APPENDIX III
A NOTE ON THE GEOLOGICAL RESULTS OF THE EXPEDITION
By A. M. HERON, D.Sc., F.G.S., Geological Survey of India.
The area geologically examined is somewhat over 8,000 square miles, comprising the Tibetan portion of the Arun drainage area, with, in the West, the headwaters of the Bhotia Kosi and its tributaries.
The circumstances of the Expedition were not favourable for work in any detail, but an endeavour was made to traverse and map as large an area as possible on a scale of ¼-inch to the mile, on skeleton maps very kindly furnished by Major Morshead and his surveyors as their plane-tabling proceeded; my work must therefore be considered as a geological reconnaissance pure and simple.
If I am accorded the privilege of accompanying the second Expedition, by which time Major Wheeler's map on a scale of 1-inch to the mile will be available, I hope to be able to make a detailed survey of the vicinity of Mount Everest and investigate the complicated inter-relationships of the metamorphosed sedimentaries and the associated gneisses and granites.
My survey continues to the Westward Sir Henry Hayden's work during the Tibet Expedition in 1903–4.
Geologically this area is divided into two broad divisions: (a) Tibetan and sedimentary, (b) Himalayan and crystalline, a distinction which is clearly displayed in the topography resulting from the underlying geological structure, for to the North we have the somewhat tame and lumpy mountains of Tibet contrasting with the higher, steeper and more rugged Himalayas on the South.
The Tibetan zone consists of an intensely folded succession of shales and limestones, with subordinate sandstone quartzites, the folds striking East-West and mainly lying over towards the South, showing that the movements which produced them came from the North.
The uppermost rocks consist of the Kampa system of Hayden, a great thickness of limestones, which, where the rocks have escaped alteration, yield an assemblage of fossils which determine their age as Cretaceous and Eocene.