MadSci Network: Earth Sciences
Query:

Re: Is there an 'Old Earth Model' solution for a bat encased in a stalagmite?

Date: Mon Jan 16 14:52:15 2006
Posted By: Gene Marlin, Graduate, Geology
Area of science: Earth Sciences
ID: 1135905746.Es
Message:

Hi Tim,


That fossil bat mentioned at: http://www.nps.gov/cave/tours/lower/bat.htm
isn't really as "shocking" as it might at first seem. The first issue 
that needs to be put to rest is the rate at which speleothems grow. I 
think that for you to be "greatly shocked" you must have approached the 
problem with the assumption that all speleothems, being a geologic 
process, must naturally take very long time intervals over which to grow. 
This seems to be a common misconception people have of geology, that the 
prevailing assumption is that everything happens very slowly. In reality, 
the pure Uniformitarianism of times past has been replaced with the 
realization that occasionally some things can happen very quickly. 
Turbidite deposits, for example, are strata that can be deposited on 
a time scale of hours. Other "events" that can be preserved in the 
geological record are tidal deposits, some pyroclastic (volcanic 
debris) deposits, landslides (though rarely preserved for long), and 
tempestites (storm-deposited strata).    

Speleothems are not produced catastrophically like the above 
examples, but they can be "rapidly" formed in that they don't 
necessarily require geologically important time intervals. For 
example, consider that speleothem growth has been documented in 
historical times, in one instance Treble et. al. (2003) correlated 
annual growth ring trace element concentrations in a speleothem that 
had grown on a boardwalk laid down in 1911 to historical climate 
data. And that is one way in which the age of a speleothem can be 
estimated, by studying thickness of annual layers and comparing them 
to other climatic records. Carbon-14 can be used, as carbon of 
organic origin is leached from the soil horizon into the cave and 
trapped in the growing ornamentation. Other dating methods can be 
used as well, as various techniques are becoming more sensitive at 
quantifying trace element concentrations with progressively 
decreasing disturbance to samples.

One common application is the fine-tuning of the paleoclimate 
record, for example Vacco et. al. (2005) did a study of the isotopic 
variation of oxygen and carbon in a speleothem from the Klamath 
Mountains of Oregon, sampling at about 50-year intervals. They were 
able to identify the Younger Dryas cooling event in the sample and 
were looking for changes in vegetation in response to the climate 
change. The second part of the problem is how long the bat would exist in 
the cave so that it could be preserved. This is another interesting 
feature of caves; they tend to preserve organic material fairly 
well. The statement mentioned in your NPS Internet link that says 
that freetailed bats don't live in the lower cave today, but the remark 
that "You will see their remains throughout the tour" tells me that we 
have plenty of time for the speleothem to encase the bat, since 
presumably the remains of many of his non-encased fellows are commonly 
seen today as well. Another page in their online tour mentions historical 
artifacts found in the lower cave, "including wooden flare handles, 
old matches, nails, rope, and even a pack of Chesterfield cigarettes".  
http://www.nps.gov/cave/tours/lower/hist.htm 

That isn't really remarkable in itself. In Mammoth Cave much of the 
wood from the ca. 1812 saltpetre works is still in good shape, 
although they've been scrounged and moved over the years. I've seen 
one cave recently where there was a newspaper from the 1950s that 
was fifty years old with the dates still legible.  The biggest threat to 
such artifacts other than maybe some microscopic invertebrates are 
people that trample over them. While that bat is very much a curiousity, 
I don't think it does any violence to accepted time frames for speleothem 
formation. 

--Gene Marlin




----------------

Pauline Treble, J. M. G. Shelley and John Chappell. Comparison of 
high resolution sub-annual records of trace elements in a modern 
(19111992) speleothem with instrumental climate data from southwest 
Australia. Earth and Planetary Science Letters 
Volume 216, Issues 1-2 , 15 November 2003, Pages 141-153. Elsevier 
Science Direct search and abstract retrieval used, 
www.sciencedirect.com

David A. Vacco, Peter U. Clark, Alan C. Mix, Hai Cheng, and R. 
Lawrence Edwards. A speleothem record of Younger Dryas cooling, 
Klamath Mountains, Oregon, USA. Quaternary Research 
Volume 64, Issue 2 , September 2005, Pages 249-256. Elsevier Science 
Online search and abstract retrieval used, www.sciencedirect.com

Carlsbad Caverns National Park (website), National Park Service. 
http://www.nps.gov/cave/tours/lower/bat.htm and  
http://www.nps.gov/cave/tours/lower/hist.htm 

 



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