Depositional and grain-scale controls on sandstone heterogeneity in arid continental settings: the Dutch Rotliegend

Abstract. Depositional processes and early grain-scale properties exert a primary control on compositional heterogeneity and diagenetic evolution in sandstones, yet their relative influence at the field scale remains difficult to quantify. As a result, regional petrographic datasets that explicitly link spatial variability in grain attributes and authigenic mineral assemblages to depositional environments are still limited. This study presents a field-wide, quantitative petrographic analysis of the Rotliegend Slochteren Formation in the Groningen area (the Netherlands), which provides exceptional subsurface coverage and stratigraphic continuity. Petrographic data from fifteen wells are used to define spatial trends in detrital composition, grain size and sorting, and cement distribution, and to relate these patterns to depositional facies and burial evolution. Despite the overall textural maturity and narrow grain-size range of the Slochteren Formation, distinct facies-controlled trends are identified. A south–north transition from proximal fluvial to distal playa deposits is accompanied by decreasing grain size and improved sorting, while aeolian dune deposits are most prominent in the central and western parts of the study area. Grain size and sorting are the dominant controls on porosity and permeability, with the highest reservoir quality occurring in well-sorted, fine to medium-grained sandstones of distal and aeolian origin. Compositional variations reflect both depositional and provenance controls: lithic fragments and polycrystalline quartz dominate coarser southern sandstones, whereas feldspar content increases northward and stratigraphically upward, consistent with a shift in sediment supply, likely related to enhanced volcanic input from the east. Authigenic mineral assemblages record the combined influence of depositional texture, detrital input, and burial evolution with many key constituents cements being internally sourced from local dissolution of more unstable precursor minerals. Illite and chlorite formation is closely associated with clay-coated grains in fine-grained playa facies, whereas quartz cementation is limited and controlled by burial depth, local silica availability, and inhibition by grain coatings. Dolomite locally exerts a strong control on porosity reduction. These results highlight the fundamental role of depositional facies and early diagenetic processes in generating spatial heterogeneity in sandstone successions and demonstrate how grain-scale attributes control subsequent diagenetic pathways in mixed depositional systems.