theImage.com     Notes on Basic Geology
Notes created & information organization based on the book:
"The Dynamic Earth - an introduction to physical geology"
Brian Skinner & Stephen C. Porter   (further book information here)
also look at www.wiley.com for additional resource information
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Sediments & Sedimentation - Page 4

Biogenic Deposits

Chemistry

Name

CaCO3

Limestone

shell fragments

Coquina

tiny floating organisms

Chalk

reef organism

Reef Limestone

CaCO3 MgCO3

Dolostone

(SiO2)N

Diatomite

C (shale & sandstone)

Coal
(> 50% plant matter)

C (shale )

Oil Shale
Limestone w/ calcite
Coquina Dolostone / Dolomite
Sedimentary rocks often mimic the conditions under which they were formed.

Sedimentary rocks can capture information about the environment under which they were formed. This is especially true if the rock is the top layer in a stack.
dinosaur footprint in limestone
Image: West Virginia Geological and Economic Survey		 Fern in limestone
The fine grained nature of the sedimentary rocks make the excellent moulding material for anything that falls into them or comes in contact with them before they are completely dry. The book also has an excellent example of ripples frozen into the surface of a sandstone at the edge of a body of water.
Today's Mud >208 million year old mud
Photos from Conrnell University Department of Geology: http://www.geo.cornell.edu/geology/classes/Geo101/101images_fall.html

The color of sedimentary rock is a function of the minerals that have passed through it or that are part of it. The dark color of most sedimentary rocks result because they formed in reductive environments. They were not oxidized during their deposition.

The reddish and yellow colors are usually caused by iron oxides and if they exist as part of the structure and not just as a stain, then they indicate that this sediment was deposited under oxidizing conditions.

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