Foreshadow: The Little Colorado

Little Colorado River from Homol’ovi Ruins State Park

Chapter six of Crucible of Pueblos brings us to the area immediately to the south and west of the areas previously considered. The region, which the authors call the Little Colorado after its main river, consists mostly of the drainage basin of that river but with some modifications. The southwestern part of the drainage around the modern town of Flagstaff, Arizona is excluded, as its culture history is quite different. Included despite being outside the Little Colorado drainage are the Chinle Wash area in northeastern Arizona and the Acoma area just across the Continental Divide in New Mexico. As the authors note early on, this region is geographically larger than all the previous regions in the book put together, but it makes sense to include it as a single chapter for several reasons. In addition to making it easier to track movement and changes across broad spatial scales, an important goal of this volume, considering this area as a whole helps to avoid some of the problems with considering its subregions separately, as is typically done. The Little Colorado straddles what have been considered the boundaries between traditional archaeological culture areas, and as a result its subregions have often been treated as peripheral to better-known areas rather than central in their own right. Particularly for understanding the Early Pueblo period (here defined as AD 600 to 925), however, it is useful to look at the Little Colorado region as a unit centered on the Rio Puerco of the West, which appears to have been the center of regional population for the period.

I say “appears” because another characteristic of the Little Colorado is that its archaeological record is not nearly as well understood as those of the regions to the north and east, especially for the early period. There are several reasons for this that the authors review:

• Surface architecture was generally less substantial and pit structures were shallower than in other areas, so they are harder to identify in surveys.
• Many parts of this region are very sandy and windy, so sites are often covered by large amounts of windblown sand to the extent that they can’t even be seen on the surface at all.
• While there has been a fair amount of excavation in connection with individual salvage projects for infrastructure like highways, much of this work has been in areas without significant Early Pueblo occupation, and there have not been any major projects on the scale of the Dolores or Chaco Projects combining extensive excavation with a focus on cultural synthesis.
• The regional ceramic sequence for the early periods is poorly defined and dated, making it hard to interpret the artifact collections that do exist from survey and excavation projects.

The authors suggest some ways to address these issues, and express a desire that this chapter serve as a starting point for synthesizing what is currently known about the Early Pueblo period in the Little Colorado region.

The overall picture they paint is of regional stability and gradual change over the centuries, which they note is quite different from the more dynamic picture emerging from work further north. This certainly is a plausible interpretation of the available evidence, but it’s worth noting (and they actually do) that a similar gradualist interpretation was also applied to the northern regions before the major excavation projects starting in the 1970s refined the picture. Could it be that the apparent gradual change in the Little Colorado is also due to the low resolution of the current data? The authors don’t discuss this possibility, but it jumps out at me.

Nevertheless, there are some differences between the Little Colorado and other regions that may well mean that developments here really were more gradual and stable. For one thing, there is strong evidence for the very early presence of maize agriculture (as early as 2000 BC) in several parts of the region, and evidence for irrigation canals in the Zuni area as early as 1000 BC. This earlier appearance of agriculture compared to areas further north isn’t necessarily surprising given its even earlier presence in the southern Southwest and Mesoamerica, but it does provide a potential reason that the arid but fertile river valleys of the Little Colorado drainage would have had more stability than the more marginal areas to the north and east.

With this regional background in mind, the authors give brief summaries of each of their subregions then address some of the key topics that are emphasized throughout the book. I will briefly summarize their summaries below.

Rio Puerco of the West and Train Tracks at Petrified Forest

As I mentioned before, the valley of the Rio Puerco of the West seems to be a key subregion during this period. Early Pueblo sites are rare in the upper valley, but are very common from the Manuelito area to Petrified Forest (where the Puerco flows into the Little Colorado). Basketmaker II and early Basketmaker III settlement (before AD 600) is concentrated around Petrified Forest at the western end of the valley, where there are large pithouse sites that seem to mainly consist of repeated seasonal occupation. Population increased dramatically in this area in early Pueblo I and continued growing more slowly through Pueblo II, with occupation largely by scattered individual households and small hamlets. Throughout the valley mobility seems to have been frequent and perhaps seasonal, with a wide variety of site sizes and types that makes the settlement pattern hard to determine. There are a few larger sites that may have been comparable to the early villages further north, but even these are diverse in size and structure and it’s not clear how many of them were actually permanent aggregated communities as opposed to sites occupied seasonally over the course of many years. Some of those sites that have been dated show continuity between Pueblo I and Pueblo II, in striking contrast to the depopulation of the Mesa Verde region at the end of Pueblo I. This suggests that the Little Colorado really did have a different history and that the appearance of continuity is not just due to limited data.

