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Sandstone Provenance (Continental Block (Source Areas (Cratonic interior…
Sandstone Provenance
Continental Block
Source
Areas
Cratonic interior
Platform
Uplifted basement
(older seds / meta / igneous)
Source
Rocks
Plutonic igenous (lil bit/none)
Metamorphic (some)
Sedimentary
(mostly)
~ rift basin
Sediments derived from adjacent rift shoulders
Signatures of rocks from which they eroded
Diagnostic sandstone assemblage
Rich: quartz & K-feldspar
Less: metamorphic lithics & plagioclase feldspar
Little/no: Igneous lithics
Magmatic Arc
Source
Areas
Volcanogenic highlands
arc itself undissected
Exposed underlying granitics
dissected arc
Scraped off downgoing oceanic crust
Source
Rocks
Volcanic - andesitic
Granitic (plutonic)
less unless in dissected arc
Diagnostic Assemblage
Rich: volcanic lithics & plagioclase fsp
Sparse: K-fsp & quartz
(unless in dissected arc with granitic rock)
Sediment
Source
Trench fill
basin fill sediments accumulate on seaward side
Accretionary
Wedge
sediment eroded/scraped off downgoing oceanic crust)
wackes - matrix rich
Back-arc
zone
Shed from arc to continent
Andesitic
Volcanoes
uplift/erosion of volcanics from beneath
Imbricate subduction complex
sediment eroded from oceanic crust
Provenance
A sandstone will contain mineral grains which records its source
provenance informs:
palaeogeography
burial changes
= where rock components come from (source/origin)
Dickinson 1979
Sediments from different tectonic settings
Plot in characteristic way on ternary diagram (comp plot)
Can deduce tectonic environment from composition
3 Tectonic Settings
Dickinson Discriminated
1. Continental
block (rift)
qtz & fsp rich
2. Magmatic Arc
volcanic lithicss & feldspars
3. Orogenic belt
lithics - sed/metased/meta
Orogenic Belt
(Recycled orogen)
Tectonics
Continent-continent collision & subduction
Uplifting basement/sedimentary rocks / granite
e.g. Himalaya / Alps / Pyrenees
Source
Areas
Uplifted & deformed in continental margin
Basement rocks (metamorphic)
Sedimentary rocks
from great depth
already matured/eroded
Diagnostic Assemblage
Rich: quartz & K-fsp
(qtz > fsp)
(second cycle sediments ∴ mature)
Abundant Lithics:
metamorphic
metasedimentary
sedimentary