What does a Pre-columbian Mesoamerican ceramic factory look like?

I don’t have a very good answer to this question, and I suspect most Mesoamerican archaeologists would be similarly hard pressed to answer it. Ethnographic parallels, like the circular subterranean kilns and associated waster dumps of Coyotepec, Oaxaca, give us some possible models. A few archaeological features, like the pyrotechnological installations in Belize that Murata (2011) has described recently, also give us some ideas.

This question has been at the back of my mind for about thirty years, since I first started doing research on the production and distribution of Plumbate pottery. Neutron activation analysis of clays from near the Pacific coastal border between Mexico and Guatemala seems to have identified the areas where clays for Plumbate were procured: as shown in Figure 1, the lower Rio Naranjo in Guatemala has clays that match San Juan Plumbate, and the lower Rio Cahuacan has clays that match Tohil Plumbate. Within the lower Rio Naranjo area, rumor has it that Edwin Shook observed the destruction of a Plumbate kiln during road construction near La Blanca in the 60s or 70s, but he apparently didn’t photograph the feature, and he never published a description of it.

I have done some exploration on the Guatemalan side of the border, looking for additional features like the one Shook observed, but I found no clear evidence of pyrotechnological features with associated Plumbate waster dumps. Currently, the Proyecto Arqueológico Costa del Soconusco (PACS) is inventorying archaeological remains in the mangrove forest on the Mexican side of the border, where we might expect Tohil workshops to be located. As detailed on other posts to this blog, many mounds in this area include massive deposits of fired sediments, which, based on excavation, appear to be related to salt and/or ceramic production. But we haven’t yet tested any of the mounds west of the Rio Cahuacan, in the specific area identified as containing Tohil Plumbate clays.

Mounds in the mangrove forest west of the Cahuacan have large quantities of Plumbate sherds on the surface together with utilitarian vessels and solid ceramic cylinders that we believe are pot stands used in sal cocida salt production. But which of these mounds, if any, might have been sites of Tohil Plumbate production? The LiDAR imagery generated for the PACS give one viable and testable hypothesis.

Figure 2 shows the LiDAR imagery from the area just west of the Rio Cahuacan. I have visited many of the “CONQ” mounds and many of the “PIN” mounds, where I observed the Plumbate, salt production, and firing features discussed above and elsewhere on this blog. I have not yet had the opportunity, however, to visit the “CAH” mounds located in the southeast corner of the image. The complex consisting of Mounds CAH-12 through CAH-17 sits almost exactly on the peak of the probability surface shown in Figure 1, some features of this complex and its environs lead me to wonder if this is a Tohil Plumbate factory.  

Figure 3 zooms in on the CAH-12 complex. The labeled mounds and several smaller ones form a complex on what appears to be a slight rise on the dry land that forms the inland edge of the mangrove swamp at this location. Perhaps most tantalizing, there is one large depression and three smaller ones located within about 200 meters of the mound complex. The largest depression is almost 100 meters long by 50 meters wide, and approximately one meter deep. Could this be where Tohil Plumbate potters mined the clay that they formed into serving vessels for the local market and fancy effigies for the export market? If so, then Figure 3 would represent an answer to the question posed at the top of this blog entry.

Currently, identification of the CAH-12 mound complex as a Plumbate factory is pure speculation. I will travel back to Soconusco for a couple of weeks this June, however, at which time I will visit the mound complex and associated depressions. I will post a brief report of my observations on this blog by the end of June.

Shovels and Science

Shovels and science in the quest for knowledge about Soconusco’s past

Most students who have taken an introductory archaeology class appreciate that archaeology isn’t about treasure hunting and that “Indiana Jones” is at best a caricature of an archaeologist. Somewhat less well appreciated is the central role of science in creating an understanding of the past. Even people with some archaeological training tend to think of archaeology as digging holes for some unstated purpose, such as to see what stuff from the past looks like. Here my premise is that archaeology is about building verifiable knowledge about some component of the human past.

Archaeology as just defined depends on science in at least two ways. First, it uses the scientific method, which means that it is hypothesis-driven and builds knowledge through successive attempts at falsification. Second, archaeology depends on analytical techniques that are derived from physical and biological sciences; that is, it borrows techniques that extend the human ability to describe physical and chemical properties of matter beyond what we can accomplish with our visual, auditory, and tactile senses. Although one might argue (and I would agree) that use of the scientific method is the more important connection of archaeology to science, here I want to discuss the various analytical techniques we are using in our fieldwork in eastern Soconusco and how they relate to each other. Hopefully the discussion will also implicate the underlying scientific structure of our endeavor, and perhaps even some of the specific hypotheses and attempts at falsification that guide our research.

The activities of the Proyecto Arqueológico Costa del Soconusco (PACS) can be characterized in a variety of ways, as other entries in this blog have indicated. I have touched on the various ways we are collecting data in other entries, but here I want to discuss these data-collection strategies in some detail. Although I say we are “collecting data”, perhaps a better summary statement of what we are doing is “creating data”. My point is that data (observations about the world) only exist because some detector (our senses or our analytical instruments) has been used to make some kind of measurement on the physical world. 

Sampling the Archaeological Record

We are trying to develop knowledge about the past of a particular region, the lower coast of eastern Soconusco, between the Rio Suchiate (the international border between Mexico and Guatemala) and Puerto Madero. We are investigating this region’s past by sampling the archaeological record from the region and “creating data” based on this sample. Our sampling strategy is hierarchical: first, we have utilized LiDAR imagery as a guide to where archaeological deposits (mounds) are located within and around the lower coastal mangrove swamp; second, we are clearing a sample of these mounds, so that we can carry out magnetic surveys and obtain a sample of the archaeological materials on the mounds; third, we are carrying out controlled excavations on a much smaller sample of the mounds that we have visited.

LiDAR (light detection and ranging) offers the first and only available means of systematically documenting the surface archaeological features within a mangrove swamp environment. The combination of dense mangrove roots and other vegetation, sometimes deep water, and mud effectively precludes any kind of systematic pedestrian survey. But, as examples shown elsewhere in this blog make clear, the LiDAR imagery provides an incredibly detailed picture of the ground surface underneath the mangrove-forest canopy. Based on our visits to LiDAR-mapped mounds over the past couple of months, the LiDAR imagery is not only detailed, it is extremely accurate, down to the depiction of small pits excavated on the mounds by iguana hunters.

