descriptive details: monero and dulce 615 



Descriptive Details 

 monero and dulce 



The details noted in the Durango region have been given in the de- 

 scription of the type section. The next place east of Durango in which 

 the writer made observations is between Chama and Dulce, on the Denver 

 and Eio Grande Eailroad, in northern New Mexico. Here the Dakota 

 sandstone was observed in a small canyon about 2 miles southeast of 

 Chama. The Mancos shale occupies a broad valley between Chama and 

 Monero, and near its base is a sandy zone, which represents in a general 

 way the Tres Hermanos sandstone typically developed farther south. 

 The writer collected no fossils from the Mancos in northern New Mexico, 

 but Schrader obtained Inoceranius fragilis H. & M., ScapJiites warreni 

 M. & H., and Prionocyclus ivyomingensis Meek from a locality on Chama 

 Eiver 2 miles northwest of Elvado, New Mexico, at a horizon estimated 

 by him to be about the middle of this shale. According to Doctor Stan- 

 ton, these fossils denote Upper Benton age. 



Just east of Monero the railroad passes through a sharp canyon in 

 which the basal sandstone of the Mesaverde forms conspicuous cliffs. 

 The westward dip of the rocks brings the coal beds that overlie this basal 

 sandstone down to the level of the railroad at Monero, where the coal has 

 been mined for many years. The Mesaverde here does not differ notably 

 in character from the Mesaverde. of the Durango region, and according to 

 Schrader (100), was traced from Durango to Monero. 



A few very poorly preserved leaves were found associated with the 

 Mesaverde coals near Monero. They are Brachyphyllum sp., Myrica or 

 Eucalyptus (n. sp.), and Ficus n. sp. The fossil plants seem to be re- 

 stricted to very narrow zones, and the sandstone both below and above 

 the coal beds contains marine fossils. Ostrea sp., Pecten sp., Inoceramus 

 barabini Morton, and Baculites anceps var. obtusus Meek (United States 

 Geological Society locality number 7206) were collected near Monero 

 from a sandstone a few feet above the highest bed of coal. 



The Lewis shale occupies a broad valley between Monero and Dulce. 

 Its thickness was estimated at 1,000 feet, but this estimate may be too 

 low, inasmuch as the measured thickness both west and south of Monero 

 is 2,000 to 2,500 feet (100, page 242) and (110, page 339). Schrader 

 traced this shale continuously around the northern rim of the San Juan 

 Basin, and thus proved it to be the eastward extension of the typical 

 Lewis shale. About half a mile north of Dulce tliis shale is very fossil- 

 iferous, and the following shells were collected from it at two horizons. 

 They occur in limestone concretions distributed somewhat sparingly 



