week 4 - marine sediments

Question 1

two types of classification of marine sediments

Answer 1

1. genetic
2. descriptive

Question 2

genetic classification basic information (2 things)

Answer 2

1. sediments are distinguished according to the process by which they originate
2. originates by three processes
   - biological
   - chemical
   - physical

Question 3

genetic categories used to classify sediments

Answer 3

1. terrigenous
2. biogenic
3. chemogenic
4. cosmogenous
5. volcanogenic

Question 4

terrigenous sediments

Answer 4

derived from weathering of the continents
- erosion by rain, rivers and glaciers delivers sediments from the continents to the oceans

Question 5

biogenic sediments

Answer 5

derived from biological processes such as secretion of skeletal materials by marine organisms
- most of it is biologically produced inorganic matter
- when organisms die, their remains sink to the ocean floor and eventually lithify

Question 6

two types of biogenic oozes

Answer 6

1. calcareous oozes
2. siliceous oozes

Question 7

calcareous ooze

Answer 7

contains skeletal materials of CACO3
- controlled by the preservation (destruction) of biogenic carbonate
- deep cold water with high CO2 concentrations are corrosive for carbonate
- found in shallow regions of the ocean floor

Question 8

siliceous ooze

Answer 8

contains skeletal materials of SiO2* and H20
- distribution is controlled by preservation of biogenic opal
- surface waters tend to dissolve opal, which have a low silica concentration
- accumulates on the ocean floor where the bottom waters are close to saturation with respect to silica
- high production around volcanic islands and nutrient rich upwelling zones

Question 9

phosphates

Answer 9

skeletal material of bones and teeth of vertebrates

Question 10

what is the carbonate compensation depth?

Answer 10

the depth at which the rate of dissolution of CACO3 is equal to its rate of accumulation
- controlled by temperature, pressure local chemistry and biological productivity

• concentration of CO2 is higher in colder deeper water

Question 11

chemogenic sediments

Answer 11

inorganic sediments that originate by the precipitation of minerals inside the sediments
- found only in small portions of marine sediments

ex. manganese nodules

Question 12

volcanogenic sediments

Answer 12

sediment that originates from volcanic eruption or weathering volcanic material
- found only in small portions of marine sediments

Question 13

cosmogenous sediment

Answer 13

inorganic sediments that originate by the accumulation of materials from outer space
- very rare except near ancient metoerite impact

Question 14

genic vs. genous

Answer 14

genic refers to the process that formed the sediment (i.e. by biological processes)

genous refers to the local origin of the sediment (e.g. from land)

Question 15

different ways that descriptive classification is separated

Answer 15

by texture (size) or composition

Question 16

types of sediment sizes

Answer 16

1. boulder
2. cobble
3. pebble
4. sand
5. silt
6. clay

• grain size of a sediment gives an indication of how fast it sinks and where the grains were transported and deposited

Question 17

marine sediments and plate tectonics

Answer 17

1. mid ocean ridges are shallow, poking above the CCD
2. sediments near the ridge are dominated by calcaerous oozes

Question 18

descriptive classification by composition

Answer 18

1. well sorted to poorly sorted
2. well rounded to very angular