Lab Work Update

Hi all!

Apologies for the long delay between posts, but things have been busy in the lab!

As of yesterday, we have finally (FINALLY!) finished washing, drying and carrying out the preliminary catalog of the material recovered during the 2011 field season.

Over the last couple of months, I have washed and cataloged during the week while Angel Mario, Walter and more recently, Jonathan (local community members and farm workers participating in the project) have joined me to lend a hand on weekends.

Washing mainly entailed scrubbing thousands and thousands of ceramic sherds. Not terribly exciting, but a necessary step, that can be interesting as one reveals diagnostic decorative elements hidden under caked on dirt. Washing also helps give a sense of what kinds of materials are found in the different units, and allowed me to actually handle/briefly examine practically all the ceramic artifacts recovered, something almost impossible to do in the field when multiple test units are being dug at once and one is under pressure to maximize actual digging time.

None of the bone recovered was washed, only dry brushed, as it is all in a very poor state of preservation due to the very marked wet/dry season, the coarse/abrading nature of the volcanic deposits and the slightly acidic soil present on the volcano.

None of the lithic artifacts were washed either, in order to improve the recovery of starch and/or phytoliths from the surfaces (and adhering soil) of the various obsidian blades and groundstone manos and metate fragments recovered. These artifacts will be washed in a controlled lab setting at Stanford next year in order to recover as many of these remains as possible.

Very little metal was recovered, most of it nails, although we did find what appears to be a fragment of a lead shot in Test Unit 16 (see image below). Metal artifacts were not washed, but simply dried, separated and re-bagged in clean bags.

Possible lead shot fragment?

The cataloging we carried out is a very basic one. After washing, the material is left to dry for at least 2 days (usually 3-4), after which we separate, count and weigh all the artifacts by material categories (ceramics, lithic, groundstone, carbon, metal, structural [mainly bricks, roof tiles, daub, etc], glass and bone).

Now for some site stats!

Over the course of the 7 week field season, we (a crew of about 4 people) excavated a total of 14 2x1m test units, the majority of which (10) reached to at least a meter in depth, with some going down to 2m.

These test units yielded:

Ceramics: 11,613 sherds, weighing 109.3 kilos

Lithics: 80 mainly obsidian blades, fragments, etc weighing 336.7 grams

Bone: 445 (mostly small pieces) weighing 871.2 grams

Carbon: 748 (mostly small fragments) weighing 213.6 grams

Groundstone: 8 (fragments of manos and metates) weighing over 2.17 kilos

Metals: 31 fragments (mostly nails) weighing 127.2 grams

Structural: 77 fragments of bricks and roof tiles, etc weighing 3.94 kilos (note: this is only a sample of bricks and ALL roof tiles, daub etc encountered. Sector 3 yielded so many brick fragments due to the extensive brick patio located there, that we took only a small sample).

Based on this, it is pretty clear why ceramics will play a large role in the project and in my dissertation research in particular!

I’ll be posting up some more stats broken down by Test Unit and Strata in a new update, as well as giving some info on the next big step in lab work that is already (a month or so) in progress (thanks to Heather Law Pezzarossi): the ceramic analysis! At this point the ceramics from Test Unit 17 are almost completely analyzed and they have served as the starting point for the ceramic paste, attribute and type analysis for the project. Details on this next time.

Thanks for reading and a huge thanks to all (Heather, Isolda, Natalia, Corey, Cristina) that have pitched in with the washing and other phases of lab work over the last couple of months.

More soon!



Field Season: Complete!

Hi all!

Apologies for the lag in posts, but we have been busy wrapping up excavations last week and as expected has been a dash to the finish. The last days at the site were spent intensely exploring the new site in order to get a handle on what exactly is out there, while wrapping up the last couple of test units in the previous sector.

At the moment, we are diving right into lab work (mainly washing artifacts, preliminary cataloging and data entry/database tweaking). As a result, expect lab-related updates in the next few weeks! However, I’ll be putting up some delayed field updates to get everyone up to speed on what exactly we found in the last few weeks. The rest of this post will be exactly that:

In early December we opened up Test Unit 12, located in Sector 2 of the site over a large GPR anomaly located about 40m NE of Test Unit 16, which yielded evidence of a dense community midden deposit complete with much bone, charcoal and ceramics (including plenty of comales). At about 50cm below surface, we noticed an increase in the number of artifacts coming out, followed by an impressive increase in the size of artifacts (in some cases we found at least 50% of some large vessels). As we continued excavating, it became clear that this dense deposit continued very deep, but only in the Eastern portion of the test unit (reaching to about 1.5m below surface!). The Western part of the test unit had some very different and quite complex stratigraphy, with various compact floor/surface like strata interspersed with sandy/gravelly sterile volcanic strata.

