past basis determining sedimentary features rock record formed comparing similar features today features rock record example comparing modern sand dunes dunes preserved ancient aeolian sandstones geologists reconstruct past environments sedimentary rock types middle triassic marginal marine sequence siltstones sandstones southwestern utah four primary types sedimentary rocks clastics carbonates evaporites chemical clastic rocks composed particles derived weathering erosion precursor rocks consist primarily fragmental material clastic rocks classified according
Natural science Earth science Sedimentology