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Show 92 western strike. They were as elsewhere of a soft yellowish sand and clay, including shale beds, and contained abundance of Inoceramus, like those found on the Gallinas. Ten miles to the southward, the underlying Cretaceous heds are capped by a horizontal table of basalt, thus forming a mesa, through which the Puerco passed in a canon. I supposed this to be the forerunner of the great basaltic plateau, which, according to Lie utenant Wheeler, constitutes the country south of the Rio Chaco for a great distance, one of little promise to tho agriculturist. These tracts are known as the Mesa Fachada and Mesa de los Lobos. The season being well advanced, ( October 22,) I thought best to commence the return march, which we accordingly did. The soapy marls, or, as they may be called, the Puerco marls, have their principal development at this locality. I examined them throughout the forty miles of outcrop which 1 observed for fossil remains, but succeeded in finding nothing but petrified wood. This is abundant in the region of the Gallinas, and includes silicified fragments of dicotyledonous and p 4 m trees. On the Puerco, portions of trunks and limbs are strewn on the hills and ravines; in some localities the mass of fragments indicating the place where some large tree had broken up. At one point east of the river I found the stump of a dicotyledonous tree which measured 5 feet in diameter. As already remarked, the Puerco marls belong to the Eocene series in their strict conformability to the superincumbent rocks of that age. They do not appear to represent the FortUuion or Lignite beds of Northern Colorado and the North, as they differ in almost every respect. They contain no lignite nor coal, although their occasional black color may be due to a small amount of carbonaceous matter. They have no resemblance to the Fort Union beds in mineral character or fossils. I conclude, as a result of the investigation, that the latter formation has no existence iu this part of New Mexico. The presence of such quantities of petrified wood gives weight to the probability that the Puerco marls are a lacustrine formation. Iu exploring the hills of this formation along the Puerco, I found the horns of an elk, ( Cervus canadensis.) This locality must be near the southern limit of its range. I learned that it is not uncommon on the high plateau near Tierra Ainarilla on the northeast. I made a second section of the upper or Green River beds to the west, starting from opposite the middle of the northern bad- land cove. About the middle of the marl series there is usually present a bed of nearly white sandstone, frequently quite hard, in which the fossils have generally a worn or rolled appearance. Here occurred the greater number of the sharks' teeth, but not all. Above this horizon the most abundant fossils are the gars and crocodiles, while the greater number of the mammals I Ki. 17.- Ead lauds of the " Wahsntcb beds near camp No. 2. come from below it; but this distinction is of a very general character. On climbing the western escarpment of these marls, the summit is found to be a plain sloping at a |
