Sedimentological characterisation of continental sabkhas: an example from the cedar mesa sandstone of the Paradox Basin, Utah, USA

Abstract

Continental sabkhas are present within many arid sedimentary basins, however they are often overlooked compared to coeval aeolian and fluvial deposits, despite their potential to record and preserve sedimentary signatures relating to basin formation and fill.
The relationships between evaporitic sabkha deposits and genetically-related coeval clastic sediments are strongly influenced by complex processes between autocyclic and allocyclic controls, including climate, however within arid continental settings these signatures are often difficult to detect within the preserved sediments.
This thesis presents results from the margin of the Cedar Mesa erg of the Paradox Basin, Utah, USA, which preserves complex interactions of clastic and evaporitic sediments. Studies are based upon extensive regional fieldwork examining the sedimentology, geometries, and interactions, complemented with outcrop gamma ray data and microfacies analysis. The sedimentology shows large variations spatially and temporally which grade through aeolian, sabkha and lacustrine settings with complex interactions occurring where these sediments transition.
This work details the facies present in a continental sabkha allowing for identification and interpretation of these complex interbedded relationships over a regional scale. The results have been developed into idealised models and recognisable log signatures which characterise and assess their impact on reservoir quality. Cyclic climatic trends, on various orders of magnitude, have been identified in relation to distinct spatial facies changes. Identification of these allows for basin-wide correlation and prediction of where facies will occur in space and time. These results are applied to evolutionary models applicable to subsurface data from the arid Permian basins of the North Sea, in order to better characterise basin-scale migration and reservoir quality in terms of the evolving basin fill.