The LoDaisKa (Sanger) Site, about a mile and half south of Morrison,
Colorado, is a rockshelter under a projecting ledge of Paleozoic
(Pennsylvanian) sandstone that dips steeply east. The pre-ceramic
occupation layers at this site are believed to correlate with the Piney
Creek alluvium (Hunt, 1954, p. 114). The accompanying map (Fig. 66)
illustrates the general geologic setting of the site; it shows the
general distribution of one upper Pleistocene and two Recent units.
[2] Publication authorized by the Director, U. S. Geological Survey.
The upper Pleistocene unit (Qg on the map) is a bouldery gravel with
which is included some variegated, silty and clayey alluvium. This
bouldery gravel is exposed in Strain Gulch upstream from the site,
and it covers much of the upland northwest of that part of the Gulch.
Downstream from the site this bouldery gravel is southeast of the Gulch
and forms the high terrace extending from the site to the highway.
Because the deposit is bouldery, and because the boulders are little
weathered the deposit is assumed to be Wisconsin in age.
The alluvium with variegated colors mapped with this bouldery gravel
is exposed in Strain Gulch about 700 feet northeast of the site, and
in the tributary from the west that joins Strain Gulch about 200 feet
upstream from the highway. In this latter tributary the alluvium rests
on strata of Paleozoic age. At both localities the variegated alluvium
is overlain by dark-colored, sandy and silty alluvium.
The variegated alluvium has a distinct, lime-enriched zone, probably
representing the alluviated layer of an old soil from which the upper
layers have been eroded. The lime-zone is comparable in thickness to
that found in soils in Wisconsin age in the Denver area. Moreover, at
the outcrop in Strain Gulch, the lower part of the alluvium is stained
with iron oxide about the way deposits of Wisconsin age are stained
in the Denver area. However, the dating of the deposits is uncertain
because it has not been established whether the layers enriched in lime
and iron are the result of surficial weathering or ground-water action.
Probably, though, these deposits are late Pleistocene in age, and
fossils in them probably will include the Pleistocene forms.
[Illustration]
[Illustration: FIGURE 66—GEOLOGIC MAP OF LODAISKA SITE]
Overlying the bouldery gravel and the variegated alluvium is a
dark-colored, sandy and silty alluvium (Qp on the map), 1 to 6 feet
thick, that looks quite like the Piney Creek alluvium in the Denver
area. Both the Piney Creek and this alluvium are of Recent age. Fossil
bones were found in the alluvium at two places near the site (A and B
on the map). At A, 1 foot below the surface, articulated bones were
found; at B, a single bone was found and it was not in place, but
from a plowed surface on the upland. At this locality a chert flake
was found also. The bones were examined by Edward Lewis of the U. S.
Geological Survey and C. B. Schultz and L. G. Tanner of the University
of Nebraska State Museum and Geology Department. Their identifications
are as follows:
Locality A, fragments of a vertebra, femur, epiphysis,
and ribs of _Bison bison_ (Linnaeus) of Recent age,
and
Locality B, the badly weathered astragalus of a large
bovid, either _Bos Taurus_ or _Bison bison_ (Linnaeus)
of Recent age.
The unconformity at the base of the dark-colored alluvium is well
exposed at the localities indicated on the map.
Fragments of charcoal were found in the alluvium 200 feet upstream from
the site. This alluvium probably correlates with the pre-ceramic layers
of the occupation levels at the site, which, as reported by Lewis in an
accompanying paper, also contains vertebrate remains of Recent age.
The youngest deposit, a bouldery gravel confined to the present washes,
is a lag concentrate of the boulders and cobbles that are left by
washing out finer grained sediments from the Pleistocene deposits. This
deposit, and the arroyo-cutting with which it is associated, probably
developed throughout the period of the ceramic levels.