Our explorations have, however, documented a number of “false negatives,” which consist of mounds that were smaller than our initial size cutoff. Our field crews ran across these mounds in the course of accessing larger mounds, and a few minutes exploration turned up archaeological material. When we went back to the LiDAR imagery, it was clear that the imagery was accurate and that our size criterion was too conservative. Our initial estimate of slightly more than 200 mounds in and around the swamp is thus too low, perhaps by 50% or more. A reassessment of the LiDAR imagery with a less-conservative size criterion is currently under way.

So far we have documented two “false positive” mound identification based on the LiDAR imagery. One example is shown in Figure 1. Mounds GE12, GE13, and GE14 form a complex that lies at the ecotone between the sandy beach and mangrove forest, about 4 km northwest of the beach town of El Gancho. Mound GE13 is a slightly raised peninsula that extends into the mangrove swamp, while GE12 and GE14 lie just off the shore of the peninsula. During our visit to this complex on 11 February 2012 we noted that the peninsula is pure beach sand with no artifacts whatsoever. GE12 and GE14, in contrast, are clearly archaeological; along with the usual pottery recovered by surface collection, we also recovered about half of a basalt metate (maize grinding stone).

So, with the LiDAR imagery we have created extremely detailed data on the locations, sizes, and configurations of archaeological deposits within our study area. If there are non-mound archaeological deposits within the study area, they are essentially undiscoverable with current technology, as they must lie below the surface on which the mangrove trees are growing, which means they are currently below the water level of the swamp. Thus, we have close to a 100% sample of detectable archaeological deposits within our study area.

The next level of sampling entails obtaining materials that will permit an assessment of chronological and functional variation among the various archaeological contexts in our overall sample. We are doing this by finding routes to some of the mounds, clearing them, and then conducting (1) magnetometer survey; (2) surface collection; and (3) shovel testing. In a few cases of very inaccessible, small mounds or mounds on private property that could not be cleared, we have only obtained surface collections.

Surveys with the magnetometer are intended to reveal subsurface features that might have been related to pyrotechnology. By detecting the strength of the earth’s magnetic field, a magnetometer can identify locations where surface or subsurface features of the sediments enhance or reduce the strength of the field. Such anomalous locations may indicate the locations of sediments heated to high temperature, since heating will lead to realignment of iron particles in the soil so that they point to magnetic north, thus enhancing magnetic readings on one side the heated area and reducing readings on the opposite side. We have been running the magnetometer in gradiometer mode, with one sensor positioned approximately 45 cm above the other, so that gradient data (bottom minus top sensor) are obtained.

Figure 2 shows the gradiometer map from site RS3. The largest anomaly is at the far northern end of the unit, where the map shows a large magnetic anomaly centered at x=1011, y=1018. We hypothesized that this anomaly is created by the presence of intensely heated sediments in the deposits underlying this location, a hypothesis that was borne out by subsequent excavation.

When surface visibility is good and artifact density is relatively high, surface collection is an efficient means for obtaining a sample that will permit an initial assessment of the chronological placement of the underlying archaeological deposit and of some of the activities that led to the deposit’s creation. On our project, the main purpose of surface collection is to obtain a sample of ceramic fragments (sherds) that can be compared to published ceramic type descriptions from nearby sites and regions, thus permitting an initial estimate of the site’s chronological placement. Because surface visibility, disturbance, and other factors have profound effects on the apparent density of artifacts on the surface, we explicitly do not intend these collections to be used for estimating artifact density. For chronological assessment, the most informative sherds tend to be rims, bases, necks, and any sherd with incised or painted decoration; in keeping with archaeological tradition, we term these sherds “diagnostics”. Although we collect some large body sherds, we ignore many small ones, unless we are having a great deal of difficulty finding diagnostics; sometimes the thickness and surface texture of a tiny sherd can suggest a possible period of manufacture.

Another means we are using to obtain a sample of artifacts quickly and with a minimum of damage to the deposit is with “shovel tests”. These are non-controlled excavations of approximately 50 cm diameter and 60 to 100 cm depth. We generally do one shovel test on the top of the mound and one at the edge, near water level, hoping to increase the chance of hitting deposits of different time periods by sampling these two distinct depositional environments. The sediment is screened through quarter-inch mesh, and all artifacts, bones, and shells found in the screen are bagged. When completed, we measure the dimensions of the shovel test so that, unlike with the surface collections, we can use the shovel tests to estimate artifact density. We also take sediment samples from the excavation side wall for FTIR and XRF analysis, samples for luminescence dating, and samples for radiocarbon dating (if encountered). The shovel tests can’t be used to characterize site stratigraphy or change over time, and older, deeper deposits are more likely to go undetected. These tests do, however, provide a systematic sample of the later periods of the site occupation.  

Our most intensive level of sampling of the archaeological record is the controlled excavation unit. So far, we have only initiated three excavations. One of the excavations targeted the magnetic anomaly at the northern end of RS3; another targeted a similar anomaly on RS23. Currently, Richard George is excavating a location on BER19 where both the magnetometer and a later GPR survey detected an anomaly in subsurface sediments.

We excavate in arbitrary 20 cm levels, although the surface zone of heavy root disturbance is typically excavated as a single unit of up to 50 cm depth. Pottery, amorphous fired clay, lithics, shell, and bone are retrieved systematically by screening the sediment through quarter-inch mesh. Features, such as heavy sherd concentrations, areas of intensely heat-affected soil, or bone concentrations, are uncovered with trowel and brush. Two of the units have been expanded beyond the initial 1 x 2 m size in order to obtain better exposure of features. Excavation generally stops at the water table, but we excavate a bucket auger below the water table to obtain some indication of how much deeper the archaeological remains may continue.

A variety of samples are taken during and after excavation. These include charcoal for radiocarbon dating, sherds for luminescence dating, and column samples from the unit sidewall for FTIR and XRF analysis as well as fine sieving to attempt to recover small bones and charred remains. Samples of sediments from features are bagged for analysis as well.
Sampling the Paleoenvironmental Record

People leave a mark on the landscape outside of archaeological deposits, such as the mounds discussed above. By cutting and burning the forest and firing the salt- and ceramic production facilities in the swamp zone, past peoples’ activities affected the content of sediments that were accumulating in low-energy fluvial environments, such as the lagoons of the swamp zone.