The authors include the Zuni and Acoma areas as a single subregion, divided into three “districts”: Lower Zuni, Upper Zuni, and Acoma. The Lower Zuni and Upper Zuni are those parts of the Zuni River valley downstream and upstream of the modern Pueblo of Zuni respectively. There has been a lot of survey in the Upper Zuni district in recent years, but much less in the Lower Zuni and Acoma districts. This is unfortunate for understanding the Early Pueblo period, when the Lower Zuni was the main area of settlement. This is probably linked to its proximity to the Puerco (of which the Zuni is a tributary), given the extensive occupation there described above. There were small populations in the Upper Zuni and Acoma districts during Pueblo I that expanded rapidly in Pueblo II. Large settlements were rare throughout the subregion during Pueblo I except in the Hardscrabble Wash and Jaralosa Draw areas of the Lower Zuni district. Hardscrabble Wash includes the important but poorly understood site of Kiatuthlanna, excavated by Frank H. H. Roberts in the 1920s, and there are a couple of large settlements along Jaralosa Draw showing continuity between Pueblo I and Pueblo II.

Northeastern Arizona, considered as a single subregion here despite its size and diversity, had only a small and scattered occupation during Pueblo I, in contrast to marked increases in population after AD 1000 in several parts of it. Despite its small size, the early occupation in some parts of this subregion such as Black Mesa shows evidence for substantial storage implying year-round sedentism, in contrast to the apparent mobility in the more densely populated Puerco Valley. It’s worth noting that Black Mesa is one of the areas with very early evidence for maize agriculture. Despite the low overall population, there were some large and apparently permanent sites during Pueblo I, some of which, especially on the Defiance Plateau, continued to be occupied into Pueblo II when they began to include great houses and other Chacoan features.

The final subregion is the Mogollon Rim Margins at the southern edge of the region. This area forms the boundary between the Anasazi and Mogollon culture areas as traditionally defined by archaeologists. It was relatively sparsely populated during Pueblo I, but some areas saw a substantial increase in population around AD 850. There were some large sites, but as in other subregions they are hard to interpret and it’s not clear how many of them were permanent villages rather than long-term seasonal occupations. As might be expected, many sites in this subregion show mixed pottery assemblages of “Anasazi” gray wares and “Mogollon” brown wares, but what this means in terms of population movements and contacts is hard to say given the sparse data available.

Turning to bigger questions, the authors make an attempt at reconstructing population dynamics but it is very tentative given the limited data. What it does seem to show is that the Puerco and Lower Zuni areas were important population centers throughout the Early Pueblo period, with the Defiance Plateau becoming an additional center late in the period. A more scattered but persistent population elsewhere in the region supplemented these centers throughout the period.

Public architecture mainly involved great kivas, which existed in this region throughout the Early Pueblo period and were often associated with larger settlements with large amounts of storage capacity, implying a role as community centers for a large area. There were also a few isolated great kivas without associated settlements, which are hard to interpret. Several of the communities with early great kivas also had later Chacoan great houses, another piece of evidence for the persistence of these places as important centers. Interestingly, the general pattern in this region is of continuity between Pueblo I and Pueblo II, with an abrupt break and change in settlement patterns (though not a regional depopulation) at the end of Pueblo II associated with the decline of Chaco. This contrasts with the Mesa Verde region, where there was an abrupt break and regional depopulation at the end of Pueblo I, a repopulation late in Pueblo II associated with Chacoan influence, and continuity between the Pueblo II occupation and later Pueblo III communities before the total and permanent depopulation of the region at the end of Pueblo III. It’s not clear what this implies about the culture history of the two regions, but it certainly is interesting.

There seems to be little evidence for violence in the Little Colorado region during the Early Pueblo period, again in contrast to the Mesa Verde region, although it’s worth noting that the available data is much more limited. Still, the generally small size of sites and lack of defensive settings or defensive features like stockades does suggest that, for whatever reason, things were generally more peaceful here.

Cultural diversity and migration have long been topics of interest in this region due to its position across traditional boundaries, but the authors argue that some lines of evidence that have been used in the past to assess cultural differences and connections, especially ceramic styles and pit structure architecture, could use a fresh look in the light of new theoretical approaches and the much larger dataset available from salvage projects. Again, the need for a new emphasis on synthesis and a broader perspective in understanding this region becomes apparent.

