Sandstonedominated

Sandstonedominated is a geological descriptor used to indicate that sandstone is the predominant lithology within a rock unit, formation, or landscape. The term is applied when the cumulative thickness or relative volume of sandstone exceeds that of other rock types such as shale, mudstone, limestone, or chert, producing a sequence whose properties are controlled largely by sandstone.

Composition and texture: Sandstones are clastic sedimentary rocks composed mainly of sand-sized grains, typically quartz; feldspar and lithic fragments may be present. Grain size ranges from fine to very coarse; well-sorted and well-rounded sandstones often indicate high-energy transport (aeolian or braided rivers), while poorly sorted textures point to proximal sedimentation (turbidites, alluvial fans). Porosity and permeability depend on grain packing and cementation; primary porosity is common, while diagenetic cements such as calcite, silica, or hematite can reduce pore space. Color variations reflect cement and iron oxide content.

Formation and environments: Sandstonedominated sequences occur in many settings, including braided rivers, fluvial floodplains, deltas, shoreface sand systems, eolian dunes, and submarine fans. Diagenetic processes and burial history affect porosity, permeability, and mechanical strength; cementation reduces porosity; fracturing or dissolution can create secondary porosity.

Significance: Such sequences are important in hydrocarbon exploration as potential reservoir rocks due to their typically good porosity and permeability; they also serve as principal aquifers in groundwater systems and contribute to landscape morphology by forming resistant cliffs and ledges.