We obtain our samples of the paleoenvironmental record by coring in locations that are likely to have been inundated during most of the past several thousand years. Perennially wet conditions preserve organic matter, including pollen. In past work, I have found such depositional environments near the inland margins of mangrove swamps. We use a “vibracorer”, which is basically a gasoline-driven concrete vibrator attached to 3-inch metal tubes of 3 – 6 meters length. The cores are taken in one or more drives in the same hole. After pulling the tubes containing the sediment out of the hole, the tubes are sealed and taken back to the field laboratory for sampling.
The Field Laboratory

Materials recovered during surface collection, shovel testing, excavation, and coring are returned to the PACS field laboratory for processing. Artifact collections, which mainly consist of fragmentary ceramic remains, are washed, dried, and labeled according to provenience unit by laboratory workers. Samples for luminescence and radiocarbon dating are catalogued and prepared for export. The coring tubes are opened, described, and sampled for various analyses.

One crucial task in the field laboratory is the typological study of the large collection of excavated ceramics generated by our project. Paul Burger is working with the collections from the three excavations undertaken this year, developing a preliminary taxonomy and descriptions of the identified types. Comparison with other ceramic reports for our region and nearby regions permits a more-or-less secure preliminary assessment of when the excavated deposits accumulated. We are also assessing the surface collection and shovel test pit ceramic samples for chronological placement and functional characterization.

One of the ways we are attempting to innovate on the PACS is by carrying out many “high-tech” analyses in the field laboratory, as soon after excavation as possible. Miniaturization of analytical instruments over the past 10 year or so has made this innovation a no-brainer. For instance, we have a portable x-ray fluorescence spectrometer (XRF) and a portable Fourier-transform infrared spectrometer (FTIR) in our field lab, so that we can do analyses “on the fly” that 15 years ago would have required exporting samples to a university or museum laboratory in the US. A small, high-temperature furnace gives us the ability to experiment with heat-effects on sediments. We also have a stereoscopic microscope and light source, which we are using to process and count the charcoal in our cores.

The XRF and FTIR complement each other in the analysis of sediments from archaeological excavations. XRF measures elemental concentrations rapidly and with minimal preparation of the sediment samples. FTIR characterizes the sediments at the molecular level, including identifying the presence of clays and other mineral components. If, say, the XRF analysis shows enriched calcium in a sediment sample, the corresponding FTIR spectra can be examined for the presence of pyrogenic calcite, which is produced by the complete combustion of wood.

Beyond characterizing sediments, the portable XRF also gives us the ability to characterize the elemental composition of artifacts that we have recovered. Artifact elemental characterization is particularly useful for obsidian, since elements determined by XRF easily discriminate the various Mesoamerican obsidian sources. So far, only three obsidian artifacts have been encountered on our project (the small number perhaps an indication of the functional specialization of the mangrove-zone sites); all of these artifacts have been sourced to the El Chayal source, in the highlands of Guatemala. XRF can also be used to analyze ceramic compositions; this will be important for evaluating the relative abundance of ceramics from different local and non-local sources on the sites we are investigating.

The FTIR is really a key instrument for the current project because of its ability to detect the presence of different mineral phases. In soils and sediments, clay minerals are expected to constitute a major component. When exposed to high heat, however, the clay minerals begin to lose their hydroxyl groups starting at around 500^o C, and by 900^o C vitrification begins, with the eventual formation of high-temperature silicate minerals. FTIR spectra of clays (or clay-containing sediments) heated to different temperatures thus differ systematically, and essentially provide a thermometer that monitors the heat to which the sediments were subjected. In work undertaken before our current fieldwork, Scott Bigney heated a sediment from Soconusco to temperatures ranging from 300 to 1100 degrees, and then obtained FTIR spectra from these samples; these samples form a library for assessing heat exposure of the sediments we are excavating in controlled excavations and STPs. We have also collected additional sediments from the immediate vicinity of one of our excavated mounds, and the FTIR spectra from these samples, with different heat treatments, are being added to the spectral library.

Scott Bigney is also using a procedure developed by geographer Megan Walsh to determine the concentration of charcoal at different depths within our sediment cores. Small samples of sediments are disaggregated and sieved through very fine screens. The samples are then placed into plastic Petrie dishes on which lines have been scored at regular intervals. Under a microscope, charcoal is counted by moving up one line and then moving over and counting down the next line. The total number of charcoal particles divided by the volume of sediment processed gives an estimate of charcoal concentration per cc. Eventually, when radiocarbon dates have been run on samples from the cores, we will be able to identify when the coastal plain was subjected to intense burning, which would be times when the most forest clearance was taking place.
Specialized Laboratory Analyses

While we are doing far more in the field laboratory than is common on most archaeological projects, some of the data we need to address this project’s goals have to be generated in more-specialized analytical laboratories. In particular, the chronometric analyses, which will give us information on when the deposits we have sampled accumulated, have to be undertaken in specialized radiocarbon or luminescence-dating laboratories. Isotopic analysis and analysis of pollen from the cores also has to be done in specialized laboratories; these analyses will complement the charcoal data being collected by Scott Bigney, and together they will document the history of forest clearance on the coastal plain.

All samples to be exported to the US for specialized analysis have to be entered into a catalog that lists all descriptive and contextual information. The catalog indicates the priority for analysis of each sample. For instance, samples from lower levels of the cores are a high priority, since they give a rough idea of the rate of sediment accumulation, so that we can estimate dates for the high-charcoal levels identified by Scott Bigney’s analysis. Paired luminescence and radiocarbon samples are also a high priority, since we want to validate the luminescence dates, which are still used very rarely in Mesoamerican archaeology and thus may be viewed skeptically by some archaeologists.
Some Preliminary Results

Ultimately, the data generated by this project will show how human use of the mangrove estuaries of eastern Soconusco varied in intensity and nature over time. So far, some of the broad outlines of this history are coming into focus, allowing us to refine hypotheses for future testing.

To begin with, in our area, as elsewhere on the Pacific coast east of the Isthmus of Tehuantepec, Early Formative people of the Locona and Ocos Phases lived at the inland edge of the estuaries and amassed large, tell-like habitation mounds that contain evidence of exploitation of estuarine resources. Cerro del Tigre (RS31) and El Castaño (RS19) exemplify this Early Formative focus, as does MA20, a site we have not visited but which was visited by Robert Rosenswig in 2011 (personal communication). Bermudez-1 is also most likely an Early Formative site, although we have yet to obtain a definitive surface collection or shovel test pit sample. The settlement and subsistence focus of the Early Formative in our area is consistent with observations on many other projects that have investigated Early Formative contexts in Pacific coastal Chiapas and Guatemala. Richard Lesure (2009) has recently published an excellent synthesis of current understanding of Early Formative adaptation to the estuarine environment.

