PUMACEOUS POTTERY: AN INSIGHT INTO THE ANCIENT GUANGALAN PEOPLE VIA CERAMIC TEMPER ANALYSIS Niki Apollonia Buechel, Sabrina Rose Casavechia, Matthew Christopher Guido, Gabrielle Hoang, Abhiram Karuppur, Sangho Andrew Lee, Heather Amelia Newman, Dorothy Yingtao Qu Advisor: Dr. Maria Masucci Assistant: Kaushaly Patel ABSTRACT The Guangala people of southwest Ecuador have a relatively unknown culture. However, recent research has shown that the Guangala had a profound knowledge of ceramic technology. Analysis of the Guangala ceramics reveals an extensive use of pumice as an inclusion to make finely decorated pottery, though the pumice was not available locally to the Guangalan potters. There are different hypotheses that describe the reasoning and source behind the presence of pumice in the ceramics. One hypothesis contends that the pumice was derived from ashfall from explosions of volcanoes in the Andes mountains. Another hypothesis details that the pumice was obtained through trade from people inhabiting the Highland areas surrounding the volcanoes. Evidence from analysis of Guangala ceramics using optical petrography, a technique used to analyze the mineralogical contents of ceramics, supports trade in pumice. These results will help in determining the relationship between the Guangala and other contemporaneous cultures and will shed light on the activities and technology of a relatively unknown society. INTRODUCTION The Guangala were an indigenous people who inhabited southwest Ecuador from 200 BC- AD 800 (1). While little information is known about the Guangala, studying their unique ceramics can lend insights into technology, culture, and their interactions with other ancient peoples. Archaeologists often pursue provenance studies in order to reach these ends, and in this study, a particularly puzzling question of provenance with respect to ancient ceramics is encountered. Namely, the ceramics of the Guangala people (Figures 1, 2) appear to be tempered with pumaceous ash, and yet geological studies of the area have not identified pumice in the region where the Guangala lived. This material is present in the volcanically active Ecuadorian Highlands 249 km from the Guangala region (1). Identifying the source of the pumice found in Guangala ceramics is the motivation of this provenance study, in which three possibilities for acquiring the pumice temper will be investigated: trade, direct procurement, and ashfall. Using optical petrography, the project analyzes Guangala ceramic samples, to be compared with pumice and ash samples and experimental samples of clay with pumice and ash. [6-1] Figure 2. Guangala polychrome bowl Figure 1. Guangala masculine figurine with geometric decoration. (Private whistle with engraved body decoration and collection; photograph from Valdez and hammered gold earrings. From the Veintimilla 1992: Figure 70). (4) collection of the Museo del Banco Central del Ecuado r, Guayaquil. (MBCG No. GA 2-2164 -82; photograph from Valdez and Veintimilla 1992: Figure 65). (4) By attempting to determine the source of the pumice found in ancient Guangala pottery new information can be offered on the ancient ceramic technology of coastal Ecuadorian people. In addition, the findings could offer information on trade, economy, and cultural practices of the ancient Guangala as well as possible relationships between the Guangala and groups from other geographical regions. The research could also contribute to archaeological methods by demonstrating the utility of petrographic analysis for studying artifacts and materials. From a global standpoint, the results of the study could add new comparative information to research done on other ancient peoples such as the work of Anabel Ford of the University of California at Santa Barbara on the Mayans in El Pilar, Belize. Ford contends that volcanic ash, a volcaniclastic material related to pumaceous ash, is present in Mayan pottery and was derived from ashfall from volcanic eruptions, rather than trade or direct procurement (2). In the present study, Ford’s hypothesis is tested as one potential explanation for the source of the material in Guangala ceramics. This case is tested only on a comparative basis, as the case of the Maya and Guangala are not identical. The research done on the Guangala ceramics could either serve to reinforce Ford’s hypothesis or serve as a contrasting case if a difference in type of source is found. An analysis of archaeological and experimental samples was undertaken to consider the likelihood of the three explanations. By comparing type samples of volcanic materials, experimental ceramic samples made by mixing clay with various pumaceous tempers, and a sample of archaeological ceramics spanning the Guangala time period, it may be possible to determine the specific origin of the pumice found in the Guangala ceramics as well as the means by which it was procured over several centuries. This study leads to the postulation that the pumice was obtained through trade from the highlands. It is unlikely that the Guangala would travel to the Highlands to mine the pumice