Overall, this was one of the most informative chapters in the book for me. This region is very important for understanding the rise of Chaco, given the apparent southern connections of some of the migrants who contributed to its rise, but it has remained much less understood than the well-studied areas to the north that contributed other migrants. This chapter shows clearly how much less is known but also how much potential there is to know more, and hopefully it will spur further investigations of these important issues.

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Importing Food

Exterior of Reconstructed Great Kiva, Aztec Ruins National Monument

One of the most interesting and potentially productive lines of research in Southwestern archaeology these days involves the use of chemical analyses of various archaeological materials to extract more information about the societies that used them than is apparent just from looking at them.  The oldest and most established type of research like this is radiocarbon dating, which has historically been used less in the Southwest than elsewhere because it’s both expensive and less precise than tree-ring dating, which was invented in the Southwest and has been extremely important in the study of its prehistory.  Lately, however, archaeologists in the Southwest have been using radiocarbon more and more, since it can be used on anything organic (useful for sites which produce no datable wood but plenty of other organic material) and it’s been around for so long that the dates are considered very reliable.  They’ve also begun to use some other techniques that are newer but have enormous potential, which is already starting to be realized, to illuminate aspects of the past that have been the cause of much debate.

Intact Roof at Aztec Ruins National Monument

The most important of these is strontium isotope analysis, which we’ve seen before in the analysis of the wood brought to Chaco for architectural use.  Like radiocarbon dating, strontium analysis is based on looking at the ratio of two isotopes of an element, one of which is stable and the other of which is produced by the radioactive decay of another element and therefore varies.  Unlike radiocarbon, however, strontium cannot be used for dating on archaeological timeframes, since the half-life of the radioactive decay process involved (the conversion of rubidium-87 to strontium-87) is 48.8 billion years.  It can, however, be used to identify locations, since the amounts of strontium and rubidium in different areas vary a lot and strontium is absorbed unchanged by organisms from their environment.  Thus, in theory, one could test an organic artifact for its strontium ratio, then compare that to the strontium ratios of the water or soil in various places where the artifact may have originated and figure out where it came from.  This would then allow all sorts of archaeological conclusions.

Intact Roof at Pueblo Bonito

Of course, it’s never quite that simple, as the case of the wood shows.  It was relatively easy to use this analysis for the high-elevation types of wood that occur in relatively few places in the Southwest, but when the technique was extended to the very common ponderosa pine beams the number of possible origins increased so much that few definite conclusions could be reached.  There is also the problem of making sure that the strontium ratios found in the archaeological material actually resulted from growth processes rather than contamination by later mineral deposits.  Since this technique is relatively new, the methodology for it is not yet totally worked out, and not every attempt to use it ends up working.

Row of Metates, Aztec Ruins National Monument

Both the promise and the pitfalls of strontium analysis are shown clearly by a new paper by Larry Benson of the United States Geological Survey.  Benson has made something of a name for himself as the main player in the increasingly important analysis of corncobs found in Southwestern archaeological sites.  Corn is a useful plant to use for this sort of thing for a number of reasons:

• It’s pretty common, especially in sites like cliff dwellings and Chacoan great houses with especially good preservation of organic material.  The Anasazi depended heavily on corn for their diet, so there are corncobs all over the place.
• It grows quickly.  This is not important from the perspective of strontium analysis, but it means that radiocarbon dating can provide a very accurate range of dates within which the corn was grown and eaten.  This is in contrast to slow-growing plants, such as trees, which have the problem that the part tested may happen to be much older than the date of use.  The combination of accurate dating with strontium-based source determination makes corn a very powerful source of information.
• It bears directly on a variety of important cultural questions.  Since corn was the main source of food for the Anasazi, finding out if they were growing it themselves or importing it from elsewhere has major implications for models of cultural systems and their means of support.  This is a longstanding issue in the study of Chaco specifically.

This particular paper addresses several issues, both substantive and methodological.  Substantively, Benson analyzes a set of corncobs excavated from the Gallo dwelling in the Chaco campground in the 1950s and adds the data derived from them to the data from earlier studies of cobs from this site as well as from Pueblo Bonito and Chetro Ketl.  He also reports on strontium isotope ratios from several agriculturally productive areas of the Zuni Reservation and adds them to the previously reported data from other parts of the Colorado Plateau.  He then combines this new information with the previously reported data to draw some specific conclusions about the sources of some of the cobs.  Importantly, however, he does not come to any conclusions about the sources of the newly analyzed Gallo cobs.

