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The Lower Cretaceous sediments (mainly limestones with a few
horizons of sandstones and conglomerates) are present south of
Mashhad along the Binalood Mountain range. Petrographic studies
reveal that the carbonate rocks were deposited on a shallow carbonate
platform of ramp type including open-marine, shoal, lagoon and tidal-flat
facies belts. Diagenetic processes include compaction,
cementation, micritization, replacement (silicification), neomorphism
and fracturing.
Oxygen and carbon isotope signatures of the limestones range from
-11.2 to -2.1‰ and 0.2 to 4.3‰ PDB respectively. This variation
reveals meteoric and burial diagenetic environments. Decreasing trend
in the value of oxygen isotopes with increasing the amount of Fe and
Mn as well as decreasing Na and Sr also indicate that these rocks may
have been exposed to the meteoric diagenetic environment too. The
calculated temperature for the ambient water in which calcite was
deposited is about 26 ? C