In following the road log outlined below, you will
see a number of geological features which are described in other
sections of this report. Keep your eyes open for the various terrace
levels. Briefly, these are the number 1 terrace or the present stream,
the number 2 terrace about 15 feet above the present stream, the number
3 terrace about 25 feet above number 2 and the number 4 terrace which is
at varying heights above the number 3. Also note the great amount of
slumping on both banks of the river. This is the cause of the steeply
dipping beds along the road. You will also see sandstone concretions and
peculiar weathering shapes and forms. We hope that from this short
geologic report you will learn something of the geology of this
fascinating area.
0.00 | Entrance. Set speedometer at
0. |
0.1 | Road to left of Park
headquarters. |
0.3 | You are riding over the Number 3
terrace. Note slump blocks to your right. |
0.6 | Road starts up over slump
block. |
0.7 | Note lignitic black shales straight
ahead. |
1.0 | Number 3 terrace again. This terrace is
most prominent in the Park. Note the bedded or laminated nature of the
terrace deposits resting on the bedrock under this terrace. This flat
surface probably represents cutting by water action when the stream ran
at a higher elevation than now. It might also be cut by wave action when
a lake temporarily occupied this valley.
Note how the terrace extends up the tributary
valleys. Good exposure of undisturbed Sentinel Butte formation to the
right. Note the sandstone concretions (round or irregularly shaped
sandstone masses) in the beds near the base of the cliff. |
1.3 | Cross small bridge. Note bedded terrace
material in side of ravine on your right. |
1.6 | Start over another slump area.
Rusty-looking small chips on right are ironstone or limonite
concretions. |
1.7 | Note lignite in slump block in road
ditch to right. Note that the beds in the slump block dip into the hill.
See the section of this report on slumping for explanation of what
happened here.
Note large iron-stained sandstone concretions just
ahead to right. |
1.9 | Begin Number 2 terrace. Nate small
rain-eroded columns to right. The beds of the Sentinel Butte are very
easily eroded. |
2.1 | Here the Number 2 terrace has
practically regraded or eroded away the Number 3 terrace. Only small
remnants of Number 3 terrace are here near the bluffs. |
2.3 | Note small pillar on right formed by
the sandstone concretion serving as a protective cap keeping the soft
material immediately below it from being rapidly eroded away. |
2.5 | You are on Number 3 terrace again. Look
back to your right and you can see that this terrace is formed both of
alluvial material and cut in the bedrock itself. |
2.7 | Slump blocks to right. |
2.8 | Iron stone concretions abundant to
right. |
2.9 | Excellent view of slump block dipping
into cliff straight ahead. The slump block you are now driving past has
slipped down the hill at least 150 feet by actual measurement. This
measurement was made by matching beds in the slump block with those on
the cliffs which are not disturbed by the slump. Some small erosional
caves can be noted on this cliff also. These features erode away rapidly
and form just as fast. |
3.5 | Cross small ravine. Note how the Number
2 level is extending itself up into the Number 3 level. Eventually it
will destroy the Number 3 terrace and higher levels. |
3.8 | Note the red rock in the hill ahead of
you and to your right. This is locally called "scoria" and is formed
when the lignite burns and bakes the overlying rocks turning them red in
color. |
4.0 | Road is crossing slump block in Number
3 terrace. |
4.3 | Road crosses small gully. This is an
extension of Number 2 terrace into Number 3 terrace. |
4.6 | Road is on top of another slump block.
Note "scoria" in cliffs to right. |
4.8 | You are at edge of Number 3 terrace and
about to drop down on to the Number 2 terrace. Note the sandstone
concretion in the cliff to your right. Also note the fluted appearance
of the soft easily eroded sandstone. These flutings are due to erosion
by water running down the face of the cliff. These flutings are
important in the formation of these steep sided cliffs. |
5.1 | Bridge and entrance to Squaw Creek camp
and picnic ground to left. The Squaw Creek campground is a good place to
see the river in action and to get some idea of how sediments are
carried and deposited by running water. The sand and silt carried by the
high water is left when the water goes down and shows the current ripple
marks of the water. The banks of the stream are constantly changing by
being eroded here and built up by deposition there.
The Little Missouri is a heavily-loaded stream but it
carries a great deal of material in high water. It is probably still
deepening its bed in spite of the high amount of sediment it
carries.
