518 DEPARTMENT OF THE INTERIOR 



2 GEORGE V., A. 1912 



Tamihy Series. 



For about two miles from the Boundary line down Tamihy creek, the 

 southwestern slope of the deep valley is underlain by an important series of 

 rocks which have not been discovered with certainty at any other point in the 

 Boundary belt this side of the Skagit river. This group of rocks was first 

 seen in 1901 and given the provisional name, ' Green Quartzite Series.' It 

 was unfossiliferous but it was thought to be older than the Chilliwack series.* 

 During the season of 1906 much better exposures were found on the heights 

 west of the creek and especially on the south side of the Boundary line. The 

 relations are such as to enforce the belief that this new series lies unconform- 

 ably upon the Carboniferous limestone, quartzite, and greenstone, and is very 

 probably younger than the Triassic Ctdtus formation as well. Instead of the 

 name chosen in 1901 the writer prefers to use the localizing name, Tamihy 

 aeries, for this younger group of sediments. It is not the intention to name 

 it as if it had been thoroughly analyzed and become stratigraphically under- 

 stood; the name is chosen for convenience in the present report only, though 

 possibly it may be of service in the hands of the geologist whose duty it will 

 be to investigate this important mass of strata. 



The relation of the Tamihy series to the Carboniferous rocks was determined 

 with a fair degree of finality on the summit southwest of Monument 48 of the 

 International line. At that point the quartzite noted as member 1 of the general 

 columnar section of the Chilliwack series, is overlain by a well exposed body 

 of strata, of which some 400 feet are clearly visible near tree-line. It is a 

 heterogeneous mass of gray conglomerate, black quartzitic sandstone, dark-gray 

 paper shales, gray grit, and green sandstones in rapid alternation. The pebbles 

 of the conglomerates include quartzite, vein ( ?) quartz, chert, and argillite, with 

 almost certainly a few of greenstone like that of the Chilliwack Volcanic forma- 

 tion in the immediate vicinity. The chert pebbles are apparently of the same 

 material as that so commonly found in the chert nodules of the underlying 

 limestone. A few obscure plant-remains were found in the sandstone. The atti- 

 tude of these beds is variable but the local dip averages about 30° to the south- 

 southwest. 



What appears to be the same series of rocks was followed for a mile south 

 of the Boundary line as far as the top of a long ridge which runs eastward to 

 Tamihy creek. That ridge is composed of a thick, very massive group of 

 green and gray sandstones, grits and conglomerates like that just described, 

 with little or no argillite. The dominant sandstone is extremely thick-bedded, 

 so muck so that it is rarely possible to obtain indications of strike and dip. 

 Where these could be read, as south of Monument 48, the dips were 25°-30° to 

 the southeast. 



On that traverse, as along the Tamihy creek section, the minimum thick- 

 ness is estimated to be 2,500 feet, but there is an indefinite addition to be made 

 to this estimate when the area south of the Boundary line is investigated. No 



* See Summary Report for 1901, page 51. 



