Abstract

Calcitized dolomite (dedolomite) occurs along a prominent disconformity in the Upper Martin Dolomite of north-central Arizona. Petrography, stable isotopes and field associations were used in an effort to constrain the origin and timing of the dedolomite. 18O/ 16O and 13C/ 12C ratios of the dedolomite show significant depletions relative to unaltered dolomite above and below the disconformity. This depletion trend and dedolomitization are interpreted to have resulted from (a) subaerial exposure and an influx of 18O-depleted meteoric water or, (b) descending groundwater from paleoaquifers in the Lower Pennsylvanian. Sedimentary features consistent with a subaerial exposure include detrital-filled desiccation cracks and an accumulation of iron-rich residual clays. Features suggestive of dedolomitization by paleogroundwater include calcite-replaced evaporite nodules and the great volume of water inferred to have been associated with extensive continental, Lower Pennsylvanian karstification of overlying (younger) carbonate units.

Full Text
Published version (Free)

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call