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1721 R. Bradley Gen. Treat. Husbandry & Gardening I. 31 The superficial Stratum of Earth is seldom more than nine inches, before we meet with a red Rock.

1794 J. Holt Gen. View Agric. Lancaster 11 The substratum of this soil is generally the red rock, or clay-marl.

1823 tr. A. von Humboldt Geognostical Ess. Superposition Rocks 345 The red marl (red ground, red rock, red ford)..is in England the real position of rock-salt.

1880 J. F. Carll Geol. Oil Regions vi. 72 We have two important facts to work upon—the top of the conglomerate and the presence of red rock beneath it and not far below its base.

1893 Bull. U.S. Geol. Surv. No. 109. 23 The red rock..is found in three distinct though indefinitely outlined areas... It occupies a position between the gabbro and the fragmental rocks.

1904 Dial. Notes 2 387 Red rock, the drillers' name for the red shale underlying the Panama Conglomerate.

1918 Jrnl. Geol. (Chicago) 26 632 The ‘red rock’ has become widely known under this name because of its brilliant color and the difficulty of giving it a more accurate classification... The rock here discussed is intrusive and granitoid.

1969 G. M. Bennison & A. E. Wright Geol. Hist. Brit. Isles xi. 268 Red rocks of Permian and Triassic age outcrop in south-west England.

1990 Chem. Geol. 86 29/2 Many of the core rocks are ‘red-rock’ granophyres, featuring feldspars rich in minute hematitic inclusions which give the rocks a brick-red coloration.