So far in our area, it appears that Early Formative people abandoned the estuary prior to the Cuadros phase, around 1150 BC. This presents a contrast with the region just east of where we are working, in Guatemala, where Coe and Flannery (1967) excavated a deep Cuadros and Jocotal occupation at Salinas La Blanca. Although we have yet to study the ceramics from all of our sites carefully, so far we have noted no diagnostics of periods between the Ocos phase (Early Formative) and Crucero phase (Late and Terminal Formative). Occupations of the Middle Formative Conchas phase are well represented on the coastal plain, especially at the large Middle Formative center of La Blanca, Guatemala, which has been investigated by Michael Love (2002). It is noteworthy, therefore, that the Middle Formative does not appear in our area based on the ceramic collections examined so far. More careful typological study of the ceramic collections and chronometric dating (luminescence and radiocarbon) of excavated contexts will provide additional evidence on this inference about a hiatus in estuarine settlement.

People reoccupied the swamp during the Late Formative and Early Classic, most of the sites in our area having ceramic diagnostics of the Crucero phase, which parallel types of the Guillen immediately succeeding phases at Izapa. One especially common diagnostic is the rim flange, which comes in during the Late Formative at Izapa and persists into Early Classic times. Voorhies (1976) places this ceramic mode in the Early Classic in the Acapetahua Estuary.  If the swamp zone in our area was heavily occupied during Early Classic times, as the preliminary evidence suggests, this presents a dramatic contrast with the immediately adjacent coastal plain, where Rosenswig (2008) finds a near absence of both Late Formative and Early Classic occupation.

Late Formative and Early Classic contexts that we have investigated this year pertain to at least two distinct functional categories. Two sites, RS3 and RS23, are specialized pyro-technological features dedicated to salt and/or ceramic production. The ceramic collections at these sites are dominated by a single large, coarse ceramic type that Nance (1993) has named Porvenir Coarse. These vessels were almost certainly made on site and were very crudely finished. We believe that they were used to make salt via the sal cocida technique (in agreement with Nance 1993), but evidence of fires built inside the vessels suggests that they might also have been used as saggars in the firing of smaller ceramic vessels. Both RS3 and RS23 also have very abundant, massive wood-ash concretions that testify to the importance of combustion of fuel at these locations. Fire-reddened clay is also a major component of the midden. FTIR results also indicate that even much of the sediment that does not appear to be fire-reddened was, in fact, subject to temperatures in excess of 400^o C. Ceramics other than Porvenir Coarse are infrequent in the RS3 and RS23 deposits, and no chipped or groundstone artifacts were found, and the only faunal remains found were two fragments of oyster shell at RS3.

Less-specialized contexts seem to be present at a number of sites in the central swamp. In one of these, BER19, we excavated a 1 x 2 meter unit to a depth of 2.1 meters. Although the materials from the excavation have yet to be analyzed, there appears to be greater variety and a more even distribution of different functional classes of ceramics. This together with the presence of groundstone, obsidian, bone, and a single jade bead indicate that this context is less specialized than the pyrotechnological contexts represented by RS3 and RS23.

Non-systematic surveys in the past have documented a strong Late Classic and Postclassic presence near the mouth of the Rio Cahuacan, just northwest of the area we have been investigating this year. We may have some preliminary surface collection and STP data bearing on these earlier observations by the time our field season ends on March 10. If our previous observations are confirmed, it would seem that human use of the swamp shifted from a focus closer to the Rio Suchiate during Late Formative and Early Classic times, to a focus around the Rio Cahuacan during Late Classic and Early Postclassic times. Whether the same range of functional variation is evident at the later sites and the reasons for a shift over time in where people carried out their swamp-focused activities are topics for future investigation.

References

Coe, Michael D. and Kent V. Flannery (1967) Early Cultures and Human Ecology in South Coastal Guatemala. Smithsonian Contributions to Anthropology 3. Washington, D.C.

Lesure, Richard G. (2009), editor and principal author. Subsistence and Settlement in Early Formative Soconusco: El Varal and the Problem of Inter-Site Assemblage Variation. Cotsen Institute Press, Cotsen Institute of Archaeology at UCLA, Monograph 65. 

Nance, C. Roger (1992) Guzmán Mound: A Late Preclassic salt works on the south coast of Guatemala. Ancient Mesoamerica 3:27-46.

Rosenswig, Robert M. (2008) Prehispanic settlement in the Cuauhtémoc region of the Soconusco, Chiapas, Mexico. Journal of Field Archaeology 33:389-411.

 

Humans in the Mangrove-Estuary zone of Eastern Soconusco

The intertidal environment of eastern Soconusco came into existence around 7000 years ago, as sea level stabilized along the Pacific coast of southern Mesoamerica, and an extensive system of mangrove forests and lagoons began to develop in sheltered settings behind barrier beaches. This low-energy wetland environment has acted as a trap for sediments washed down rivers and streams throughout the Middle and Late Holocene. As sediments accumulate in lagoons, open water gradually gives way to mangrove forest. Breaches in the barrier beaches and shifting river courses also contribute to geomorphological dynamics of the region. In recent times the mangrove zone has started to expand inland due to diversion of water from the Rio Suchiate for irrigation of bananas: irrigation water flowing out of the banana fields collects at the interior edge of the mangrove swamp, creating swampy conditions in what was formerly cattle pasture. Freshwater and mangrove swamps then gradually expand inland.

The mangrove-estuary zone is rich in fish, shellfish, crustaceans, reptiles, birds, and mammals. As documented by Barbara Voorhies’ investigations in the Acapetahua Estuary over the past 40 years, these rich biotic resources attracted people to the swamp as early as 7500 years ago. The Archaic period inhabitants were focused mainly on subsistence resources, the procurement and processing of marsh clams being one main activity. Technological innovations during the Early Formative period permitted exploitation of a broader range of estuarine subsistence resources; the first sedentary villages arguably appear at the inland edge of the swamp zone during this period. Following the Early Formative, a growing commitment to agricultural subsistence led to abandonment of the swamp. Human occupation of the swamp picked up again during the Late Formative, when mounds that apparently were the sites of pyro-industrial activities began to accumulate. Such industrial uses continued into historic times, when salt extraction by the sal cocida method is documented.

Currently, people live around the swamp, both on the beach and in communities just inland from the swamp. While they venture into the swamp to fish, collect oysters, hunt iguanas and alligators, and clear routes to archaeological sites, they do not live within the swamp. Workers on our project who have camped overnight in the swamp report that they easily obtain an abundance of gar pike and mojarra (fish) to eat. In addition, they report eerie noises, such as a snarling feline that may be a jaguar. Jaguars, unlike most felines, are good swimmers, and growing human population on the coastal plain may have pushed it into the most isolated local zone, namely the swamp.

