Nonmonotonic variation of seawater [sup 87]Sr/[sup 86]Sr across the Ivorian/Chadian boundary (Mississippian, Osagean): Evidence from marine cements within the Irish Waulsortian Limestone
- State Univ. of New York, Stony Brook (United States)
Detailed analysis of compositionally unaltered marine fibrous cements (MFC) from a single core through the Mississippian irish Waulsortian Limestone indicates that the variation of seawater [sup 87]Sr/[sup 86]Sr is nonmonotonic across the Ivorian-Chadian boundary. This nonmonotonic variation has not been recognized by previous studies. Furthermore, marine cement yielded [sup 87]Sr/[sup 86]Sr ratios lower than previously reported values for the Ivorian-Chadian (sagean). Marine fibrous cements are interpreted to be compositionally unaltered on the basis of nonluminescent character and stable isotope (C, O) composition comparable to previous estimates of Mississippian marine calcite. The isotope chemistry (C, O, Sr) and cathodoluminescent character of the marine fibrous cements therefore remained intact during their conversion from high-Mg calcite to low-Mg calcite + microdolomite, a conversion that probably took place in marine water during precipitation of Zone 1 calcite cement, the oldest non-MFC cement. High stratigraphic resolution was obtained by restricting the sample set to a single core, 429 m long, thereby eliminating chronostratigraphic correlation errors. The core is estimated to represent about 9.8 million years of Waulsortian Limestone deposition. The maximum rate of change in seawater [sup 87]Sr/[sup 86]Sr is [minus]0.00012/Ma, comparable in magnitude to Tertiary values. The authors data document the presence of fine-scale seawater [sup 87]Sr/[sup 86]Sr modulations for the Ivorian/Chadian, in contrast to the previously published monotonic seawater [sup 87]Sr/[sup 86]Sr curve for this interval, and emphasize the importance of well characterized intraformational isotopic baselines.
- DOE Contract Number:
- FG02-85ER13416
- OSTI ID:
- 6524239
- Journal Information:
- Journal of Sedimentary Petrology; (United States), Vol. 63:3; ISSN 0022-4472
- Country of Publication:
- United States
- Language:
- English
Similar Records
Diagenesis of skeletal and nonskeletal components of Mid-Cretaceous limestones
Regional cement stratigraphy and diagenetic history of Waulsortian Limestones, eastern Midlands, Republic of Ireland
Related Subjects
CALCITE
CATHODOLUMINESCENCE
ISOTOPE RATIO
LIMESTONE
GEOCHEMISTRY
PETROGRAPHY
SEAWATER
WATER CHEMISTRY
AGE ESTIMATION
CARBONIFEROUS PERIOD
DRILL CORES
GEOLOGIC FORMATIONS
IRELAND
MINERALOGY
STRONTIUM 86
STRONTIUM 87
ALKALINE EARTH ISOTOPES
BETA DECAY RADIOISOTOPES
CARBONATE MINERALS
CARBONATE ROCKS
CHEMISTRY
DEVELOPED COUNTRIES
ELECTRON CAPTURE RADIOISOTOPES
EUROPE
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
GEOLOGIC AGES
GEOLOGY
HOURS LIVING RADIOISOTOPES
HYDROGEN COMPOUNDS
INTERMEDIATE MASS NUCLEI
ISOMERIC TRANSITION ISOTOPES
ISOTOPES
LUMINESCENCE
MINERALS
NUCLEI
OXYGEN COMPOUNDS
PALEOZOIC ERA
RADIOISOTOPES
ROCKS
SEDIMENTARY ROCKS
STABLE ISOTOPES
STRONTIUM ISOTOPES
WATER
580000* - Geosciences