31

collected in that locality, which taken as a whole clearly indicate to me the Cretaceous age of the strata.

The flora from these beds was not so extensive as the invertebrate fossils, but the evidence it furnished of the Cretaceous age of the strata was none the less decisive. The specimens obtained belonged to the dicotyledons, and that family of plants have never been found in strata older than the Cretaceous.

There is no perceptible unconformity between the upper strata of the Plains and that of the underlying beds, except in the vicinity of the head of Fossil creek in New Mexico, where the Tucumcari beds lie between the Triassic and Tertiary, and there the unconformity is very perceptible, as the Tucumcari beds dip to the southeast at a considerably greater angle than do the beds above, yet this is only local, for the Tucumcari beds at other localities where they were seen were almost horizontal.

GEOLOGICAL FEATURES WEST OF THE STAKED PLAINS.

There is a belt of country situated between the western escarpment of the Staked Plains and the foot of the Gaudalupe Mountain range beyond, that is about three hundred miles long from north to south and from sixty to one hundred miles wide. At one period the strata composing the upper strata of the Staked Plains extended entirely over this district, as is evidenced by the fact that there are remnants of that strata still remaining at various localities throughout the entire area. At a later period occurred a deep erosion which has carried away in places the upper strata and exposed the underlying Cretaceous, Triassic, Permian and Carboniferous formations.

Through this belt of country the Pecos river has cut a deep wide valley diagonally from northwest to southeast. The immediate channel of the river for most of the way is deep and tortuous. The drainage is all from the western side of the river.

The dip of the strata is from the northwest, with an occasional fold in the strata running parallel with the mountain range.

The Triassic beds occur all along the foot of the western escarpment of the Plains and are composed of sandstone and red clay.

The largest part of this belt of country, between the foot of the Plains and the mountains, is covered by the upper beds of the Permian, composed of strata very much the same as that of the upper Permian east of the Staked Plains. The strata of the Permian comprise red clays, red sandstone, white sandstone, limestone, gypsum beds, and a peculiar conglomerate of clay nodules and iron.

The most of the red clays are heavily charged with common salt and gypsum. Interstratified with the clays and sandstones are beds of massive gypsum.