Metate at Pueblo Bonito

The reason for this lies in the methodological side of the paper, which may be the most important in the context of overall research on this topic.  The cobs Benson reports for the first time here, unlike the previously analyzed cobs, were not burned, and part of the purpose of this research was to see if the procedures used to prepare and analyze the burned cobs could be used for unburned cobs as well.  As it turns out, they can’t, and the strontium ratios from the unburned cobs appear to come from post-depositional mineral contamination rather than growth conditions.  This seems to be because the act of burning effectively “seals in” the trace minerals in the cobs, protecting them from contamination.  While this result is somewhat disappointing, in that it means that the strontium data from the new cobs can’t be used to draw any conclusions, it is important in informing others that if they want to do this kind of research on unburned corn cobs they need to come up with new procedures.  In the course of doing this analysis Benson also uses some data on recent experimental growing of Pueblo varieties of corn in Farmington that provides valuable reference material on just how closely strontium ratios in corncobs can be expected to correspond to the ratios in the soil and water in the area.  The answer is closely, but not perfectly, which is also useful information for future researchers.

Keyhole-Shaped Kiva, Aztec Ruins National Monument

Despite those issues, however, this paper does include some important substantive conclusions.  Although the new cobs couldn’t be used for strontium analysis, they did produce radiocarbon dates, which correspond very closely to the dates on the earlier Gallo cobs as well as some of the ones from Pueblo Bonito and Chetro Ketl.  Interestingly, these dates all cluster tightly around the AD 1180s.  As Benson points out, this is after the major drought of the mid-twelfth-century, which is generally interpreted as marking the “collapse” of the Chaco system and the possible depopulation of Chaco Canyon.  It has long been known that the canyon was occupied later, from the late twelfth century until the total abandonment of the region during the “Great Drought” of AD 1276 to 1299, but it’s unclear if the population at that time consisted of a remnant from the earlier Chacoan occupation or a reoccupation by people from elsewhere who may or may not have been descended from the earlier Chacoans.  In any case, whoever the people were who lived in the canyon in the 1180s, these are their corn cobs.

Keyhole-Shaped Kiva at Pueblo Bonito

They didn’t grow them, though.  In what is probably the most interesting conclusion of Benson’s paper, and certainly the most surprising, he goes through a careful analysis of the strontium data, excluding the data from the unburned cobs, and finds that the values from the cobs do not overlap with any of the locations in the Chaco area, either in the canyon or around it, that have been tested.  It’s certainly possible that they come from somewhere nearby that hasn’t been tested, but at this point a lot of potential growing locations in and around the canyon have been analyzed, so there aren’t a whole lot of additional options.  It’s not a very promising area for agriculture, after all, and pretty much all of the obvious places have now been tested for strontium ratios.

Hubbard Tri-Wall Structure at Aztec Ruins National Monument

So if these cobs didn’t come from Chaco, where were they grown?  Benson compares their strontium ratios to data from several areas in and around the San Juan Basin: in addition to the newly reported Zuni sites, these include Lobo Mesa, the Red Mesa Valley, the Rio Puerco of the West, the Defiance Plateau, Chinle Wash, the Four Corners area, Mesa Verde, the Totah, and the Dinetah.  This covers almost the whole area once occupied by Chacoan outliers, and several places beyond.  The cob ratios turn out to overlap considerably with one of the Zuni areas, the Mesa Verde/McElmo Dome area, the Totah, the Defiance Plateau, Lobo Mesa, and the Rio Puerco valley.  For some reason Benson doesn’t mention the Puerco in the text of the article, but in the figure showing the boxplots of the values for the various regions it clearly overlaps a bit with the cob values.

Tri-Wall Structure at Pueblo del Arroyo

Unfortunately, the strontium analysis itself doesn’t provide any way to choose which of these areas is the most likely source of the corn.  Any of them is consistent with the evidence.  Benson therefore turns to other lines of evidence to narrow down the choice.  He eliminates Lobo Mesa and the Defiance Plateau because of evidence that they were not occupied during this period; he doesn’t go into a whole lot of detail on what this evidence is, which is unfortunate.  As I mentioned above, he doesn’t discuss the Puerco at all, which is also unfortunate.  This leaves Zuni, the Totah, and Mesa Verde as the remaining options.  These are all areas that had Chacoan outliers during the height of the Chaco system and probably experienced immigration of people from Chaco after the system’s collapse, and they were all home to significant populations during this relatively wet period, so they are all plausible sources of corn imported to Chaco.  Benson concludes that the Totah is the most likely source based on the fact that it is the closest of the three areas and the one that seems to have had the strongest connections to Chaco, and while he acknowledges that this is little more than a guess, it sounds plausible enough to me.  Certainly Aztec, which is often interpreted as a successor to Chaco in some sense, was a major center in the late twelfth century, as was Salmon, and the material culture of the people living in Chaco at the time shows considerable influence from areas to the north (although it’s not entirely clear how to interpret this).

