University of Virginia Library

THE EAST MOUND TRENCH

In 1925 we extended this East Mound Trench in both directions,
south to Bryan's "post-Bonito channel" (Bryan, 1954, pp. 33-36) and
north to the foundations of Room 171 (fig. 24, c). Between mound
and ruin the trench averaged 10 or 11 feet deep and was irregularly
floored with clay-streaked, stratified sand. This water-laid deposit
at once identified itself as part of the same east-west watercourse
profiled by the West Mound Trench. Here, as there, the former
channel had become a common dumping place at an early date and
gradually was filled with occupational debris from Bonitian dwellings
and with waste from razed walls. Some of this channel-fill
extended north beneath the ruin and south beneath the mound.
Throughout, from bottom to top, successive layers of silt and windblown
sand remain to evidence the passing years.

Ten feet below the original surface and beneath a curious body of
compact, sandy clay interspersed with clay pellets, occasional potsherds
and sandstone spalls, we came upon a shallow, ash-filled
hearth (Station 125, fig. 24, c). It was larger and more conspicuous
than the hearth we bisected above Station 160, West Mound Trench,
but, like the latter, had been built on dry, stratified sand for limited
use.

Our East Mound Trench ended against the south wall of Room
171, the foundation of which rests 4 feet below the apparent surface
at time of abandonment. A layer of constructional waste immediately
beneath the foundation extends southward a short distance and then
is buried under a greater quantity of occupational refuse. A foot
lower, or 8 feet below the probable original surface, our trench-end
halved a second, clay-lined ash-filled hearth, this one measuring 34
inches wide by 4 inches deep (pl. 79, right).

Silt-streaked, water-laid sand spread out beneath the hearth; debris
of demolition, above. A dozen feet to the south against the eroded

bank of a small sand- and gravel-filled gully, was the discarded fragment
of a troughed metate, relic of the Late Bonitians. At intervals
throughout the 10-foot fill, village waste lay in more or less isolated
bodies as though gathered at one place and dumped at one time.
Some of this material showed unmistakable signs of water action.
On top of all lay broken masonry fallen from the upper stories of
Room 171, the uppermost courses cast outward 25 feet or more.
Partly overlying the outer limit of this fallen stonework, and therefore
of more recent origin, was a quantity of burned sand, sticks, and
cedar bark.

There can be no doubt as to the actuality of the former watercourse
exposed by our East and West Mound trenches. Depth is
comparable in both cases and the materials of the fill are the same:
wind- and water-borne sediments and debris carried out from the
village. The East Mound was already 8 or 10 feet high when some
debris-conscious individual conceived the idea of a retaining wall.
Eventually the mound accumulations crested out 10 feet higher, 12
feet or more above the present level of the plain. Our 1922 stratigraphic
column at Station 64 (fig. 24, c) was dug to a depth of 8 feet
below the plain without reaching the bottom of underlying constructional
debris, clearly reworked by water action. A nearby 1924 test
(U.S.N.M. No. 334181), 10 feet 7 inches deep, ended upon the
adobe layer at the base of the partially razed, second-type wall previously
described. Nevertheless, sherds from these two columns
show that the East Mound is later than its companion since earlytype
fragments are noticeably fewer in number. Also, the proportion
of constructional debris seemed larger—a factor that led Nelson
(in Pepper, 1920, p. 385) to identify the East Mound as the later
of the two.

In contrast to the north retaining wall that on the south is a makeshift
affair built upon what appears to be a man-made heap of
jointed sandy clay piled above an adobe bank at Station 50 (fig. 24, c).
Both the bank and the clay pile have been eroded, north and south.
On the north, water-laid sand and silt mark the course of a 30-footwide
waterway filled with village waste and a southward-sloping
mass of compacted sand containing numerous clay pellets and a scattering
of sandstone spalls. Then follows a round-bottomed channelfill
of laminated silt, a sort of mud conglomerate balled and soaked
by water. Beyond the barrier, in the midst of nonconforming beds
of silt, sand, and village rubbish, is another apparent watercourse
probably antedating Bryan's post-Bonito channel.

Sand is everywhere in Chaco Canyon and floodwaters leave silt
layers. But it was the sheer bulk of village debris rather than silt
and sand that defeated our early efforts to read stratigraphy in
Bonito's south refuse mounds. We dug a deep trench through
each—two trenches that laid bare the composition of both mounds
and the manner of their development. Laminated sand, gravel, and
round-bottomed waterways show where water once flowed. The
leveling influences of wind and water are everywhere apparent.
Pockets of blown sand occur throughout the two piles; silt streaks
and puddled adobe remain as evidence of seasonal showers. And as
this village waste continued to pile up, sandstone walls were built
to curb its dispersal. Walls nearest the pueblo were highest and
strongest. End walls, wherever we examined them, were noticeably
weaker and those on the south were weaker still.

It is the presence of these enclosing walls as much as mound content
that determines the age of the two south refuse piles. Both content
and walls are primarily products of Late Bonitian industry.
Old Bonitian housewives habitually dumped their sweepings immediately
in front of their dwellings—at least until the Late Bonitians
took over. A mixture of Old Bonitian and Late Bonitian rubbish
from bottom to top of both mounds fixes their beginnings as subsequent
to arrival of the Late Bonitians. It was this latter group that
filled the old floodway immediately south of the pueblo, a fact evidenced
by the abundance of their distinctive Hachure B. pottery
which Roberts found in two 5-foot-wide stratigraphic sections, 3
and 4, between Room 136 and the West Mound. It was the Late
Bonitians that built retaining walls about both mounds and then continued
to pile up village waste until it overflowed the barriers and
attained a height of 20 feet or more.