A major component of our research is to explore the processes that created Chacoan outlier communities in the Montezuma Valley. A recognized pattern of development repeats throughout the region. It is clear that not every old community in the valley was suited to ascend to this role. In nearly every such case, population levels in the host community were relatively high and leadership structures and land use permissions were well established and recognized.
Some archaeologists over the last 25 years have explored the economic and social aspects and implications of moving from a small-time production system consisting of cooperating households toward a community based production system focused on creating greater quantities of food and public works projects. For about 150 years, the climate was favorable for such a development but a shift in rainfall patterns and quantities in the second quarter of the 12th Century may have added a level of stress to the system that could not be mitigated with better water collection techniques. When rain doesn't fall, there is no water to harvest or distribute.
The leadership positions within these communities provided a smooth transition from a simple method of production to one that utilized enhanced water collection/distribution, mulching, irrigation and other technologies including frost protection. Such methods required far more individuals and managers than a simple production economy. Each producer's role became more important as other steps toward a successful conversion to an enhanced production system required measured methodologies and cooperation. Breakdowns within the system probably created breakdowns in other parts of the system. Socially recognized rules and leaders would have been necessary to encourage people to work as a team.
As part of this research, investigations of the exposed portions of the tri-wall and Pueblo A has led to some new and interesting discoveries over the last few months. In 1988 and 1989, tests of the tri-wall revealed an unusual architectural configuration that was somewhat different than what can be gleaned from the 8 or 10 of these buildings that are known to exist. Vivian's (1959) seminal work on these enigmatic structures is the only published work that I know of on tri-wall's that also involved excavation. He and his associates used relatively modern excavation and recording techniques for this work. No others have been tested or excavated since. Vivian tried to rebuild the record from earlier excavations that had been performed on the Pueblo del Arroyo great house tri-wall in Chaco and the Mound F and Hubbard Mound tri-wall at Aztec with limited success. Most known tri-wall's consist of three concentric walls; the innermost being the smallest circumference and the outer, the greatest. The chambers created by the concentric walls were often further divided by cross-walls creating compartments that are generally featureless. It is likely that these chambers held perishable products however, all excavations were performed before pollen and flotation techniques were developed so at this point, no proof has been detected to confirm this. It is known however that whatever may have been stored in these chambers was gone by the time excavators had an opportunity to examine the deposits.
During the process of looking at this phenomenon further, we have focused excavations on a 40 m x 40 m section within Sector 7. This part of the Mitchell Springs Community was occupied nearly continuously for five centuries. Construction began in the 700s and ended before 1230-1240 A.D. During this time, at least 2 curvilinear roomblocks were built immediately to the north of what developed into a small multi-story greathouse and appended tri-wall.
Vivian concluded that the innermost concentric walls of both Mound F and the Hubbard Mound at Aztec as well as the del Arroyo tri-wall contained a building similar to the kiva. During our 1988-89 studies at Mitchell Springs, limited testing of this building led us to believe that the inner chamber appeared to have performed as a platform used for burning large fires. Recently, during tests inside this portion of the structure, evidence to suggest the existence of an inner tower was found. The interior features of the 'tower' confirm the existence of a kiva within it. To date, a bench coated with multiple coatings of red, white and gray layers of plaster, an adobe floor, and one large masonry lined floor vault have been documented.
We are taking a closer look at the Mitchell Springs tri-wall in an effort to add more modern data to what is currently known about these buildings. To my knowledge, all known tri-walls except the one at Mud Springs are on publicly managed lands and it is unlikely that any excavation or productive analysis will ever take place on these until at least A.D. 2275 or beyond. Over the last 3 months, many new discoveries have been made during the process of exposing the tops of the walls of Pueblo A and its appended tri-wall. We are preparing a manuscript on this work and it should be ready to submit for publication early next year.
In the ninth century the population of the Mitchell Springs Community exploded, growing to many hundreds of rooms and setting the stage for the entry of the Chaco System and the construction of new public architecture. Four great houses and two 10+ meter kivas were constructed at the village center. Within the course of less than 100 years the Chacoan System had collapsed leaving diminished population levels in the Mitchell Springs community. By 1230 or 1240 A.D. the community and large portions of the Montezuma Valley became depopulated. People consolidated into fewer and generally larger villages and defensible locations with a source of fresh water and nearby arable fields.
