158 DEPARTMENT OF THE INTERIOR 



2 GEORGE V., A. 1912 



In general, the once-argillaceous material, now crystallized as sericite, 

 chlorite, biotite, magnetite, etc., grows more abundant toward the top of the 

 Beehive formation, which is there also somewhat thinner-bedded than in the 

 lower, more quartzitic members. 



The average specific gravity of ten selected specimens, 2-717, is believed 

 to be near the average for the whole formation. 



Lone Star Formation. 



The Beehive formation at its upper limit merges gradually into a division 

 of sedimentary rocks which, everywhere in the ten-mile Boundary belt, have 

 been so much disordered and metamorphosed that it has proved quite impossi- 

 ble to declare their exact thickness or their relation to the younger Paleozoic 

 formations in contact with them. There is apparent conformity not only with 

 the Beehive formation below but also with the Pend D' Oreille schistose sedi- 

 ments and limestones, strata which are believed to be mainly of Upper Pale- 

 ozoic age. All of these formations have, however, suffered complete metamor- 

 phism, crumpling, faulting, and mashing, in consequence of which the apparent 

 conformity may not exist. For the present, the schistose sediments immediately 

 contacting with the Beehive quartzites are regarded as the youngest rocks in 

 the Selkirk range which can, with any safety, be considered to be part of the 

 conformable Summit series. This uppermost member is very roughly estimated 

 as 2,000 feet in thickness and is given the name, Lone Star formation, so 

 called from its exposure on the eastern slope of Lone Star mountain. 



The formation consists principally of dark-gray or greenish-gray, often 

 carbonaceous phyllite, along with some lighter tinted, greenish sericite-quartz 

 schist and thin interbeds of light-gray quartzite. The dominant phyllite some- 

 times, though rarely, passes into true slate in which the well developed cleavage 

 cuts across the bedding-planes. As a rule, the bedding is very obscure and the 

 schistose structure is the dominant one. In nearly all the sections these schists, 

 like the conformable Beehive quartzites, dip to the eastward at high angles, 

 showing that the great monocline in which the Summit series has been studied, 

 is overturned to the westward. 



The extreme metamorphism of the Lone Star formation is due partly to 

 the original nature of the sediments, which were specially liable to alteration 

 in orogenic crush, and largely, also, to the vicinity of intrusive granites and 

 other igneous masses. It is unfortunate for the study of this upper part of the 

 Summit series at the Forty-ninth Parallel that it is thus exposed only at the 

 eastern edge of one of the greatest fields of intrusive rocks in the Cordillera. 

 One must look to the other sections, particularly to those farther south, for a 

 more satisfactory diagnosis of the Summit series in its relation to younger 

 formations. Four miles east of the Salmon river the Lone Star schists dip 

 under the Pend D'Oreille schists and therewith the entire series disappears 

 from sight, so that no rocks referable to the great Rocky Mountain GeosynclinaT 

 prism are to be found in any part of the Boundary belt to the westward. 



