August 29, 2003

Organic and Non-Clastic Sed. Rx and Metamorphic rocks

1. Organic Clastic Rocks – Biochemical Sediment

a. Carbonate rocks – Limestones

i. Organic clastic textures

A. Micrite – Fragments too small to be differentiated without the aid of a

microscope.

B. Allochems – Larger fragments which can be seen w/o the aid of a

microscope.

1. Oolites

2. Shell fragments

3. Fecal pellets

4. Fossil fragments

ii. Dolostone – magnesium rich crystalline Limestones.

b. Siliceous Rocks

i. Chert – formed from planktonic animals or the precipitation of silica out of

solution.

A. Crystalline or micro crystalline in texture

c. Coal – compacted plant material

2. Non – Clastic Rocks – Chemical Sediment

a. Crystalline to microcrystalline texture

b. Three main types

i. Rock Salt – Halite

ii. Gypsum – Gypsum

iii. Travertine – Calcite

3. Sedimentary structures p. 106. Also see Figure 6.11

a. Cross Bedding

b. Mud Cracks ( Desiccation cracks)

c. Fossils – footprints

d. Ripple Marks

e. Raindrop Impressions

4. Metamorphic Rocks

a. Types of Metamorphism

i. Regional – Appalachian Mtns.

ii. Contact – around igneous intrusions

b. Grades

i. High, Medium, Low

c. Metamorphism – types of changes

i. Recrystallization – too a larger crystal of the same composition

ii. Crystallization – from an old mineral to a new mineral

iii. Rotation

d. Metamorphic textures

i. Foliated

A. Slatey cleavage

B. Phyllitic

C. Schistosity

D. Gneissic

ii. Non – Foliated

e. Mineralogical Composition

i. Diagnostic Minerals

A. Chlorite

B. Garnet

C. Staurolite

D. Kyanite

E. Sillimanite

f. Protolith

i. Definition

ii. Compositions

A. Pelitic – High in Aluminum and Potassium

B. Arenaceous – Mostly Quartz

C. Calcareous – Mostly Calcium Carbonate

D. Mafic – High in Magnesium, Iron, Calcium

g. Isograds