Structure 25 is located at the southeast corner of Pueblo A. This building contains about 30 square meters of floor space and was probably used by a larger segment of the community rather than by a few interrelated or cooperating families. Domestic activities were still conducted inside this structure although this aspect is still under investigation. On the south side of the wingwall, the grinding of food and possibly other items was performed. Although 22 manos and 8 pecking stones have been located so far, only two incomplete metates have been found in the portion of the structure that has been excavated so far. Almost no bone byproducts, bone tools, debitage or flaked lithics were recovered south of the wingwall but 3 bone awls were evidently nested together in the ceiling immediately to the north of the wingwall. A hafted axe hammer, a large core, 2-hand polishing stone and a small abrading stone were also stored in the area south of the wingwall. Fragments of mats and fabric were collected from the floor just north of the ventilator opening and in the east section of space just south of the wingwall. More than 400 tree-ring samples of conifer or juniper and containing outside rings were processed from the burned roof. At this point in the excavation, it is clear that tools and other implements were deliberately left in the building when it was burned and is likely related to the ceremonial closing of the building.
Thanks to Joel Brisbin and Gay Ives, the complex stratigraphic profiles exposed by the excavation units inside the Sector 11 great kiva were documented and photographed. As part of my research questions related to the construction of special buildings on top of earlier special buildings, an early great pit structure built in 758 A.D. was tested. During excavations in the south and west ends of the great kiva the Structure 6 over-sized pit structure was discovered. It contained approximately 65 square meters of floor space and was ceremonially closed by burning immediately after abandonment. Just as we see in Sector 7 Structure 25, a large assemblage of usable tools, fabric, human hair twine, mats, baskets, ceramic vessels and ornaments were left on the floor when the building was intentionally burned in the late 8th century. In the mid to late 900's, a great kiva was built over it and was subsequently rebuilt at least two other times before being abandoned in the 1130's or 40's.
In Pueblo A , an effort to emulate a construction style which had roots in Chaco is apparent in the preplanned footprint of the pueblo as well as some masonry style characteristics incorporated into some of the rooms. The front two rows of storage rooms on the south end of the pueblo and the 3 or 4 storage rooms on the east side of Pueblo A were single story rooms. In one event, the burning pueblo's southern wall fell southward and because it was still articulated, it was documented to be a little over 3 maters tall. The southern two rows of rooms were added to the original configuration of the Pueblo, after the Tri Wall structure had been appended to it. All of the remaining rooms were two stories tall. The central kiva may have been built with rectangular rooms above it so in effect, it may have been a round, masonry enclosed structure that was concealed from view because contemporaneously used rooms surrounded it on all sides, including above it. During the partial excavation of Room 11 in the early 1990's, a subfloor test indicates the likely presence of earlier rooms beneath it, and beneath the central kiva.
Another interesting item in regard to the preplanned footprint of Pueblo A is that only two of the 22 ground floor rooms were habitation rooms. They are the only square shaped rooms in the pueblo, a trait that was also found at Salmon Ruins in Bloomfield NM. The second story rooms above these two rooms were also used for domestic activities such as cooking and sleeping but were evidently not used for grinding operations. Both the upper and lower floor rooms were directly connected via roof hatchways. In the Summer of 2015 or 2016, the area on the west side of the west wall doorway in Room 18 will be tested to determine how that space was used.
Kiva A has been a fascinating bit of discovery. Some of its masonry is of a finer style than appears to be the norm at Mitchell Springs. Like Room 18, Kiva A also burned in a cataclysmic fire that ended the occupation of Pueblo A and possibly the entire Mitchell Springs Community. It has no southern recess which is not the norm for kivas built and used during this time period in the Montezuma Valley. In the space that is often reserved for a southern recess, an elaborate ventilator feature was engineered and constructed. This feature brought fresh air down into the kiva chamber from either the floor of the room above it or from atop Pueblo A. The pressure differential between the dark spaces in Kiva A in the belly of the pueblo, to the sunlit intake point 20 feet above (on the roof of Pueblo A), would have created a natural circulating cooling effect in the summer months. Regulating the airflow into the ventilator would prevent too much cold air from entering during cold nights. On one of the masonry stones that was used to create the elaborated ventilator feature (see photo below Left), an interesting petroglyph was carved.
See Mitchell Springs Tab for more information on this work.......