University of Virginia Library

Section B

THE RELATION BETWEEN CULTURAL LEVELS AND
SOIL STRATA IN THE REFUSE MOUND

By Donovan Senter

In the refuse dump[9] natural strata show up in the cross-section
profiles (see Fig. 2). These strata appear to be of different types of deposit,
although all contain more or less ash, charcoal, bones, potsherds,
and cultural material of other types. In view of the work done in
1936,[10] it was felt that there might be a possibility of relating these
changes in appearance of deposition to the general changes in deposition
in the canyon over a long period of years. At all times, it was kept
in mind that these strata might be, however, merely artificially
produced by changes in the type of material thrown upon the dump
and by cloudbursts or floods.

The weather fluctuations shown for the canyon in the tree ring
chart, and responsible for the various levels of deposition and of
erosion shown on the cut taken near Chetro Ketl,[11] were taking place
at the time these two small ruins were occupied, perhaps 800 to 1080
A. D., and while their dump was being laid down. Indeed, both the
observed evidence and a priori considerations suggest that, although
the greater part of this dump material was artificially laid, sandstorms,
sheet wash, and erosion affected the surfaces of the artificial deposition
as it grew up year by year. One might think of the household
debris as sometimes being sandwiched in between the various thin
natural deposits from heavy sandstorms and torrential rains, and at
other times as being modified by other erosion. The total amount of
erosion and of deposition depended mainly upon the weather fluctuations.
The principal question which arose concerning the demarcation of
natural strata was whether any particular line of demarcation was
cultural or natural, that is, whether these strata indicated cultural
divisions, weather fluctuations, or both.

The Situation.—This dump rests upon a low ridge which runs
directly out from a point of carboniferous shale of the Allison series,

which underlies a cliff of Chacra sandstone. From the base of this
cliff the sheet wash of torrential rains, which are (now, at least)
common in Southwestern summers, spreads out over the dump surface,
the wash flowing principally toward the north in the direction of the
canyon bottom and secondarily toward the eastern and the western
edges of the mound, which probably were slightly lower than the
central area. The household refuse, with its basis of sand and ash, is
soft, lacks compactness, and is easily cut by water, and the presence
within the deposits of sherds, small pieces of sandstone, bone, etc.,
further prevents packing and exaggerates the tendency toward erosion.
A refuse mound located on flat ground or rising in a considerable
peak above the surrounding surface would be more or less equally
eroded from all sides and the lighter material from the peak of all
the lower slopes. A mound, however, which is only slightly rounded
on top and which slopes as a whole in the direction naturally taken
by runoff flowing toward the canyon floor[12] is washed principally from
one direction, and the lower side receives the accumulation washed from
the area behind it. Thus we have a constant washing northward of
sand, charcoal, the light weight sherds, and especially ash from the
more southern lenses of dumped refuse. Naturally, the lighter substances
like charcoal, if not trampled into the surface and crushed,
would be subjected to movement by a minimum of natural force (wind
or water). Similarly there is, in general, a continuous process of
migration of sherds downward into the underlying strata, for as the
sand and ash are washed from beneath and around the sherds, those
too heavy to be carried with the rivulet must sink (or be trampled in
wet soil) to the bottom of the cut.

A further dumping of refuse fills up the cuts and elevates the
ground surface, but the next storm will slightly pack and lower this
surface and introduce new cuts and rivulets. The sherds of different
periods are mixed northward and downward in movements stimulated
by natural forces. The areas most affected are those farthest north,
which have received the full brunt of both processes for perhaps a
thousand years, possibly two hundred or more during occupation of the
mounds and probably about eight hundred since. Similarly, those
farthest to the south are least mixed by washing and should give the
most dependable records of pottery type complexes and percentages
available in this refuse mound.[13]

