Online guide to the continental Cretaceous-Tertiary boundary in the Raton basin, Colorado and New Mexico

Sites to See

Starkville sites to Raton, New Mexico

Leaving the Trinidad area, go south over Raton Pass on I-25, through rocks of the Trinidad Sandstone (delta-front and barrier-bar environments) and Vermejo and Raton Formations (deltaic fluvial environments), to the contact of the Raton and Poison Canyon Formations (fluvial environments), which is near the top of the pass. Several coal beds, dikes, and sills can be observed in roadcuts along the route. Going south from Trinidad, coal dumps along the way are from early mining in the area.

The route passes gently dipping alluvial floodplain sequences of sandstone, mudstone, shale, and coal beds of the Vermejo and Raton Formations and, about six miles south of Trinidad, the Morley dome becomes evident, marked by subtle changes in dip that bring the Trinidad Sandstone and Pierre Shale to the surface. The Morley dome has about 450 ft of closure and was apparently formed by the intrusion of a Tertiary plug or laccolith, which crops out about 1 mi northeast of the abandoned town of Morley. The crest of the fold is between the town and the exposed plug, and the closing contours extend for some distance around the north and east sides of this igneous intrusion. Coal seams lacking evidence of natural coking or metamorphism have been mined to the contact with the igneous plug. A minor oil seep was recognized in one mine and in 1948 Stanolind drilled a dry hole on the crest of the structure to a total depth of 6,831 ft into "granite." The K-T boundary is exposed in several I-25 roadcuts between the Starkville exit and Morley. Palynological examination of samples from a sequence of thin coal beds beneath a south-dipping sequence of sandstone beds of the barren zone of the Raton Formation just south of the Morley coal waste pile indicates they are of Cretaceous age and the K-T boundary must lie above the coal beds, perhaps in the basal sandstone.

Morley

Morley began as a railroad town on the A.T.&S.F. line in 1879, and trains were commonly shortened here before beginning the difficult climb over Raton Pass. Inactive during the late 1800's, Morley became a coal mining company town in 1906, when CF&I opened the Morley mine. The fine grade coking coal mined here was utilized by the steel mills in Pueblo and by Santa Fe Railroad locomotives. Peak coal production reached 500,000 tons per year in the late 1920's when the town had a population of over 1,000. The Morley mine was never mechanized; the use of blasting powder and machinery was prohibited because of significant amounts of methane gas. Instead, the coal was extracted by hand labor and an underground herd of donkeys was maintained to haul the coal out of the mine; in fact, the Morley was reportedly the last mine in the U.S. to use these beasts. Cutbacks in steel production at Pueblo temporarily halted coal production in the early 1950's, and the mine was closed permanently on May 4, 1956, when all workable deposits had been exhausted. From 1907 until 1956 the Morley mine produced 11 million short tons of coking coal.

Top of Raton Pass

The view from the parking area includes the Trinidad coal field, the Spanish Peaks, and the high peaks of the Sangre de Cristo Mountains. The Spanish Peaks form a landmark that is visible throughout hundreds of square miles. The area lying between Raton Pass and the Spanish Peaks contains several hundred million tons of coal resources and probably trillions of cu. ft of related coal bed methane. The sign at rest area reads:

"Raton Pass, named by the Spanish for the rock rats found there, was crossed by the Mountain Branch (also called the Bent's Fort Branch) of the Santa Fe Trail. Originally part of an old Indian trail, the pass was used by Spanish expeditions at least as early as 1718 and probably much earlier. When the Cimarron Branch of the Santa Fe Trail was abandoned because of its dangerous desert stretches, pioneer traffic increased over Raton Pass. Kearny's Army of the West came this way in 1846 with some of the first vehicular supply wagons to cross the pass. 'Uncle Dick' Wootton, frontier scout, built a road over the pass in 1865 and collected tolls, often at the point of a gun until the coming of the railroads in 1878. For two years, a controversy raged between the Denver and Rio Grande and the Santa Fe Railroads to determine which company had the right of way over Raton Pass. After several section crew fights and much legal maneuvering, the Rio Grande gave up its claim to Raton Pass and the Santa Fe agreed not to contest another disputed right of way through the Royal Gorge."

The contact between the Raton and Poison Canyon Formations is gradational through several feet of section. It is mapped approximately at the color change from grayish-yellow-weathering rocks to grayish-orange and grayish-red and-brown-weathering rocks just below the north exit from the Rest Area. The top of the Trinidad Sandstone is about 1,250 ft below the top of the pass. The thickness of the Vermejo Formation is estimated to be about 70 ft in this vicinity, making the Raton about 1,180 ft thick. To the west, in the central part of the basin, thicknesses are greater than 2,000 ft for the Raton and about 300-400 ft for the Vermejo.

Proceeding on south from Raton Pass, follow the route of the Mountain Branch of the Santa Fe Trail (Scott, 1986) and pass back down section through the three zones of the Raton Formation. Thick coal beds are exposed in roadcuts in the upper coal zone and stacked channel sandstones make up the barren zone toward the bottom of the pass. The lower coal zone of the Raton and the Vermejo Formation are present in roadcuts near the mouth of the valley. The Trinidad Sandstone crops out just before the Raton exit. The town of Raton is built on the Pierre Shale. Enter Raton.

Turn right at the first intersection past the Melody Lane Motel to Moulton Avenue, which will continue up Goat Hill on the old Raton Pass road to stop 3, the Raton Pass K-T boundary site (Fig. 1). Proceed up Moulton past the Shady Mountain Park trailer court through the Trinidad Sandstone. At the junction, keep right. The top of the Trinidad Sandstone is approximately at the next loop in the road. The upper and lower coal beds of the Raton coal zone are exposed in roadcuts above the Trinidad. The basal conglomerate of the Raton is not present and its contact with the underlying Vermejo Formation is indefinite. Continue on up section through the lower coal zone of the Raton Formation to the saddle. Just below the saddle the Sugarite coal zone (Upper Cretaceous) is exposed in the roadcut.

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