90 REPORT OF THE MINISTER OF MINES, 1929. for depth, and search for new channels. At low water no particular channel would offer a com- plete thoroughfare without the necessity of lining and portaging over bar rapids. The valley of the river varies from %4 to 1144 miles wide. On the east side a ridged bench margins the river for a distance of about 10 miles from its mouth to the East fork. With the exception of a few places, this is above flood-water mark. At the junction of the Tulsequah and Taku rivers, on the west side, a slough and beaver-dam area 214 miles wide and 4 miles long is a marked feature. A remarkable periodical flood condition affecting the Tulsequah river is a matter to be noted by prospectors and operators. This emanates, in all probability, from the dammed-up water of a lake beneath the glacier at the head of the river. Pressure from the accumulating water during the summer months bursts the barrier, with the result that an enormous volume of water is suddenly belched into the valley, causing the river to rise 10 to 15 feet in a matter of two days, with an equally rapid subsidence. This year one of these floods was subsiding at the time of examination (September ist). They are said to occur annually, at about the same period of the year. After one of these floods the entire formation of the river-bed is changed and totally new channels and bars result. The Tulsequah Chief warehouse and river camp are situated on the east bank of the Tulsequah river, about 8% miles from its mouth. The camp of the Potlatch group (Sparling) is located about 3 miles up the Tulsequah from its mouth. GEOLOGIC FEATURES OF THE AREA. Geological work in Northern British Columbia has been mainly done by officers of the Geological Survey of Canada, although some reconnaissance has also been done by the Alaska branch of the United States Geological Survey. Information regarding mineral resources is also contained in the Annual Reports of the Minister of Mines. While the geologic work that has been done has little bearing on the small area considered in this report, some of the available information is of assistance in understanding the geologic features of the area. The following bibliography lists the more important reports and articles regarding areas in Northern British Columbia :— Name of Author. Publication. | Year. : l | Coan. National Geographie Magazine... | 1892 diaxee | Part B, Annual Report, G.S.C.. 1899 BR. E. United States Geological Survey. | 1905 D. D. Cairnes: Atlin Mining District.. Memoir No. 37, G.S.C....... | 1910 W. M. Brewer: Atlin Mining Division......0............. | B.C, Department of Mines... -| 1915 W. EB. Cockfield : Explorations between Atlin and Tele graph Creek. Summary Report, G.S.C., Part A.... 1925 Ff. A. Kerr: Dease Lake Area. Summary Report, G.S.C., Part A.... 1925 F. A. Kerr: Second Preliminary Report, | River! Areas ele sree ene Sa ee Summary Report, G.S.C., Part Aw... 1928 F, A. Kerr: The Development and Natural Resources) Canadian Mining and Metallurgical Bulletin | of Northern B.C. UL Yetiwsvassncccesenes sectu ces sseeet saa ce eee ctsees ete eam | 1929 &. A. Kerr: Recent Mining Development in Northern Do 0 eae re ee re ee Rn eee mare B.C. Miner, November.. 1929 No geological survey party has as yet been into the Taku River area; with the exception of reconnaissance-work as outlined in the bibliography, the nearest geologic mapping to the area is contained in the Atlin sheet by Gwillim. The Stikine River area, 140 miles to the southward, has been mapped by F. A. Kerr, of the Geological Survey of Canada, and this map and accom- panying report are now in course of preparation. The accurate classification of the rocks and formations of the area and their correlation with those of other areas would be of great service to operators and prospectors. It is hoped this work will be taken in hand by the Geoelogical Survey of Canada in the near future. It must be stressed that the rock classification in this preliminary report is based on field identification only. No microscopical determinations haye been made. This classification is consequently only approximate and open to revision. Accurate determination of the rocks must await a detailed study with the microscope.