Re: U of South Carolina Releases Topper Radiocarbon Dates

From: Daryl Krupa (icycalmca_at_yahoo.com)
Date: 11/29/04 

Date: 28 Nov 2004 20:40:14 -0800

Eric Stevens <eric.stevens@sum.co.nz> wrote in message news:<ssrhq0hpln3fqgg3qmtfi9lg7027iil2ln@4ax.com>...
> On Sat, 27 Nov 2004 13:57:54 GMT, Philip Deitiker
> <Donevenask@worlnet.att.net> wrote:
>
> >icycalmca@yahoo.com (Daryl Krupa) says in
> >news:c70365ef.0411262320.52358a2c@posting.google.com:
> >
> >> Beaudoin, A. B., M. Wright and B. Ronaghan, 1996.
> >> Late Quaternary Landscape History and Archaeology in the
> >> "Ice-Free Corridor": Some Recent Results from Alberta.
> >> Quaternary International, 32:113-126
> >>
> >> Zo, if the dominant vegetation at the Topper site during
> >> the
> >> mid-Wisconsinan interstadial was subject to frequent
> >> intensive fire distubance, then the lack of humic horizons
> >> might be explained by conditions tending to act against the
> >> chance of preservation of surface organic material.
> >
> >Humis can be lost from soils that are aerobic to great depth
> >over time. For example very sandy soils with no silt and large
> >grain sizes fill during wet periods and aerate upon drying
> >pumping air deep into the soil. Very clay like soils with lots
> >of soils and for example river wash or oxbow branchs which
> >collect leaves and debree accumulate rich organic clays that
> >become water impermeable blocking the flow of oxygen and
> >preserving the nature of the soil.
> > Something that might make an anoxic subsoil aerobic is the
> >cutting of a creek or catastrophic erosion nearby, such a
> >process would favor rain water going through the soil versus
> >over the top. Repeated soaking and dry from both the top and
> >sides will cause deorganification of the soil causing organic
> >material to be lost. Most soils are protected from this because
> >soils rarely loose moisture past a certain depth (below a meter
> >or so) and maintain 100% saturation beyond a certain depth.
> >However in hilly areas this is certainly not absolute.
> > Whether the topper site has such sandy soil with large grain
> >beach like sand with little intractable clay would be of
> >concern.
>
> Is it the presence of oxygen or the absence of moisture which is the
> problem?

  For preservation of humic material, oxygen is the problem.
  Without oxygen, the organic molecules cannot be oxidised.
  However, there should still be some mineral staining related to
eluviation and illuviation in lower soil horizons that might
allow some stratigraphic interpretation.
The major problem with the lack of humic staining at depth at the
Topper site is that under the modern surface we can see several cms
of humic staining.
  Thus we must wonder why we do not see paleosol-related humic
staining, and then wonder what this means in relation to the
sedimentary history of the site.

  I have a better URL for Saskatoon Mountain hilltop dune sands:

http://www.pinetreeline.org/photos/belodg/belod225.jpg

  Note the paleosols exposed in the cut at the left, which show
both humic staining and charcoal.
  This is a very-well-drained site.
  The dune sands were deposited between 10,000 and 5,000 BP.
  There has been ample time for oxidation of the organic material.
  It has not noticeably oxidised.

  Certainly the conditions at the Topper site would be different,
at least because of the generally higher temperature range there.
  Charcoal has been found at depth.
  I fear that Philip's dryness-means-no-preservation-of-'himis'
hypothesis is too simplistic to be readily applied to the Topper
site.
  Lack of oxygen explains why peat bogs preserve organic material,
but presence of oxygen does not explain lack of organic material
in dune sands.

  I still prefer my catastrophic-surface-oxidation hypothesis.

Daryl Krupa

Relevant Pages

  • Re: U of South Carolina Releases Topper Radiocarbon Dates
    ... >>preserving the nature of the soil. ... The major problem with the lack of humic staining at depth at the ... Topper site is that under the modern surface we can see several cms ... The dune sands were deposited between 10,000 and 5,000 BP. ...
    (sci.archaeology)
  • Re: U of South Carolina Releases Topper Radiocarbon Dates
    ... >>preserving the nature of the soil. ... The major problem with the lack of humic staining at depth at the ... Topper site is that under the modern surface we can see several cms ... The dune sands were deposited between 10,000 and 5,000 BP. ...
    (sci.anthropology)