Procesos de Formación de Sitios Arqueológicos: Tres Casos de Estudio en la Puna Meridional Catamarqueña Argentina

KLIGMANN, DÉBORA M.

Archaeopress - British Archaeological Reports

Lugar: Oxford; Año: 2009 p. 360

978 1 4073 0432 8

ENGLISH SUMMARY STATEMENT OF THE PROBLEM Previous research shows that both natural and cultural processes affect archaeological materials before, during and after the sites are abandoned. Despite recognizing the importance of these processes, systematic research dealing specifically with this issue remains scarce. Analyses of site formation processes in the Argentine Puna are uncommon and they are mainly devoted to answering taphonomic questions. In my opinion, understanding site formation processes is a prerequisite before inferring past human activity from the spatial distribution of the material remains recovered at any site. This book is the product of research I conducted for my Doctoral Dissertation (“Archaeological Site Formation Processes: Three Case Studies in Catamarca’s Southern Argentine Puna”) with Dr. Julie K. Stein acting as advisor and Dr. Luis A. Borrero as co-advisor. It was presented at the University of Buenos Aires, Argentina, on December 15th 2003. The main goal for my dissertation was to reconstruct the formation processes of the excavated units through the analysis of their sediments. This would provide the necessary information to discuss human occupation intensity as well as to examine site usage throughout the passage of time. The sediment analysis provided three research avenues: physical/chemical properties, microvertebrates and microfossils. A fourth avenue was explored by using information obtained through experimental control sites. ARCHAEOLOGICAL RESEARCH IN THE STUDY AREA Since 1994 archaeological research, funded by the National University of Catamarca, has been carried out in the Department of Tinogasta, Catamarca Province, Northwest Argentina. The study area, with altitudes decreasing north-south from 4250 to 3500 masl, includes the Chaschuil Valley, two tributary basins called “Las Lozas” and “Cazadero Grande” as well as a high altitude marsh called “Vega de San Francisco”. The overall goal of the Chaschuil Archaeological Project, directed by Dr. Norma Ratto, was to reconstruct the cultural and environmental dynamics of the groups that inhabited the Southern Puna in the past thus generating models to explain spatial usage. The general hypothesis held that the Chaschuil Valley functioned as a “circulation corridor” for goods, energy and information between two regions: the semi-arid valleys of Northwestern Argentina (Valliserrana) and Chile. It appears that the study area has been inhabited for the past 2000 years. This chronological framework was established by stylistic and technological characteristics of some artifacts as well as radiocarbon dating. My own research was centered on the Vega de San Francisco in the Puna region, located at 4000 masl and 21 km away from the Argentina-Chile border. The Puna, by definition an environmentally demanding region, is characterized by cold dry weather and low precipitation and atmospheric pressure. Here vegetation is sparse and salt-lakes, which are the outcome of reduced moisture and high evaporation rates, are quite common. Harsh conditions notwithstanding, the Vega de San Francisco has both rock shelters as well as open-air archaeological sites. All the sediment samples analyzed in this book belong to three archaeological sites located in the NW section of the Vega de San Francisco. One is a rock shelter named “Alero 12”, the other is an enclosure named “Corral de San Francisco” and the last one is an Inka rest house named “Tambo de San Francisco”. ORGANIZATION OF THE BOOK PART I (Chapters 1 to 5) includes, after a brief introduction, the information common to all the analyses carried out: theoretical considerations, goals, spatial and temporal framework, archaeological background, expectations and methodology. Chapter 1 informs readers about the contents of the book. After the research topic is introduced, the general project that framed my own work is presented. This is followed by some comments dealing with the way the information was organized and with the nature of the book. Chapter 2 presents the theoretical considerations that guided my work as well as the general and specific goals for each of the four research avenues followed. Chapter 3 allows the reader to understand the specific attributes that make the Puna very different from other areas. These comments are followed by a brief summary of the temporal framework available for the human occupation of the study area. Chapter 4 deals with the archaeological background and the expectations for each of the four research avenues followed. Also, a brief summary of the three archaeological sites excavated is presented. Chapter 5 describes all the steps necessary to undertake the analysis of the formation processes of the excavation layers, from the collection of samples in the field to their analysis in the lab. PART II (Chapters 6 to 9) presents and discusses the results for each of the four research avenues followed: sediments’ physical/chemical properties, microvertebrates, microfossils and experimental sites. Chapter 6 deals with the sediment’s physical/chemical properties. The chosen attributes to be analyzed were: color, organic matter, carbonates, pH, phosphorus, grain-size, microartifacts and mineralogy. I came up with a sediment model for human activity in the area. In contrast to the control samples, archaeological sites would have sediments with higher values of organic matter resulting in darker colors and higher phosphorus values. Carbonates are concentrated only around the marsh banks due to water evaporation. Accordingly, archaeological sediment samples would have lower carbonate values. Since the study area has naturally alkaline sediments, archaeological samples will have lower pH values due to the incorporation of acids through human activity that would have tended to neutralize them. Archaeological samples should also contain microartifacts rendering human presence obvious. Due to the probable existence of multiple sources and/or transport agents the sediments are more poorly sorted from a granulometric point of view. In other words, archaeological sediments should be highly heterogeneous as far as grain-size is concerned when compared to sediments that have not been impacted by human activities. The results of the sediment analyses show that the sources of the sedimentary particles were: volcanoes (e.g. tephra in layer II of the rock shelter), weathered lava flows (e.g. rock shelter walls), unconsolidated materials (e.g. pyroclastic cones and disturbed desert pavement) and the marsh per se. The stratigraphical differences identified in the field were corroborated. The sediment particles traveled short distances since the abundance of angular particles and the presence of chemically unstable minerals point to a local origin. The transport agents of such particles were found to be: wind, volcanic eruptions, gravity, animals and humans. Several post-depositional alterations have been identified for the archaeological samples: seismic activity, animal burrowing, looting and recycling of construction materials. Animal as well as human trampling causes desert pavement alteration allowing buried materials to be re-exposed on the surface. Of all the physical/chemical attributes considered, pH, available phosphorus and type and amount of microartifacts showed the greatest differences as compared to the control samples. Thus they were the most useful in providing information about changes in human occupation intensity and site usage. There is a caveat to this proposition. This combination may not necessarily be useful to interpret archaeological sites located in other environments. Chapter 7 deals with microvertebrate remains (mainly lizards) recovered at Alero 12. All the microvertebrates were classified into skeletal parts within large systematic groups (reptiles, rodents and birds) after which the NISP was calculated for all groups and the MNI just for the reptiles. From a taphonomic point of view I looked at both horizontal and vertical location of the remains, their state of preservation and the diversity of the faunal representation. There was a minimum number of 74 lizards concentrated in one place. They belong to at least two species of Liolaemus genus and to probably one species of Phymaturus genus. The state of preservation of the faunal remains was very good. Almost all the skeletal parts were represented, even the most fragile and delicate ones. Most of the bones were whole and didn’t show digestion traces or other signs of intentional human activity (e.g. cut marks or burning). These lizards did not constitute a food resource either for humans or animals (e.g. carnivores and predatory birds) and were not used in medicinal or ritual activities or as raw materials for future artifacts. Their death, due to catastrophic causes, occurred during group hibernation inside a rodent’s burrow and points to a temporary abandonment by humans of the rock shelter. Chapter 8 presents the analysis of the diatoms recovered in each of the three archaeological sites excavated. The attributes chosen were: number of species, number of cells and species ecology. In order to discuss the meaning of the presence of the diatoms in the sediment samples I took into consideration the cells’ abundance or scarcity. Each of the options could be the result of either the presence or the absence of a water body in situ, with diatoms coming through natural processes or agents, through human action or by contamination. There was a low number of cells and species in two of the archaeological sites, Alero 12 and Corral de San Francisco. However, there was a high number of cells and species in the Tambo de San Francisco deposits. All of the diatoms included in the sediments of all sites come from the marsh or from some other water body with very similar characteristics. In all the sites, the presence of diatoms is not explained by one unique agent but by multiple agents acting in combination or by one agent at a time throughout the centuries. In archaeological sites, the abundance of diatoms does not always indicate the presence of an in situ water body. The abundance of diatoms must not necessarily be associated with a period of greater humidity. The scarcity or absence of diatoms does not always guarantee the existence of an in situ water body. One cannot make interpretations based on diatoms recovered from archaeological sediments, independently of the quantity of cells and species, until proven that such diatoms are of natural origin and that they are indigenous. The diatoms recovered at the rock shelter, Alero 12, were accumulated there by wind, animals and/or unintentional human activity. The diatoms recovered at the enclosure, Corral de San Francisco, were accumulated mainly by faunal activity and, to a lesser extent, by wind and/or unintentional human activity. The huge amount of diatoms recovered at the Inka rest house, Tambo de San Francisco, would be a consequence of the intentional transportation of water by humans. Animals and wind also contributed diatoms to it, although at a lesser extent than humans. Although at first sight the huge quantities of diatoms could have been explained by marsh flooding, in the end it was evident that the marsh never flooded the archaeological sites. The sediments around the marsh have very high organic matter and carbonate values. None of the archaeological sediments are anywhere close to those values. Chapter 9 presents the results of the seven experimental sites after a 6 year period. These sites allowed me to evaluate the resolution and integrity of the deposited assemblages, that is, to identify the amount of disturbance on a spatial and contextual level undergone since their deposition. Examination of control samples from the study area is a necessary first step to identify natural (non-human) modifications in the archaeological sediments. Archaeological samples are different from control samples because the former are affected by natural as well as human processes. The higher the occupational intensity, the greater is the difference between the control and the archaeological samples. The variables chosen for measurement were: number of pieces recovered and lost, horizontal displacement, vertical displacement, direction of horizontal movement, inclination, inversion, number of processes, formal damages and possible processes or agents of disturbance. I was interested in measuring how far and in what way artifacts moved within a sedimentary matrix and if that movement was related to the characteristics of the matrix (grain-size and compaction) and/or to the artifacts’ characteristics (raw material, size, weight and shape). Two types of attributes were considered in the discussion: controlled (characteristics of the sites -such as grain-size of the sedimentary matrix-, characteristics of the pieces -such as raw material, size, weight and shape- and time of exposure) and uncontrolled (environmental characteristics -such as wind and earthquakes- and formation processes -such as deflation, animal and human disturbance). Out of the seven experimental sites laid out, I was unable to locate two of them in subsequent controls. One was lost due to the marsh’s dynamics and the other due to human activity. The artifacts underwent more disturbances on a spatial level (location) than on a formal level (fractures). 