Aztec West Great House, Aztec Ruins National Monument

This paper is part of a growing corpus of data, much of it contributed by Benson, showing that the inhabitants of Chaco at various times did in fact import corn to the canyon.  This seems to largely settle one of the longstanding disputes in Chacoan archaeology, and it further points out the pointlessness of trying to estimate the population of the canyon by first estimating its agricultural potential.  What remains puzzling is how this system would have worked, and why.  Beyond the obvious question of who was supplying the corn, which is partially addressed in this paper, the question of what leverage the canyon inhabitants would have had to get those people to supply them remains open.  This paper, in fact, seems to raise more questions than it answers in this respect.  While during the height of the Chacoan system it is relatively easy to come up with theories for how the canyon inhabitants could have acquired supplies from the surrounding area, in the post-collapse period, when the canyon population was tiny and regional importance had clearly shifted elsewhere, explaining how the few people left at Chaco managed to get others to grow food for them becomes a daunting task.  It’s this sort of challenge, however, that I think makes Chaco so fascinating and ensures that it will continue to be a place worth studying for a long time to come.

Benson, L. (2010). Who provided maize to Chaco Canyon after the mid-12th-century drought? Journal of Archaeological Science, 37 (3), 621-629 DOI: 10.1016/j.jas.2009.10.027

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2 Rivers 1 Name

Bridge over Rio Puerco of the East, Cuba, New Mexico

One of the more confusing aspects of the geography of the Southwest is the fact that there are two completely different rivers with the exact same name, and they’re quite close to each other.  The name is “Rio Puerco,” meaning “dirty river” in the New Mexico dialect of Spanish.  It’s an apt name, since rivers in the area tend to carry a lot of sediment and the water in them tends to look rather dirty.  Nevertheless, the use of it for both rives can lead to considerable confusion, and while in technical and scholarly contexts they tend to be carefully distinguished, in more accessible public contexts there isn’t much clarification out there.

Rio Puerco of the East, Cuba, New Mexico

One Rio Puerco originates in the Jemez Mountains and flows south through the village of Cuba, then parallels the Rio Grande for a considerable distance before joining it south of Belen.  In contexts where careful disambiguation is necessary this river is generally called the Rio Puerco of the East, on maps and signs where highways like US 550 cross it it’s usually just labeled “Rio Puerco.”  Today the Puerco of the East forms a rough eastern boundary for the Navajo culture area, and the communities along it (especially Cuba) serve as important points of contact between the Navajos and the New Mexico Hispanic culture area.

Rio Puerco of the West and Train Tracks at Petrified Forest

The other Rio Puerco originates on the southern slope of Lobo Mesa near the Continental Divide and flows generally southwest through Gallup and the Red Mesa valley, paralleling the railroad and I-40 into Arizona.  It passes through Petrified Forest National Park before flowing into the Little Colorado River at Holbrook.  This river is generally called the Rio Puerco of the West, and it forms a very rough southern boundary for the Navajo culture area, with the area further south dominated by the Zunis along the eastern portion and by Anglos (largely Mormons) along the western portion.  The towns along the river are mostly nineteenth-century railroad towns.

Sign at Bridge over Rio Puerco of the East, Cuba, New Mexico

Clearly, these two rivers are very different and have nothing to do with each other.  They are on opposite sides of the Continental Divides and belong to completely different drainage systems: the East flows into the Rio Grande and ultimately into the Gulf of Mexico, while the West flows into the Little Colorado, which flows into the Colorado just upstream from the Grand Canyon and ultimately ends up in the Gulf of California.  Confusingly, though, they’re really quite close.  If you drive from Albuquerque to Flagstaff on I-40 you cross both of them, and each is marked only by a sign saying “Rio Puerco.”  They are also both close to Chaco, and both areas were integrated into the Chacoan system, though probably to different degrees.  The only major Chacoan site known from the Puerco of the East is Guadalupe, while the Puerco of the West has a whole string of sites that have been identified relatively recently as Chacoan outliers, including Allentown, Chambers, Sanders, and Navajo Springs.  Unfortunately, the names are so entrenched at this point that there’s little prospect of changing either (or both) to something less confusing, so it looks like this is something we’ll just have to keep dealing with.  Hopefully this post will help reduce the amount of confusion over this issue.

Bridge over Rio Puerco of the West at Petrified Forest

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