Method.—Section 6 (see Fig. 1) of the refuse mound was about
midway between the northern and the southern extremities. This
long east-to-west cut provided opportunity for study of the appearance,
composition, and dip of the succession of strata making up the dump at
this longitude. These strata were traced and were drawn on coördinate
paper (see Fig. 3), each stratum being marked for composition
and general appearance, and photographs were taken. From trenches
3, 7, 11, and 15 the columns were removed in 6″ arbitrary levels,
and from the area near the walls of Bc 51 at the eastern end of the
trench a column was removed by natural strata or levels. In both
cases the material was screened for sherds and for other cultural
material. All sherds were washed, classified in the field laboratory,
percentages taken, and the results tabulated on the drawing of the
strata of the trench. Rarely did the line of the natural strata cross
near the center of an arbitrary level, but in those exceptional cases
the percentages for that arbitrary level were not used in averages
for either stratum. Where the line of the arbitrary level crossed
near either extremity of the natural strata, the percentages were
averaged with those of the stratum of which it was largely a part.
The removal of natural strata from a column which had been isolated
so that the dip of strata in the deposit could be observed on all sides
was not tried. The strata were numbered down from the top, although
all were not present in every part of the cross-section.

Results.—Stratum I, described as humus, organic material, sand,
charcoal, and sherds, was light in color and heavily permeated with
sand. The bottom of this stratum ran from four inches to a foot
below the present surface and was easily distinguishable from the
stratum below as being softer, although the general composition of
both was similar. This upper stratum appeared to consist entirely of
material which had washed from the southern surface of the dump
and had covered over the original surface of this central section.
The sherd complex found within it, then, might be expected to be
somewhat mixed but in general to represent as late or perhaps a later
period of deposition than the complex of the stratum immediately
under it.

Stratum II, described as sand, charcoal, sherds, and cultural
material, is separated from the upper stratum in places by occasional
stringers of sand which washed or blew over it before the heavy
wash from above covered it over. In other places the two merge, almost
imperceptibly. The second layer is slightly darker in color than the
first and shows scattered lenses of ash and of charcoal.

The sherd composition of the two may be compared in Table 1. It is
apparent that Strata I and II are made up of essentially the same
complex of sherds and that in many cases a type holds the same relative
place in both strata.

Table 1
SHERD PERCENTAGES OF THE REFUSE MOUND BY STRATA
(Section 6) Trenches 3, 7, 11, 15

                               

	Stratum	Stratum	Stratum	Stratum	Stratum V
	I	II	III	IV	A	B
Lino Gray	28.7	22.9	53.1	69.4	72.3	100.0
Exuberant Cor.	19.4	23.2	13.6	1.6	3.2
Gallup B on W	16.7	10.6	5.1	4.7	3.4
Escavada B on W	13.6	19.3	10.5	7.0	13.7
Red Mesa B on W	9.0	16.8	14.4	10.1	3.2
Chaco Cor.	4.5		.8	.3
Kana-a Gray	4.4	2.2	.5	2.2	5.1
Chaco B on W	1.0	.9		.3
McElmo B on W	.9	1.6	.9	.4
Wingate B on R	.6	1.7	.2	.5
Deadman's B on R	.4	.8	.2	.3	3.2
Sunset Red	.2	.7
Kana-a B on W	.2	.1	.5
Total number of sherds in sample	276	1592	239	379	61	8

The most plausible inference which, it would seem, might be
drawn from these facts is that of but a short difference in time[14]
between deposition of the two strata, both perhaps representing one
culture period which it is tempting to identify with "Pueblo II." The
upper stratum shows decrease of Red Mesa Black on White, and the
three trade types, Deadman's Black on Red, Sunset Red, and Kana-a
Black on White; and an increase of Gallup Black on White and the appearance
of Chaco Black on White and Chaco Corrugated. The rise and
fall of types within a span of over more than one period or even within
the same culture period is to be expected, but the consistent rise and
fall of more than one type might be considered a good criterion of some
distinction in time, and here the upper stratum would appear not only
to have been washed over the other but to have been orginally deposited
later than the other.