81% of the originally installed artifacts were recovered. Every single one of the recovered artifacts underwent horizontal displacements with a minimum travel distance of 1 cm and maximum one of 3.7 m. 25% of the recovered artifacts moved vertically but only 10% of them were completely buried, in no case deeper than 3 cm. No single attribute by itself could account for the observed movements. These movements are surely due to a combination of factors acting as a group. Since the observations of the experimental sites were widely spaced in time, in this type of experiment the changes recorded cannot be correlated to the agents or the processes that caused them. One can observe the beginning and the end of an experimental site but one is left to wonder as to what happened in between. On a temporal level (6 years) the results work as a minimum expectation of what could have occurred archaeologically. However on a spatial level the results show the greatest movement expected for an archaeological site. This is due to the fact that there were no physical boundaries for the experimental sites. In the archaeological sites there were walls all around them that limited movement. On the surface, there is a greater rate of deposition for artifacts than for sediments, creating palimpsests of low integrity and resolution. But under it, the artifacts recovered during excavation were buried because the rate of deposition for sediments was equal to or greater than the rate of artifact deposition, creating deposits of high resolution and integrity. The marsh seems to change only slightly, although continually, in its shape and size. In the study area there seems to occur a differential destruction or burial of the sites according to their location. As far as formation processes are concerned, there seems to be two distinctive environments inside and outside the marsh. Due to the relative geomorphological stability, the objects have a high probability of being exposed for prolonged periods of time on a same topographical surface before being buried, thus creating palimpsests of artifacts coming from different assemblages. PART III (Chapter 10) summarizes the site formation processes affecting each one of the three case studies: Alero 12, Corral de San Francisco and Tambo de San Francisco. At the rock shelter Alero 12, the rodents’ disturbance was localized, therefore the deposits can be considered as having high resolution and integrity. The differences between the four stratigraphic layers were the result of changes in the natural depositional conditions independent of human activity. The microvertebrate accumulation was of natural origin unrelated to human activity. The analysis of both sediments and microvertebrates allowed me to propose a model of an alternate occupation by different human and natural agents (rodents and lizards) with a later abandonment of the site all together. At the enclosure Corral de San Francisco, the rodents’ disturbance was also localized, therefore the deposits can be considered as having high resolution and integrity. Given that the natural depositional conditions did not change the differences between the two stratigraphic layers can largely be explained by changes in human activity. Humans had a greater impact in the formation of these deposits than in those of the rock shelter. The current animal enclosure was built upon a previous occupation unrelated to animal husbandry. This indicates a change in site usage throughout time. The re-occupation of the same site can be explained by the fact that this area has almost no adequate locations for human installation. Even though the rodents’ disturbance seems to be localized, the two buildings (Recintos 3 and 10) excavated at Tambo de San Francisco are very disturbed. Not all these disturbances were caused by rodents. This Inka rest house was built on top of previous occupations. Human disturbance seems to account for the low resolution and integrity in both buildings. The disturbance at the site created conditions of differential visibility of the artifacts. The sediments, and the artifacts within, possibly ended up “scattered” on the surface due to the disappearance of the buildings’ walls surrounding them. The sedimentological results do not agree with the expectations for a site with human occupation, even one of low intensity. Finally, I came to the conclusion that the water from the marsh never flooded the archaeological deposits. The diatom analysis allowed me to propose the intentional transportation of water to the site, although I cannot yet explain when or what for. My research has proved that it is possible to identify disturbance based on sedimentological analyses. This is fundamental for sites in which there are no visible evidences of disturbance during excavation. Despite their proximity, the three studied sites produced different results regarding the formation processes involved in their depositional history. A single type of remain can be interpreted in radically different ways depending on whether its presence responds to either natural or human causes (e.g. lizards and diatoms). In all the sites I confirmed the stratigraphy observed in the field but I also added information not visible during the excavation. Overall the results of the sediment analyses showed that the human occupation in the Vega de San Francisco area was a low intensity, occasional and/or periodic one, confirming the general research hypothesis of the Chaschuil Archaeological Project. Therefore, the study area can be considered as a stopover on a well-traveled route, connecting different regions rather than an area that was occupied year-round. The sites were probably used by a small number of individuals to do specific activities (e.g. re-sharpening of lithic instruments). Certain sectors were re-occupied at different times and/or for different purposes (e.g. the enclosure and the Inka rest house were built on top of previous occupations with different usages). PART IV (Chapters 11 to 13) includes two appendixes that contain the complete data bases used in chapters 6 through 9 and the bibliography.