Ordovician meteoric carbon and oxygen isotopic values: implications for the latitudinal variations of ancient stable isotopic values

Columnar and clear blocky calcite cement from a Middle Ordovician carbonate succession in east Tennessee is interpreted as meteoric in origin. Columna r and clear blocky calcite from this succession does not show extremely lar ge C-13 depletions reported from meteoric phases of younger rocks. Meteoric fluid delta(18)O values calculated from clear blocky calcite are congruent to 2 to 3 parts per thousand more negative than approximately coeval sea w ater; a relationship typical of modern, low-latitude, coastal meteoric wate r. Comparison with meteoric delta(18)O values from Ordovician units elsewhe re suggests that the geographic distribution of these values may be broadly similar to that observed today. Therefore, we tentatively suggest that geo graphic distribution of meteoric delta(18)O values during both icehouse and greenhouse eras are similar. Published by Elsevier Science B.V.