sedpet review Flashcards
2 types of weathering
mechanical and chemical
physical destruction of the original rock
mechanical weathering
decomposes minerals in the rocks
chemical weathering
Loose deposits are converted into rocks by the processes of ____ and ____, which include ____ and ____ of the loose materials
diagenesis and lithification
compaction and cementation
2 products of mechanical weathering
detritus/clastic material
terrigenous sediments
solid fragments and mineral particles from mechanical weathering
detritus or clastic material
sediments with clastic textures
terrigenous sediments
2 sediment products from chemical weathering
orthochemical sediments and allochemical sediments
truly chemical sediments which are products of chemical decomposition
orthochemical sediments
organisms have caused the precipitation of the major sedimentary mineral components, or the precipitated minerals have undergone substantial movement (and redeposition) after their crystallization, different
allochemical sediments
what two points are important for sediments to be classified as allochemical?
- organisms caused the precipitation
- or precipitated minerals have repositioned after crystallization
describe the flow of source rock to sedimentary rocks
source rock
> (mechanical and chemical weathering) detritus > (transportation) clastic sediment > (burial and lithification) terrigenous sedimentary rock
> (chemical weathering) solution > (transportation and precipitation) chemical precipitate
breaks into
> (diagenesis and lithification) orthochemical sedimentary rock
or
> (cementation, fragmentation and transport with basin) allochemical sedimentary rock with clastic texture
what are the three major categories of sedimentary rocks
I. terrigenous sedimentary rocks (clastic texture)
II. allochemical sedimentary rocks (biochemical/biogenic, with clastic texture)
III. orthochemical sedimentary rocks
type of sedimentary rock that includes conglomerates, breccias, sandstones, mudstones, agglomerates and volcaniclastic sandstones
terrigenous sedimentary rocks
type of sedimentary rock that includes limestone, dolostones, phosphorites, chert and coal
allochemical sedimentary rocks
type of sedimentary rock that includes cherts, travertine and iron formations
orthochemical sedimentary rocks
consist of detrital grains, which form the framework of the rock, and which are joined together by cement
Terrigenous sedimentary rocks
T or F: Variable amounts of matrix, which consists of fragmental material substantially smaller than the mean size of the framework grains, may also be present in terrigenous sedimentary rocks
T
The texture is a composite of the ___, ____, ____ and ____ of the framework grains.
grain size, grain shapes, sorting, and angularity
draw the udden wentworth and krumbein scales
refer to notes
conversion formula from mm to phi
phi = -log2 d
consists of large clasts (boulders, cobbles, pebbles, and granules) with or without a sandy matrix;
conglomerates and breccias
show pronounced rounding of the clasts
conglomerates
contain more angular clasts
breccias
coarse-grained pyroclastics (volcanic debris) with a grain size over 32 mm
agglomerates or volcanic breccias
finer-grained (grain size between 2 and 0.062 mm) and most easily classified by determining the amounts of clastic (framework) grains composed of quartz (and chert), feldspar, and lithic fragments
sandstone
when the sandstone matrix constitutes more than 10 volume percent of the rock
wacke
mostly dark gray sandstones with abundant matrix
greywacke
sandstones made up of chiefly volcanic fragments, volcanic glass, and crystals.
volcaniclastics
why do volcaniclastics tend to be green
bc of chlorite
draw the sandstone classification diagram
refer to notes
general term for sediments composed mainly of silt-sized, (0.062 to 0.004 mm) and clay-sized (<0.004 mm) particles
mudstone
silt particle size
siltstone
clay particle size; nonfissile, commonly with a massive or blocky texture
claystone
characterized by its fissility (ability to split into thin sheets), generally parallel to bedding
shale
with a well-developed cleavage, which may or may not be parallel to the bedding, and is commonly the result of metamorphism
slate
process when calcite is easily replaced, often destroys the texture of the original carbonate
dolomitization
what typically replaces original calcium carbonate
secondary dolomite
what are the orthochemical components
microcrystalline ooze and sparry calcite cement
a very fine-grained carbonate precipitate that has settled to the bottom of the basin
microcrystalline ooze
coarser in grain size than the ooze and tends to be clear or translucent; a pore-filling cement that was precipitated in place
sparry calcite cement
what are the 4 allochem components
intraclasts, oolites, fossils, and pellets
fragments of weakly consolidated carbonate sediment that have been torn up, transported, and redeposited by currents within the basin of deposition
intraclasts
in a size range of 0.1 to 1.0 mm in diameter, are spherical, show radial and concentric structures, and resemble fish roe. They are commonly formed by chemical accretion around nuclei such as shell fragments, pellets, or quartz sand grains
oolites
remains of organisms
fossils
well-rounded, homogeneous aggregates of microcrystalline calcite in a size range of 0.03 to 0.2 mm in diameter; feces of mollusks, worms, and crustaceans
pellets
three types of limestone under folks classification
type 1 2 and 3
consist of a matrix of allochemical constituents and sparry calcite cement
type 1
variable percentage of allochemical grains in a microcrystalline matrix
type 2
microcrystalline calcite matrix only (micrite)
type 3
emphasizes the depositional texture
dunhams classification of limestone
consists of more than 10% grains in a microcrystalline ooze (micrite)
wackstone
grain-supported limestone with micrite matrix and sparry calcite cement
packstone
grain-supported limestone with very little micrite.
grainstone
a limestone made up of organic structures that grew in situ (in place), forming a coherent rock mass during growth
boundstone
what is boundstones equivalent
biolithite
formed by direct precipitation
orthochemical sedimentary rocks
