Pleistocene-Holocene sedimentary rocks, which outcrop along the northern Gulf of California coast in the vicinity of Puerto Peñasco, Sonora, have a very heterogeneous, mixed carbonateclastic composition. Carbonate grains are primarily molluscan, echinoderm, bryozoan and calcareous algal fragments. Terrigenous grains are primarily silicate minerals (e.g., quartz and feldspar) derived from three nearby igneous prominences (the basaltic Punta Peñasco and Cerro Prieto and the granitic Punta Pelicano).
Porosity of the sedimentary rocks, which commonly exceeds 50% in many units, may be intergranular and/or moldic. Cements in eolianite, precipitated within the vadose zone, are mainly of the meniscus spar type at grain contacts. Cements in beachrock, precipitated within the intertidal or shallow subtidal zone, include isopachous calcite spar and/or acicular aragonite.