Clastic sediments and sedimentary rocks that are pigmented by red ferric oxide which coats grains, fills pores as cement, or is dispersed as a muddy matrix. These conspicuously colored rocks commonly constitute thick sequences of nonmarine, paralic (marginal marine), and less commonly shallow marine deposits. Clastic redbeds accumulated in many parts of the globe during the past 10⁹ years of Earth history.

They were among the first sedimentary deposits to be considered climatic indicators, because their color was assumed to reflect a unique, identifiable condition of deposition. On the contrary, development of red pigment in most redbeds was complex and is difficult to decipher in detail. Ferric oxides also pigment marine chert, limestone, and cherty iron formations and ooidal ironstones, but these chemical deposits are not usually included among redbeds.