Sedimentary Rock

deposition within different sedimentary environments can produce a range of structures such as:

- bedding (stratification) - cross-bedding - graded bedding - ripples - bioturbation - bedding sequences

carbonate sediment slide too lazy to ask questions

- calcium carbonate CaCO3 formed by direct or indirect precipitation by organisms - calcite is the most abundant carbonate material - aragonite is a less stable polymorph

three classes of chemical and biological sedimentary environments

- carbonate environments - siliceous environments - evaporate environments

describe clastic sedimentary environments:

- characterized by terrigenous sediments (from land) - include continental and shoreline environment - may include marine environments

> ________ % of the land surface is sedimentary rock

75 %

more than ____% of all sedimentary rocks are ______ how are they are characterized?

85% are clastic they are characterized by grain size

mud, mudstone shale .. majority of particles how big

< 0.0062mm varying proportions of clay and silt sized particles fined grained are mudstone and shale (lithified)

limestone forms by accumulation and lithification of ?

CaCO3

clastic sed rock are distinguished by ?

grainsize and shape, grain type (mineralogy), texture of the grain, matrix and cements

what is the coarsest clastic sediment ?

gravel > 2 cm includes boulders, cobbles and pebbles

sea water contains dissolved minerals which are concentrated during evap to form ?

halite - nacl gympsum - caso4

what characterized the alberta floods in mountain region?

high velocity - turbulent flow - high suspended load - high bed load

does natural gas form at higher or lower concentrations than gas

higher

most bedding is nearly _____ at the time of deposition with some exceptions

horizontal

physical weathering

increase surface area

iron oxide sediments

indirectly precipitated by micro-organisms lithified after oxygen increased in oceans

diagenesis

is the change of sediments or existing sedimentary rocks into a different sedimentary rock during and after rock formation (lithification), at temperatures and pressures less than that required for the formation of metamorphic rocks. It does not include changes from weathering.

tyndall stone

limestone with extensive bioturbation structures pressured in dolomite burrows originally created in soft sediments on ancient sea flow differences in chemistry or porosity caused formation of dolomite in burrows in calcite-dominated rocks

comglomerate is _____ equivalent of _____

lithified, gravel

sedimentary basins are regions of:

long-term subsidence that create space to accommodate infilling sediments - depressions are formed when are of crust subsides (sinks) relative to surrounding crust

what characterized the alberta floods in calgary region? or perhaps later on in the flood? no clue

lower velocity - high suspended load - deposition of silt / clay

sand particles are transported by ___ currents, such as:

moderate such as: rivers, waves, shorelines, wind

there are few sedimentary environments where current is strong enough to transport gravel what are they ?

mountain streams rocky beaches with high waves and glacial meltwater

sed rocks contain direct and indirect evidence of what ?

of life and its evolution

saltation

particles is lifted from the bottom and transported a little bit than deposited, process happens over and over when the fluid moves over top of it

erosion

processes that dislodge rock particles produced by weathering and move them away from source area - energy from moving water, ice and air

sedimentary rocks are important sources of ?

resources: metal, building materials and energy

what is bigger: sand or silt and clay?

sand

mud > shale sand > gravel >

sand > sandstone gravel > conglomerate

gravel > conglomerate sand > silt > clay and silt >

sandstone siltstone shale

types of sediment is determined by ?

sediment's history: transport energy and distance, weathering intensity, and composition of source rock

siliceous environments

silica (SiO2) - forms in marine sedimentary environments by: - chemical precipitation - water reaches saturation with Si / O2 - bio mineralization - diatoms precipitate amorphous silica

shales are composed of ? bedding planes?

silt and significant clay - break along distinct bedding planes

what makes up most clastic ? what makes up mall portion of clastic ?

siltstone, mudstone and shale less - sandstone, conglomerate

_______ dictates the size of clastic particles that are transported or deposited at a given location

size

ripples

small ridges often observed in modern sands and ancient sandstones. generated by flowing water or wind - sand bars in streams - sand beaches - sand dunes

sedimentary rocks reflect physical and chemical characteristic of their ______ ________ and _________ processes

source environments and depositional processes

fast, moderate, and weak currents talk about speed and the size of things they carry

strong - >50cm/s - carry gravel and large solid load moderate - 20-50cm/s - carry and deposit sand weak > 20cm/s - carry fine clastic sediments - silt and clay

eddy

swirling of fluid and reverse current when it encounters an obstacle

symmetrical ripples create ? asymmetrical ripples create ?

sym - beach, looks like waves going either way asymm - dune, steeper slope on other side of direction of wind/ water - (cross beds?)

foreland (flexural) basins - form on ______ side of mountain belt due to ____ deformation at ______ plate boundaries

these form at continental side of the mountain belt due to crustal deformation at convergent plate boundaries

how are oil and gas generated ?

they are generated during diagenesis of sediments that contain organic matter - diatoms - subsidence and burial over time increases temperature - oil forms between 60-150

true or false: sediment is scarce on earths surface?

this is false, most of earths surface is covered with layers of loose sediment

what dictates mineralogy of sediments

weathering intensity

how is sedimentary rock formed?

weathering, transportation, deposition, lithification

dissolved ions accumulate in water due to chemical weathering, why is this significant for this unit

- chemical and biological reactions precipitate minerals from these dissolved ions biogenic sediments - produced by bio precip chemical sediments - produced by inorganic precip reactions

western Canadian sedimentary basin - _____ and crustal ____ during mountain building - tectonically-induced ____ produced broad _______ basin

- deformation and crustal-thickening during mountain building - tectonically-induced subsidence (sinking) produced broad foreland basin

why do foreland (flexural) basins form? how? example?

