Downloaded via UNIV OF CALIFORNIA SANTA BARBARA on July 23, 2018 at 05:10:52 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.
Chapter 12
Chemical, Technological, and Social Aspects of Pottery Manufacture in the La Quemada Region of Northwest Mexico E. Christian Wells and Ben A . Nelson Department of Anthropology, Arizona State University, Tempe, A Z 85287
Using scanning electron microprobe analysis and simple refiring experiments, this study reconstructs the operational sequence of production and decoration of incised-engraved pottery sherds from the prehispanic site of L a Quemada, Zacatecas, Mexico. The results of these analyses suggest that certain steps in the firing and decorative processes were manipulated by local producers over time, which resulted in some of the conditions conducive to craft specialization.
Reconstructing the process of ceramic production has long been a focus of archaeological research concerned with the underlying practices involved in technological innovation, as well as the forces shaping cultural traditions. Over the past century, archaeological chemistry unquestionably has made significant contributions to these research objectives. Chemical studies alone, however, can seldom be used to answer anthropological questions about the relationship between pottery manufacture and technological innovation. Instead, archaeologists must employ multiple lines of evidence from independent datasets
© 2002 American Chemical Society
Jakes; Archaeological Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 2002.
185
186 to evaluate critically information produced from chemical characterizations. In this paper, we present the results of a series of chemical and physical analyses to reconstruct the operational sequence of production of incised-engraved pottery vessels from the Malpaso Valley in south-central Zacatecas, Mexico, manufactured roughly A D 500 to 900, with the greater goal of elucidating how ceramic technology articulated with the local craft economy. To this end, three basic questions about the production process are addressed: 1) What raw material sources were utilized?, 2) How were the vessels formed and decorated?, and 3) What techniques were involved in the firing process? The results of this study suggest that certain steps in the firing and decorative processes were manipulated increasingly by local producers. These efforts resulted in significant technological innovations, specifically, the establishment of a consistent firing temperature and a shift to a post-fire engraving procedure that required the decoration of only those vessels that survived the sintering process. More broadly, these findings inform about some of the ways in which technological innovations can result in conditions that are conducive to craft specialization in middle-range societies.
Geological and Archaeological Context of the Malpaso Valley The Malpaso Valley is a relatively narrow floodplain (ca. 2000 m asl), approximately 10 km wide, and is currently cut on its easternmost edge by the Malpaso River (Figure 1). The region is bounded on the east and west by foothills, which give way to the Sierra Fria to the east and the Sierra Madre Occidental to the west. The valley floor adjacent to the main course of the Malpaso River is composed of alluvium that was deposited by lateral migrations of the river channel and by the deposition of fine-grained sediments deposited when river waters periodically covered the floodplain. A sedimentary conglomerate characterizes the eastern side of the valley extending from the valley's northern extreme to the southwestern portion of Villanueva. The Miocene extrusion of volcanic material in the valley resulted in the deposition of rhyolitic flows and tuffs, andesites, and basalts, the latter of which are restricted to the eastern and western valley margins. The rock-forming minerals found in these predominant extrusive igneous rock types include quartz, plagioclase feldspar, biotite, and olivine. These minerals occur to varying degrees in Malpaso Valley pottery (1), as well as in naturally occurring inclusions in local outcroppings of clay-rich sediments, which can be found eroding out of arroyo cuts into the alluvial floodplain and the surrounding foothills.
Jakes; Archaeological Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 2002.
187
Figure 1. The geology of the Malpaso Valley, showing the locations of L a Quemada (the largest dot in the northeast quadrant), outlying settlements (represented by smaller dots), and the clay outcroppings (numbers 1 and 2).
The valley contains three main archaeological zones, the largest of which includes the site of L a Quemada, a sizeable civic-ceremonial center situated roughly 250 m above the valley floor on a prominent hilltop at the north end of the valley. The site is composed of a monumental core that contains a
Jakes; Archaeological Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 2002.
188 central ballcourt, a large colonnaded hall, at least 12 pyramids, and a series of sunken-patio compounds that were probably elite residences (2). In addition, there are more than 56 artificial terraces that flank the upper southwest side of the hill, most of which support residential patio complexes that are interconnected by stairways and causeways (3). In addition to the site of L a Quemada, the valley contains three major clusters of habitation sites, linked together by an extensive network of raised pathways (4). One cluster, the " L a Quemada Aggregate," is located along the banks of the Malpaso River at the base of the hill upon which L a Quemada rests. A second, the "Los Pilarillos Aggregate," lies to the southwest of L a Quemada and is centered around the small ceremonial site of Los Pilarillos on the Arroyo de Coyotes. The third, and smallest, the "Villanueva Aggregate" is located at the southern end of the valley at the confluence of the Malpaso River and the Arroyo de Coyotes. Each settlement aggregate consists of approximately 50-100 "villages," each composed of residential patio complexes that likely represent households or other social units. Recent excavations indicate that L a Quemada and its outlying settlements were initially occupied around A D 500, experienced a period of major architectural growth about A D 700, and were largely abandoned by A D 900 (5). L a Quemada was the central place in the Malpaso settlement hierarchy and most likely was also the center of political power for the immediate region (6). However, imported materials, such as obsidian and marine shell, were not concentrated in the hands of L a Quemada residents, but were acquired by all sectors of Malpaso society, both as raw materials and as finished products (7). Further, evidence suggests that craft specialization did not characterize the production industries of chert (8) and obsidian tools (9) or shell ornaments (10). Recent studies suggest that L a Quemada's rulers may have exercised their control over subordinate populations in the valley through a combination of ancestor veneration and the institutionalized use of violence, as suggested by the abundance of human skeletal deposits and their associated mortuary patterning focused on above-ground displays of human remains (11).
