The Cyclic Preservation of Clastic and Evaporitic Sabkha Sediments: Insights from the Cedar Mesa Sandstone Formation of the Cutler Group, Utah, USA

The strata of arid continental basins commonly comprise evaporitic sediments deposited in sabkha settings combined with clastic sediments derived from aeolian, fluvial and/or lacustrine settings. The sedimentary character of these mixed successions and the degree to which evaporitic strata influence their composition, both contribute towards the economic potential of the evaporitic and the clastic component. This work describes, interprets, and provides predictive models for the preserved deposits of sabkha settings that interact with contemporaneous and competing arid continental environments, using the Permian Cedar Mesa Sandstone Formation of the Colorado Plateau, USA, as a case study. Detailed analysis of the sediments reveal a number of distinct sedimentary successions in which the interplay of clastic and evaporitic strata describe deposition in continental sabkha-influenced settings that gradually become drier with time. Each succession is separated from the subsequent one by a sudden ‘wetting’ of the setting in which sediments were deposited. The drying upwards successions show two distinct assemblages, an aeolian erg-margin sabkha, and a lacustrine-margin sabkha. For both settings, the preserved strata demonstrate that the intercalation of clastic and evaporitic sediments on the small (facies) scale is prevalent to such a degree that it would have economic implications for the exploitation of both resources. However, in the lacustrine marginal sabkha, the interbedding of evaporitic and clastic sediments at a larger (association) scale is significantly rarer, with dominantly evaporitic strata giving way to dominantly clastic strata abruptly in upward succession. These observations are considered in the context of climatic variation to construct models of the interplay between climate, clastic and evaporitic sediment supply, and accommodation space. The models provide a means of subsurface prediction where sediments are deposited in similar settings, and the observations provide important new insight for the interpretation and exploitation of economic continental sabkha sediments in the subsurface