[NHCOLL-L:4725] Re: Salvage of Thawed Soil Cores?

[Steve Halford]

>From our resident palynologist:

Steve:
   Freezing and then thawing will "dewater" organic sediments, and they will
be more crumbly with some disturbance of fine sediment structures like
laminations.  However, the pollen and plant remains should still be fine,
and the sample can be refrozen or cut up into bags for later analysis.  One
potential problem from the meltwater inside plastic liners is that movement
of the cores will cause sloshing of water (with pollen)and the outer parts
of the core may be contaminated.  Samples should then only be taken from the
inside portions of the core.  Good luck


Rolf W. Mathewes
Professor and Associate Dean of Science
Department of Biological Sciences
Simon Fraser University
8888 University Drive, Burnaby, B.C.V5A1S6
Phone: 778-782-4472
email: mathewes at sfu.ca

On Mon, Mar 1, 2010 at 3:51 PM, Clevenger, Liz <lclevenger at presidiotrust.gov
> wrote:

>  Dear Listers –
>
>
>
> We have a series of soil cores from the bottom of a local lake that have
> been stored in a freezer in our facility for a number of years. We
> discovered today that the freezer they are in has malfunctioned, and
> currently registers a tropical 85 F inside. There is standing water at the
> bottom of the freezer and in the plastic core sleeves themselves; everything
> is thoroughly defrosted and warm to the touch. The last time we checked the
> freezer was at least a month ago, and it appeared to be functioning normally
> at that point.
>
>
>
> I am wondering whether there is any utility in attempting to re-freeze the
> cores or whether they are beyond salvage at this point. They have been
> curated primarily for their biological record (e.g. pollen) rather than
> their geological or stratigraphic record, which is one of the reasons they
> were frozen in the first place. Because this freezer is second hand, it is
> highly possible that this kind of defrost may have happened before without
> our knowledge.
>
>
>
> Any advice or resources would be helpful. Thanks in advance.
>
>
>
> aloha
>
> ~Liz
>
>
>
> Liz N. Clevenger, MA, RPA
>
> Curator of Archaeology
>
> (415) 561-5086
>
> lclevenger at presidiotrust.gov
>
>
>
>
>
>
>
> Presidio Archaeology Lab  |  www.presidio.gov/history/archaeology  |
> (415) 561-ARCH  info  |  (415) 561-5089 fax
>
> The Presidio Trust  |  P.O. Box 29052, San Francisco, CA 94129
>
>
>
> Please consider the environment before printing this e-mail.
>
>
>
>
>



-- 
Steve Halford (halford at sfu.ca)
Museum Technician
Department of Biological Sciences
Simon Fraser University
8888 University Drive
Burnaby, B.C. Canada               Phone
V5A 1S6                                  778-782-3461
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