through direct procurement; the mining regions in the Highlands were inhabited, and these people likewise have been linked to trade with the Lowlands already, through obsidian. Moreover, the volcanic expulsion model is unlikely as [6-2] pumice would have to reach El Azúcar Valley (Figure 3), where the Guangala inhabited, regularly enough to account for the abundance of pumice found in ceramics spanning the entirety of the Guangala time period. Also, this ashfall is unlikely, because of the generally northward wind patterns in Ecuador (3). In order to test the trade hypothesis, ceramic petrography was used to compare the experimental samples, whose sources of temper are known, with the archaeological samples of the Guangala people. By obtaining this information, it will be possible to further characterize a relatively unknown people who demonstrated a profound knowledge of ceramic technology. These results will help in uncovering the process used by the Guangala people to create their pottery and will also help in detailing the environment of El Azúcar Valley and the trading networks of the region. In addition, knowledge of the ceramic production methods of the Guangala people may aid other provenance studies in pre-Columbian ceramics, such as Ford’s investigation of ancient Maya pottery. Figure 3. Map of Ecuador adapted from Reitz and Masucci, showing the Guangala area of interest, El Azúcar, and northwestern wind patterns (5). [6-3] BACKGROUND Geology The geology of Ecuador itself is the result of a Mesozoic-Tertiary age (250-2.6 mya) volcanic belt, which formed at the convergence of the oceanic Nazca tectonic plate and the continental South American plate forming the Andean mountain chain (7). Ecuador contains one of the most volcanically active zones of Latin America and is an ideal location for finding volcanic materials. Pyroclastic materials like pumice, however, are concentrated only near the volcanic zones in the highlands. The geology of El Azúcar Valley within the Santa Elena Peninsula region, which is the source of the Guangala ceramics in the study, is characterized by sedimentary materials including chert and sandstone, among which the minerals include varying quartz, feldspar, and muscovite; neither ash nor pumice is found (7). El Azúcar Valley is in the lowlands, less than 30 km from the ocean and 25 km south of the coastal hill range referred to as the Chongon-Colonche hills. The hills expose igneous rocks of the Pinon and Cayo Formations. The Pinon contains basaltic lavas and phenocrysts such as plagioclase, augite and Fe-Ti oxides, and the Cayo contains volcanic breccias, tuffs and basaltic lavas. The Chongon-Colonche hills are composed of volcanic and volcaniclastic rocks, and these sediments do reach the lower coastal valleys but they are intrusive igneous materials and not pyroclastic materials such as pumice (8). The presence of these volcaniclastic rocks affects the clays of El Azúcar Valley, but would not result in the presence of pumice or ash naturally in the clays. This distinction indicates that pumice would have to be intentionally added from a separate source. Samples of El Azúcar clays were tested in previous research to confirm the absence of natural pumice (7). It is important to make the distinction between the igneous rocks available to the Guangala people only kilometers away at the Chongon-Colonche hills, and the pumice and ash in the ceramics. The latter materials would only be available through active volcanic activity, i.e. ash and phenocrysts ejected and transported by wind, and rock formations found at the base of the volcano. For example, volcanoes such as Tungurahua have the proper igneous rocks that would be added to fine pottery, however Tungurahua is greater than 250 km from El Azúcar Valley (Figure 4). Figure 5 illustrates the ash and pumice deposits of Ecuador in the Qc region. El Azúcar Figure 4. A map showing the major volcanoes in Ecuador, the closest of which is Tungurahua (6). [6-4] El Azúcar Valley Figure 5. A geological map of Ecuador. The yellow-brown region labelled Qc represents the highland region which is a possible locus of trade from which the Guangala may have obtained the pumice that is widespread throughout their ceramics. The map also shows that pumice deposits are not local to El Azúcar (8). Culture During the Guangala era, the people of Ecuador were going through a phase of regional development, where each region obtained a unique identity. One way people marked or showed this identity was through fine paste decorated pottery. The Guangala made some of the most beautiful and colorfully decorated pottery in Ecuador, creating black “sombreware” and two and three colored “bichrome” and “polychrome” pottery (1, 9). This pottery was an innovation of the [6-5] Guangala, although little is known of how they created their ceramics. Accordingly, this innovative pottery feature unique to the Guangala disproves the theory that the Guangalan pottery could have be traded from other sources, e.g. the Highlands, as the ceramic style of the pottery being studied is unique to the Azúcar region.