Dear Bill
I think you are in the right track. Thin section and CL will be the best
way to identify recristalization, and dissolution (present and previous).
Staining is not very sensitive.
There is one more thing you have to be aware that sometimes CL zoning might
not represent isotopic zoning.
In other words you can find the same isotopic signature in different cement
bands.
I am sure you knew this before
Regards
Renee
UCSB

To add to Bill's comments, if you're d18O amplitudes are decreasing with
>age, it might be due to increasing time averaging with decreasing growth rate.
>
>Cheers,
>
>--Donna
>
>
>At 12:51 PM 5/12/00 -0500, you wrote:
>>Dear Listmembers,
>>
>>We are looking at shallow water marine Miocene clams to determine growth
>>rates from O-18 measurements determined every mm.  We seem to get pretty
>>good annual "wiggles" but the magnitude of the seasonal signal changes as
>>the specimens get older. Is it real or alteration in the older thinner
>>parts of the shells?
>>
>>Is there a consensus on what the best method of determining carbonate
>>alteration might be in Miocene to Cret age samples of bivalves?  We are
>>discussing thin sectioning, acetate peels & SEM analysis, or staining with
>>Feigl's solution (a mixture of AgSO4, MnSO4 and water) which stains calcite
>>white and aragonite black?  Are staining techniques sensitive enough?
>>
>>Bill Showers
>>
>>----------------------------------------------------------
>>William J. Showers
>>Dept. of Marine, Earth, & Atm Sciences
>>1125 Jordan Hall
>>North Carolina State University
>>Raleigh, NC  27695
>>
>>(919) 515-7143 - voice
>>(919) 515-7802 - fax
>>[log in to unmask] - email
>>
>>"Never be afraid to try something new. Remember: Amateurs built the
>>ark.  Professionals built the Titanic."
>>
>_________________________________
>Donna Marie Surge
>Department of Geological Sciences
>University of Michigan
>425 East University
>1022A CC Little Building
>Ann Arbor, MI  48109-1063
>Office: (734) 647-5732
>Lab:    (734) 763-9381
>Fax:    (734) 763-4690