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Geology of the North Unit, Theodore Roosevelt National Memorial Park


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.

Theodore Roosevelt National Memorial Park North Unit

(Numbers on left refer to distances from Park Entrance)

0.00Entrance. Set speedometer at 0.
0.1Road to left of Park headquarters.
0.3You are riding over the Number 3 terrace. Note slump blocks to your right.
0.6Road starts up over slump block.
0.7Note lignitic black shales straight ahead.
1.0Number 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.
1.3Cross small bridge. Note bedded terrace material in side of ravine on your right.
1.6Start over another slump area. Rusty-looking small chips on right are ironstone or limonite concretions.
1.7Note 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.
1.9Begin Number 2 terrace. Nate small rain-eroded columns to right. The beds of the Sentinel Butte are very easily eroded.
2.1Here 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.
2.3Note 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.
2.5You 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.
2.7Slump blocks to right.
2.8Iron stone concretions abundant to right.
2.9Excellent 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.
3.5Cross 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.
3.8Note 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.
4.0Road is crossing slump block in Number 3 terrace.
4.3Road crosses small gully. This is an extension of Number 2 terrace into Number 3 terrace.
4.6Road is on top of another slump block. Note "scoria" in cliffs to right.
4.8You 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.
5.1Bridge 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.
5.4Start up grade. This is contact between Number 2 and Number 3 terraces. Note the sandstone outcrop in road cut to left.
5.5Road 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.
5.8Note harder sandstone beds to left. Also note fluted weathering.
6.0Trail up Squaw Creek to right.
6.2Good view of Number 3 terrace up Squaw Creek to right.
7.1Note 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).
7.5You are now on what remains of terrace Number 4. Very irregular here as you can see.
7.6Note gray clay on right. Note how it has "flowed" down hill.
8.0Note lignite in cliff to right.
8.1Note "scoria" to left.
8.3You are now above all the terraces and are on the upland plain.
8.4Lookout. 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.
9.0At this point the road is very close to the Number 4 level which is just below the road on the left.
9.4Road 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.
10.3Looking 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.
12.9Note disc-shaped sandstone concretion on right.
13.1On 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.
14.5Sperati 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.

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Last Updated: 28-Mar-2006