Because of the isolation and relative impenetrability of the mangrove forest, archaeological resources within the swamp are remarkably well preserved. Whereas many archaeological sites on the coastal plain have been leveled and trenched for a succession of agricultural uses, the most recent of which is bananas, sites within the mangroves have never been affected by mechanized equipment, and are only infrequently even visited by people. People who do visit stay for an hour or so to hunt iguanas or other animals that sometimes live on the archaeological mounds. Even more rarely, fishermen and hunters may stay on the mounds for a couple of nights. Human damage to the archaeological deposits is mostly limited to shallow excavations into iguana burrows. Otherwise, burrowing animals and tree roots, especially from the fast-growing palms of the region, have the biggest impacts on deposit integrity.

Proyecto Arqueológico Costa del Soconusco

I intend this blog to be mostly about the science – testing and refining our understanding of what processes created the archaeological record, especially in the estuary zone of far southern Chiapas. Before getting to the science, however, there’s a lot of project management stuff that has to get done, and I think a realistic account of the science has to include some record of the logistics, personnel, field conditions, and so on. Therefore, this and some subsequent entries will describe a bit of what we have faced in our work on what I am currently calling the “Proyecto Arqueológico Costa del Soconusco” (PACS).

I arrived at the Tapachula airport on Wednesday, December 7, 2011, and was met by Don Jorge Hernandez, my foreman in Chiapas. Don Jorge had brought Alejandro, the guy who had agreed to rent me his truck. We headed down the highway toward Cuauhtemoc, which was to be my home for the next several months.

I had arranged previously to rent Don Jorge's daughter's house. It was clean, but devoid of furnishings, so my first couple of days were devoted to trips into Tapachula, to buy things like chairs, shelves, beds, and other necessary items. I bought a lot of stuff at the WalMart, a practice that Don Jorge viewed dimly because of the comparatively high prices. For me, however, the time saving and convenience of finding everything in one place outweighed the added cost.

On Friday, December 9 I went out to the field for the first time. Don Jorge had had a crew working on clearing mounds on the ex-Rancho Soledad since mid-November, so access issues for this area were pretty well worked out and something like 10 mounds were cleared and ready for survey with the magnetometer. As of early December, the water level in this area was knee-high, so getting to the mounds required wading through deep water and mud and/or a canoe ride. The mounds themselves are above water, their summits being from one to maybe 10 meters elevation above water. The clearing operation had left large palms and other trees, which create good shade and overall pleasant working conditions.

Javier and Emanuel

On Friday, December 9, two students from Guatemala, Javier Estrada and Emanuel Von Serich, arrived at the Tapachula bus station. They had a week and a half or so before the Xmas holiday began and had accepted my invitation to come learn a little bit about the archaeology of the coastal swamps. I knew them from January, 2011, when they helped me on a magnetometer and GPR survey at Kaminaljuyu. Their experience was a perfect fit for the first couple of weeks on this project, when I would need people who could work on their own as I continued to wrestle with logistical issues. I was not disappointed, as they took over the magnetometer work and completed all of the cleared Rancho Soledad mounds before returning to Guatemala City on December 20.

Barbara Voorhies also came for a visit on Monday, December 12 and stayed for a couple of nights. Our project area is 50 Km or so southeast of the Acapetahua Estuary, where Barbara has been working since the early 1970s. Her main focus has been on the Archaic Period shell middens, which apparently are confined to the Acapetahua region and have not been found farther east, either in my study area or further east, in Guatemala. Barbara helped Javier and Emanuel with the mag survey, and demonstrated her affinity for early stuff by surface collecting a tecomate on RS-3, a site I had previously assumed to be exclusively Classic (tecomates -- neckless jars -- are Formative usually Early Formatice).  After her stay with us, Barbara headed to the Acapetahua area for some social activities with her friends there.

On December 13, while Javier and Emanuel were doing mag survey at RS-2, Don Jorge and I walked to the site of Bermudez (Ber-1) from RS-1. Although it is only 1.2 km straight line distance, the trail wound around a lot, making the actual distance much longer. Additionally, the water/mud was almost waist deep in places, making for extremely slow going

Tim, Paul, Evan, and Scott

My US archaeological crew chiefs started to arrive on Thursday, December 16, the first being Tim Garfin, a MA student from CSUN. Tim had a couple days to work with Javier and Emanuel on the mag, so some of the skills were passed on. On 17 December Tim and I used the new bridge/trail to Bermudez And took some footage for later viewing by my class. We also explored south of Ber-1 with Ramon Grajales, who led us to a small archaeological mound that we had not picked out on the LiDAR. It does appear on theLiDAR, however, so the lesson is that we were too conservative in picking out mounds. It is designated Ber-1a. Noteworthy too is the fact that we have found no false positives so far, so we have abundant proof of the usefulness of LiDAR to identify neArly 100% of archaeological remains in the swamp.

Evan Zufah (CSULB senior) and Paul Burger (CSULB MA student) arrived on December 20, giving me two days to get them oriented before leaving for a Xmas holiday with my family on San Cristobal de las Casas. I decided to minimize logistical headaches by putting them all on excavations during my absence. Tom started a test excavation at RS-23, while Paul and Evan started one at RS-3. Both excavations were placed over magnetic anomalies, which we hypothesized would represent firing features. The excavations continued, with some well justified expansions during Xmas week. Scott Bigney (recent CSUDH graduate) arrived on 28 December, and began helping with Tim's excavation.

Although excavation results are beyond my current purpose, it is worthwhile to note that both excavations produced abundant, clear evidence of the firing features that we hypothesized should exist at the sites. Another striking result is the very high sherd density encountered. This is especially striking because surface remains were almost absent; thus, surface collection would be a poor strategy for recovering samples from these sites.

Vehicles

The 1990 Ford Ranger that I rented from Alejandro worked, at least at first, but it provided insufficient transportation for 10 workers plus four archaeologists. Fortunately however, used trucks are fairly easy to find along the Guatemalan border, A little shopping turned up a 1993 Toyota that a mechanic assured me was in good shape, despite the 344k miles showing on the odometer. Interestingly, the truck had been sold to a wholesaler by Cerritos Nissan in 2007, and had about 13,000 miles added over the past few years in Mexico. It did require some new tires, brakes, and a few other minor things. The brakes, in particular, proved to be a continuing problem: despite the best efforts of the mechanic over the course of several days, the car still pulls slightly to the right, and the brake fluid drops over the course of several days.

