sed/strat midterm 2 - depositional environments

fluvial

• meandering (commonly muddy and vegetated)

• braided

• anastomosing

• straight

• commonly muddy and sandy

oxbow lakes

site of thick and persistent vegetation

crevasse splay

small delta shaped body of anastomosed channels

alluvial

• feldspathic arenite - arkose

• course grain sediment

• immature and angular

swamp/padual

• lots of vegetation

• anaerobic conditions

• siltstone and shale (organic rich)

• peat alters to coal after lithification

glacial

• tills (may be overlain by braided gravel bars or cross bedded sands and gravels)

• diamictite (dropstones, striations on clasts/bedrock pavements)

• poorly sorted and rounded

• mud flows and debris flows

aeolian

• quartz arenites

• well sorted

• well rounded

• surface of quartz are pitted and frosted

• beds are tabular-planar

• wind ripples (asymmetrical)

lacustrine

• shale

deltaic

• breccias

• lithic sandstone

lagoonal

• supratidal

• algal mats

• gypsum

• very salty and hot

beach

well sorted, well rounded quartz sand

shallow sea (eperitic sea/big and shallow)

ooids

continental shelf

• quartz arenites

• cross bedding

• hummocky cross stratification

• wave ripples (lower bounding surface)

• lenticular and flaser bedding

• accumulate carbonates (tropical)

• fine sands/silts/muds (cold water/high siliciclastic areas)

continental slope

• olistoliths

• slumped and deformed shales

• debris flows

• turbidites

deep marine

• greywacke

• marcellous shale

distributary complexes

• fan shaped bodies of coarse sediment

• proximal fans - massive beds

• distal fans - planar bedded and current rippled beds

slumps and slides

• contorted bedding

• inherited bedding

debris flow

• contorted massive bedding

• outsized clasts

abandonment/drape

• planar bedding

• planar laminated pelagic fallout

• organic enrichment

• dilute turbidites

• pelagic fall out

• no sediment reaches the deep ocean

midfan sheets

• well sorted

• well stratified

• cross bedded

coorong lakes

• dolomite formation

• lagoons

supratidal

• high abundances of organic matter

• coal likely to form

peritidal

• deposits laterally

• evenly bedded limestone and dolomite

• carbonate (dolomites) mudflates

• evaporites

• herringbone x-stratification

• shell debris

• rip-up clasts

• plate breccias

• mud cracks

• algal mats

• fenestral porosity (birds eye structures)

subtidal

• bioturbated

• thick carbonate blankets (up to 1000s m thick)

dolomite formation

• elevated temperature

• Mg/Ca ratio must increase (5:1 or greater)

• salinity

• high evaporation

• areas where fresh and salt water mix

  • overcomes hydration shell around Mg2+, SO4 concentration, and salinity

• SO4 inhibiter to formation