Martin,
A student provided me with some references during his class presentation
on whitings:
Lowenstam and Epstein, 1957. J. Geology 65: 364-375
Shinn et al., 1989. Whitings: a sedimentological dilemma, J. Sedim.
Petrol 59: 147-161.
Both I believe present isotopic data on the aragonite needles which
characterize the phenomenon.
Regards,
Ian Clark
Geology
University of Ottawa