LOWER JURASSIC LATERITIC REDBEDS FROM CENTRAL ARABIA

Some 40 samples of the Marrat redbeds, of Toarcian (Lower Jurassic) age in central Arabia have been examined mineralogically and chemically. The dominant mineral kaolinite is associated with minor amounts of illite and smaller amounts of feldspar. The red pigment is dominantly hematite, but goethite occurs in some samples. Contents of Ti, Zr, Nb and Y associated with the kaolinite are higher than in ordinary redbeds, but the contents of K and Rb are much lower than those in ordinary redbeds. These redbeds seem to be different from illite-dominated redbeds and are considered to be lateritic soils formed on the Arabian Shield to the west and later deposited in and around the Toarcian Sea. © 1979.