Lab 2: Sedimentary rocks and Fossilization

Question 1

Sediment make up

Answer 1

made up of raw minerals (grains) from weathering and erosion

Question 2

2 types of sedimentary rocks

Answer 2

1. Clastic sediment- formed from weathered, eroded, and transported grains of pre-existing rocks
2. Chemical sedimentary rocks- formed from minerals chemically precipitated out of water solution, using elements derived from the previous dissolution of minerals in other rocks

Question 3

which rocks are fossils often found in

Answer 3

sandstone and/or shale

Question 4

What specific environmental information is provided by the grain size of clastic detrital sedimentary rocks?

Answer 4

high/low energy environment and slope (higher slope= bigger rocks, lower slope= smaller)

Question 5

What factors contribute to an angular rock vs rounded rock

Answer 5

time and distance of travel.
more time and distance= more travelling the rock has done= more wear and tear and erosion done to it, rounding it.
Angular rocks= less time and distance travelled

Question 6

In which clastic rock type would the fine details of leaves most likely be preserved, why?

Answer 6

Shale
- no sandblasting/weardown
- low energy environment
- small particles

Question 7

direct preservation

Answer 7

part or all of the organism material composition still remains. Complete and nearly unaltered remains (insects in amber or wooly mammoth frozen in ice)

Question 8

Preservation with alteration

Answer 8

involves several fossilization processes.
1. Recrystillization
2. molecular substitutions
3. permilization
4. reduction of organic material to a carbon residue

Question 9

recrystillization

Answer 9

recrsytilizes one mineral into another without change in composition (aragonite to calcite)

Question 10

perminalization

Answer 10

infilling of pore spaces with new minerals, leaving bone unaltered

Question 11

carbonization/Reduction

Answer 11

reduction of organic material to a carbon residue

Question 12

Indirect preservation

Answer 12

the fossil is only an impression or trace of the organism- in the form of molds/casts.

Question 13

replacement

Answer 13

when the bone material itself is replaced by minerals

Question 14

petrified

Answer 14

fossil has undergone bone permilization and replacement

Question 15

describe “Nacre”

Answer 15

-shiny
-irridesent
-reflects light
-made of aragonite

Question 16

whats one way to tell a shell is old vs new

Answer 16

new- presence of nacre from recrystallization
old- powder white colour

Question 17

Is a cast a negitive (impression) or a positive (replica) of an organism?

Answer 17

positive (replica)

Question 18

how is a cast made

Answer 18

they cavity (from the mold) can later fill in with material precipitated from solution, giving a replica of the original.

Question 19

why is a swamp/bog a good place for carbonization to occur

Answer 19

O2 preserved, rich in CO2, sediment coverage, low energy