Summary and Key Points
During our few days in the field we observed and compared two Permian carbonate platforms deposited in different paleogeographic settings, paleoclimatic modes and tectonic settings. The Lower Permian, Wolfcampian, strata represent the basin fill of the Orogrande Basin and the platform studied forms the leeward side of the Diablo Platform. These deposits followed a major tectonic re-organization of the area and formation of the “Mid-Wolfcampian” unconformity. The Upper Permian, Guadalupian, represents the basin fill of the Delaware Basin in a “near” windward position following a time of tectonic quiescence. The Lower Permian was a time of major continental glaciation, thus with major glacio-eustatic sea level changes and a humid climate. In contrast, the Guadalupian was a transition from ice- to hot-house conditions and an arid climate.
The paleoclimatic conditions impacted some of the architectural elements of the platform. For instance, the decrease in the amplitude of sea level change through the Permian can be seen in the expression of the sequence boundaries and the amount of shelf-margin exposure. The Wolfcampian margin and slope was often exposed to subaerial conditions and the Guadalupian reef-margin was mostly submerged. Additionally, the more arid conditions in the Guadalupian favored the expansion of eolian ergs and the delivery of siliciclastics to the shelf and basin. ‘Thus, cyclicity is well marked by the influx of siliciclastics.
The nature of the relationship between reef biota, paleoecology, and paleoclimate change is still unclear. However, there is a parallelism between tectonic and paleoclimatic changes and evolution of the Permian