Stratum III, found only on the east end of the dump, is of the same
composition as II, although of slightly darker color, but its pattern
complex is similar to that of Stratum IV, not to that of Stratum II
(see Table I).

Stratum IV (see Table I) is described as composed of sand, charcoal,
clay, and cultural material, and it varied but little in color from
Strata II and III above it. As in the other strata Lino Gray is preponderant,
Red Mesa Black on White and Escavada Black on White hold

second and third places. Gallup Black on White holds fourth place
and Kana-a Gray and Exuberant Corrugated are barely represented.
It is interesting to note that Kana-a Gray was seventh in Stratum I,
ninth in Stratum III, fifth in Stratum IV, and third in Stratum V.
Stratum IV would appear to represent mixed debris slightly earlier
than Stratum III and directly overlying Stratum V, which shows,
perhaps, an earlier but mixed representation of much the same period.

Stratum V is made up of charcoal, clay, sand, and cultural
material, but the sand is less in proportion than above. By cultural
material and sometimes by appearance it is divided into 2 parts,
A and B. Stratum V (see Table I) in section 6 shows a heterogeneous
pottery complex, the upper section, A, being Red Mesa Complex, and
the lower section, B, being 100% Lino Gray.

The lowest level of section 6 represents probably the natural
ground surface at the time of the Lino Gray Complex occupation, but
was not a dump. Sherds from the Red Mesa Complex dump, just to
the south and higher, washed over it and were later mixed with other
sherds from a later part of the same period. This later material was
finally covered over with sherds. The small sherd totals, ranging
from 8 to 61 in the lower levels in this section, suggest that it was
not used to any extent as a dump area until the final occupation of
the site. The sherds would have been washed and tramped into the
surface clay, which became mixed to some extent with small deposits
of ash and of charcoal.

The sherd complexes within a natural stratum were found to run
fairly consistently through the center of section 6, so it was decided to
test this area further. Near the walls of Bc 51 in trench 34, and 42′
east of trench 15, a column 3′ square was isolated on two sides. These
profiles were studied as a preparation for removal by natural levels.
Each stratum was removed by troweling, the sherds taken out by
hand, and the material from each was classified separately. Profile
Strata I and II were taken off as units, but Stratum III was divided
into two layers, A and B. A showed natural deposition of sand within
the cultural deposition. It contained considerable charcoal. Layer
B was of less laminated sand with a little charcoal at the bottom.
Strata IV and V were not removed. The percentages for the various
strata follow:

TRENCH 34

                             

	Stratum	Stratum	Stratum III
	I	II	A	B	A & B[15]
Exuberant Cor.	49.0	42.0	20	34.5	27.3
Escavada B on W	25.0	19.0	30	27.0	28.5
Lino Gray	7.5	16.5	10	16.6	13.3
Gallup B on W	8.0	5.8	10	14.0	12.0
Chaco Cor.	1.0		30	1.0	15.5
Red Mesa B on W	2.5	2.8		4.7	2.4
Deadman's B on R	.62	2.0		1.2	.6
Chaco B on W	.62	1.8
McElmo B on W	3.4	1.3
Kana-a Gray		1.3
Wingate B on R	.31	1.3
Flagstaff Red	.93
	323	223	10	84	94

One first notices that the percentages in this test do not at all
agree with those running consistently through the same strata in
the center of section 6. It is apparent that the prevailing type in
the column is Exuberant Corrugated with Escavada Black on White a
good second, and Lino Gray third. The fact that Gallup Black on White
and Chaco Corrugated are more prevalent in the lower levels might
indicate some accidental reversal of stratigraphy due to the building
of the nearby kiva or the disturbance caused by the nearby
burial Bc 51 60/31.

The one point which is apparent from comparison of the sherd
complexes and proportions taken from this test near the rooms with
those taken from the same natural strata toward the center of the
dump is that the same strata at two different points do not contain
the same relative amounts of single types or of groups of types.
These natural strata are traceable from one end of the dump to the
other on the face of an east to west profile revealed on the south side
of section 6. The area of Strata I and II, which lies toward the center
of the dump shows a consistent sherd complex, but the eastern ends of
the same strata give a different complex, perhaps later.

