Abstract

The Permian System of the Paradox Basin (Cutler Group and Kaibab Limestone) reflects interaction of sea-level and climate change. Stratigraphic analysis of the Cutler suggests that relative sea-level highstands were correlative with wet conditions, whereas lowstands were synchronous with aridity. This relation is consistent with simple glacial-eustatic forcing. It does not hold for the Kaibab Limestone, however, possibly indicating diminution of late Paleozoic icehouse conditions.

The Cutler Group is composed primarily of arkosic conglomerates, sandstones, and siltstones derived from the Ancestral Uncompahgre uplift and transported southwestward into the Basin. The Uncompahgre elastics interfinger distally with quartzarenitic eolian sandstones and marine carbonates. The Cutler Group is divided into four units (in ascending order): lower Cutler beds, Cedar Mesa Sandstone, Organ Rock Formation, and White Rim Sandstone. The lower Cutler is composed mainly of shallow marine sandstone and limestone, and Uncompahgre-derived red-beds containing abundant channels, paleosols, freshwater fish and plant fossils. Loess deposits are also locally present. The Cedar Mesa and White Rim are dominantly eolian sandstones. Based on paleocurrent and composition data, the source of the sands is interpreted to lie to the northwest of the Paradox Basin. Organ Rock Formation sediments were derived primarily from the Uncompahgre uplift and consist mainly of fluvial, floodplain, and/or muddy tidal flat deposits interspersed with minor eolian strata that increase in thickness and abundance upsection. In the western Paradox Basin, the marine Kaihab Limestone overlies the Cutler Group.

The lower Cutler beds are interpreted to reflect relatively wet conditions (because of the presence of freshwater fish fossils, channels, and paleosols) as well as high relative sea level ( because of the presence of marine facies). The Cedar Mesa and White Rim are interpreted to reflect aridity (due to the dominance of eolian deposits), and low relative sea level (because of the influx of quartz-rich material from the northwest across an area that experienced marine conditions during lower Cutler deposition). Extensive fluvial, floodplain, and tidal flat deposits in the Organ Rock indicate wet conditions and high relative sea level. Deposition of the marine Kaibab Limestone across the top of the White Rim suggests relative sea-level rise. The basal and uppermost Kaibab contain features consistent with evaporitic conditions, so this unit also indicates aridity.

AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah