Fossils and time

Question 1

What is catastrophism?

Answer 1

The theory that changes in the Earth crust have resulted from sudden, violent events and also account for the extinction of species.

Question 2

What is gradualism?

Answer 2

The theory that change comes about gradually or that variation is gradual. Also applied in the theory of evolution.

Question 3

What are the geological periods in order?

Answer 3

Oldest
Chris - Cambrian
Ordered - Ordovician
Some - Silurian
Delicious - Devonian
Crusty - Carboniferous
Pizza - Permian
Then - Triassic
John - Jurassic
Caressed- Cretaceous
The- Tertiary (Contains the: Paleogene, Neogene)
Queen- Quaternary

Question 4

What influences fossilisation?

Answer 4

ODORSET
-Original composition
-Diagenesis
-Oxygen levels
-Rapid burial
-Sediment size
-Energy levels
-Transport distance

Question 5

What are the different types of preservation of fossils?

Answer 5

-Substitution/Replacement of original material by another - Moulds + Casts
-Aragonite replaced by calcite
-Wood replaced by silica
-Anaerobic bacteria (pyritisation)
-Carbonisation

Question 6

What are moulds and casts?

Answer 6

Where a solid material dissolved leaving its shape in sediment, allowing for new material to precipitate in the shape of the fossils.

Question 7

What are death assemblages of fossils and life assemblages?

Answer 7

Death assemblages - Preserved in their death position
-Broken
-Disarticulated
-Eroded
-Sorted
-Aligned by currents
-Mixed organisms that didn’t live together

Life assemblages - Preserved in a position that would represent what their mode of life would be like.
-In life position
-Complete
-Rare

Question 8

What are derived/reworked fossils

Answer 8

Eroded out of original rock
-Transported (Often eroded)
-Redeposited in a younger rock
-Eg, Jurassic belemnites in quaternary till

Question 9

What are trace fossils?

Answer 9

Fossils that are evidence of a life’s mode or life/behaviour

Question 10

What are 5 trace fossil categories?

Answer 10

1. Trails
2. Tracks
3. Burrows - Soft material excavated
4. Borings - Hard material excavated
5. Coprolites - Fossilised shit

Question 11

What can footprints tell us about an organism?

Answer 11

-Foot structure
-How the animal moved
-Body size
-Speed
-How the tail was carried
-Hip bone = 4 x foot length - this is used to estimate size of an organism
-Distance of prints shows stride length which is then used to show the speed of an organism

Question 12

What do the following terms mean:
Nektonic
Planktonic
Epifaunal
Infaunal
Pelagic
Benthonic

Answer 12

Are modes of life
Nektonic = Free swimming such as fish
Planktonic = Drifting with currents such as jellyfish
Epifaunal = On sea bed such as starfish
Infaunal = In substrate (Worms)
Pelagic = In the water column
Benthonic = On sea floor/in

Question 13

Name 3 people that estimated the age of the Earth and state how they found this information.

Answer 13

Conte De Bufon 1779 - Cooled a model of the Earth and scaled it. Said the Earth was 75K Years old
Lord Kelvin 1899 - Molten iron ball rate of cooling. Said it was 20-100 million years old
John Joly 1899 - Used the salinity of the oceans (Added / yr) said it was 90 million years old

Question 14

What is relative and absolute dating?

Answer 14

Relative = putting events in order (oldest first)
Consists of:
-Sequence in order
-Principles of stratigraphy
-Bio, litho and chronostratigraphy

Absolute = getting actual numerical dates for a geological rock feature which is measured in MA
Consists of:
-Actual numerical
-Usually MA/GA
-Radiometric
-Varves
-Ice cores
-Dendrochronology

Question 15

What is radiometric dating?

Answer 15

Uses radioactive decay to determine how old a rock is by using half lives

Question 16

What is a half life?

Answer 16

The time taken for half of the unstable parent atoms to decay into stable daughter atoms

Question 17

What are the 4 isotopes we use for radiometric dating?

Answer 17

1. Uranium 238 -> Lead 206 - used for rocks 4470 MA
2. Uranium 235 -> Lead 207 -rocks 704 MA
3. Pottasium 40 -> Argon 40 - rocks 1256 MA
4. Rubidium 87 -> Strontium 87 - rocks 48,800 MA

Question 18

What are 4 problems with radiometric dating?

Answer 18

-Weathering releases argon gas, which will alter the parent:daughter ratio making the dating inaccurate
-Potassium 40 is rare in sedimentary rocks, mostly only glauconite.
-Sedimentary rocks are made of fragments of older rocks so the dating will be of the fragments not of the rock itself
-Metamorphism causes isotopes to leave/enter the minerals causing them to become open systems at different temperatures.

