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.

The off-site archaeological record

Archaeologist and non-archaeologists tend to think of archaeology as something that takes place at "sites". Yet, much of what humans did in the past happened away from their homes or places of work. Further, a lot of evidence about past human activities accumulated at locations far from what we would call "sites". A good example is pollen and other micro-fossil evidence for landscape changes in the past. In the photograph below, my colleagues and I are extracting a sediment core, IZT091, from a location on the coast of Guatemala that is several kilometers from any known archaeological site. The basal radiocarbon date from this core indicates that the 5.6 meters of sediment we extracted represent about 2700 years of accumulation. Pollen, phytolith, charcoal, and stable-isotope analysis of this core are currently in progress. Ultimately, these analyses will provide a 2700-year history of changes in forest cover, including human-induced changes, upstream from this location.

LiDAR imagery from Pacific coastal Soconusco

The first image below is a Google Earth image showing part of the area on which fieldwork over the next several years will focus. This area is just west of the Rio Cahuacan, which can be seen at the right side of the first two images. The mouth of the Rio Cahuacan is about 13.7 km west of the mouth of the Rio Suchiate, which is the international border between Mexico and Guatemala. The red polygons are areas indicated as "sites" in the Mexican (INAH) site records. Markers labeled "DB" are also from the INAH records. The other markers are mounds that my colleagues and I have visited over the past several years.

The next image is the same area from Google Earth, but with minimally processed LiDAR images overlain. The labeled white spots on the LiDAR imagery are archaeological mounds, and the others, clearly, are mounds as well, just ones that haven't been checked yet on the ground.

The final image, below, zooms in on the area with the visited archaeological mounds and uses hillshade to highlight the mounds that show up on the LiDAR imagery. The blue dots indicates mounds that we have visited, the large one at the very top being "Conq1" (Conquista-1) from the previous images.

NSF award for work in the estuarine zone of Pacific coastal Soconusco

I recently learned that a NSF proposal submitted last December for work in coastal Soconusco was successful. Following is the public abstract for the award:


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 (forerunners of the Aztec, Maya, and other Native American groups of Mexico and Central America) became fully committed to agricultural subsistence, probably during the Middle Formative period (~800 - 400 BC), 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, and recent research has indicated that large-scale ceramic production was another such activity. To date, there have been very few systematic investigations of these coastal Mesoamerican industrial sites. There is some urgency to initiate such studies because sea-level rise and environmental degradation threaten to submerge or destroy coastal sites over the coming few decades.

The National Science Foundation has provided funds to support a three-year effort to document archaeological remains on one section of the Mesoamerican coast, the far-southern Pacific coast of Chiapas, Mexico, a region known as Soconusco. One fundamental issue that this NSF project will address is whether the boom and bust cycles posited for Soconusco are real or whether they may be artifacts of the coarseness of the existing chronological framework. By investing heavily in chronometric analysis (radiocarbon and luminescence dating) this project will dramatically improve chronological resolution. If demographic change still appears to be abrupt and cyclical once a better chronological framework is available, then it becomes sensible to begin evaluating possible causes of collapses, population explosions, and prolonged abandonments. Unlike the cases discussed by Jared Diamond in Collapse, all of the instances of 'collapse' and recovery listed above took place in a single region, so geography is held constant, and other possible causes of demographic change, such as climatic downturns or amelioration, population movements, local political events, and organizational or technological innovation, can be examined without the confounding effect of geographic variability. 

Not only did prehistoric Soconusco people use the mangrove zone for industrial activities, leaving an abundance of archaeological remains, the zone itself acts as a catch basin for plant parts and charcoal brought down rivers and streams or blown in from the coastal plain. This means that changes in vegetation cover in the coastal-plain agricultural zone are recorded in sediments of the mangrove zone. Thus, while mangrove-zone archaeological remains document industrial activities that people engaged in away from their inland agricultural villages, the sedimentary record documents upstream land clearance, which correlates with population levels on the coastal plain. The archaeological and geo-archaeological research recently funded by NSF will sample and analyze these complementary historical records. 

According to current archaeological understanding, the records targeted for investigation on this project were shaped by momentous changes that swept across Soconusco at various times during prehistory and history: 

- The region was a center of pre-Maya sculptural art, but the sculptors abruptly closed up shop around 2000 years ago, and much of the coastal plain seems to have been abandoned. 

- Emissaries or militarists from the highland Mexican empire of Teotihuacan arrived around AD 400, apparently initiating a period of sustained population growth that lasted at least through Terminal Classic period (~AD 1000). 

- During the Terminal Classic, potters of the estuary zone produced Plumbate, the most technologically sophisticated and widely traded pottery every made in Mesoamerica. 

- Population appears to have collapsed again around AD 1100.

- Late Prehistoric population resurgence began around AD 1250. 

- At the time of the Spanish conquest (AD 1521), Soconusco was the most distant province of the Aztec empire and paid tribute to the rulers of Tenochtitlan (Mexico City).

- Population again plummeted soon after the conquest, as introduced European diseases decimated the population, a collapse from which it did not recover until the early 20th century. 

The project will provide research opportunities for MA students at several California State Universities in the Los Angeles area and for Ph.D. students at Washington State University, SUNY-Albany, and UCLA.