The Ford Ranger has also gone through some rough times. The oil pressure gauge had been registering mostly 0 oil pressure from the beginning, and Alejandro had assured me it was just the gauge, and as long as you changed the oil every month it would run fine. At just around a month, the motor started making a horrible rattle – as if it had no oil in key areas. An oil change did stop the noise, but only for five days this time. The mechanic contradicted Alejandro’s assessment, and diagnosed the problem as a bad oil pump and delivery system. He pulled the motor, and in fact the pump and circulation system were completely plugged with melted plastic and metal – the car had been running with no oil circulation for weeks!  Miraculously, a new oil pump and a set of crankshaft bearings returned the motor to functional status.

Other miscellaneous problems with the vehicles have included flats, a starter motor rebuild for the Ford, and dead batteries. Additionally, in order to carry canoes and the 6-meter coring tubes, I had a rack (called a redila in Spanish) made for the Toyota. Beyond the considerable direct expense to the project of vehicle acquisition, modification, and maintenance is a considerable time cost; I calculate that I spent more than half of my time during the first four weeks of the project running back and forth to mechanics shops, auto parts stores, alignment shops, and so on.

Other vehicles important to the project include three canoes, one purchased by the project and two smaller ones rented. These are short, shallow-draft boats that can negotiate the sharp bends and submerged mangrove logs that sometimes block access to the sites. Finally, a cart pulled by a 30-year old horse named Gorrión serves for getting the canoe into some tight, muddy locations where we couldn’t take the trucks.

Getting around in the swamp

Eleven workers are currently employed on PACS. By far the biggest job they have to do involves clearing paths and canals through the swamp and then clearing the mounds of vegetation, so that we can run geophysical surveys, surface collections, and, test excavations. Machetes are by far the most useful tools for these tasks, but very large downed trees that sometimes block the canals require something bigger, namely a 4.5-horsepower chainsaw that we bought in Tapachula.

The week of January 15 the workers started staying out on one of the mounds, so that they wouldn’t lose time traveling to and from work. Fishing in the evenings yields an abundance of gar pike and mojarra. This week they plan to hunt an alligator. Food is plentiful, but after dark the swamp apparently becomes a bit creepy. Some of the workers claim to have heard a “man of the swamp” who is irritated at their presence. More concretely, they have heard a snarling feline at night, which could be a panther; although panthers are native to coastal southern Mesoamerica, a growing human population has pushed them to marginal areas, such as the swamp. Two of our archaeologists, Tim Garfin and Paul Burger are also planning to spend three nights camped out in the swamp this week.

Bringing fieldwork into the classroom

My project in Chiapas, Mexico was originally scheduled with a 1.5-month season December and January and a two-month field season in May - July. During a logistical/planning trip in July, 2011, however, I became convinced that fieldwork in the mangrove swamp during the summer rainy season would be a fool's errand. High water, rain, and mosquitos would conspire to create a miserable, possibly dangerous fieldwork environment. Working only a month or so during January, however, would severely limit what we could get done. But how to extend the period of fieldwork during the dry season when I'm committed to teaching at CSULB?

I am fortunate this year in that, with release time, I only have one actual class, Mesoamerican archaeology, and it occurred to me that I could bring the Mesoamerica fieldwork experience into my classroom via blogs, YouTube, and other sorts of on-line venues that seem to be where a lot of college-age people spend much of their time anyway. Partly for the benefit of my class, in which following this blog will be mandatory, I post below my draft plan for the first six weeks of the spring semester.

NOTE: Please feel free to comment on this plan, especially if you might have ideas about how to improve it.

First, since I will have at least three field crew chiefs working on the project (see attached list of personnel), I will be able to fly back to Long Beach for the first week of classes in order to get the class started. Here are the topics and assignments for the first week:

Date	Topic	Reading/assignments
January 24	Introduction to Mesoamerican archaeology and prehistory Format of the class	Text (Evans, Ancient Mexico and Central America) pp. 1 – 70 Google Earth assignment: Mesoamerican cultural and physiographic regions
January 26	Overview of the prehistory of southern Chiapas (my fieldwork location)

On January 27 I will return to Chiapas, where fieldwork will have continued in my absence. For the next two weeks, students in the class will be virtual participants in the fieldwork via materials posted on BeachBoard and other web venues. Here are the topics and assignments for weeks two and three:

Date	Topic	Reading/assignments
January 30 – February 4	Overview of southern Chiapas prehistory continued Fieldwork in the lowland tropics of Mesoamerica Overview of the prehistory of southern Chiapas (the fieldwork location)	Blog posts by Neff and field crew describing daily life, the purposes of the project, some of the difficulties and high points of fieldwork Videos, each of which documents a day of fieldwork on the project Essay assignment 1: a typical field day in Soconusco (4 pages, due February 6)
February 6 - 11	Human use of the lower coastal plain and estuaries in Soconusco	Neff blog entries documenting human activities in the mangroves ·     Archaic ·     Early Formative ·     Classic period Salt production Ceramic production Videos: Present-day uses of the estuaries: fishing, shrimping and iguana hunting Essay assignment 2: Changing patterns of human exploitation of the mangrove forests (4 pages, due February 14)

I will return again to Long Beach for the period February 13 through 22, and will give three lectures focusing on the major Formative and Classic period archaeological manifestations of the Pacific coast of southeastern Mesoamerica.

Date	Topic	Reading/assignments
February 14	The Olmec and the “mother culture vs sister culture” debate	Text , pp. 127 – 205 and 261 – 292. Love, Michael (2007) Recent research in the southern highlands and Pacific coast of Mesoamerica. Journal of Archaeological Research. 15: 275-328.
February 16	Artistic descendants of the Olmec: Izapa  and Early Maya
February 21	Teotihuacan and the Classic period on the Pacific coast

I will return to Chiapas on February 22 for the final 2.5 weeks of fieldwork, which will last through March 10. During this period, students will again participate in “virtual fieldwork” via video footage and blogs posted to the web. Topics for weeks 6 and 7 are:

Date	Topic	Reading/assignments
February 22 – March 2	Field archaeology of salt- and ceramic production	Blog posts and videos by Neff and field crew on ·     use of GIS in archaeology ·     magnetometry ·     ground-penetrating radar ·     soil probes ·     excavations
March 5 - 10	Processing and analysis of material remains in the field laboratory	Blog posts and videos by Neff and field crew on basic laboratory processing and analytical work that can be done in the field lab ·     Washing and labeling artifacts ·     Microscopy ·     XRF ·     FTIR Essay assignment 3: Work flow on an archaeological field project in Mesoamerica (4 pages, due March 13).

