Re: U of South Carolina Releases Topper Radiocarbon Dates

From: Eric Stevens (eric.stevens_at_sum.co.nz)
Date: 11/27/04 

Date: Sun, 28 Nov 2004 10:27:48 +1300

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?

Eric Stevens

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