Reconstructing Incised-Engraved Ware Technology Incised-engraved wares were produced in the Malpaso Valley perhaps from A D 500 until approximately A D 900. Incising and engraving occur on highly burnished tripod vessels, fired dark brown to black in color. Designs are restricted to simple, geometric motifs often filled with red and/or white mineral pigments that appear on a continuous band, usually no more than 5 cm wide, just below the rim. It is conceivable that the use of incised-engraved vessels was restricted to certain segments of Malpaso society or to certain activities, as
Jakes; Archaeological Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 2002.
189 suggested by the relatively low frequencies o f vessels and their somewhat sophisticated production technology. Holien and Pickering (12) place Michilia Red-Filled Engraved pottery o f the Alta Vista region to the northwest (ca. A D 750-900) in context with aspects o f Chalchihuites ceremonialism, and Kelley (13) makes similar observations for Vesuvio Red-Filled Engraved wares (ca. A D 600-750) recovered from the same region. Given that Malpaso incised-engraved pottery may have been reserved for ritual use, it is important to caution that the present study of its manufacturing technology may not reflect trends in plainware pottery. Incised-engraved wares from the Malpaso Valley can be divided into three ceramic complexes with possible chronological significance based on their particular design styles (Table I) and on similar distinctions made by Kelley and Kelley (14): the Malpaso (ca. A D 450-600), the L a Quemada (ca. A D 600-750), and the Murguia (ca. A D 750-900). While the raw materials and resource zones used by ancient Malpaso potters probably changed little over time, the decorative and firing processes underwent significant changes that resulted in greater control over the manufacturing process.
Table I. Ceramic Inventory for the Malpaso Valley. La Quemada La Quemada Site Aggregate Pottery Wares n n % % Plain 104,532 61 9,138 5 Slipped 10,969 5 57 1,004 Painted 10,307 837 5 66 Negative 1,226 91 13 1 Pseudo-cloisonne 340 78 0 0 Incised-engraved 2,141 47 256 6 Historic 0 0 0 0 2,797 Indeterminate 57 5 231 Totals 132,312 61 5 11,479 Note: All totals and percentages are calculated by row.
Los Pilarillos Site n % 23,169 13 3,680 19 2,000 13 101 7 18 77 936 21 0 0 343 7 14 30,306
Los Pilarillos Aggregate n % 20 33,711 18 3,434 2,401 15 I 13 5 20 26 1,162 100 207 31 1,516 19 42,464
Other Valley Sites Totals n % 1,449 I 171,999 178 19,265 I 93 15,638 1 0 1,353 0 437 0 0 4,541 46 1 207 0 0 0 1 4,888 1,767 I 218,328
What raw material sources were utilized? Generally, Malpaso clays are the products o f the decomposition of feldspathic rocks, which contain abundant concentrations of alumina (AI2O3) and silicate (Si0 ) along with varying amounts of potassium (K-feldspars, or orthoclase), and sodium and calcium (Na/Ca-feldspars, or plagioelase). Incisedengraved pottery fabrics are medium-textured pastes with angular grains of quartz, sub-angular grains of plagioelase feldspar, and angular shards of volcanic glass. Accessory aplastics include hematite, limonite, and pyroxene, all appearing in protracted quantities compared to other Malpaso fabric classes (15), In order to determine the range of materials used in die manufacturing process o f 2
Jakes; Archaeological Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 2002.
190 incised-engraved pottery, we sampled and analyzed clay-rich sediments from some of the geological formations exposed by stream cuts along the Malpaso River and the Arroyo Coyotes in the Malpaso Valley. We collected twenty clay samples of approximately .5 liter each from several points across the valley that represented both visual and stratigraphic differences. We processed the samples by drying them, mixing them with distilled water, forming them into small briquettes, and firing them for one hour in an oxidizing atmosphere at 750°C. We then analyzed each sample with a scanning-electron microprobe and energy-dispersive x-ray (SEM-EDX) spectrometer (16, 17) to determine the range and proportion of elements specific to each clay type. The principal reason for selecting S E M - E D X spectroscopy is the technique's ability to conduct point analyses, thereby avoiding chemical signatures produced from included, clastic materials that might prevent the identification of discrete chemical groups (18, 19). For the present analysis, a JEOL JSM-840 scanning-electron microscope, configured with backscattered and secondary electron detectors and an energydispersive spectrometer, was used at the Center for Solid State Science at Arizona State University. The x-ray detector was mounted at a take-off angle of 40°. A l l assays were made using an accelerating voltage of 15 keV and a beam current of 10 nA. The electron beam diameter was held constant for each analysis at 2 um, and x-ray counting time averaged 30 seconds per assay. For each sample, three spots were analyzed from different clay particles and the results were averaged together. In order to determine whether or not the clays that we collected in the Malpaso Valley were similar to those used by ancient Malpaso potters, we also used the S E M - E D X to characterize the chemistries of 57 incised-engraved sherds (from the Malpaso Complex) collected from the L a Quemada (n=24) and Los Pilarillos (n=33) settlement aggregates. The S E M - E D X study enabled us to identify two main pottery groups with distinct chemical compositions using a hierarchical cluster analysis and a principal components analysis conducted on ten element concentrations identified for each clay sample and pottery sherd (Figure 2): aluminum (Al), silicon (Si), potassium (K), calcium (Ca), scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), and iron (Fe). The results of the principal components analysis are statistically significant at the
