AS Sedimentary Processes

Question 1

Facies

Answer 1

includes all the characteristics of a sedimentary rock that are produced by its environment of deposition and allow it to be distinguished from rock deposited in an adjacent environment.

Question 2

Lithofacies

Answer 2

include all the physical and chemical characteristics of a rock.

Question 3

Biofacies

Answer 3

include the palaeontological characteristics of a rock.

Question 4

Facies association

Answer 4

describes a group of sedimentary facies that occur together and typically represent one depositional environment.

Question 5

Polymictic conglomerate

Answer 5

a coarse grained sedimentary rock containing clasts of many different rock types.

Question 6

Oligomictic conglomerate

Answer 6

a coarse grained sedimentary rock containing clasts of few different rock types.

Question 7

Monomictic conglomerate

Answer 7

a coarse grained sedimentary rock containing clasts of a single rock type.

Question 8

Till fabric analysis

Answer 8

a method of tracing the former movement direction of ice by taking compass bearings on the long axes of large clasts in till deposits.

Question 9

Fluvio-glacial deposits

Answer 9

sediments produced by meltwater streams flowing from a glacier.

Question 10

Littoral zone

Answer 10

is the area between the extreme low and extreme high water of the spring tides.

Question 11

Palaeo-environmental indicator

Answer 11

a sedimentary structure formed in specific environmental conditions in the ancient past.

Question 12

Palaeocurrent indicator

Answer 12

a sedimentary structure that allows the direction of an ancient current to be deduced.

Question 13

Way-up structures

Answer 13

allow geologists to work out whether rocks are in their original orientation or whether they have been inverted by folding.

Question 14

Point bar

Answer 14

deposits of sand or coarser grained sediments on the inside of a meander bend.

Question 15

Channel lag

Answer 15

coarse grained sediment left in a channel after finer grained particles have been transported away.

Question 16

Flood plain

Answer 16

flat land adjacent to a river over which it spreads when in flood.

Question 17

Upward fining

Answer 17

describes a series of layers in which average grain size decreases upwards as energy decreases.

Question 18

Flash floods

Answer 18

brief but very high energy flows of water over a surface or down a river channel, usually caused by heavy rainfall.

Question 19

Wadis

Answer 19

river channels in a hot desert regions in which flow may occur very occasionally.

Question 20

Playa lakes

Answer 20

temporary lakes formed by storm run-off in deserts having inland drainage.

Question 21

Evaporites

Answer 21

sedimentary rocks resulting from the evaporation of saline water.

Question 22

Spring tides

Answer 22

the tides with the greatest range, and occur about every two weeks.

Question 23

Longshore drift

Answer 23

the combination of littoral drift and beach drift.

Question 24

Glauconite

Answer 24

a green-coloured mineral, an iron and potassium silicate of the mica group, formed on continental shelves.

Question 25

Transgression

Answer 25

occurs where the sea spreads over the land.

Question 26

Regression

Answer 26

occurs where the sea retreats from the land.

Question 27

Macrofossils

Answer 27

fossils large enough to be visible with the naked eye.

Question 28

Microfossils

Answer 28

usually less than 1 mm and can only be seen with a lens or microscope.

Question 29

Detrital

Answer 29

describes fragments derived from the mechanical weathering of rocks.

Question 30

Cryptocrystalline

Answer 30

material is too fine grained for individual crystals to be distinguished using a petrological microscope.

Question 31

Radiolaria

Answer 31

planktonic animals with a siliceous test.

Question 32

Tests

Answer 32

the hard shell of some planktonic animals.

Question 33

Calcareous ooze

Answer 33

pelagic clay containing >30% biogenic skeletal material made of CaCO3.