Transcript Ichnofossils – Trace fossils

Ichnofossils – Trace fossils
Fossilized Bahavior
There is no branch of detective science
so important and so much neglected as
the art of tracing footsteps.
Sherlock Holmes
Sir Conan Doyle, A Study in Scarlet, 1801
• Biogenic sedimentary structures or
ichnofossils (Greek ichnos, trace)
• Ichnofossils are signs of animal
activities preserved in rocks.
• Ichnology: study of ichnofossils,
involves identifying the activity and
making deduction about the animal
resposible for it.
• Trace fossils made skeletal and nonskeletal organisms.
• Rarely do the tracemarker and the
organisms occur together
• Trace fossils: represent behavioral
response of organisms, and are
controlled by the environments,
substrate consistency, rates of
sedimentation, temperature and salinity.
• PALEOENVIRONMENTAL
RECONSTRUCTION: some ichnofossils
are restriced to particular environment
What are ichnofossils?
• Locomotion (footprints and crawling
trails); Laetoli (Tanzania)
some 3.6 to 3.75 my ago
• Resting and dwelling (suface depression,
burrows and borings);
• Feeding process (tooth marks, grazing
furrows, mining burrows, stomach
contents, gastroliths);
• Faeces (coprolites, faecal pellets)
• Reproduction (nests)
• Use of tools (flint implements)
Classification
• Adopted system of giving each trace
fossil a Linne’s taxonomic name
complete with genus and species. Based
upon morphology of the respective
biogenetic structure.
• There are no ichnofamilies and higher
category.
• Because one organism can produce
several different types of traces, and
several different organisms may leave
the same trace and the same activity
can produce different traces within
different substrate this name gives a
misleading connotation
• One organisms
leaves different
traces
• Same activity done
on different
substrates produce
different traces
(Stratinomic
classification)
• The same behavior of the different
organisms can leave the indentical
traces.
• Comensalisms of two or more organisms
leabves only one trace.
Ichnofossil’s categories
• On the sediment surface (tracks and
trails)
• In the sediment (signs of dwelling,
feeding and locomotion)
Ichnofossils and etholological
classification
• Seilacher (1953) : relation between
traces morphologies and animal’s
behavior
• Behavioral categories are:
• Cubichnia – resting traces, impressions
caused when the animal interrupted its
locomotion for rest and refuge.
• Domichnia – dwelling
traces such as deep
elongate burrows or
excavations that
served as long term
residence of the
animal.
• Repichnia – moving
traces (crawling
motion). They are
continous, elongated
trails with delicate
marks from the leg
motions.
• Agrichnia – farming
traces. Regularly
patterned burrow
system reflecting
permanent dwelling
& feeding behavior.
• Fodichnia – deposit
feeding traces formed
when orgainsm made 3D
burrows, eating the
sediment to digest out
all of the food within it.
Ichnofossils categories:
behaviorlogy
• Fugichnia – signs of forced escape (9)
• Pasichnia – grazing traces (3)¸
horizontal pattern showing that
organism was systematically combing
the surface
What kind of activities represent
these photos?
Marine trace fossils
• Certain types of trace fossils are related to
certain types of sedimentary environments
and depth condition (four regions).
Marine ichnofacies: Intertidal
zone
• High energy zone with a variety of
substrates ranging from rocky
foreshore and sheets of well sorted
shifting sands to more sheltered bays
where muddy snads and silts occur.
Skolithos (Sk) Ichnofacies
• infaunal filter-feeders living in burrows,
vertical or U shaped.
• Skolithos: unknown organisms that lived in
rapidly moving water and shifting sands made
vertical tubes resamble to organ pipe (Cm – K)
• Ophiomorpha: P- rec. (crabs) vertical burrows
with bumpy outer surface, pellets that lined
the burrow are used to reinforce the walls
• Diplocraterion
• The traces are signs of dwelling and
escaping.
Skolithos
Ophiomorpha
Subtidal zone
• Region of moderate to low energy, that
passes to a region unaffecetd by storms
and merges into the bathyal zone.
Cruziana (Cr)
• Cruziana: Trilobites crawling trails (two
parallel grooves separated by median
ridge, common Cm-P)
• Thalassinoides: vertical and oblique
feeding burrows made by crustaceans
• Asteriacites: resting traces
• Rhizocorallium: U shaped burrow with
horizontal attitude (feeding burrow)
Cruziana ichnofacies: the most diverse ichnofossil communities,
Repinchia (Cruziana, Aulichnites), Cubichnia (Asteriacites),
Fodichnia and Domichia (vertical burrows Thalassoinoides)
Asteriacites
• Cubichnia of sea-stars
Thalassinoides (Fodichnia and
domichnia)
• Complex 3D network of cylindrical burrows that form
an irregular web of crisscrossing tubes.
Rhizocorallum
• Animal moved horizontally through the
sediment in a systematic feeding
pattern.
Bathyal: Zoophycos (Z)
• Region (continental slope) of low energy
(below storm wave base) of muddy fine sands,
silts and muds rich in organic matter
• In place the oxygene level may be low.
Depost-feeders graze the surface or
mine along shallow tunnels parallel to
the substrate
Zoophycos
• Zoophycos ichnofacies indicates lowered
oxygen levels and abundant organic
material in the sediment in quiet water
settings.
