Vertebrate Diagenesis - Soils
• For environments such as floodplains - soil formation is an important consideration (early mineralization or dissolution)
• Soils form in situ
• What are soils?

Soils
-> the regolith or pedosphere (unconsolidated sediments):
soil = upper part of the regolith or pedosphere that supports life
A. Components = what is in soil…..
1. Sand, silt and clay
2. Organics (litter & humus)
3. H2O & nutrients

Controls => what determines how much or how fertile a soil is?
1. substrate : residual vs. transported soils
->controls texture and amount of nutrients
2. duration: controls soil maturity-> amount and quality

3. Climate: most important factor=> soil type

4. Topography: slope angle => gravity
aspect = amount of sunlight.......
5. Vegetation - plant types

Soil profile: * soil horizons.......

1. O-horizon => organics (litter and humus)
2. A1& A2-horizons => zone of leaching:
O+A = topsoil
3. B-horizon => zone of accumulation: subsoil
4. C-horizon => broken up parent material (bedrock)

=> Detailed Soil types

United States = 12 major types “Soil Orders of the
Seventh Approximation” - 12,000 total types
- Based on soil forming factors influence on horizons

Soil types: climate
Temperate = alfisol & mollisol: moderate leaching of Fe&Al from A: good accumulation of humus..…acidic, early mineralization

Arid = aridosol: little leaching in A: evaporation=> precipitation of calcite= caliche: poor input of organics - alkaline, clacite nodules

Tropical = oxisol: thorough leaching in A: left with insoluble Fe&Al - oxides: little or no humus=> decay in the tropics is very efficient....…
- very acidic - dissolution

Ancient Soils - indicators of past climate
- Problems - diagenesis alters components and horizons
- recognition - texture & color
- identifying components: Example: Caliche Nodules
- Fossils: root traces, trace fossils
- associated with major unoconformities

Soils and Taphonomy
• Assumption = preservation always poor
• Bioturbation and compaction
• Ph - Eh conditions
• Acidity and oxidation
• Mineralization and dissolution
• Where are plants best preserved? Why?

Soils and Taphonomy
• Well drained soils = acidic and oxidizing
• Waterlogged soils = reducing
• Alkaline soils - arid conditions
• Some of the best preserved bone beds -
– Documented in alkaline soils
• Teeth?

Soils and Taphonomy
• Diagenesis and soil formation
• Soils evolve through time
• Young soils
• Floodplain - entisol
• Leaching - inceptisol
• Horizon development
– Utisol
• Nutrients used up
– Spodisol