Chapter 6: Sedimentary Rocks

Question 1

Sedimentary Rock

Answer 1

forms at or near the surface of the Earth by

• cementing together loose clasts
• growth of mounds of shells
• cementing together of shells and shell fragments
• the accumulation and subsequent alteration of organic matter derived from living organisms
• the precipitation of minerals directly from surface-water solutions

Question 2

basement

Answer 2

the igneous or metamorphic rock that lies under sedimentary rock beds

Question 3

Clasts

Answer 3

solid fragments and grains broken off of pre-existing rocks

note: comes from the Greek work Klastos, meaning broken

Question 4

Classes of sedimentary rocks

Answer 4

• clastic sedimentary rock
• biochemical sedimentary rock
• organic sedimentary
• chemical sedimentary

Question 5

How are clasts produced?

Answer 5

• weathering
• erosion
• transportation
• deposition
• lithification

Question 6

transportation

Answer 6

gravity, wind, water, or ice that can carry sediment

Question 7

deposition

Answer 7

the process by which sediment settles out of the transporting medium

Question 8

lithification

Answer 8

the transformation of loose clasts into solid rock, takes place in two stages

1. compaction; weight of over burden squeezes air or water out from between grains so the grains can fit together more tightly
2. cementation; when minerals (commonly quartz or calcite) precipitate from ground water and fill the remaining spaces between clasts to form a cement that binds grains together

starts as sediment —-> lithifies into sedimentary rock

Question 9

well sorted v. poorly sorted

Answer 9

well sorted: the clasts in the sediment are generally the same size

poorly sorted: the clast sizes in sediment are ranging in sizes (big and small)

Question 10

breccia

Answer 10

cemented angular clasts

Question 11

conglomerate

Answer 11

burial or lithification of gravel bars/mounds that occur at former rivers

Question 12

arkose

Answer 12

lithification of quartz and sometimes feldspar clay

Question 13

siltstone

Answer 13

lithified mudflats/deltas

Question 14

shale

Answer 14

lithified mud (aka mudstone)

Question 15

examples of biochemical sedimentary rock

Answer 15

biochemical limestone

• made from shells/broken up shell of sea creatures
• largely CaCO3, also know as (carbonate rock)

fossiliferous limestone
- has fossils in it

biochemical chert
- formed from the shells of silica-secreting plankton that accumulated on the sea floor

Question 16

organic sedimentary rocks

Answer 16

coal, oil shale

Question 17

chemical sedimentary rock

Answer 17

Halite (when when 90% of water evaporates) and gypsum (when 80% of water evaporates)
Travertine (Chemical limestone): forms as hot springs and in caves
Dolostone: carbonate rock containing the mineral dolomite
Chemically precipitated chert: flint

Question 18

bedding

Answer 18

a single layer of sediment or sedimentary rock with a recognizable top and bottom

Question 19

strata

Answer 19

several beds together

Question 20

why does bedding form?

Answer 20

Bedding forms from sediment accumulation by water, wind, glaciers. Changes in climate, water depth, water current velocity, or sediment source control the type of sediment deposited.

Question 21

stratigraphic formation

Answer 21

a sequence of strata that is distinctive enough to be traced as a unit across a fairly large region

Question 22

cross beds

Answer 22

distinct internal layers within sand dunes

Question 23

depositional environments

Answer 23

the conditions in which sediment was deposited

examples: beach, glacial, river environments

Question 24

non-marine depositional environment, and some examples

Answer 24

Terrestrial depositional environments

• glacial environments
• mountain stream environments
• alluvial-fan environments
• desert environments
• river environments
• lake environments

Question 25

Examples of coastal and marine depositional environments

Answer 25

• marine delta deposits
• coastal beach sands
• shallow-marine clastic deposits
• shallow-water carbonate environments
• deep marine deposits

Question 26

subsidence

Answer 26

places where the surface of the earths lithosphere sinks, providing space in which sediment can collect

Question 27

categories of basins

Answer 27

• rift basins: form at continental rifts
• passive-margin basins: form along the edges of continents that er not plate boundaries
• intracontinental basins: develop in the interiors of continents
• foreland basins: form on the continental side of a mountain best

Question 28

transgression

Answer 28

when the shoreline migrates inland

the opposite of transgression is regression

Question 29

diagenisis

Answer 29

all the physical, chemical, and biological processes that transform sediment into sedimentary rock and that alter characteristic of sedimentary rock after the rock has formed