1. Taphonomy
Taphonomy – everything that happens to an organism after death and before study.
Conversion of Biocenosis to Thanatocenosis yields a “bias” in the fossil record. Population Dynamics – rates/conditions of birth, growth, death – determine the translation. What does a graveyard tell us about life?
Fossil assemblages are Time Averaged

2. Recruitment (birth) Growth Death
Generally seasonal (may be localized for vagrant taxa)
Larval stages rarely preserved
Infant mortality usually extremely high
Larvae/young recruits may be in a different niche from adults
Growth
Initially very rapid, often declines with age
Early stages may be destroyed (resorbed)
Growth may be seasonal/environmental
Molting leaves instars
Death
Mortality is usually age/season/environment dependent
Type of mortality may determine preservability
Mass kills are uncommon

3. DESTRUCTION OF REMAINS
Thanatocoenosis to Taphocoenosis
Biological
Bacterial decomposition – reduced O2 enhances preservation
Fungal decomposition retarded by acids
Organic-rich parts attacked first
Bioerosion/Disarticulation/Breakage results from predation and scavenging

4. DESTRUCTION OF REMAINS
Thanatocoenosis to Taphocoenosis
Chemical
Acids produced during decay of organics may dissolve mineralized elements
Bicarbonate released during decay may aid in fossilization
Many mineralized hard parts are unstable/metastable in native waters – leading to dissolution, mineral conversion, or ppt of new mineral species

5. DESTRUCTION OF REMAINS
Physical
Disarticulation
Fragmentation
Abrasion
Transport and sorting – look for transport fabrics
Keep in mind, some fossils in assemblage may have different history than the rest

6. BURIAL
Burial in sediment can retard destruction by reducing access to organisms and active chemicals. Will also preserve an impression of whatever remains.
Required burial rates are at odds with long term average sedimentation rates (few cm’s/kyr), suggesting most fossils are buried episodically.
Obrution – fossil assemblage preserved by very rapid burial – very rare

7. Mechanisms of burial Normal sedimentation Storm Deposits
Lag deposits on unconformities
Grass bed blowouts
Landslides, -flows, slumps
Mixing through bioturbation
Burial through life habit
Look for in situ (non-gravimetric) orientation, sorting, breakage, abrasion, surrounding sediment.