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Isotope geochemistry of crinoids from Burlington-Keokuk Formations: implications for diagenesis

Conference · · Geol. Soc. Am., Abstr. Programs; (United States)
OSTI ID:6611154
Petrographic studies suggest that early calcite cements are present within the intraskeletal pores of crinoids from the Mississippian Burlington-Keokuk Fms. of Illinois, Iowa, and Missouri. Procedures have been developed for analyzing the Sr isotope ratio, Sr and Rb abundances, and C and O isotope values for sample sizes of 2 mg or less. Drilled crinoids have Sr that is more radiogenic (0.70810-0.70845) than Mississippian sea water (0.7076), but generally less radiogenic than whole rock samples (0.7080-0.7089), drilled apatites (0.70880), plucked crinoid grains (0.7085-0.7090), drilled micrite (0.70853-0.71255), or late vug saddle dolomite (0.70967) and calcite (0.70890). Shale layers within the Keokuk Fm. have initial Sr of 0.708 to 0.714. Mass balance considerations suggest that these shales cannot be the primary source of the radiogenic Sr. The variations in C and Sr may reflect various extents of interaction with regional ground waters or brines. The micrite and apatite were apparently more strongly affected by later fluids than were the coexisting calcite cements within the crinoids.
Research Organization:
State Univ. of New York, Stony Brook (USA)
OSTI ID:
6611154
Report Number(s):
CONF-8510489-
Conference Information:
Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Journal Volume: 17
Country of Publication:
United States
Language:
English