TO YELLOWSTONE NATIONAL PARK. 123 
only here the dip is reversed, and the abrupt side is toward the east. Thestrike remains the same, 
but the dip is gentler, averaging 40°. After some 5,000 feet of strata, the dip is reversed. An 
exposure of rock on the east side of the trail shows a laminated sandstone, generally soft and friable, 
but in some places very hard. The dip of the first layers is 30°, and this increases as we proceed 
to 45°, the inclination being here toward the east or northeast. A mile farther on, near the head 
of Flathead Creek, we notice another fold. The rock is here a soft yellowish sandstone, dipping 
west at a small angle, 15° to 20°. This contained many oval clayey conerctions, and in the seams 
in the rock there was more or less calcite. Ripple-marks were noticed in one or two places. Still 
farther on, the opposite side of the fold is seen, and here it appears that the dark-green and gray 
rocks seen just after leaving the south branch of Deep Creek underlie the soft yellowish sand- 
stone observed near Flathead Creek. For a mile or two more, we pass over the sandstones, chiefly 
the dark rock, but occasionally noting beds of the lighter-colored. This latter is much cracked 
and broken, scaling off into platter-like slabs, so that good exposures of it are seldom seen. Another 
fold is passed over just before reaching the broad valley of Norton’s Creek. We have thus 
the indications of three great folds between South Deep Creek and Norton’s Creek, a distance of 
ten miles in a straight line. The strike varies from north to west, the dip is generally as much as 
40°, and sometimes much more. A mile or two before reaching Norton’s Creek, we pass to the 
left of a high butte formed by three narrow dikes of eruptive rock, seemingly conformable to the 
sandstone. 
At Norton’s Creek, the country changes a little more, and we come upon a broad fertile syn- 
clinal valley. In this neighborhood, igneous rocks, before rare, beome very common, and beds of 
trachyte and basalt are repeatedly seen interstratified with the sandstones. The most conspicuous 
example of this is just to the west side of the meadow through which Norton’s Fork flows. Here 
is a bed of trachyte apparently conformable to the sandstone, and evidently having been erupted 
between two layers of that rock. It has asemi-columnar structure; the heads of the columns point- 
ing toward the east, thus appearing as if it dipped west, though in reality the sedimentary rocks 
have an inclination in the opposite direction. In the broad meadow of Norton’s Fork, a num- 
ber of isolated buttes of trachyte may be seen; some of these having taken quite peculiar forms. 
In these folds, it is seldom possible to trace any single layer of rock, because the characters are not 
distinctive enough; occasionally, however, this may be done, asin the case mentioned above. A care- 
ful plotting of the successive exposures would doubtless show the continuity of the strata, and 
give an exact estimate of the thickness of the rocks involved, together with the width of each of 
the folds. This we were of course unable to undertake. 
On the east side of Norton’s Meadow, the dip is westerly, and the strike northwest. Here a 
brown sandstone is exposed, followed by a gray trachyte in beds, which, at a distance, look like a 
solid sandstone, and might easily be confounded with sedimentary rocks. Opposite where the 
South Fork of the Musselshell is joined by Flathead Creek, is the extremity of a little range of hills, 
trending northwest, and forming a sort of spur of the Elk Range, conforming in direction to the 
low folds we have been tracing, and seemingly like one of them, a little deeper, and having brought 
up lower strata. Following the sandstone, which is without fossils, we have, as we cross the east 
end of this hill, some beds of red clay, making a red soil, but not apparently very thick. Above on 
the hill isa hard, red quartzite, in massive blocks, which are scattered over the surface of the 
slope. On the east side of the hill, near the creek, we have several exposures of a gray and yellow 
sandstone dipping east, strike northwest, followed by a reversal of dip in the same beds. Tue rocks 
here observed are a dark ochery-yellow sandstone, firm, and in rather thick layers, and a whitish 
sandstone, sometimes in very thin, papery layers, sometimes massive, but not often very firm; much 
the same association as at Hopley’s Hole. 
The foldings here are not nearly so extensive as those described before; the thickness of rock 
involved being perhaps not more than 1,000 feet. Near the hill, the dip is steep; but a mile from 
it the inclination becomes very gradual, and insensibly the strata subside, becoming nearly hori- 
zontal. <A slight eastward dip in the white sandstone is, however, reversed before reaching the 
Forks, where there is a broad alluvial country. This Seems tu be the dying out of the action which 
was more intense to the westward. Beyond the Forks, on the road to the Judith Gap (before trav- 
eled), the same brown sandstone and white sandstone are seen again, with a slight dip, which is 
