Question
• What are the two major categories of biostratinomic agents?

Types of Fossil Assemblages

• Biocoenosis (life assemblage)
• Thanatocoenosis (death assemblage)
• Taphocoenosis (fossil assemblage)
(how do you tell the 3 apart?)
• life orientations -- fragile organisms well preserved in life orientation - in situ
• refugee communities -- escape burrows
• Time averaging

Taphonomy - the study of fossil Preservation

• 3 subdivisions
• Necrology - how did it die?
• Biostratinomy - sedimentary and biological interactions
• Diagenesis - types of preservation

Biostratinomy
• Many German contributions
• Can apply uniformitarian/actualistic approach
• decay, disarticulation, disintegration (the 3 D’s)
• Biological and sedimentological factors

Biostratinomy - biological
• biological factors
• predation
• bacterial decay
• Scavengers
• borers and encrusters
• biological factors don't end with burial - bioturbation
• biological destruction inhibited by low dissolved oxygen

Biostratinomy
• What might prevent biological destruction?

Biostratinomy - mechanical
• mechanical factors -- breakage and abrasion caused by environmental disturbance

- high energy environments

- Chave (1964) tumbling experiments
- Voorhies (1969) flume experiments Biostratinomy - mechanical
• Mechanical destruction = the result of
– Transport
– Chemical dissolution
– Burial
• Corrassion

Biostratinomy - chemical
• chemical factors -- dissolution
- skeletal dissolution can occur at sed/water interface or down under sediment
- different skeletal materials have different stabilities in different environments

Biostratinomy - transport
• post-mortem transport

• very few body fossils are preserved in situ
• some fossils can't be preserved in life position
• differential transport (teeth versus bones)
• most sessile, benthic organisms don't get transported too far……how can you detect transport?

Biostratinomy - transport
• Detecting post mortem transport
• find a fossil in a 'wrong' depositional environ
• see signs of breakage and disarticulation or sorting & orientation

Biostratinomy - burial
• Rates of burial
• burial is usually slow and gradual
• when really slow can get a lag or time-averaged assemblage or a tapho assemblage

Biostratinomy - burial
• rapid or catastrophic burial can happen due to storms, turbidites, volcanic eruptions; can lead to:
• whole community at one point in time preserved together = Lagerstatten

Rules of Taphonomy
1. Hard Parts
2. Rapid Burial
3. from life to death assemblages = change in community structure

Rules of Taphonomy (cont.)
4. Fossil assemblages may consist of a) autochthonous, b) paratochthonous, or c) allochthonous remains
4. 5. Taphonomic loss is most severe in shallow-marine environments and most terrestrial environments

Rules of Taphonomy (cont.)
6. Information loss in terrestrial environments is largely the result of transport, disarticulation, sorting, and breakage by water, predators, scavengers, and trampling.
7. Taphonomic processes = time averaging of fossil assemblages

Rules of Taphonomy (cont.)
8. Taphonomic processes = information gain
9. Lagerstatten = “snapshots” in time