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Earth history and life - 29202 > Trace fossils > Flashcards

Trace fossils Flashcards

1
Q

What is another name for trace fossils?

A

Ichnofossils

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2
Q

What can trace fossils be used as?

A

Palaeoenvironmental indicators

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3
Q

What is endogenic trace fossils?

A

Made/ found within the rock (type of preservation)

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4
Q

What is epirelief trace fossil preservation?

A

Preserved on the top of beds

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5
Q

What is hyporelief?

A

Located at the base of beds

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6
Q

What is full relief?

A

Located within beds

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7
Q

What are exogenic traces?

A

Made on the sediment surface

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8
Q

How are full relief trace fossils preserved?

A

burrow preserved in 3d

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9
Q

What is another name for epirelief and hyporelief?

A

semi relief

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10
Q

Where is hyporelief most common?

A

Interbedded sands and muds

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11
Q

Where is an example of hyporelief?

A

Aberystwyth Grits (Silurian)

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12
Q

What are natural casts, true track, undertracks? (trace fossils)

A

Natural - made by infilling of original track
True - actual imprint
Undertrack - dent in sediment by animal pressure

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13
Q

What is the bias with trace fossils/ undertracks?

A

Bias towards heavier that can leave a greater impression

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14
Q

What is an example of undertrack preservation?

A

Sauropod footprints in the Morrison Formation Colorado

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15
Q

What problems are associated with trace fossil identification?

A

Single organism can produce many trace fossils
Different organism can produce similar trace fossils

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16
Q

What do invertebrate trace fossils names tend to reflect?

A

Morphology of trace (shape and ornamentation)

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17
Q

What can be used to describe the morphology of trace fossils?

A

Ichnogenus and Ichnospecies

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18
Q

How many trace fossils are produced by the Uca (modern day fiddler crab)?

A

4 traces

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19
Q

What are the trace fossils produced by Uca?

A

Psilonchnus - domichnion (living burrow)
Diplichnites - repichnion (walking trail)
Pascichnion - grazing trail
Coprolites - feacal pellets

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20
Q

What is the name for the resting trace? (cubchnia)

A

Rusophycus

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21
Q

What is the problem associated with identifying resting traces?

A

Originally thought just trilobites hunkering down on sediment but found other organisms can produce aswell

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22
Q

What are some examples of organisms which can produce resting fossils?

A

Polychaete worms
Snails
Brachiopod shrimps
Trilobites

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23
Q

What is repichnia?

A

walking or crawling trace

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24
Q

What is an example of a crawling trace?

