st. JOHN.| GROS VENTRE BASIN—-CONGLOMERATE AND COAL. 223 
and in the regular order of stratigraphical superposition to the varie- 
gated Jura and unmistakable “red beds” of the Trias, all of which, so 
far as can be made out at a distance, belong to the northerly-inclined 
flank of the northwestern extremity of the Gros Ventre Range. But 
these deposits appear over a comparatively narrow belt in this northern 
slope of the basin, at least not of greater width than along the Gros 
Ventre, while in the crest of the Mount Leidy highlands they are super- 
seded by later deposits, presently to be mentioned. 
The main branch of the Gros Ventre, after leaving the elevated 
mountain flats, flows in a gradually deepening narrow valley, in whose 
sides fine exhibitions of the Tertiary are met with, extending as far down 
as a point about 4 miles above the two principal forks, where the stream 
enters the above-mentioned Upper Cretaceous horizons. The Tertiary 
deposits are based upon a heavy accumulation of brownish-drab con- 
elomerate, several hundred feet in thickness, and which is composed of 
thoroughly water-worn and rounded pebbles and small bowlders consist. 
ing almost exclusively of variously-colored quartz and quartzitic frag- 
ments, rarely a metamorphic pebble being seen. The conglomeritic char- 
acter predominates through a great vertical extent of the horizon, with, 
however, intercalations of soft yellowish sandstone of’a more or less local 
extent, and which is essentially of the same character as the fine brownish 
drab or gray and slightly calcareous matrix of the conglomerate. Above, — 
the sandstone layers increase in thickness and frequency of occurrence, 
alternating with thinner layers of conglomerate and green and drab clays. 
The main mass of the conglomerate in the wierdly-eroded exposures along 
the canoned portion of the stream was found to contain fragments of tree- 
trunks, but which are so changed by ferruginous infiltrations and decayed. 
as probably to be indeterminable. 
In the section (a diagram of which is associated on the plate illustra- 
_ ting the last preceding section with which this is in direct continuation 
to the northeastward) exposed along the northeast fork of the Gros 
Ventre, the conglomerate reappears in the hills at a place about a mile 
above the forks, where it is seen to rest with apparent non-conformity 
upon the sandstone No. 12 of the section last described. The dip is to 
the northeastward at an angle of about 10°; on the main stream at the 
first-mentioned exposures of this horizon the inclination is about 5° in 
the same direction. The exposures continue about a mile before they 
finally pass beneath the level of the stream, the inclination gradually 
lessening, ascending the valley to the northeast. This horizon is repre- 
sented by No. 13 of section diagram referred to. 
The conglomerate is conformably overlaid by a still greater thickness 
of soft yellowish sandstones, light and drab clays, forming broken hills 
and slide-benches, in which the strata are usually more or less concealed 
by the soil derived from their degradation. The latter deposits also 
incline gently northeastwardly, occurring along the valley for the dis- 
tance of perhaps a couple of miles. This series is also finely developed 
on and to the east of the southeast fork, where, at a point about 8 miles 
above the furks, Mr. Perry secured a very interesting detail section. In 
a vertical thickness of about 1,000 feet, made up of generally light buff 
calcareous sandstones and clay shales in about the proportion 2 to 1, 
and including five beds of limestone aggregating 40 feet in thickness, 
there were found eighteen distinct lignite horizons, composed of 47 lay- 
ers, varying from thin seams up to beds 24 feet thick, and aggregating 
about 28 feet. The exposed outcrops of the coal beds usually are more 
or less decomposed, and while, in the main, the beds are thin seams from 
less than’: inch to 8 inches thick, there are at least 11 showing a thick- 
