Sedimentary Rocks (& Fossils): Environments & Time (Chapter 2,3, &4)

Question 1

Photic zone

Answer 1

• upper body of marine (or other aquatic) environment that has abundant light
• usually 100m from surface with typical daylight
• limits photosynthesis & organisms that depnd on photosynthetic organisms

Question 2

plankton

Answer 2

• organisms ath the top few meters of water surface
• invertebrate (graptolites), plants, & microorganisms

Question 3

nekton

Answer 3

swimming organisms in open water

e.g. squids

Question 4

Benthic epifauna

Answer 4

bottom dwelling benthic organisms living on surface of seafloor

e.g. corals

Question 5

Benthic infauna

Answer 5

bottom dwelling benthic organisms living underneath sea floor

e.g. some clams

Question 6

Carbonate Compensation Depth (CCD)

Answer 6

• depth at which calcium carbonate dissolves
• usually 4-5 km below ocean surface

Question 7

Aragonite Compensation Depth (ACD)

Answer 7

• depth at which aragonite mineral dissolves
• usually 1-2 km below ocean surface

Question 8

Desert Environment

Answer 8

• low water, terrestrial environment
• temperature fluctuates
• sandstone usually found, clay also found (from playa lakes)

Question 9

Glacial Environment

Answer 9

• low temperature, terrestrial
• mostly ice & water
• rocks - abraded, striations
• boulders different from indegenous rock found

Question 10

Fluvial Environment

Answer 10

• terrestrial, running water
• running water = mechanism for sorting by grain size
• braided & meandering
• fossils rare unless flood events preserve some aquatic & terrestrial organisms

Question 11

Swamp Environment

Answer 11

• terrestrial with poor drainage & waterlogged
• common near shorelines
• if preserved, plants fossils and/or rocks with high carbon content

Question 12

Lacustrine Environment

Answer 12

• lake with periods of stratification where anerobic bottom allows for preservation of both aquatic & terrestrial
• rocks - fine grained made of detrital or chemical sediments

Question 13

Reef Environment

Answer 13

• near shore
• in photic zone of marine environment
• stable temperature
• abundant & diverse fossils
• rocks - fine-grained bioclastic limestone; complex reefs may result in coarse-grained

Question 14

Estaurine Environment

Answer 14

• river (fresh) meets sea (salty)
• rare if bioturbation occurs
• epifauna, infauna or mixed found
• sandstone, siltstone, or clay

Question 15

Beach Environment

Answer 15

• along sea or lake shores
• reworked silt, sand, or gravel deposits associated with trangression & regression
• sandstone & limestone - most likely beach

Question 16

Nearshore Environment

Answer 16

• along shore with sand, silt, & clay beds
• marine macrofossils, photic zone species, ichnofossils - rare to common

Question 17

Offshore Environment

Answer 17

• distance from shore
• sand, silt, & clay beds
• terrestrial fossils less common than marine macrofossils
• nekton & plankton spcies, ichnofossils, epifauna & infauna - rare to common

Question 18

Deep Water Marine Environment

Answer 18

• dominated by clay
• marine macrofossils, ichnofossils, & nekton & plankton
• terrestrial & benthic fossils - rare

Question 19

Continental Slope Environment

Answer 19

• marine environment between continental shelf & ocean
• rocks: silt & clay, only sometimes sand due to storm events