Across from the campground is an abandoned school.
Near this school are deep but very small diameter pits which were dug by
the Indians and used as cache pits to store their food. Also nearby but
outside the Park boundary are tepee rings. All this suggests repeated
occupancy of this area by the Indians prior to the advent of the white
man.
To the north of the Squaw Creek campgrounds in the
rough terrain bordering the side of the valley is the unmarked grave of
"Scrap Iron Bill" Bryant, a cousin of the poet William Cullen
Bryant. |
5.4 | Start up grade. This is contact between
Number 2 and Number 3 terraces. Note the sandstone outcrop in road cut
to left. |
5.5 | Road to Squaw Creek campgrounds to
left. Good view of Squaw Creek to right. Most prominent terrace is
Number 3 terrace but the Number 2 terrace can be seen to have made
considerable inroads into it. The top of the cliff ahead of you and to
the left probably is a remnant of the Number 4 terrace. The Number 4
terrace in the Park proper is not well shown as it has been badly eroded
and slumped. Therefore it appears to be a number of different levels.
Furthermore as it represents several streams not entirely governed by
the same conditions it might be expected to have varied
levels. |
5.8 | Note harder sandstone beds to left.
Also note fluted weathering. |
6.0 | Trail up Squaw Creek to
right. |
6.2 | Good view of Number 3 terrace up Squaw
Creek to right. |
7.1 | Note you have followed Number 3 terrace
up to this point in the ravine. This shows how intricate this terrace is
and how it extends up every draw. It has a very high gradient (drop in
feet per mile). |
7.5 | You are now on what remains of terrace
Number 4. Very irregular here as you can see. |
7.6 | Note gray clay on right. Note how it
has "flowed" down hill. |
8.0 | Note lignite in cliff to
right. |
8.1 | Note "scoria" to left. |
8.3 | You are now above all the terraces and
are on the upland plain. |
8.4 | Lookout. Get out of the car and walk to
left to lookout house. The view is grand and the walk will do you good.
At the lookout you will see below you an excellent exposure of the blue
clay you have seen in the sides of the cliff previously. This blue clay
is a bentonitic clay which is very plastic and which swells three or
four times its regular size when wet. This member is herein locally
called the "Big Blue" and can be traced for many miles up and down the
river as well as to the north.
A good "scoria" outcrop is visible to the west.
The Number 1 terrace is the present stream. The Number 2 terrace is just
above the Number 1 terrace and is wooded. Above it and extending up into
the ravines (i.e. just below the lookout) is the Number 3 terrace.
Number 4 terrace is just below lookout and is poorly developed.
Note the thin lignite just below lookout house to the west.
The lookout house is made of local sandstone. Note the irregular ripple
cross bedding in the sandstone blocks. This suggests that the sand
forming this rock was deposited when currents were actively moving the
sand about. |
9.0 | At this point the road is very close to
the Number 4 level which is just below the road on the left. |
9.4 | Road at Number 4 level here. The level
well developed to right. Also note extensive outcrops of "Big Blue"
bentonitic clay bed to right. The yellow beds to the right are also
prominent in this area. They are siltstones and silty clays. |
10.3 | Looking straight ahead for several
miles you can see a valley running northeastward. This is the Number 4
level and this valley was part of the Little Missouri valley when it
flowed northward to Hudson Bay prior to the drainage changes outlined in
another part of this report. You can see in this view and later views
how gradually the Number 4 level grades into the upland and vice versa.
This is because they developed together for a long time without
interruption, geologically speaking. Then came rejuvenation of the
streams with rapid downcutting and the later levels were cut into the
upland Number 4 terrace. |
12.9 | Note disc-shaped sandstone concretion
on right. |
13.1 | On left note how cedars grow well on
north side of bluffs but hardly at all on the south side of the bluffs.
This is probably due to moisture staying longer on the north side as sun
doesn't strike north facing slopes so directly. |
14.5 | Sperati Point-parking overlook. End of
the road log. Get out and enjoy the magnificent view. Immediately below
you is one of the most obviously slumped areas in the Park.
Note the cut off portion of the stream. This is called a meander scar or
when it has water in it an oxbow lake and is due to the stream changing
its course. The stream has done this many times in its lifetime.
All terrace levels are present in this view but the slump area accounts
for most of the Number 3 level. |