1/8 Bulletin of Labor atones of Denison University [voi.xi. 
Three horizons can be recognized in the Tertiary compos- 
ing this mesa, the uppermost being a layer of marl varying from 
ten to over twenty-five feet thick and found over all parts of the 
mesa where this level is reached. In some places, imme- 
diately beneath the thin surface loam or sand, what seems to be 
buffalo wallows have been excavated in it for the basis of which 
it was adapted by its impervious character. Thin layers of veg- 
etable charcoal are occasionally seen in connection with the marl 
justifying the idea that they are of lacustrine origin. No study 
has so far been made of the organic remains but they will no 
doubt prove interesting. A curious question arises as to the re- 
lation of this supposed Tertiary marl to the so-called Albu- 
querque marl described in the American Geologist, Vol. XXII, 
page 34. The latter is evidently fluviatile in origin and it may 
be suggested that, inasmuch as there are fragments of the Ter- 
tiary marl scattered through the river materials, it is possible 
that the superficial marly layer is due to erosion and redisposi- 
tion of the older formation. The diference in height of these 
marls is over 400 feet. The existence of a barrier in the Rio 
Grand valley below Albuquerque is suggested very evidently by 
the relations of the present to older river channels between 
Albuquerque and Socorro. These points are, however, reserved 
for another occasion. Beneath the marl is a sandy series which 
rarely is much indurated but is definitely stratified. The upper 
portion of this for perhaps seventy-five feet is of a reddish color, 
while the lower portions are lighter in color and contain less 
of gravel. The gravel is largely of chert and flint and may be 
traced to the Cretaceous while there are also granite fragments 
and andesite and trachyte pebbles. It is probable that the 
whole series from the infra-carboniferous granite and schist to 
the Cretaceous has been laid under contributions for the materi- 
als of the Tertiary sands but it is noticeable that in the vicinity 
of the red bed (Jura-triassic) these layers are prone to assume 
the red character of that formation and that in the neighborhood 
of the great tufa sheets of the Cochiti, for example, the materi- 
als are largely of a tufaceous and obsidian nature. Strata that 
may be the chronological equivalent in the vicinity of the bases 
