

Answer 6

False. They are post depositional

Question 7

T or F : Planar Stratified bed are beds that does not contain internal layers that are essentially parallel to the bounding bedding surfaces are said to be planar - stratified.

Answer 7

False. They contain internal layers

Question 8

This is a cross stratified bed and is often sometimes referred to as a set of cross-strata and a succession of such sets.

Answer 8

Coset

Question 9

T or F: The mode of formation of Laminated bedding is through suspension settling and transport transport mechanism

Answer 9

True

Question 10

This is an ideal graded-bed sequence in rocks of probable turbidity current origin

Answer 10

Bouma Sequence

Question 11

Explain the Process of Bouma Sequence

Answer 11

The Bouma Sequence illustrates how sediment is deposited as a turbidity current loses energy while moving downslope. The sequence typically fines upwards, reflecting the decreasing energy conditions as sediment settles out

Question 12

T or F: Massive bedding are beds of sedimentary rocks that contain few or no visible internal laminae.

Answer 12

True

Question 13

These are strata in which internal layers, or foresets, dip at a distinct angle to the surfaces that bound the sets of cross beds.

Answer 13

Cross Bedding

Question 14

It is a bedding type that is marked trough-shaped or scooped shaped.

Answer 14

Festoon Bedding

Question 15

T or F: Cross-bedding is called cross lamination is the thickness of the foresets is greater than 10mm

Answer 15

False. Less Than.

Question 16

These are inclined surfaces that separate adjacent foresets, with similar orientations, and truncate the lower foreset laminae.

Answer 16

Reactivation surface

Question 17

A type of cross stratification that has the general appearance of waves when viewed in outcrop sections cut to the wave (ripple) crest

Answer 17

Ripple Cross Lamination

Question 18

T or F: Ripple-cross lamination forms under conditions where there is no abundant sediment is present in suspension, which quickly buries and preserves rippled layers.

Answer 18

False. Abundant Sediment.

Question 19

This is a special type ofr cross-lamination in which streakes of mud occur between sets of ripple laminae. This develops under fluctuating depositional conditions.

Answer 19

Flaser Bedding

Question 20

This term is used instead of flaser bedding for interbedded mud and ripple cross-laminated sand in which the ripples or sand lenses are discontinuous and isolated in both vertical and lateral directions

Answer 20

Lenticular Bedding

Question 21

Originally called “truncated wave-ripple laminae. Undulating sets of cross laminae that are both concave-up (swales) and convex up (hummocks). Cross bed sets cut into each other which curved erosional surfaces.

Answer 21

Hummucky cross-stratification

Question 22

These marks are small, wave-like features formed on the surface of sediment, typically as a result of the movement of water, air, over loose sediments.

Answer 22

Ripple Marks

Question 23

T or F:

Current Ripples = Symmetrical
Wave Ripples = Assymetrical

Answer 23

False.

Question 24

This name is applied to complexly folded or intricately crumpled beds or laminations that are commonly, not invariably confined to a single sedimentation unit.

Answer 24

Convolute Bedding

Question 25

These are flame shaped projections of mud that extend upward from a shale unit into an overlying bed of different composition, commonly sandstone

Answer 25

Flame structure

Question 26

T or F: Flame structures are good paleocurrent indicator.

Answer 26

True

Question 27

Structures that resemble the structure of pillow lavas and may have pillow, hassock, kidney or ball shapes.

Answer 27

Ball and pillow structures

Question 28

These are isolated sand massess that form within a mud matrix, typically fdound in sedimentary deposits where the sand has become detached from overlying layer.

Answer 28

Pseudonodules

Question 29

Structures formed from unconsolidated sediment that moves downslope under gravity under decollment-type movement

Answer 29

Synsedimentary fold, faults, and rip-up clasts

Question 30

Vertical to near vertical cross-cutting columns and sheets of structureless or swirled sand that cut through either massive or laminated sands that commonly also contain dish structures and convolute lamination

Answer 30

Pillar Structure

Question 31

Features found in sandstone and siltstone beds, characterized by thin, dark-colored subhorizontal clayey lamination that can be **flat or concave upward**

Answer 31

Dish Structure

Question 32

Sediment-filled troughs that show a U or V-shape in cross section and that cut across previously formed bed or laminations

Answer 32

Channels

Question 33

These resemble channels but tend to be somewhat snaller, more asymmetrical in cross-sectional shape, and shorter in length

Answer 33

Scour and Fill/ Cut and Fill

Question 34

Type of Biogenic structure commonly composed of fin silt or clay sized carbonate sediment.

Answer 34

Stromatolitic Bedding

Question 35

Particularly common, typically consisting of**positive-relief casts and various irregular markings**, especially on the **soles of sandstones** and other coarser-grained sedimentary rocks that overlie shales.

Answer 35

Sole markings

Question 36

Most common tool-formed structures. Elongate, nearly straight ridges that result from the infilling of grooves produced by some object dragged over a mud bottom.

Answer 36

Groove Cast

Question 37

Elongated welts or ridges. One end a bulbous nose and other end that flares out. Merges gradually with the surface of the bed.

Answer 37

Flute Cast

Question 38

crescent-shaped sedimentary features formed by the action of currents. These structures typically develop in areas where sediment is deposited in a curved pattern due to the flow of water.

Answer 38

Current Crescents

Question 39

muddy sediments dry out and contract. These features are indicative of environmental conditions where water levels fluctuate, leading to the drying of fine-grained sediments such as clay and silt.

Answer 39

Mud cracks

Question 40

Resemble mudcacks but are discontinuous

Answer 40

Syneresis Cracks

Question 41

Small dendritic channels or grooves that form on beaches by discharge of pore waters at low tide.

Answer 41

Rill marks