- immense mass associated with crustal thickening causes lithospheric flexure - wedge-shaped depression oriented adjacent and parallel to mountain belt - fills with sediment eroded from mountain range Persian gulf

cross bedding

- near horizontal sedimentary units that are internally composed of inclined beds - can be inclined as much as 35 degrees from the horizontal - I guess formed by wind or water currents

sedimentary structures are important in geological structures for examining:

- original position of the lithostratigraphic sequences in geologically complex terrains - processes occurring in paleodepositional environments

which particles undergo extensive abrasion during stream transport? what happens to these particles as a result of abrasion ?

- particles transported with bedload (sand/gravel) - particle size: diameter decreases as material removed - particle shape - edges become more rounded so as these particles get further away from the surface they go from angular to rounded

sedimentary basins

- receive dissolved ions and clastic particles produced by weathering - beaches - sand/gravel - stream - clay/silt - lake bed - rock/mineral fragments

bioturbation structures

- remnants of burrows and tunnels excavated by marine organisms in muds and sands examples: clams, worms, shrimp - commonly occur as cylindrical tubes that may extend across bedding planes - infilled and preserved sedimentary rock - characterized by different mineralogy

rift and passive margin basin examples

- rift valley - new ocean basin - (red sea) - mature ocean - (Atlantic)

diagenesis

- sediment or sedimentary rock changed to different sedimentary rock - occurs at temperatures and pressures lower than those required to produce metamorphic rock

lithification

- sedimentary rock formation - squeeze water out of pores - cementation: ions precipitating between grains , kinda form bridges between the existing grains

area of sediment deposition characterized by:

- specific climatic conditions; and physical, chemical and biological processes

what is a passive margin ?

- trans between oceanic and continental crust which is not an active plate margin - it is constructed by sedimentation above an ancient rift - can be volcanic or non

key characteristics of depositional environments include:

- type and amount of water - transport type and strength - topography - biological activity - tectonic setting - climate

describe the surface processes that produce sedimentary rocks

- weathering breaks down rocks physically and chemically - erosion carries away particles produced by weathering - transportation via streams, glaciers and wind moves particles downhill - deposition ( or sedimentation ) occurs when particles settle out or dissolved minerals precipitate - burial occurs as layers of sediment accumulate and compact previous layers - diagenesis lithifies the sediment to make sed rocks

sand includes particles ranging from ___ to ___

0.062mm to 2mm in diameter

clastic rock

Clastic rocks are composed of fragments, or clasts, of pre-existing minerals and rock. Geologists use the term clastic with reference to sedimentary rocks as well as to particles in sediment transport whether in suspension or as bed load, and in sediment deposits.

graded bedding

a graded bed is one characterized by a systematic change in grain or clast size from the base of the bed to the top. Associated with turbidity current. Usually a graded bed has the finer stuff at the top

moving water - a major driver of erosion - involves several processes: (3)

abrasion - scouring of stream bed by transported particles scouring and lifting - flowing water dislodges and loosens rocks dissolution - stream flows over soluble bedrock

sedimentary environments are classified?

also classified according to sediment type and sediment-forming processes

sediment transport - clastic particles and ___ ions are transported downhill to _____ ______

and dissolved ions are transported downhill with gravity to sedimentary basins

sediments and sedimentary rocks are generally characterized by _______ or ________

bedding or stratification

mudstones are ___ and show poor ____

blocky, poor bedding - initial sediment bedding lost to bioturbation

clastic sediments

broken and eroded pieces of rocks and minerals - produced by chemical and physical weathering of common silicate-bearing rocks - range in size from boulders to sand, silt and clay

how are sedimentary rocks differentiated ?

by rock or mineral type and particle size

phosphorite sediments lithify to form ?

calcium phosphate

carbonate environments

chemical precipitation or bio mineralization

dolomite forms when

chemical reaction between CaCO3 and dissolved magnesium

evaporites

chemically precipitated from evaporating sea water and sometimes lake water

Siliceous sediments lithify to form ?

cherts - flint

diatoms > oil and gas plant material >

coal

important clastic sedimentary rocks

conglomerate breccia quarz sandstone arkose lithic sandstone siltstone claystone shale

________ grain size with increased transport distance and _______ energy level

decreased, decreased

how are different types of sedimentary basins defined ?

defined in the context of plate tectonics - rift basins - passive-margin basins - foreland (flexural) basins (convergent)

what increases with transport distance?

degree of sorting increases with transport distance

direct and indirect mechanism of biomin

direct - organisms utilize dissolved ions or molecules to produce shells or skeletons indirect - minerals precipitate due to environmental conditions created by organism

reefs

direct precipitation of carbonate sediments - bahamas example - built in warm shallow seas by organisms that precipitate calcium carbonate

define weathering

disintegration of rock into separate grains by chemical and physical weathering

chemical weathering

dissolves and weakens rock

whens is stream erosion most efficient ?

during floods - large volumes of fast-moving turbulent water

what is the processes that allows chemical sediments to form

evaporation - mineral precipitation due to seawater evaporation from chemical sediments

true or false: when a sediment is weathered and than is transported to its depositional environment It remains the same?

false, they change as they are transported across earths surface

organic sediments

formed from accumulation of wetland vegetation burial and diagenesis converts peat to coal

sedimentary rocks can be interpreted to understand what?

geological history

variations sort particles according to _____-size and density

grain size