POLLEN PRESERVATION

Pollen grains vary in their resistance to degradation. If decay has taken place, the pollen abundances are different from that which was originally deposited.

The Study of Deteriorated Grains:

1. indicates the amount of information lost if fossil spectrum too different, can't interpret
2. can indicate the history of the pollen grains

FACTORS OF PRESERVATION

POLLEN PRESERVATION = f(W,E)

1. The pollen Wall

   Grains with thin walls (very little sporopollenin) tend not to be preserved. e.g., Aquatic Pollen such as pond weed (Potamogeton)

   In order of increasing resistance to deterioration (Sangster and Dale): Maple, Hazel, Alder, Oak, Ash, Cattail, Willow, Birch, Elm, Pine.

2. The Environment of deposition

   Acidic, anoxic, abiotic environments with constant temperature and moisture are best.

Deterioration classes indicate the history of the pollen:

1. DEGRADED
   Subaerial oxidation (particularly before final sedimentation)
   • herbarium sheets
   • surface samples
     
     degraded grass, AZ:AA:10:22, Pima Co., AZ
     
     degraded Compositae, AZ:AA:10:22, Pima Co., AZ
2. CORRODED
   Biological oxidation
   • fungi = rounded holes
   • bacteria = "etching", sculpturing gone
   • some bats, insects "EXINASES" sculpturing gone
     
     corroded fern, Las Flores, CA 759 cm
     
     broken and corroded Pseudotsuga Hunters Ridge, CA
     
3. CRUMPLED
   
   • Diameter / Wall Thickness Ratio
     e.g., Poplar, Sedge
   • Drying of sediment
   • Compaction of sediment
     
     crumpled grass, Las Flores, CA 1153 cm
4. BROKEN
   
   • Transport
     • Alluvial transport: abrasion of some grains
     • Lake surface transport: broken Pine grains shores
   • Wetting-Drying Cycles (Campbell & Campbell, 1994)
5. HIDDEN
   
   • fine organic matter: surface samples, archeological samples
   • charcoal: archeological sites, some lakes
   • palynomorphs: (e.g., algal spores) some lakes
   • some feromagnesian minerals: some lakes (removed with dilute HNO₃)
   • colloids: inorganic samples from arid environments (removed with dilute HNO₃, KOH)
     
     pine containe pyrite crystals, John Wayne Marsh, Ca 190 cm
     
     mixed pollen clump (turd) pine, ambrosia, Cheno-Am, San Nicholas Island, surface

METHODS for recording deteriorated grains

1. Record only those grains too poorly preserved to identify (UNIDENTIFIABLE CATEGORY)
2. Record preservation of all grains (too much work)

3. Note preservation of 1 (2?) common types

RELIABILITY OF DATA

• <= 25% DETERIORATED: acceptable for archeological samples
• <= 10% DETERIORATED: is acceptable for lakes and bogs
• When > 10% are deteriorated RECOGNIZABILITY becomes an issue
  • easily recognized: Chenopodiaceae - Amaranthus, Compositae
  • hard to recognize: rare types
• Poorly-preserved samples have FEWER POLLEN TYPES
  Suspect poor preservation if fewer than 15 pollen types present in 300 grain count
• SÁNCHEZ-GOÑI (1994) proposes criterion: sample NOT RELIABLE if types < 20, sum < 100

Deteriorated pollen should be included in POLLEN SUM.

Exclusion results in bias in favor of well-preserved types.

REFERENCES

Bright, R.C. 1981. Pollen in high-mountain snow, western United States. Striae: 14:55-57.

Campbell, I.D., and C. Campbell. 1994. Pollen preservation: experimental wet-dry cycles in saline and desalinated sediments. Palynology 18:5-10.

Cushing, E.J. 1964. Redeposited pollen in late-Wisconsin pollen spectra from east-central Minnesota. Amer. J. Sci. 262:1075-1088.

Delcourt, P.R. and Delcourt, H.R. 1980. Pollen preservation and Quaternary environmental history in the southeastern United States. Palynology 4:215-231.

Havinga, A.J. 1974. An experimental investigation into the decay of pollen and spores in various soil types. pp. 446-479 in J. Brooks et al., eds, SPOROPOLLENIN Academic Press

O'Rourke, M.K. The implications of atmospheric pollen rain for fossil pollen profiles in the arid Southwest. Ph.D. dissertation, Univ. Arizona.

Sánchez-Goñi, M.F. 1994. The identification of European upper palaeolithic interstadials from cave sequences. AASP Foundation Contribution Series 19:161-181.

Scott, L. and S.K. Srivastava. (in press) Reworked cretaceous palynomorphs in late quaternary deposits from central Colorado, U.S.A. Pollen et Spores.

Sangster and Dale. 1961. Pollen preservation. Can. J. Bot Vol. 39.