REPORT OF THE CHIEF AtSTRONOHER 183 



SESSIONAL PAPER No. 25a 



A more recent table of correlation has been published by Calkins, who 

 "has similarly equated the Kitchener with the Ravalli and Burke horizons; 

 Wallace and Blackfoot with Newland and Altyn.* The present writer has not 

 been able to agree with these correlations. As stated in his summary report 

 for 1905, the Kitchener quartzite passes into, and is the equivalent of the Siyeh 

 limestone; and part of the Creston quartzite is equivalent to the Appekunny 

 metargillite. In 1907 the writer came to suspect that the Blackfoot limestone 

 is the equivalent of the Siyeh limestone, and the next year Walcott proved 

 this to be the ease.f It seems necessary, therefore, to make significant alter- 

 ations in Calkins' table. His ' Newland ' limestone in the Philipsburg and 

 Cabinet Range districts, if the equivalent of the Blackfoot limestone, as he 

 states, must belong to the Siyeh horizon. The other members of each strati- 

 graphic column must be correspondingly shifted. These changes are noted in 

 the general table VIII. Though it may be at fault in details, that table is 

 believed to express the main relations subsisting among the different sections 

 in the 'Belt terrane.' Walcott's discovery of the equivalence of the Blackfoot 

 and Siyeh limestones has clearly simplified the whole stratigraphic situation 

 in Montana and Idaho. 



Evidence of Fossils. — The principal difficulty in the correlation with 

 recognized systems is, of course, the rarity of fossils which can in any sense 

 determine horizons. The only well characterized fossil horizons yet found in 

 the Belt terrane as defined by Walcott, occur in the lower part of the Greyson 

 shales of the Belt mountains and in the upper part of the Altyn formation in 

 the Lewis range. These two horizons may well be practically contemporaneous, 

 as they occur in similar stratigraphic relations and both carry the abundant 

 species, Beltina danai. Neither that species nor any of the associated obscure 

 organisms can directly date the horizon, which has never been found in 

 undoubted association with the Olenellus zone or other general horizon of the 

 Cambrian. So far as purely paleontological evidence is concerned, it is quite 

 within the bounds of possibility that the Beltina horizon is really a lower phase 

 of the Lower Cambrian, Olenellus zone, or is but slightly older than that zone. 



No organic remains giving decisive indications of age have been found in 

 the overlying Spokane, Empire, Helena, and Marsh formations of the Belt 

 mountains or in the equivalents of these, either at the Forty-ninth Parallel or 

 in the thick deposits of Idaho and western Montana. 



"Walcott recognizes the Cambrian-Ordovician equivalent of McConnell's 

 Castle Mountain group as occurring near Belton, Montana, and at Nyack creek, 

 Montana. § At these localities, massive bluish and greenish limestones bearing, 

 a species of Raphistoma and a Stromatoporoid form, were found in great 

 development. As shown by Plate" 6 of Walcott's paper, the field-habit of these 

 limestones is extremely similar to that of the Siyeh limestone at Mt. Siyeh, 



*F. C. Calkins, Bull. No. 384 and Professional Paper No. 62, U.S. Geological 

 Survey, 1909 and 1908. 



t Information supplied by letter. 



§ Bull. Geol. Soc. America, Vol. 17, 1906, pp. 12, 19, 22. 



