7.1 Taphonomic Processes

What is taphonomy

the study of process of preservation (in fossils) by ways in which material moves through the biosphere into the lithosphere and how they affect information in fossil record

it is critical to recostruct anatomy and ecology of fossil record

Describe the taphonomical processes from a living organism to the fossil record

necrotic processes (immediate burial)

OR

biostratinomy (delayed burial and biological reworking)

THEN

diagenesis

What are nectrotic processes

the death and decay of soft tissues

What is biostratinomy

the physical, chemical and biological changes occurring before burial, e.g.:

breakage, transport, disarticulation

What is diagenesis

organisms being changed by post burial changes, e.g.:

flattening, dissolution

List the taphonomic processes

• disarticulation

  • seperation

• fragmentation

  • breakage

• abrasion

  • from movement

• bioerosion

  • boring and burrowing

• corrosion and dissolution

  • tissue loss from acid

• flattening

  • comapction

• chemical diagenesis

  • post-depositional chemical alteration

Describe how taphonomical process change over time

processes do not happen in isolation and often overlap over time scales ranging from minutes to millions of years

necrotic processes → biostratinomy → diagenesis → metamorphism

What are assemblages and assemblage fidelity

assemblage = concentation of fossils

fidelity = how well it represent life, how much information has been lost due to taphonomy processes

What are autochthonous assemblages

fossils preserved as they were in life from a particular moment, accurate picture of how other organisms lived together as it is a snapshot in obrution deposites

Ediacaran fossils = autochthonous

What are allohthonous assemblages

where fossils have been transported, sorted and reworked

shows time averaging so can show organisms which may not have coexisted in same place at the same time

Rhaetic Bone Bed = allochthonous

What can this orientation tell use about current type and direction

unimodal and imbricated = unidirectional flow like a river

What can this orientation tell use about current type and direction

biomodal and stacked = oscillatory flow like wave action

How can we determine transport in assemblages

assemblage → less bivalve = more transport

fragmentation → more fragmentation = longe transport

packing/ sorting → all together ould suggest transported by water for dense packing

What is concetration and conservation Konzentrat-Lagerstätten deposits

concentration = exceptional concentrations of fossils e.g. bones and shells

• Jurassic ammonites

• Miocene Rhinos

conservation = exception preservation e.g. soft tissue

• Cambrian Burgess Shale

• Miocene amber