The Age of the Duruma Sandstone, East Africa

Abstract

West of the marine Jurassic rocks near Mombasa the Uganda Railway traverses for 46 miles a belt of sandstones and shales which are grouped together as the Duruma Sandstone. The few fossils hitherto obtained from this series have not given any definite evidence as to its age, which is, however, shown by the relations of the sandstones to the Kambe Limestone to be pre-Bathonian. The Mazeras Sandstone, one of the upper members, contains many trunks of Dadoxylon, the age of which, according to Professor Seward, may be anything from Trias to Kainozoic. An Estheriella and some plants were found in the Maji ya Chumvi beds by Maufe and have been regarded as either Permian or Triassic. The lowest division, the Taru Grit, has not yet yielded any certain fossil, but it has been regarded as continuous with the shales in the Sabaki Valley, which yielded the Permian mollusc, Paleanodonta fischeri, and with the plant bearing Tanga beds in the north-eastern corner of Tanganyika Territory. A bore in quest of water was made near Samburu Station to the depth of 527 feet in the Taru Grits. The cores are preserved by the Uganda Railway at Nairobi, and Mr. David Harris recently re-examined them and made the useful discovery of two fragments of fossil plants. They have been kindly sent to me by Dr. A. W. Rogers and examined by Professor A. C. Seward. He identifies them as a Voltzia and an Ullmania. For the drawings, Fig. 1, I am indebted to Mr. L. D. Currie. Both fossils are specifically indeterminable, but Professor Seward states that they certainly belong to the flora collected by Dr. Teale in the Tanga beds, which was described in 1922. Professor Seward assigns that flora to an age between the Upper Permian and the Rhaetic, and seems inclined to regard it as probably Trias.