Geological Survey Bulletin 613 Guidebook of the Western United States: Part C. The Santa Fe Route

Opposite Hilton siding (see sheet 9, p. 54), about three-quarters of a mile beyond milepost 526, is old Fort Lyon, a well-known military post on the Santa Fe Trail, which was an important depot of supplies. A regiment of soldiers was garrisoned there to give protection to travelers. The old fort is on the top of the bluff of Dakota sandstone on the north side of the river, and the few remaining buildings are plainly visible from the railway. They are now utilized as a United States naval sanitarium. Seven miles northeast of this fort a boring was sunk 815 feet by the United States Government in 1881 to test the underground-water conditions. It cost more than $18,000 and obtained only a very small flow of water, but it gave considerable information as to the succession of strata.

SHEET No. 9 (click on image for an enlargement in a new window)

At milepost 534 the railway crosses Purgatoire River, which flows from the south and drains a large area of the western Great Plains in southeastern Colorado; the railway reaches it again at Trinidad. This river was named Río de las Ánimas Perdidas (river of lost souls) by the Spaniards because of the loss of a party of travelers in its treacherous waters. The French visitors translated this to Purgatoire, which the frontiersmen pronounce and spell "Picketwire," and that name is now in local use.

Las Animas (ahn'ee-mas), the seat of Bent County, derives its name from the Spanish name for Purgatoire River. It is said that from this locality in 1806 Lieut. Zebulon Pike first saw the peak which now bears his name.¹ One of the principal industries of Las Animas ls a large beet-sugar factory, the beets for which are raised at many places in the vicinity by means of irrigation from ditches extending along the north side of the valley. Besides beets, of which the yield is 25 tons to the acre, much wheat is produced here, and all along the valley from Las Animas to Rocky Ford the famous Rocky Ford cantaloupes are raised.

---

¹Pike's expedition ascended Osage River and crossed the country northwestward to the Pawnee Republic, in Republic County, Kans., where he compelled the Indians to haul down the Spanish flag. He then proceeded southwestward to Great Bend, Kans., and ascended the Arkansas to the foot of the mountains in Colorado.

---

On the outskirts of Las Animas, not far west of the station, on the south side of the track, is a small settlement of Mexicans living in characteristic adobe houses. This is the first of these settlements to be observed on the Santa Fe route, but they are very numerous through southwestern Colorado and New Mexico. The old home of the noted scout Kit Carson, at Las Animas, is still in existence, and another survivor of the old days is the stage coach in which Horace Greeley toured the West in 1859.

A few miles west of Las Animas, on the north bank of the river, was Bents Fort,¹ a noted place on the Santa Fe Trail. This fort was very prominent in the days when the Army of the West marched through in 1846, but it was demolished in 1852 because the Government would not purchase it at the price asked. The building was a very large (180 by 135 feet) one-story structure 15 feet high, with walls 4 feet thick, situated several miles above the junction of Purgatoire and Arkansas rivers, where the trail crossed Arkansas River. In early days the Arkansas was the northern boundary of Mexico westward from a point near Fort Dodge. On crossing the river the caravans passed from the protection of United States troops to that of Mexican soldiers.

---

¹The Bent family was prominent in frontier history and established successive trading posts, each known as Bents Fort, among the Indians. The original post, up the river toward Pueblo, Colo., was built in 1828. The fur-trading firm of Bent & St. Vrain was next in size to the American Fur Co. Charles Bent was appointed Territorial governor of New Mexico by Gen. Kearney when the Army of the West took possession of Santa Fe. William Bent, one of the brothers, was a "squaw man," having married the daughter of a Cheyenne chief. His son after receiving a good education in St. Louis, gathered about him a band of savage Indians and became so dangerous an outlaw that the Government offered $5,000 for his capture.

---

Five miles west of Las Animas the railway approaches bluffs of dark Graneros shale capped by the Greenhorn limestone, which extend along the south bank of the river for some distance to the west. A slight westerly dip finally carries the shale below the surface of the alluvial filling of the valley, but cliffs or ledges of the limestone are almost continuous nearly to La Junta. These ledges consist of alternating thin beds of limestone and dark shale, a feature which is highly characteristic of this formation and is shown in Plate VI (p. 52). In an exposure 20 feet high there may be thirty alternations of such beds. This feature indicates that, at the time of their deposition, there were rapid and repeated changes from muddy water, depositing dark clay, to clear water, from which the calcium carbonate, now represented by the limestone, was separated. It is thought that these changes were due to changes in climatic conditions. As this feature is characteristic of the Greenhorn limestone in a region more than 2,000 miles from north to south and 500 miles from east to west in the Great Plains province, it shows that the conditions of deposition were uniform over a wide area.

On the north side of the river flat west of Las Animas is the edge of a table-land showing bluffs at intervals, in which are many small outcrops of the Timpas limestone, a formation about 200 feet higher in the geologic column than the Greenhorn. Outlying areas of this table-land some distance south of the tracks may be seen at intervals for 6 miles. A few rods east of milepost 552 a small canyon south of the railway shows the characteristic alternation of shale and limestone beds in the Greenhorn limestone.

La Junta (hoon'ta), the seat of Otero County, is a railway division point where all trains stop for change of engine and meals are served. Here also the line for Colorado Springs and Denver branches off, continuing westward up the valley of Arkansas River to Pueblo. La Junta is a very old town for this part of the country. Seventy years ago it was an important trading center on the Santa Fe Trail which crossed the river a short distance below and from La Junta continued southwest near the line of the present railway to Trinidad. A stone monument a block south of the station marks its location in La Junta. The principal industrial interests here are the large railway shops, but the city also has the trade of an extensive adjacent ranch country. The name is a Spanish term, meaning junction, and refers to the convergence of the old trails at this place. Much of the water supply of La Junta is obtained from artesian wells sunk through the limestone and shales to the porous Dakota sandstone, in which the water is under enough head to afford a flow.

