http://apps.usd.edu/escistudy/geoltime.pl. 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
Go to the above
URL to test
of the Geologic
Quiz on Thursday.
from Tucker (1991)
SO4-- + C (organic) + H20H2S + 2HCO3-
Hydrogen sulfide then combines with available
iron oxide to make pyrite.
Major Ions in: SeawaterRiver water
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
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.
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
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
from P.E. Potter
Beach sand with abundant volcanic rock fragments, Pacific coast of Costa Rica.
With burial, what will happen to the porosity?
Origin of Wackes-- grain crushing during compaction! coast of Costa Rica.
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.
From: R.H. Dott, J.Sed.Petrology, v. 53, p.15