On Tuesday, March 13, after my return from the field, my lecture will summarize the season’s fieldwork and the material presented on line. On Thursday, March 15, I will give a midterm that will cover both the archaeological field and laboratory techniques and the substantive information about southeastern Mesoamerican prehistory. The following week I will return to standard lecture format, and will begin coverage of key topics in Mesoamerican archaeology and prehistory, such as Paleoindians in the region, domestication of maize, rise and collapse of the Classic Maya, etc.

Proposal for acquisition of a FTIR for IIRMES

In case you missed my review of Stephen Weiner's "Microarchaeology: beyond the visible archaeological record" in Geoarchaeology, one mild criticism I voiced was that he devoted a whole chapter (the concluding chapter) to a single technique, FTIR, which is only one of a bunch of techniques that can be useful in characterizing the micro-record. In planning my own research in Pacific coastal Soconusco, however, and partly as a result of some correspondence with Weiner, I later came to appreciate the importance of FTIR for characterizing components of archaeological sediments. The following miniproposal provides part of the rationale for FTIR in archaeology from my perspective.

We did secure funds and a Bruker Alphas portable FTIR was delivered in early August.

Mini-proposal: Rationale for Acquiring a Portable FTIR Spectrometer for IIRMES Archaeometry Research

Hector Neff

Applications of FTIR (Fourier-Transform Infra-Red) spectroscopy in archaeology range from dating (determination of obsidian-hydration rates) to provenance determination (mineralogical characterization of ceramics and lithics and comparison to source raw materials). Although acquisition of a FTIR instrument for the IIRMES archaeometry program could be justified on the basis of potential contributions in any of these areas, the most immediate and compelling need is for a portable instrument that can be used in the field during investigation of prehistoric industrial sites in Pacific coastal southern Chiapas, Mexico. A NSF proposal for this research, which preliminary indications suggest will be awarded, is appended to this mini-proposal. The project budget does not include funds for a FTIR instrument.

Prehistoric industrial activities on Mesoamerica’s coasts

The tropical coasts of Mesoamerica are lined with mangrove forests and estuaries that, while rich in many food resources, are of little use for agricultural production. As a result, once Mesoamerican people became fully committed to agricultural subsistence, probably during the Middle Formative period (~800 -- 400 BCE), human habitation shifted away from the coasts. The coastal margins continued to be utilized for hunting, fishing, and shellfish collecting, but increasingly over time as well for industrial production. Salt extraction is one well-documented activity (e.g., Andrews 1983; McKillop 2007), and several lines of evidence are now indicating that large-scale ceramic production was another such activity. Moreover, excavation data from the Caribbean coast of Belize (Murata 2011) and survey data from southern Chiapas, Mexico indicate that the two activities were often carried out side-by-side, perhaps by the same workers. The intimate connection between the two industries appears to have stimulated technological innovation, perhaps including the invention of an alkaline glaze by Plumbate potters of southern Chiapas (Neff 2010).

Identification of large-scale ceramic production facilities within the coastal wetlands may partially answer a question that has long puzzled Mesoamericanists, namely, why, given the super-abundance of archaeological pottery in post-Archaic Mesoamerican deposits, do surveys and excavations almost never encounter convincing evidence of ceramic production? At least for settlements proximate to coastal wetlands, the answer may be that ceramics were not produced near habitations but instead at special-purpose locations dedicated to industrial production that have rarely been the focus of archaeological investigation (Murata 2011).

The project described in the accompanying NSF proposal seeks to develop a historical record of wetland industrial activity and inland population trends over the past 2000 years in Pacific coastal Chiapas, Mexico. As discussed in the proposal, available evidence suggests several possible "collapses," one at the end of the Formative period (AD 1 - 200), one at the end of the Terminal Classic period (AD 1000 - 1200), and one at the beginning of the Colonial period (AD 1521). There was also, apparently, a dramatic population explosion associated with the Late Classic Plumbate ceramic industry, which eventually exported fancy pots to the farthest corners of Mesoamerica.

In large part, the southern Chiapas project is about building a better chronology of how humans adapted to and exploited the coastal zone over the past 2000 years. The archaeological chronology for Soconusco, like for many regions, is inherently discontinuous, so it is possible that "collapses," "abandonments," and "population explosions" are wholly or partly artifacts of the coarseness with which archaeologists measure time. Much of the planned fieldwork, therefore, focuses on collection of samples for chronometric analysis (radiocarbon and luminescence dating) and measurement of relative population levels (land clearance, intensity of littoral-zone industrial activity).

Additionally, if demographic change was rapid in some cases, can rapid growth or contraction be linked to environmental deterioration or amelioration, population movements, local political events, or organizational or technological innovation, i.e., to circumstances that are potentially observable in the archaeological and paleoenvironmental records? Sensible answers to these latter questions require that field and laboratory research efforts also be designed to infer what specific past human activities were increasing or decreasing in frequency. This is where the need for a portable FTIR instrument arises.

Plan for fieldwork and in-field analysis

As mentioned above, there is mounting evidence that salt production and ceramic production were carried out intensively within the estuarine zone of Mesoamerica’s coasts from the end of the Formative period on. In Soconusco, the focus of this project, more than 30 mounds that appear to fit this “pyro-industrial” characterization have been located within about 40 sq km of mangrove forest. All have abundant clay cylinders that are thought to have been used as supports for brine boiling in the sal cocida method of salt production (Andrew 1983; McKillop 2002; Murata 2011). Evidence of ceramic production is as-yet more circumstantial, but Plumbate, a technologically unique and widely traded ceramic type of the Late Classic and Early Postclassic periods has been unambiguously matched to raw clays from near the mouth of the Rio Cahuacan, which drains through the estuarine zone (Neff 2002, 2003), and Plumbate sherds constitute the dominant ceramic type at a number of the sites within this zone. Finally, as Figure 1 shows, the sediments making up the mounds is bright red in color, an unmistakable, qualitative, sign of exposure to high heat. These observations together with the relative dearth of domestic debris make a strong prima facie case that these mounds accumulated as the result of intensive pyro-industrial activity.

Fieldwork on this project is intended both to collect samples from pyrotechnological and other features for chronological analysis and to document functional variability between mounds and between features. An exhaustive inventory of mounds within the region will be compiled from Airborne LiDAR data that were collected on April 30 and May 1, 2011. All mounds will be visited, and those with post-Formative remains will be investigated further with near-surface geophysical survey and subsurface testing.

A magnetometer will be used in gradiometer mode to identify areas on the mounds that might have been exposed to especially intense heat. Ground penetrating radar will be used to gain some preliminary understanding of the vertical extent of these features. Finally, subsurface samples will be collected by a combination of augering and split-core sampling on an evenly spaced grid placed over magnetic anomalies.

