1b ~ intro to clastic sediments

what are the 4 main types of sandstone?

quartzarenite

arkose

lithic sandstone (litharenite)

graywacke

what are the features of quartzarenite?

composed of entirely quartz grains

well rounded + sorted

mature to super mature

found in aeolian dunes, beaches, shallow shelf

what are the features of arkose?

contains feldspar + lithic frag

poorly sorted

immature

found in alluvial fan deposits, rivers in hinterland areas

what are the features of litharenite?

abundant lithic fragments

angular to sub-angular

sub-mature to mature

found in fluvial areas, hinterland areas with active uplift

what are the features of greywacke?

abundant lithic fragments, quartz grains

poorly sorted

found in submarine fans, slope, abyssal plain deposits

what are 2 methods of sandstone classification?

QFL plot

toblerone plot

what are the 4 types of textural maturity?

immature

sub-mature

mature

super-mature

what is textural maturity?

measure of how much sediment has been altered from parent

what is immature?

>5% clay

poorly sorted

angular to subrounded

abundant feldspar + lithic fragments

what is submature?

<5% clay

poor to moderately sorted

more rounding than immature

feldspar + lithic fragments common

what is mature?

<5% clay

well sorted

subangular to subrounded

few feldspar + lithic fragments

what is super mature?

<5% clay

very well sorted

round to sub round

barely any feldspar + lithic fragments

what is a paraconglomerate?

matrix supported clast supported

what is orthoconglomerate?

what are the different clast compositions for conglomerates?

monomict - all clasts same lithology

polymict - clasts of many diff llithology

oligomict - clasts of few diff lithologies

what are primary sedimentary structures?

produced during deposition of sediment

eg. stratification, bedforms

what is stratification?

tabular or lenticular layers of sedimentary rocks

what is planar bedding?

vertical aggradation of sediment

what is graded bedding?

distinct vertical graduation in texture+ grain size

what are the 2 types of graded bedding?

normal - fining upwards

reverse - coarsening upwards

what are turbidites?

classic normal sequence

produced by density driven (turbidity) currents

what is massive bedding?

structureless bed with no internal laminae

rapid sedimentation

no traction current

what are bedforms?

structures produced by migration of bedforms (eg. ripples, dunes)

what is cross bedding?

inclined beds produced by migration of bedforms

at a 30-40 degree angle

what are the two types of cross bedding?

planar - straight crested ripples/dunes

trough - sinuous crested ripples/dunes

what are sets + cosets?

set - bed w crossbed produced by single ripple/dune

coset - stacked sequences of sets

what are scour marks/flutes?

crescentic/horse shoe shape scour formed in mud by turbulent eddies

sand infills cast creating positive mold on underside of bed

what are grooves?

linear grooves made as object is pushed across bed

on underside of bed

what are mudcracks?

drying of mud surface

indicates up direction

***** what are soft sediment deformations?

form at time of deposition

what are biogenic structures?

tracks + burrows produced by organisms

evidence of bioturbation

what is bioturbation?

sediment getting mixed up by organism

lose some structure

what are rhizoliths?

fossilized root moulds + cast