Custer weekly chronicle. [volume] (Custer City, S.D.) 1890-1931, 1896-05-16
GEOLOGY OF THE BLACK HILLS.
The Peculiar Structure and Scenery o.
the Interesting Region Elab-
orately Described.


The following description of thu
geology along the b. & NJ railway in thu
Black Hills by Prof. J. L. Todd, Stats
Geologist, will be perused with much
interest by large number of CnRoSIcL,
readers:
Through the courtesy of the genera
manager Of this railway, MIR. u. w
Holdrege, it was my privilege TO make 9
rapid tour oyer this line last season. II
affords rare opportunity TO become
acquainted with the peculiar structure
and scenery Of the Black Hills. II
traverses the Hills from south to north
and within the state has vertical range
nearly 5000 feet. IL affords unusual op
portunities for comprehensive views
especially as it passes over the top oil
Terry's Peak; and exhibits fine examples
OF engineering skill, particularly IN
descending the canyon of Spearfish
creek. 1t enters the state little north
Of Pine Ridge, in the valley of Hat
Creek, and passes nearly due north "a
Deadwood, sending of branches tc
Sheridan Wyo., Hot Springs and to th'
mouth of Spearfish canyon.
Before entering upon detailed ie-
scription Of the journey, IT is vel for
the reader to gain general view o the
peculiar structure Of the Black Hills, as
well as TO recall few prominent points
OF geological history.
The Black Hills are an irregular dome
shaped uplift rising 1000 feet above the
surrounding plain, or 5000 feet above
the sea. In its elevation ii seems to
have pushed up the everything forma-
tioss and burst through them, especially
along the the east side. These later for
nations lie at the angle of 1850 degrees,
dipping away from the center Of the
hills The interior Of the hills consists
of dark colored states and schists stand
ing up nearly vertically, and worn into
Jagged peaks or gentle slopes, according
to the degrees of hardness. These states
with masses ofgranits " hich lie in them,
belong to the oldest geological time,
known as the Archean or Eozoic. Rest
ing upon the states on all sides is the
brown sandstone known as the Potsdam,
which is l50-250 feet in thickness Over
lying this is the Carboniferous forma-
ton containing 400-500 feet of limestone,
capped with 100000 feet of colored sand
stones, the latter usually Of a red color I;
oyer this 800 or 400 feet of marly clay :,
in which is layer of purple limestone
or marble, about 40 feet thick, which are
referred to the Triassic. As the latter
are easily worn away, their location is
marked by red valley encircling the
hills on every side. On thi. formation
lies 100000 feet Of sandstone divided
into several separate beds, separated by
clay and shale. Most of the lower por-
ton ere usually Of reddish color and
are referred 10 the Jurassic psriod, while
the upper are of yellowish brown and
belong to the Cretaceous. These sand.
stones stand as a rampant, 300-500 feet
in height, surrounding the hills, forming
their more distinct boundary. On the
outside everything the sandstones are
thick deposits that form the surround.
ing plains consisting of grayish clay,
with occasional layers OF Calcareous
concretion, or thin beds Of sandstone.
These constitute the 50 called Colora.sl
ing the state, is located upon the upper
layers of the Colorado, or as some may
classify it, the lower portion ofthe Mon
tana. The surface is clothed with sparse
grass, and shows the undulation com
monty appearing as the result of erosion
upon the western plains. From Ard
more to Rumford the railroad follows
the valley of Hat Creek. From that
point the grade turns to the north west,
follows up a valley-like depression until
it reaches the Summit at Provo. To the
south Of that station sharply cut ridge
of Insignificant height is the distinguish
ing feature. In il little further on a
shslly sandstone appears at about the
laval Of tho atatinn nasnAn1inry fy,, . h.
valley of cottonwood Creek, on the west,
little attracts the attention until the
shally limestone ledge, belonging to the
Niobrara portion of the Colorado, APP
pears. Following down the valley of
Cottonwood Creek, Edgemont is reach
ed. the last station before entering the
hills. From this point appears the
valley of the south branch Of the Chey
enne, and beyond it the imposing ridge
of Dakota Sandstone.
A bed of quite valuable coal has been
discovered five or six miles east of this
point. Its workable extent has not been
determined. West of Minnekahtta the
same bed has been traced, but is not of
sufficient thickness for profitable work.
ing. These belong to the same geological
formation as the well known beds Of
Cambria and Newcastle in Wyoming.
Within the next six miles the railroad
climbs up the ridge reaching the center
Of il at Chilson From that point an ex-
tended view Of the valley of the Chey-
enne to the south is seen. From this
point the road although still ascending,
seems to pass between the higher points
of the ridge and enters the Red Valley,
which is there three or four miles in
width. Minnekahtta station is the
junction of the Hot Springs branch
which runs eastward along the Red
Valley to Eureka, where it enters the
higher and on the north through gap
in the Purple Limestone. Soon after il
meets Warm Brook a. it breaks from
the Carboniferous rocks from the north,
and follows it with the descent of nearly
700 feet frem Minnekahtta to Hot
Springs, which is again In the Red Vaf-
ley. This valley attracts common atten-
ton on account of the brick red soii
Much of it lies in favorable condition
for farming, and with sufficient moisture
is quite fertile. 1t contains valuable de-
posits OF gypsum everywhere.
Hot Springs has deservedly become a
prominent pleasure resort. Ii 10 located
in the valley Of Fall River. which above
the town divides into two streams one
called Hot Brook and the other Cold
Brook These streams seem to be main
ly formed from subterranean channels,
breaking from the inner side of the
valley. In the vicinity OF The town are
high ledges of conglomerate lying 40 or
80 feet above the station. These are OF
recent origin, probably dating from the
Glacial epoch. BY undermining, the
cliffs have been broken into large blocks
giving an air of wildnsss to the rayine.
Southeast Of the town is high point Of
Dakota Sandstone. North of Hot Springs
about ten miles is another attraction 10
the vicinity, known as Wind Cave,
which is noted for its numerous intricate
passages and delicate formations of
crystals and stalactites. The traveller is
peculiarly impressed In passing along |
the stream above Hot Springs In seeing |
large Persian water wheel constructed |
and doing its part in irrigating the valley.
At Hot Springs valuable cement works |
have been erected for the proper pre- |
paration OF gypsum. which is abundant |
In this vicinity as elsewhere.
The locality Of Minnekahtta has at |
tanned considerable notoriety ameng
geologists because Of tie recent finding |
near there Of low stump like petrifed |
tree trunks Of q palm-lIke pine. called |
t'ycad These are believed to belong 10 |
the Jurassic epoch, and probably may
be found at other points around the |
hills. They have been reported from
Hot Springs and Rapid City.
From Minnekahtta the railroad fol. |
lows the Red valley nsrthward gradually