A1261870220xUIXC

1
Sedimentary Rocks
Organic Sediments
2
Sedimentary Rocks
carbonate
limestone
argillaceous limestones
bituminous limestones
calcareous shale
bituminous coal
coal bitumen
shale
cannel coal
carbonaceous shale bone coal
clay
organic matter
Complete continuum!!
3
Sedimentary Rocks
Organic Sediments
Organic matter
Bitumen high in C H, low in O liquid
petroleum solid asphalt
origin animal fats proteins Humic - high
in C O, low H liquid kerogen
solid coal, peat origin plant lignins
cellulose
4
Sedimentary Rocks
Organic Sediments

• Coal
• high percentage carbon
• high molecular weight
  compounds
• small amounts H, O, N
• may contain S, P, U, Ge
• gt 3000 plant species identified

5
Sedimentary Rocks
Organic Sediments
Coal
Environment of Formation fresh water swamps on
deltas or coastal plains inland lake basins
environment requires rapid accumulation and
burial of plant matter under anaerobic conditions.
6
Sedimentary Rocks
Organic Sediments
Origin of Coal

• Coal metamorphism
• With increased burial decomposition, increase
  in T P
• volatiles (CO2, methane, H2O) driven off
• C increases, H O decreases
• amount of plant remains decreases
• hardness increases
• calorific value (BTUs) increases

7
Sedimentary Rocks
Organic Sediments
Origin of Coal
Transgression and regressions produce multiple,
wedge-shaped coal seams.
8
Sedimentary Rocks
Organic Sediments
Coal Rank
Meta-anthracite Anthracite Semianthracite
Anthracite Bituminous Subbituminous Lignite
Peat
Hard Coals
Low volatile Med. Volatile High Volatile A
B C
A B C
Brown Coals
A B
9
Sedimentary Rocks
Organic Sediments
Coal constituents (lithotypes)
Anthraxylon
bright, lustrous hydrocarbon-rich sapropelic
(bitumen-like from organic slime)
Attritus
dull, sooty humic
10
(No Transcript)
11
Sedimentary Rocks
Organic Sediments
Megascopic components of anthraxylon attritus
Clarian - laminated, silky or glossy luster,
smooth fracture perp. to bedding, clean to
touch Durain - homogeneous, dull matte luster,
granular fracture, lead-gray or brownish
black Fusain - mineral charcoal, friable to
powdery, porous, satiny or silky luster, dirty
to touch Vitrain - homogeneous, vitreous
luster, concoidal fracture, brittle, clean to
touch
12
Sedimentary Rocks
Organic Sediments
Microscopic components of anthraxylon attritus
Macerals
vitrinite degraded cell structure cutinite
- leaf or bark surface fusinite - carbonized
wood sporinite - compressed spores resinite
- tree sap micrinite - sub-optical plant
detrital material
Also semifusinite, sclerotinite, inertinite,
exinite, alginite, liptonite maceral groups,
maceral suites
13
Sedimentary Rocks
Field distinctions for coals
Peat
Lt. tan to dk. brown. Spongy mass of matted,
partly decayed plant remains. Burns readily when
dried w/ smoky flame strong odor. Responsible
for distinct taste of Scotch Whisky.
14
Sedimentary Rocks
Field distinctions for coals
Lignite
Chocolate brown to nearly black, dull
luster. Dense to earthy fragile, crumbles when
dried. Partially decayed plant fragments
preserved. Burns w/ smoky flame strong odor.
Does not coke grades into sub-bituminous coal,
which cokes.
15
Sedimentary Rocks
Field distinctions for coals
Bituminous
Dark gray to black, typically banded
w/alternating layers of dull vitreous. Brittle,
tends to break in blocks due to jointing
perpendicular to beds. Does not crumble in
air. Does not contain megascopic plant
debris. Burns readily w/ oily odor.
16
Sedimentary Rocks
Field distinctions for coals
Anthracite
Semianthracite megascopically indistinguishable
from bituminous
higher BTUs wont coke Anthracite lustrous
gray to jet black subconcoidal fracture
sometimes iridescent (peacock coal) ignites w/
difficulty but burns w/out smoke or odor
17
Sedimentary Rocks