CAVE STUDIES:

www.cr.nps.gov/history/online_books/glimpses1/glimpses25.htm www.routledge-ny.com/caves/burials.pdf www.burlingtonnews.net/hanion.html www.burlingtonnews.net/mammothcavemummies.html

• Dissolution by streams, groundwater
  
• Eolian erosion
  
  

• Autochthonous: rare
• Allochthonous: primary basis of study (materials from outside cave)

1. Biotic Transport
   • Self
     
   • Predators: Hyenas, Bears, Owls & Hawks, Bees, Neotoma
     
   • Dung: Guano, Extinct animals: RAMPART, Bechan 2, Cowboy
     
   
   
2. Aquatic Transport
   • Deposition: Lacustrine, Fluvial, Crevice Runoff
     
   • Erosion: Ventana Cave
     
3. Eolian Transport
   • Important for rockshelters, caves with strong air flow
     

     FISHMOUTH CAVE, UT

   • Example, Pollen, Volcanic Ash, Sedimentation Rate: 1000 yr/cm
     

     MIDDLE BUTTE CAVE, ID

     
     

• Less Transport and dissociation: burial/preservation in situ
  
• Less Trampling and bone eating: fewer organisms
  
• Less Nutrients and light: less biological activity
  
• Constant Environment
  
  Fewer hydration - dehydration cycles and freeze - thaw cycles
• Aridity: as effective as anoxia or permafrost at retarding biological decay
  Examples: skin, hair, dung, pollen, plant fossils, archeological materials
  preservation poor in wet sediment and deeper (moist) sediment in cave
  In Arid North America 100s of caves studied
  
  
  

1. Aridity
   
   • Regional Climate, local topography, internal runoff channels
     

     VENTANA CAVE

2. Biotic Activity: Trade Off
   
   • TOO MUCH = MIXING, Destroyed Stratigraphy
     
   • TOO LITTLE = NO FOSSILS & NO ¹⁴C DATES
     
3. Sampling Location
   
   • Stratigraphic samples where accumulation thickest
     
     • Near Mouth, Beneath Runoff Crevices
       
     • Within Drip line: so sediment dry
       
     

• Minerals (e.g., uranium) in solution give speleothems their color
  
• Dust layers accumulate when dry, & CaCO₃ not deposited
  
• Sediment layers accumulate during floods (pollen)
  

DATING:

1. "Annual" layers (annual resolution "unproven")
2. radiocarbon dates (TAMS)
   
3. U/Th dates, the uranium is in solution, precipitated without Thorium
   
   ²³⁴U decays to ²³⁰Th, stays in speleothem: range from 350 - 10 Kyr B.P.
   Problem: contamination by clay, on which Th can be absorbed
   
4. Thermoluminscence of mineral inclusions
   
5. Electron Spin Resonance of mineral inclusions
   
6. Paleomagnetism

PALEOCLIMATE:

1. Growth Periods - frequency histograms of dated speleothems
   
   Sea level:
   speleothems can't grow or are erroded under sea water
   encrusted with aragonite after sea fills cave
   
   
   Temperate Regions: growth during interglaciations
   
   • less available subsurface water (water tied up in permafrost)
     
   • less CO₂ from organic decay, results in less CaCO₃ in solution. e.g., Canadian Rockies
     
   Arid Regions: growth during pluvial periods (Harmon & Curl, 1978)
   
   • increased precipitation leads to greater subsurface water
     Travertines in Grand Canyon (Szabo, 1990): Periods of travertine growth coincide with pluvial lake high stands (15,000, 71,000, 111,000, 171,000, 338,000 yr B.P.) (cf. Searles L., Smith, 1984)
   • more vegetation permits more organic decay, greater solution and redeposition of CaCO₃
     
   
   
2. Growth Bands: thicker layers when groundwater greater
   
   
3. Contents of Speleothems
   
   Mineral grains in speleothems
   periods of aridity, active wind transport reflected in mineralogy and grain morphology
   
   
   Oxygen & Carbon isotope studies:
   ¹⁸O/¹⁶O ratios lowest during glacials
   
   • Fractionation during percolation, precipitation.
     
   • Spring Carbonates in Great Basin (Winograd et. al., 1988)
     
     • curve matching and ²³⁴U-²³⁸U, ²³⁰Th-²³⁴U ages
       
     • earlier time scale than marine record for Termination II
       

   "...the Devils Hole chronology is the best we have..." (Broecker, 1992) [link] [link]

   
   Interpreting the δ¹³C curves [graph]
   1. Climate: ¹³C/¹²C ratio reflects the dominant plants photosynthetic pathway
         more negative = cooler & wetter
   • C₃ Plants predominate in cool - wet regions ¹³C -22 ‰
     
   • C₄ Plants characteristic of warm - dry ¹³C -9 ‰
     
   2. Fractionation: lighter ¹²C deposited preferentially in oceanic and terrestrial organic matter
         more negative = more atmospheric CO₂
   
   Pollen Analysis:
   Pollen grains trapped in growing speleothem: e.g., pollen of more mesic savanah species
   (Brook et al., 1989)