Sedimentary Rocks

Question 1

Sedimentary defined

Answer 1

• rocks formed at the surface of the earth either in water or on land
• produced by movement of sediments, precipitation from solution and organic remains
• layered accumulations of sediments
• cover 75%-80% of the Earth’s land
• environments: continental, transitional (delta/intertidal), Marine

Question 2

Bedding

Answer 2

• primary compositional layer in a sedimentary/volcanic rock
• most important discontinuity in a sedimentary/volcanic rock sequence
• Types: page Q04-2-7
• vary in size and can be folded/tilted due to tectonic activity

Question 3

strata

Answer 3

horizontal planes and layers

Question 4

lithification

Answer 4

-sediments are converted into rocks through cementation and compaction where the common cementing materials of quartz, calcite, and iron oxides

Question 5

Particle shapes

Answer 5

angular: no evidence of wear
sub-angular: shows some wear
sub-rounded: considerable wear
rounded: only some flat faces remain
well-rounded: well rounded

Question 6

Particle sorting

Answer 6

well sorted: poorly graded, particles occur in narrow size range ex: beach sand
poorly sorted:well graded, particles occur in near equal amounts in all size range ex: river channel/glacial deposits

Question 7

Clastic Sedimentary Rocks

Answer 7

-Mechanically-formed sedimentary rocks
derived from the chemical and mechanical breakdown of pre-existing rock
-often contain rock frags (ortho feldspar, quartz, and clay) and are classified on grain size

Question 8

sedimentary classifications

Answer 8

• classified by source of their sediments and by methods of development:
• mechanically-formed
• chemically-formed
• organically-formed

Question 9

conglomerates

Answer 9

• mechanically formed
• consolidated gravels with part size >2 mm
• defined by cementing material

Question 10

breccia

Answer 10

• mechanically formed
• consolidated gravels with part size>2 mm
• particles are sharp
• defined also by cementing material

Question 11

sandstones

Answer 11

• mechanically formed

- consolidated sand (.062-2 mm)

Question 12

siltstone

Answer 12

• mechanically formed

- particls between .002 to .063 mm

Question 13

shale

Answer 13

• mechanically formed
• consolidated mud (<.0062 mm)
• rich in organic matter

Question 14

mudstone

Answer 14

• mechanically formed
• constituents originally mud (<.0625 mm)
• need microscope for grains

Question 15

strength and resistance to weathering (mech formed)

Answer 15

type strength res. to weathering
mudstone small weak
shale
siltstone
sandstone
conglomerate large high
and breccia

Question 16

Chemically formed sedimentary rocks

Answer 16

-formed when minerals in solution oversaturate and precipitate
-2 environments: marine and evaporating
Halite
Limestone
Gypsum
Dolomite

Question 17

limestone

Answer 17

• chemically formed
• primarily calcite
• accumulation of fossilized remains of organisms in sea
• important for fertilizer and building (contains C, N, K, P)

Question 18

Dolomite

Answer 18

• chemically formed
• contains mostly dolomite
• aka dolostone

Question 19

Clastic Sedimentary Rocks in HK

Answer 19

conglomerates, sandstones, and mudstone

Question 20

heterogeneity

Answer 20

diverse combination