arkosic sandstone

Arkosic sandstone, also known as arkose, is a type of sedimentary rock primarily composed of quartz and feldspar grains. It is distinguished by a feldspar content exceeding 25% of the sand grains and a lighter color compared to graywacke.1

The geological significance of arkose lies in what it indicates about its source area and depositional environment. Feldspar typically decomposes into clay minerals during weathering. However, the presence of unaltered feldspar in arkose suggests either an arid or glacial climate where decomposition is inhibited, or rapid rates of uplift, erosion, and deposition that prevent complete weathering. Therefore, arkose can signify extreme climatic conditions or high-relief landscapes. Most ancient arkose deposits are believed to originate from high-relief areas. Arkosic sandstones can form in environments like alluvial fans or desert settings.12