LARAMIE PLAINS RED BEDS AND THEIR AGE 415 
North Park road, where they occur through a thickness of at least 80 or I0o 
feet, and are interstratified with dark, intensely red sandstones. South of the 
road are some remarkably eroded forms suggestive of ruined cities. 
West of Antelope Creek the Trias extends twelve miles to the south of 
the Wyoming and Colorado boundary, filling a bay-like depression in the 
Archean body. Here are exposed, along the eastern side of Laramie Valley, 
1,200 feet of beds having a very slight dip to the north and west, a high, 
abrupt wail of nearly 1,000 feet presented toward the plains. Upon the front 
of this escarped precipice may be seen the interstratified marls and lime- 
stones of the Jura, overlying the heavier red gypsiferous beds of the Trias. 
In contact with the Archean body the sandstones are of coarse, ash-colored 
materials containing angular fragments and rounded pebbles, with more or 
less calcareous matter in the cement, followed by a hard, thin, cherty lime- 
stone which passes up into reddish-gray sandstone, and above this the usual 
beds of coarse red sand, with numerous red clay beds, varying shaly, which 
give a prevailing argillaceous character to a wide zone of sandstone. Within 
this red argillaceous series are thin beds of pure clay and white gypsum, the 
latter varying from two or three inches up to several feet, with one solid body 
of twenty-two feet inclosed between two series of intensely red, dark, indu- 
rated sand-rock. Above the gypsiferous zone occur heavy red sandstones, 
which pass through yellowish friable beds with marly intercalations into the 
calcareous beds of the conformable Jura. 
The following section illustrates the chief features of the Triassic series, 
as displayed here, beginning at the summit: 
1. Yellowish-red sandstone, passing down into fine, deep-red, evenly bedded, strongly 
coherent sandstone - - - - - - - - 375 to 400 feet. 
2. Argillaceous shales and argillaceous sands, with interstratified layers of fine pure 
clay, the whole prevailing red, with grayish and yellowish-red zones carrying four 
or five beds of gypsum, one reaching twenty-two feet in thickness; in all 150 feet. 
3. Red compact sandstones, beds of varying thickness, some coarser and some 
finer - - - - - - - - - - - - 250 feet. 
4. Reddish-gray sandstones carrying a bed of cherty limestone four or five feet 
thick; the whole - - - - - - - - - - 175 feet. 
5. Coarse, friable, ash-colored sandstones of remarkably loose texture, matrix con- 
taining more or less calcareous matter, with sheets of pebbles, partly rounded and 
partly angular cherty masses, together with some fragments of Archean schists, 
both hornblendic and granitoid - - - - - - 150 to 200 feet. 
There is no question but that King visited the Red Mountain 
area while making his survey; for there is no other place on the 
Laramie Plains where the Red Beds rise in nearly vertical walls 
upward of 500 feet. At the beginning of the chapter from 
which the above extracts were taken King states that he will 
