A Level Sedimentary Rocks

chalk

A type of limestone made of coccoliths

organic matter

material responsible for making shale dark or black in colour

turbidity current

Submarine landslide that forms a turbidite

200 degrees centigrade

temperature at which sedimentary processes become metamorphic

coal

an organic sedimentary rock formed from the remains of plants in a tropical swamp

graded bedding

formed by the rapid deposition of poorly sorted sediment in water.

70

percentage of the Earth's surface that has sedimentary rocks outcropping at the surface

evaporites

deposited by precipitation from saline water e.g. gypsum and halite

clastic

sedimentary rocks made up of the weathered and eroded fragments of older rocks

organic

sedimentary rocks made up of the remains of once living organisms

chemical

sedimentary rocks that have been precipitated from solution

cement

minerals precipitated from pore waters to bind the grains in a sedimentary rock together

Coarse grained

clastic rocks with most of the grains over 2mm in diameter

Medium grained

clastic rocks with most of the grains between 1/16 and 2mm in diameter

Fine grained

clastic rocks with most of the particles below 1/16mm in diameter

ooliths

small spherical grains of calcium carbonate that form a limestone

clay minerals

a group of minerals found in shale

well sorted

name of the texture of a clastic rock when all the particles are the same size

poorly sorted

name of the texture of a clastic rock when the particles have a wide range of sizes

quartz

the most common mineral found in sandstones

bed

a layer of sedimentary rock greater than 1cm thick

lamination

a layer of sedimentary rock less than 1cm thick

porosity

the proportion (percentage) of a rock that is air space

permeable

the ability of a rock to let water flow through it

lithification

the physical change from loose sediment to a solid sedimentary rock e.g. compaction and cementation

conglomerate

a coarse grained sedimentary rock with well rounded particles

breccia

a coarse grained sedimentary rock with very angular particles

breccia

a sedimentary rock produced by a flash flood in a desert

greywacke

a poorly sorted sandstone with a muddy matrix

haematite

mineral cement in desert sandstone

limestone

any sedimentary rock that contains more than 50% calcium carbonate

uniformitarianism

a concept that can be simplified to 'the present is the key to the past'

desiccation cracks

sedimentary structure formed when a lake dries up. Mud contracts.

cross bedding

Large scale sedimentary structure found in desert sandstones

5

percentage of the Earth's crust that is composed of sedimentary rocks

Glacial till

clastic sedimentary rock formed underneath a glacier or ice sheet

ripple marks

sedimentary structure formed by wave action in shallow water or by the wind

black shale

most common sedimentary rock being formed on the deep ocean floor. Graptolites are often preserved in this rock.

bedding plane

formed by a pause or break in the deposition of sediment

aeolian

sedimentary processes associated with the wind

fluvial

sedimentary processes associated with rivers

marine

sedimentary processes associated with the sea

abrasion and attrition

two most important erosional processes that cause sedimentary grains to become smaller and more rounded

clast

fragment or grain in a sedimentary rock

reef-building coral

fossils that indicates a tropical, high energy, shallow marine environment

marine fossils

corals, trilobites, ammonites and graptolites

plants fossil

fossils that indicate a terrestrial environment

burrow

a trace fossil indicating shallow water

track

a trace fossil indicating an terrestrial environment

matrix

smaller grains surrounding the larger fragments or clasts in a sedimentary rock