A

Cruziana - Ordovician Anzaldo Fm Bolivia

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25
What is an example of domichnion? (living burrow)
Arenicolites
26
What do arenicolites produce?
U shaped burrows which makes a worm cast and depression
27
What do arenicolite worm burrows do to the rock chemistry?
Anoxic rock is made oxygen rich by when oxygenated water is pulled into the sediment
28
What is the difference between diplocraterion and arenicorlite?
Scars of where burrow used to be (spreite)
29
What is the name of the burrow behaviour of diplocraterion?
fugichnia - escape trace
30
What is the ichnogenus and ichnospecies name of diplocraterion?
Diplocraterion yoyo
31
Why is the name diplocraterion yoyo given?
Due to the changing position of the organism burrow due to erosion and deposition to avoid burial or exposure
32
What is pascichnia? (trace fossil)
surface feeding trace
33
What is an example of pascichnia?
Helminthoidea
34
What is fodinichnia? (trace fossil)
Mining feeding trace
35
What is an example of where fodinichnia can be found?
Chondrites in hardening sandstones from Ordovician Colorado or Zoophycos
36
Where is fodinichnia produced in the sediment layers?
close to the water sediment interface
37
Why is the pattern distribution in swooping motions for fodinichnia?
To avoid eating poop Maximise exploited sediment
38
What are chondrites produced by?
A worm
39
What is agrichnia? (trace fossils)
Cultivation trace (hexagon pattern used to cultivate algae)
40
What is an example of agrichnia trace?
Paleodictyon
41
What trace fossil is the base of the cambrian defined by?
Phycodes
42
What are hycodes followed by?
Trace fossil assemblage containing Rusophycos and Cruziana
43
What are phycodes like?
Looping structure
44
What is the prominence of Rusophycos and Cruziana appearing so early in the fossil record?
They precede trilobite body fossils
45
What is tiering in trace fossils?
How many layers are exploited by burrowers
46
What has happened to tiering over time?
Mid Ordovician 3 tiers Remains like that till Early Jurassic Then large diversification as deep seafloor exploited leading to 9 tiers in late cretaceous
47
What are Thalassonoids?
Wide shape burrow produced by shrimp typical of littoral deposits (shore face)
48
What are the names of trace fossil communities? (ichnofacies)
Nereites Zoophycos Cruziana Skolithos Scoyenia Glossifungites
49
What trace burrows make up the Nereite ichnofacie?
Spiroraphe Lorenzinla Chondrites Paleodictyon Nereites Cosmorhaphe
50
What are Nereite ichnofacies like?
Absence of vertical burrows Deepwater environments Found in muds (deposited from suspension) Mud and siltstones of distal turbidites
51
What traces make up Zoophycos ichnofacies?
Phycosiphon Zoophycos Spirophyton
52
What are the characteristics of Zoophycos ichnofacies? (distribution, conditions)
Complex fodinichnia Deep traces - Thalassinoides Tiered arrangement Abyssal to shallow continental shelf Might occur in normal background conditions
53
What traces are found in the Cruziana ichnofacie?
Asteriacites Cruziana Rhizocorallium Aulichnites Thalassinoides Chondrites Telchichus Arenicolites Rossella Planolites
54
What are the characteristics of Cruziana ichnofacies? (orientation, environment and position)
Horizontal and vertical burrows Mid and distal continental shelf Below normal wave base (storm activity potential)
55
What traces make up the Skolithos ichnofacies?
Ophiomorpha Diplocraterion Skolithos Monocraterion
56
What are the characteristics of skolithos ichnofacies? (orientation, environment and sediment)
Low diversity vertical burrows Intertidal situations Sporadic sediment deposition (shifting sand and intertidal environments, storm sand sheets and top of turbidity flows)
57
What are the trace fossil ichnofacies thought to be controlled by?
Sediment type Water depth Rate of deposition
58
What is a sub trace fossil community?
Scoyenia ichnofacie Glossifungite ichnofacie
59
What traces make up the scoyenia ichnofacie?
Scoyenia Acorichnus Cruziana Skolithos
60
What traces make up the Glossifungite ichnofacie?
Thalassinoides Bivalve boring Polychaete burrows Rhizocorallium Psilonichus
61
What are the characteristics of Glossifungite ichnofacies? (sediment, environment)
Sediment firm but not lithified (mud/ silt) Low energy salt marshes, mud bars, high intertidal flats or shallow marine)
62
What are the characteristics of scoyenia ichnofacies? (orientation, sediment)
Horizontal (occasionally vertical) Fluvial and lacustrine sediment Aeolian sands and paleosols
63
What are some examples of substrate dependant trace fossils?
Teredolites (wood) Trypanites (limestone)
64
What traces make up the trypanites ichnofacies?
Echinoid grooves Barnacle borings Sponge borings Polychaete worms Bivalve boring Sypuncullid boring
65
What are the controls on distribution of trace fossil communities?
Average grain size of sediment Sediment stability Water content Chemical conditions
66
How does average grain size affect trace fossil community distribution?
Affect sediment ingesting burrowers Organisms require particular sediment size to line burrow Filter feeders avoid fine sediments
67
How does water content affect trace fossil community distribution?
Affects consistency of sediment
68
What are black shales have through to represent on the sea floor?
Soupy sediment cant burrow in
69
How do chemical conditions affect trace fossil community distribution?
Oxygen levels are particularly important, with trace fossils being absent in totally anoxic environments

Earth history and life - 29202 (29 decks)

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