The long westward journey across the plains terminates a short distance west of La Junta, and beyond may be seen the eastern edge of the Rocky Mountain ranges, rising above the western edge of the plains and extending from north to south, presenting a magnificent panorama. The sight of these mountains cheered the hearts of the overland wagon-train immigrants after their dreary marches across the plains, and it still cheers the sons of the West as they return to their mountain homes and also welcomes the stranger to the Cordilleran country. These ranges extend 270 miles southward, to Glorieta Pass, and in order to get around them the railway now begins to turn in the same direction and will soon enter a region that presents interesting phenomena along their foothill margin.

A short distance west of La Junta the route leaves the valley of Arkansas River. It crosses the plains toward the foothills of the Rockies, following a course nearly due southwest to Trinidad. It is close to the old Santa Fe Trail all the way. There is a continuous upgrade, at first on long, gentle slopes of the Timpas limestone,¹ a rock which appears in numerous cuts and small outcrops along the track to and beyond Timpas siding.

---

¹Timpas limestone, which was so named from its occurrence on Timpas Creek, is widespread in the central Great Plains region and constitutes the lower formation of the Niobrara group. The principal body of limestone is from 50 to 60 feet thick in most places and grades upward through 100 feet or more of limy shales and thin-bedded limestone to the Apishapa shale, the upper formation of the Niobrara group. The gray shales of the Apishapa constitute the hills west of Timpas siding and they are also crossed by the railway farther southwest.

---

In this region the strata rise southwestward at a rate slightly greater than that of the railway grade. This structure is shown on the cross section on sheet 9, which represents not only the attitude of the rocks but also the relative thickness of the formations and facts revealed by deep borings at intervals.

The old Santa Fe Trail passed 400 feet east of the site of the station at Timpas. A short distance beyond this place the Timpas limestone caps mesas¹ or buttes of considerable prominence, especially along the east side of the track, and a little farther southwest it extends southward in a long line of low westward-facing cliffs. Below these cliffs, are slopes of Carlile shale, at the foot of which, near Ayer, is a bench of the Greenhorn limestone. Along this portion of the valley of Timpas Creek, on both sides, are excellent exposures of long, sloping mesas capped by the Timpas limestone. This rock, though soft as rocks go, is much harder than the shales and remains where the overlying shale is washed away. The limestone caps project in a cliff presenting the greater part of the thickness of the formation. Most of the mesas slope to the northeast because the limestone dips in that direction.

---

¹Mesa (may'sa), a Spanish word meaning table, is applied to a flat-topped butte or hill, while one that has a sloping tabular surface is called a cuesta (kways'ta), from one of the Spanish words for hill.

---

FIGURE 6.—Section across Timpas Creek valley near Bloom, Colo. looking southwest. a, Timpas limestone b, Carlile shale; c, Greenhorn limestone; d, Graneros shale,

From Symons to and beyond Bloom the ordinary features presented in the Timpas Creek valley are a low, wide bench or shelf of Greenhorn limestone at or near the bottom and a slope of about 200 feet of Carlile shale, rising to a cliff at the edge of the tabular surface of the mesa of Timpas limestone. (See Pl. V, A, p. 29, and fig. 6.)

The areas of Timpas and Greenhorn limestones carry a small growth of "cedars" (Juniperus occidentalis), termed sabina by the people of the country. The cane cactus (Opuntia arborescens) becomes conspicuous in this vicinity and is abundant to the south and west through Colorado and New Mexico, together with flat-leaved cactuses of various species. (See footnote on pp. 155-156.)

The Dakota sandstone is exposed a short distance west of the railway at milepost 590, being brought up by a low dome, as shown in the cross section on sheet 9. The outcrop of this sandstone extends to Delhi and beyond, with the adjoining higher slopes of shales and limestone in a relation closely similar to those shown in figure 7.

FIGURE 7—Section across Timpas Creek valley at Thatcher, Colo. looking southwest. a, Timpas limestone; b, Carlile shale, with sandstone at top; c, Greenhorn limestone; d, Graneros shale; e, Dakota sandstone; f, Purgatoire formation.

At Delhi the railway crosses the Santa Fe Trail, the old wheel tracks of which are plainly visible in the slope rising to the west. A few rods west of Delhi a deep canyon cuts through the Dakota sandstone and exposes the beds of the shales and sandstones of the underlying Purgatoire formation (Lower Cretaceous). At West siding the Dakota sandstone again appears in the bottom of the valley west of the railway, and from a point a few miles south of West to and beyond Thatcher the railway runs along the top of this sandstone and the lower edge of the Graneros shale is a few rods to the east. This feature is due to a slight upward arching of the beds that are cut into by the valley. The relations of the formations in this vicinity are shown in figure 7.

PLATE VI.—GREENHORN LIMESTONE NEAR THATCHER, COLO. Shows characteristic alternation of thin layers of limestone and shale, indicating rhythmic changes in conditions of deposition.

A short distance east of Thatcher is a bench of Greenhorn limestone with scattered junipers, and at the top of the mesa beyond is the Timpas limestone with numerous junipers. The old Santa Fe Trail extends southwestward along the west slope of the valley in this vicinity, its course being marked by a granite monument a mile west of Thatcher. A few miles farther southwest the railway again crosses the trail.