Question 19

Why are layers of lava flows and volcanic ash useful to date using radiometric methods?

Answer 19

-Contain suitable isotopes
-Rapid cooling gives more reliable results
-Unlikely to become open systems as they are crystalline

Question 20

What is stratigraphy and its 4 principles?

Answer 20

Is the study of strata
-Original horizontally
-Principle of superposition (Way-up, younger beds at the top)
-Included fragments
-Cross cutting relationships

Question 21

What is biostratigraphy?

Answer 21

Use of fossils to date/match different rocks
Problems:
Derived fossils

Question 22

What is lithostratigraphy?

Answer 22

Use of rock types to date rocks/match up different rocks
Problems:
-Lateral variation separated by bedding planes
-Diachronous- Same bed, different ages

Question 23

What is chronostratigraphy?

Answer 23

Relates to placing rocks in sequence of geological time
-Era
-Period
-Epoch
-Volcanic ash are useful time markers, related to a short, specific period of time.

Question 24

What time range did ammonoids live in, what was their mode of life and what is their category called?

Answer 24

1. Lived in the Ordovician - Cretaceous
2. Nektonic, Marine, Hunter/Predator. Gas fills in chambers to rise, chambers fill with water to sink
3. Cephalopod

Question 25

What are 4 features of an ammonoid (External)?

Answer 25

1. Ribs - Gives strength and protection
2. Umbilicus - Marking the inner diameter of coils
3. Keel - The ridge that sticks out that may have helped it to move
4. Sulcus - The dip next to the keel

Question 26

What are 5 features of an ammonoid (Internal)?

Answer 26

1. Siphuncle - Tube connecting chambers
2. Septal Neck - Supports the siphuncle
3. Aperture - Opening where the ammonoid emerges out of
4. Septum - The wall that closes flood chambers
5. Protoconch - First chamber occupied by the juvenile, added to the next chambers as it grows

Question 27

What time range did Trilobites live in, what was their mode of life and what is their category called?

Answer 27

1. Lived in the Cambrian - Permian
2. Marine predators/scavengers which grew by ecdysis (Malting)
3. Arthropod

Question 28

What are the three sections of a Trilobite?

Answer 28

Top/Head - Cephalon
Middle/Body - Thorax
Bottom/Tail - Pygidium

Question 29

What are 4 features of a trilobite?

Answer 29

1. Glabella - Part of the cephalon that covered the stomach
2. Compound eye - Made of calcite (Similar to fly eyes)
3. Genal angle -Different spikes/points on the side of the trilobite, could extend into a spine
4. Pleuron - The outer, part of the thoracic segment

Question 30

What time range did bi-valves live in, what was their mode of life and what is their category called?

Answer 30

1. Lived in Cambrian - Quaternary
2. Benthonic - live by filtering waterborne food particles at sea bed
3. Molluscs

Question 31

What are 8 features of a Bi-valve (Interior)

Answer 31

1. Cardinal teeth (Hinge line) - Radial are which sockets on right valve
2. Ligament - Holds two shells together
3. Pallial sinus - Indentation in pallial
4. Socket (Hinge lines) - Depression which fit over teeth
5. Abductor muscle scar - Muscles attached to shell
6. Umbo - Area which marks first growth
7. Pallial line - Marks the limit of attached tissue
8. Adductor muscle - Contracts to shut shell

Question 32

What are 4 features of a Bi-valve (Exterior)

Answer 32

1. Ligament - covers the hinge plate
2. Hinge line - plane of symmetry where two valves are joined together
3. Commissure - Where the left and right valve meet
4. Growth lines - Represent new layers of shell as the animal grows

Question 33

What is the difference between a brachiopod and bi-valve?

Answer 33

Brachiopods rely on currents within the shell to feed and respire and have more complex muscles to open and close
Bi valves have two identical sized shells, brachiopods have to uneven shells

Question 34

What time range did brachiopods live in, what was their mode of life and what is their category called?

Answer 34

1. Lived in Cambrian - Quaternary
2. Marine benthonic
3. Superficially similar to bivalves

Question 35

What are 7 features of brachiopods

Answer 35

1. Dentidal plate - Cover a triangle area below the foramen
2. Pedicle foramen - Opening where the pedicle emerges
3. Umbo - First point of growth
4. Growth lines
5. Pedicle valve
6. Brachial valve
7. Commissure

Question 36

What are the 3 types of coral groups?

Answer 36

Rugosa
Tabulate
Scleractinia

Question 37

What time range did cnidaria live in, what was their mode of life and what is their category called?

Answer 37

-Cnidaria - Organism that stings
Rugosa + Tabulate = Ordovician - Permian
Scleractinia = Triassic - Quaternary
Marine benthonic, lived in shallow, warm water, little sediment and well oxygenated