Conclusions.—If the strata in the dump do not include throughout
cultural material of the same period, how can these division lines be
accounted for?

At the base of the dump is a layer preponderantly of early material,
Stratum V. This is a thin stratum largely composed of clay
but mixed with some sand and a little ash, some charcoal, and a
scattering of sherds. The sherd totals are scarcely enough to warrant
calling this layer dump material. Small deposits of ash, charcoal

and sand accumulated on the surface were trampled and washed into
the clay and gradually built up the surface to an average depth of 6″.
Then, upon this hard base, a people began to throw their trash in such
amounts that a dump of daily sweepings began to rise, Stratum IV.
Its lenses and pockets resembled those of the later Strata I and II.
Its composition differed from that of the hard cumulative surface of
adobe below which contained sherds. One was an occupational surface
and the other was an actual trash mound. Stratum III, seen only in
the eastern section of the dump, accumulated over trash but was
slightly later, the sherd complexes being very similar.

The transition in pottery and in house types perhaps took place
around the middle of the 9th century. In this case the severe drouth of
900 to 907 A. D. would have come not long after this transition. The
succeeding erosion period which cut the surface of the canyon, and
would likewise affect the surface of the dump, was hypothetically
traced in erosion surface number 1 in the trench sunk near Chetro
Ketl in 1936. It seems quite possible that the upper limiting line
between Strata III, IV and Stratum II was caused by the erosion after
this drouth and is comparable to erosion surface 1 of the Chetro
Ketl cut.

A highly tentative interpretation follows: The upper levels of the
central area of Stratum IV show high percentages of the Red Mesa
Pottery Complex types, so much so that in drawing the cultural divisions
of the dump by pottery alone, the line between the Red Mesa and
Escavada Complexes is some inches below that drawn by the top of
natural Stratum IV (see Fig. 2). Examinations of the sherd complex
and percentages given for Stratum IV show far from a pure Red
Mesa Complex. Stratum III likewise shows considerable Escavada
Complex material. If the Red Mesa Complex dump grew up to make
most of Stratum IV, which was completed by debris of early Escavada
Complex, and then the surface was badly cut by the erosion following
the drouth of 900 to 907 A. D., we would find the Escavada Complex
sherds partially cut into the Red Mesa Complex material by wash.
Thus, in taking the entire Stratum IV together for sherd percentages,
we would expect just the confusion of Red Mesa and Escavada complexes
which we do find, a confusion of complex much greater than any
found in the Escavada Complex Strata I and II.

The division line between Strata III and IV, both of Escavada Complex
material, may very possibly have been caused by rains beating on
the central section of the dump for some years while the people threw
their trash farther to the north or to the south. Stratum III does not
extend farther to the north or to the south. Stratum III does not extend
farther westward than trench 14 and hence could have been, in this
section, of only temporary use. Later the people again used the

central and western parts of the dump for deposition and thus laid
down Stratum I.

The prehistoric people presumably, in the modern Pueblo manner,
used different areas of the mound surface at different times as
depository for their household trash. Material washing from one
area onto another would more or less modify the original complex of
both areas.

Strata II and III are similar to each other in composition and differ
from Stratum I, the surface soil, in being harder, showing fewer streaks
of sand,[16] and in having more undisturbed lenses of household debris.
Yet Stratum III represents the Red Mesa Complex, and Strata I and
II represent the Escavada Complex.

Stratum I, the surface layer, is obviously disturbed and may owe
its color, its looseness, and its stringers of sand to the sheet wash, the
sand storms and the other disturbances which have passed since the
last household debris was deposited on the mound. The drouth of
1035 to 1041 and its attendant erosion period must have cut the dump
surface while Bc 51 was still occupied to some extent, but its effects
would have disappeared in the surface erosion since that time.