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  • Updated On : This is from Tim Heaton’s Webpage. Go to the above URL to test your knowledge of the Geologic Time Scale. Quiz on Thursday. Devonian black shale I-64 roadcut, eastern Kentucky. Bioturbation. Laminated mud, Fissile rock. from Tucker (1991)

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This is from

Tim Heaton’s


Go to the above

URL to test

your knowledge

of the Geologic

Time Scale.

Quiz on Thursday.

Devonian black shale

I-64 roadcut,

eastern Kentucky


Laminated mud,

Fissile rock

from Tucker (1991)

p. 104

Sulfate Reduction

SO4-- + C (organic) + H20H2S + 2HCO3-

Hydrogen sulfide then combines with available

iron oxide to make pyrite.

Major Ions in: SeawaterRiver water

(ppm) (ppm)

Chloride Cl- 18,000 7.8

Sodium Na+ 10,770 6.3

Sulfate SO4-- 2715 11.2

Magnesium Mg++ 1290 4.1

Calcium Ca++ 412 15.0

Potassium K+ 380 2.3

Bicarbonate HCO3- 140 58.4

Pyrite is abundant in marine mudstones, but, because the sulfate concentration in most streams and groundwater is low, it is absent from most non-marine





(Pennsylvanian Age)

This is where petroleum

originates:organic matter

in black shale (photosynthesis

by marine algae). This organic

material is commonly called


After burial and heating, the

hydrocarbons migrate upward,

and are (possibly) trapped

before they reach the surface.

Battlement Mesa, Colorado-- where Exxon had a go at

production from oil shale in the middle 1970’s, but

went bust in the early 1980’s.

Oilshale--mudrock rich in kerogen (a potential source rock

for petroleum) that has not been buried deeply enough to

generate oil.

Optimum temperatures for formation of hydrocarbons from kerogen--

about 20º-90º C (burial to between about 600 and 6000 meters)

Traps-- places where upward-migrating hydrocarbons accumulate

to make an oil reservoir. (oil and gas are buoyant-- less dense than water)

Tar sand-- oil reservoir has been exposed at the surface or degraded

by bacteria; volatiles have been lost, only heavy molecules remain

(tar, asphalt; Athabaska Tar Sands near Ft. McMurray, no. Alberta)

Wackes-- sandstone with a muddy “matrix”.

Are they sandstone / mudrock hybrids?? NO!

Textbook p. 110 doesn’t explain origin of “matrix” of wackes

Costa Rica

from P.E. Potter

Beach sand with abundant volcanic rock fragments, Pacific coast of Costa Rica.

With burial, what will happen to the porosity?

Trace fossils coast of Costa Rica. are structures produced

in sediments and rocks by the life

processes of organisms.


From: R.H. Dott, coast of Costa Rica. J.Sed.Petrology, v. 53, p.21

Bioturbation = sediment mixing by organisms to the

extent that individual traces are difficult to see.

Most trace fossils have high preservation potential.


Amalgamate-- “to mix so as to make a unified whole; blend;

unite; combine”


From: R.H. Dott, J.Sed.Petrology, v. 53, p.15