THE 



JOURNAL OF GEOLOGY 



APRIL-MAY, igo8 



GEOLOGY OF THE HAYSTACK STOCK, COWLES, 

 PARK COUNTY, MONTANA 



WILLIAM H. EMMONS 



INTRODUCTION 



The Haystack stock is a mass of coarse-grained gabbro, diorite, and 

 allied rocks, situated at the head of Boulder River, near Cowles Post- 

 Ofhce, Park County, Montana, in the southeastern quarter of the 

 Livingston quadrangle, about 65 miles by stage from Livingston. The 

 geology of this portion of the Livingston quadrangle was mapped in 

 1890 by Professor J. P. Iddings, but the Haystack stock, and its 

 relations to the surrounding rocks, were regarded by him as of sufficient 

 interest to warrant further study, and, accordingly, in 1903, additional 

 field-work was done by the writer, assisted by Robert Butler, A. C. 

 Ellsworth, and James Walker. No claim for originality is made for 

 the geological map, Fig. i, since it is essentially that published in 

 the Livingston folio. Mr. Iddings further directed the ofiice work, 

 and placed in the hands of the writer his field notes and a large 

 amount of material collected during the mapping of the Livingston 

 quadrangle. Analyses of six type specimens, and of two mineral 

 separations were made in the laboratory of the U. S. Geological 

 Survey by Mr. George H. Steiger. 



PHYSIOGRAPHY 



Topography. — The area included within the limits of the map, 

 (Fig. i), is a part of the high dissected plateau which is somewhat 

 indefinitely called the Snowy Mountains. The general elevation of 



Vol. XVI, No. 3 193 



