HISTORICAL REVIEW OF THE LAEAMIE PROBLEM. 



51 



In 1894, in the Livingston folio, Weed 81 

 described and mapped the several formations 

 under discussion with the signification and 

 limits given to them in the bulletin above 

 cited. In 1896 the Three Forks quadrangle, 

 which adjoins the Livingston, quadrangle on 

 the west, was described in a folio by A. C. 

 Peale. 82 He accepted the Dakota, Colorado, 

 Montana, Laramie, and Livingston formations 

 as defined by Weed and wrote of the Laramie 

 as follows: 



The formation consists essentially of light-gray or 

 whitish sandstones, with interlaminated argillaceous beds, 

 some of which are locally much indurated. The two areas 

 in which the strata are best exposed are in the Nixon 

 basin, north of the Gallatin Valley, and in the Gallatin 

 basin, lying between the Gallatin and Madison ranges. 

 The total thickness of the formation is from 800 to 1,000 

 feet. In the Nixon basin Unios and other fresh-water 

 shells are found in connection with the coal. 



Concerning the Livingston formation he 

 said: 



The Livingston formation occupies at the present time 

 comparatively little area within the limits of the Three 

 Forks sheet, and nowhere is it likely that the entire 

 thickness of the formation is shown. The largest area is 

 probably that in the vicinity of the Sphinx Mountain, 

 where the Sphinx conglomerate rests unconformably upon 

 it. This area is about 1 5 to 20 square miles in extent, and 

 the deposits are made up of a mass of volcanic materials 

 indistinctly bedded, mostly andesitic in nature, and of a 

 somber hue. At one or two places conglomerates made up 

 of all sorts of volcanic pebbles are seen near the base. 

 This generally black mass rests unconformably upon the 

 eroded surfaces of the previously deposited Cretaceous 

 formations, contrasting strongly in color with the Laramie 

 sandstones and the Dakota conglomerates, with both of 

 which it is in contact at different points. 



The unconformable relation near Sphinx 

 Mountain described by Peale, which was 

 known to Weed, was one of the factors upon 

 which Weed based his contention of an un- 

 conformity between so-called Laramie and 

 Livingston. 



Weed 83 published in 1896 a short paper 

 which was devoted mainly to the Fort Union, 

 with only incidental mention of the Laramie 

 and Livingston formations. The immense 

 section of strata forming the eastern foot 

 slopes of the Crazy Mountains on Lebo Creek, 

 Mont., was divided as follows: Laramie, 1,080 

 feet; Livingston, 7,136 feet; Fort Union, 4,649 



feet. 



^j 



si Weed, W. H., U. S. Geol. Survey Geol. Atlas', Livingston folio 

 (No. 1), 1894. 

 82 U. S. Geol. Survey Geol. Atlas, Three Forks folio (No. 27), 1896. 

 S3 Weed, W. H., Am. Geologist, vol. 18, pp. 201-211, 1896. 



The Little Belt Mountains quadrangle, im- 

 mediately north of the Livingston quadrangle, 

 was described by Weed 84 in 1899. The Da- 

 kota, Colorado, and Montana were grouped 

 together in the Yellowstone formation, which 

 was said to be followed conformably by the 

 Laramie formation. The Laramie was de- 

 scribed in much the same terms and assigned 

 the same thickness as in the Livingston and 

 Three Forks folios. The Livingston, believed 

 to rest unconformably on the Laramie, was 

 described at considerable length and was given 

 a maximum thickness of 7,000 feet. In the 

 text of the folio the Livingston was placed 

 under the heading "Rocks of the Cretaceous 

 period," and in the generalized section of the 

 sedimentary rocks of the Crazy Mountains it 

 was given as "Cretaceous?" Although in- 

 cluded with the Livingston formation in map- 

 ping, the upper 4,000 feet of beds were in the 

 columnar sections differentiated as the Fort 

 Union. 



The, next paper in chronologic order is one 

 by Earl Douglass, 85 published in 1902, entitled 

 "A Cretaceous and lower Tertiary section in 

 south-central Montana," in which the inter- 

 pretation, was radically different from that 

 given by Weed. The area covered by this 

 paper lies east of the Crazy Mountains and 

 south of the Big Snowy Mountains, in the basin 

 of Musselshell River. The section, according 

 to Douglass, comprises the following units: 



The Livingston formation was not recog- 

 nized in this section, although the locality is 

 only a few miles from the Lebo Creek section 

 recorded by Weed, in which it was given a 

 thickness of over 7,000 feet. Douglass appar- 

 ently included the Livingston in whole or in 

 major part within the so-called Laramie, con- 

 cerning which he wrote as follows : 



What is supposed to be Laramie in the present section 

 is very thick, probably approximately that of Lindgren's 

 measurements [7,000 feet]. But here, as everywhere 

 else, the boundaries of the Laramie are uncertain. Here, 



s< Weed, W. H., U. S. Geol. Survey Geol. Atlas, Little Belt Moun- 

 tains folio (No. 56), 1899. 

 85 Am. Philos. Soe. Proc, vol. 41, pp. 207-224, 1902. 



