The oil regions of India lie in the north-west and in the east, within broad strips of Tertiary rocks stretching in a general southerly or south-westerly direction from the Himalayas to the sea. On the eastern side of India the main Tertiary outcrop runs from the head of the Assam Valley south-westwards through part of the Central Assam Range into the Surma Valley and thence southwards to the Bay of Bengal at Chittagong, whence the Tertiary beds continue along the Arakan Coast of Burma. This strip forms one geological province, distinct both from the better-known Tertiary development of western India and from the Tertiaries of the Chindwin–Irrawaddy Valley of Burma. This Assam–Arakan region includes parts of the provinces of Assam and Bengal and part of the western coast of Burma: although Burma is now separated from India, it is convenient to consider the Assam–Arakan oil-belt as a whole, without regard to political divisions.

The country in the vicinity of Toodyay, which is situated approximately 60 miles north-east from Perth, is occupied by a series of Archaeozoic metasedimentary and igneous rocks (Text-fig. 1). The metasediments include interbedded sillimanite-and andalusite-mica-schists, extremely pure quartzites and occasional narrow bands of calc-silicate rocks. The igneous rocks occur as (1) narrow bands of schistose plagioclase-amphibolite (interbedded with the metasediments) which appear to have been originally sills or flows of tholeiitic character; (2) wider bands of fluxion microcline- (and oligoclase-) granite-gneisses occurring as concordant thick sill-like bodies in the metasedimentary strata; (3) Quartz-dolerite dykes, intrusive into all the above-mentioned rocks. Some of these rocks, which are developed in the Jimperding valley (about 6 miles southwest from Toodyay), have been previously described (Prider, 1934).

This work was undertaken in an attempt to assess the significance of minor variations in composition and properties of sand samples collected from the same locality and derived from a common source.

The publication by the Geological Society of America of that momentous work by the late A. C. Veatch and P. A. Smith (1939) with its beautifully executed charts, following closely Douglas Johnson's stimulating contribution on the subject (1938), again focuses attention on those stupendous erosion-features—the “Submarine Canyons”. Through stressing the relatively brief space of time available for their evolution, this latest pronouncement only renders more of an enigma those gigantic furrows that would now seem to fringe so much of the continental margins. As Daly has remarked (1936, p. 402), they appear to be planetary and not merely regional. It is in the Atlantic, however, that they have been most thoroughly studied.

During the excursion of the Sedgwick Club to Pembrokeshire at Easter this year the junctions between certain of the rock groups were examined under unusually favourable conditions with interesting results.

In a recent paper (1940) I discussed the origins of the Indus, Jhelum, and Sutlej rivers. I suggested that the upper Jhelum resulted from the final severing of marine communications with Tibet by the rise of the north-west Himalayan axis at the close of Laki (Lower Eocene) times. The upper Indus probably originated rather later, from the overflow of Tibetan drainage ponded by the rise of this axis. The upper Sutlej I held to be much younger, and due to a geologically recent collapse of the main Himalayan axis along the line of an old (Gondwana) fault-trough.