• Zoophycos is not depth indicators
(occasionally occurs in the Cruziana and
Nereites ichno-region)
Abyssal: Nereites (N)
• Deposits are very fine (pelagic) muds
associated with turbidites
• Condition are though at times disturbed
by turbidity currents.
• It is dark, pressure is high, uniformly
cold. Scavengers and deposit fedders
live there.
• Traces include crawling, grazing and
shllow feeding-cum-dwelling traces
Nereites ichnofacies: horizontal
burrows in the muddy bottom
• Nereites burrows are elaborate and
complex in design.
• They indicate a systematic searching
for food.
• Meandering (Nereites, Neonereites,
Helminthoides), spiral (Spirorphaphe),
honeycomb (Paleodictyon) structures,
and dendritic systems are present.
Nereites ichnofacies
Paleodictyon
Nereites
Ichnofacies: oxygen
Bioturbation and bioerosion
• Bioturbation: biogenic activities in sediments
depend on rate of sedimentation, rate of
erosion, population density of organisms,
degree of physical energy, supply of
nutrients…
• Epiliths vs. Endoliths
• Golubić (1981): active and passive bioeroders
and, those that inhabit natural cavities
• Endoliths had a great success during the
Mesozoic
Trypanites (Tr), Glossifungites (G) and
Teredolites (Te)
• Controled by the nature of the substrate, no depth
dependant (known from a variety of depths).
• Glossifungites from firm, unlithified
substrates common in in coastal shallow
water or in deep submarine channels
• Trypanites are dominchia formed in
fully lithified substrates by boring
organisms . Hard substrate include
reefs, rocky coastlines, beachrocks and
hardground surfaces.
• Teredolites: burrows in wood. It occurs
wherever the wood is exposed to water
(lakes, rivers , oceans)
Marginal marine region and
trace fossils
• Coastal sand dunes, washover fans and
supratidal flats
• Psilonichus ichnofacies: J-, Y- or U-shaped
burrows formed by spiders, horizontal
tunnels formed by insects and tetrapods and
plant root traces.
Continental trace fossils
• Scoyenia (contiental red beds of lakes, rivers)
ichofacies made of variety of small,
horizontal feeding burrows, sinuous crawling
traces, tracks and trails of different kind of
vertebrates
Continental (Terrestrial) trace
fossils
• A few environments in which trace
fossils are likely to be preserved
• Low-lying areas of river flood plains,
deltas and lakes, volcanic area (imprints
in damp volcanic ash, quickly covered by
another ash-fall).
Continental trace fossils
• The most common are locomotion traces.
• Traces of dwelling and feeding are sometimes
preserved.
• Evidence of feeding is restricted to fossil
leaves with edge chewed by insects or
caterpillars.
• Animal track-markers are: insects and
vertebrates (fish, amphibia, reptiles, birds
and mammals)
• Bones which have been gnawed by
rodents or carnivores
Coprolites
Nests, but eggs are not
ichnofossils
Animal locomotion
•
1.
2.
3.
4.
5.
From trails and the individual imprints
we deduce the following:
Quadrupeal or bipedal animal
Full foot or digitigrade walking
plantigrade
Shape of foot and number of digits
Claws or hoofs
General indication of size
Animal locomotion
•
1.
2.
3.
4.
5.
From trails and the individual imprints
we deduce the following:
Quadrupeal or bipedal animal
Full foot or digitigrade walking
plantigrade
Shape of foot and number of digits
Claws or hoofs
General indication of size
Animal locomotion
•
1.
2.
3.
4.
5.
From trails and the individual imprints
we deduce the following:
Quadrupeal or bipedal animal
Full foot or digitigrade walking
plantigrade
Shape of foot and number of digits
Claws or hoofs
General indication of size
Animal locomotion: trackways
•
•
•
•
.
Weather animal was moving slowly or running;
Weather animal was alone or in herds;
The direction of animal moving
How did animal move (giat type: the pace or
the trot). Biomechanical analysis of the
trackways reveal the gaits employed by
animals: moving both limbs on the same side
of the body in union vs. moving diagonally
opposite limbs in union
• The pace
The trot
• The size of footprint is rough guide to
the size of animal which made them.
• The distance between successive prints
madeby the same foot, the STRIDE,
may give an idea of the speed at which
the animal was moving
L RL R
R
R L
Acrocanthosaurus
L
R
Footprint Evidence
R
L
R
RL
L
R
R
L
L
R
R
L
Glen Rose Limestone, Early K, Texas
Sauroposeidon
Animal tracks
What we have learned from
terrestrial ichnofossils?
• Anatomy of the foot
• Increased efficiency of locomotion by
changes in foot and limb structures
• Vertebrates: changes from sprawling,
undulating movements on four legs with
tail trails, to developmet of speed
shown in horse.
Laetoli (Tanzanija)
The history of oldest
hominidal footprints
,
Trace fossil through time
1. The oldest are of the Proterozoic age
2. Diversity of ichnofossils increses by
time.
3. Ichnofossils penetrated deeper and
deeper into the sediments (from 0.5
to 1 m in the Permian, more then 1 m in
the Cretaceous)
4. The oldest terrestial ichnofossils are
of the Ordovician (Early Devonian age)
5. Ichnofossils show migration from
nearshore area into basin.