Stratigraphic Patterns, Sedimentology and Diagenesis of Capitan Backreef Strata, Permian, Guadalupe Mnts, New Mexico

Abstract

Capitan backreef strata, Yates Formation, are characterized by six cycles, each with a lower siliciclastic and an upper carbonate unit. The factors controlling the deposition of these packages remain controversial. Traditional sedimentary and stratigraphic approaches have been integrated with diagenetic events to understand the main controls on the genesis of these cycles. Syndepositional and syn-unconformity diagenetic features are: (1) marine calcite or aragonite cementation, (2) dissolution of metastable mineral phases, and (3) dolomitization (both replacive and primary precipitate). Geochemistry of dolomites is consistent with evaporation-concentrated and slightly reducing marine waters. Meteoric calcite cements were not found associated with the subaerial exposure surfaces at cycle tops in shelf strata. Arid climate probably prevented the establishment of stable freshwater lenses. Postdepositional diagenesis includes meteoric and shallow burial calcite cements, dissolution vugs, kalinite, and vadose calcite cements. Combination of sedimentologic and diagenetic studies of Guadalupe Mountains outcrops suggests that sea level fluctuations probably were responsible for the deposition of cyclic strata and syndepositional diagenetic features. Relative sea level falls exposed parts of the shelf driving dolomitizing fluids through shelf strata. Relative sea level rises flooded the shelf and deposited subtidal to intertidal siliciclastic and carbonate rocks.