Samples obtained by split-core probes will provide charcoal for radiocarbon dating and sediment for luminescence dosimetry. Because ceramics are such a dominant component of these deposits, it is also anticipated that ceramic artifacts will be brought up by the subsurface sampling, and these will be retained for luminescence dating. Although large-scale excavations are not planned, small, 1 x 1 meter units may be excavated in order to obtained charcoal and other materials in secure association with pyro-industrial features.

Another major purpose of the split-core sampling is to obtain materials for archaeological-sediment characterization. A portable x-ray fluorescence instrument will be used for horizontal mapping of elemental concentrations across features detected with the magnetometer and for detecting down-core elemental variation. Fifteen to 20 elements will be measured, but the instrument will be optimized especially for detection of phosphorus, an indicator of organic accumulation (e.g., in middens) and calcium and potassium (e.g., in wood ash). Very high aluminum may indicate deposits of stored potting clay.

The FTIR for which funds are currently sought would be used primarily as a second kind of materials characterization for sediments recovered by the split-core sampling of features detected by geophysical survey. Portable-FTIR complements portable-XRF by providing information about the molecular structure of the deposits, both crystalline and non-crystalline. Since exposure to heat induces little or no change in elemental concentrations measured by XRF but may dramatically alter the chemical bonding of sedimentary materials, FTIR, a molecular-characterization technique, is ideally suited for investigation of pyro-industrial features such as the Soconusco estuary sites.

FTIR is widely used for investigating the firing history of archaeological sediments (Weiner 2010). Perhaps the best-known applications involve complementary use of micromorphology and FTIR to understand the depositional history of caves that were occupied by Paleolithic hominins (e.g., Berna and Goldberg 2008, Goldberg and Berna 2010). More closely analogous to the present study is a study of Late Bronze and Iron Age pyrotechnology at Tel Dor, Israel (Berna et al. 2007). A copy of the report on the Tel Dor study is appended to this mini-proposal.

The basic design of the Tel Dor study (Berna et al. 2007) can be borrowed and implemented in other studies of archaeological sediments associated with pyro-industrial activity. The Tel Dor investigators first characterized transformations of natural sediments from the region as they were subjected to different temperatures in controlled (furnace) and open firings. Changes in the FTIR spectra with increasing temperature could be attributed to breakdown of clay minerals and formation of high-temperature silicate minerals. Applied to sediments from the excavations fire-affected sediments could be easily identified (despite the absence of reddening), firing temperature could be estimated for the fire-affected sediments, and, in combination with micromorphological observations, secondary deposits (e.g., kiln clean out remains) could be distinguished from sediments fired in-situ and left undisturbed. FTIR together with XRF identified sediments associated with bronze smelting in some levels.

In the coastal Soconusco project, baseline data on firing changes in sediments will be generated on samples obtained from the mudflats of the estuary zone, which are the most likely sources of sediments accumulated on the mounds. Samples will be fired to a variety of temperatures in a muffle furnace installed in the project field laboratory, and FTIR and XRF characterization will then be undertaken on the fired and unfired samples. Model FTIR spectra will also be obtained from other materials that might be encountered in subsurface sampling, such as wood ash from burning of mangroves and other available fuels, mixtures of fired sediments and wood ash, sediments that are mixed first with wood ash and then fired, mixtures of fired sediments and midden materials, etc. The library of FTIR spectra of known derivation will serve as a starting point for interpretation of spectra obtained from the archaeological sediments.

Beyond materials identification, the FTIR spectra can be quantified in various ways and the measurements can then be mapped in a mode analogous to mapping of elemental concentrations. This would provide a means to map variables that correlate with firing duration and temperature, proportion of wood ash in the sediments, etc., across the magnetic anomalies selected for subsurface sampling. Positions of IR peaks, ratios of peak heights, and other quantified descriptions of features in the spectra can be chosen so as to optimize their value as indicators of pyro-technological variation. Spectra representing maximally high or low points on the generated surface can then be subjected to more detailed analysis and interpretation. Similarly, down-core variation in quantified spectral features can be used to examine intensity of pyro-industrial activity over time and whether the pyro-industrial activities were episodic or continuous.

A key feature of the overall research design for this project is that collected materials will be analyzed either immediately in the field or within a short time in the field lab. This will allow adjustments to be made as appropriate. For instance, materials that do not match any of the model sediments can be evaluated more carefully both elementally and by comparison of FTIR spectra to available libraries. Preparation of additional model pyro-industrial materials may provide secure identification.

Some technical considerations

A research program stressing rapid in-field measurements requires instruments that are portable and, ideally, battery powered. Our Bruker Tracer portable XRF spectrometer is an example of such an instrument. Field FTIR analysis entails similar demands for durability, portability, battery power, and rapid sample throughput but without sacrificing repeatability of spectral measurements. Both Bruker and Thermo-Nicolet market instruments as “portable” FTIR instruments, and both would be evaluated.

An important consideration in implementing FTIR in a field or field-laboratory situation is whether analyses will be conducted in transmission or ATR mode. The traditional approach, which permits very good stability and reproducibility, is transmission mode. Stephen Weiner (personal communication April 2011) favors this approach and states that sample preparation, which involves pressing a KBr wafer mixed with a small amount of the sample powder, takes only a few minutes.

Andrews, Anthony P. (1983) Maya Salt Production and Trade. Tucson, University of Arizona Press.

McKillop, Heather (2002) White Gold of the Ancient Maya. Gainesville, University Press of Florida.

Murata, Satoru (2011) Maya Salters, Maya Potters: The Archaeology of Multi-crafting on Non-Residential Mounds at Wits Cah Ak’al, Belize. Unpublished Ph.D. dissertation, Department of Archaeology, Boston University.

Neff, Hector (2002) Sources of raw material used in Plumbate pottery. In Incidents of Archaeology in Central America and Yucatan, edited by M. Love, M. P. Hatch, and H. Escobedo, pp 217-231. University Press of America, Lanham, MD.

-- (2003) Analysis of Plumbate pottery surfaces by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Journal of Archaeological Science 30(1):21-35.

-- (2010) Plumbate technology revisited. Physical and Chemical Methods in Archaeology. Proceedings from the 2nd Latin-American Symposium on Physical and Chemical Methods in Archaeology, Art and Cultural heritage Conservation and Archaeological and Arts Issues in Materials Science, Cancun, August, 2009.

Weiner, S. (2010) Microarchaeology: Beyond the Visible Archaeological Record. Cambridge University Press, Cambridge.