Starting at 1.5-1.7m below surface, we encountered artifacts in a strat below a stereile volcanic layer that appears to be precolonial in date, based on the types of artifacts present, and the lack of any assuredly colonial artifacts (an exciting find that feeds the diachronic approach to colonial effects critical to the project).

By the time we finished Test Unit 12, we had recovered a massive amount of colonial artifacts, some almost complete vessels, a couple of groundstone artifacts and plenty of charcoal, lithics, flot and pollen samples. Plenty of artifacts were present in the Eastern profile wall, indicating that this deposit continues of to the East and South (which informed the placement of Test Unit 14 to the South).

In particular, we found some almost complete pitchers (bulbous bottom with a tall neck, the bottom of one and top of other visible in video below) in this profile wall, a rather interesting find as this vessel form is usually encountered only in the colonial period, yet the ceramic type is very similar to the precolonial/local ceramic types identified at the site.

See video below for some more photogrammetry fun, showing two of the pitchers in place in the profile wall of Test Unit 12 (as well as various other artifacts poking out). These vessels are about 2/3 of the way down in the colonial period deposit that reaches very deep in the Eastern portion of Test Unit 12 (officially this deposit is labeled Feature 12).

Pretty exciting to get such great preservation in this midden! Once we get artifacts from Test Unit 12, Feature 12 washed, expect to see plenty of great images of the various artifacts recovered.

Thanks for reading, and more soon!


Quick Site/New Sector Update

Hi all!

Since the last post, we have been trying to chase out the brick floor, in the hopes of finding material to date it with, and any walls or other structural remains associated with the brick floor.

Well, we may be on the right track! Today we opened Test Unit 20, about 1om East of Test Unit 19 (featured in the last post) in an area where we found brick AND roof tile fragments on the surface. We were hoping to hit an intact wall abutting the brick floor, but we got something close: a collapsed wall overlaying the brick floor feature! (see pic, and video below).

Feature 15 Brick Floor in Test Unit 20 with possible wall fall on top.


We are pretty excited about this, as it indicates we are getting near the remains of the structure abutting the brick floor. In addition, Walter’s father, who worked on the farm a few decades ago and brought this site sector to our attention, mentioned that when they found the remains of this building during farm work, the walls were made of stone underneath brick. The wall collapse appears to be mainly brick on the bottom with stone on the top, indicating the remains of a wall made of, you guessed it, stone on the bottom and brick on the top!

We also FINALLY hit on some cultural material associated with the brick floor, in this case a small concentration of ceramics in the NE corner of TU 20 (directly beneath some of the wall fall rubble). The ceramics -while only a few and quite fragmentary- appear to be early colonial types, indicating that the site is from the early colonial period and thus potentially an earlier site component than what we have been excavating further to the north. This is all very preliminary at this point, but it is quite exciting that we are getting closer! Tomorrow we will open a test unit directly to the North of TU 20 in order to seek out the base of the wall that appears to have collapsed onto the brick floor in TU 20.

Will update as soon as something new turns up! Thanks for reading!



New Site Update!

Hi all!

As promised (albeit slightly delayed…) we have an update on a new find at San Pedro de Aguacatepeque!

Late last week, Walter G. a farm worker at the site who has helped us excavate, mentioned the location of a site (an old church to be exact) located to the Southwest of where we have been working. We had heard similar information back in 2010 about the component of the site we have focused on, and a similar note is mentioned in Eugenia Robinson’s 1990 survey of the site (Robinson 1990), so this seemed as though it might be a retelling with slightly different spatial information. Nevertheless, we decided to go take a peek during lunch, in case we found another site component to sample (mainly for pollen, in the hopes of hitting a part of the site that was used for different activities, i.e gardens, groves, orchards, maize plots, etc).

We looked around the area indicated by Walter, and while we found some colonial surface scatter it was not unlike that found at lower elevations around the site, likely carried down by the intense washes that happen during the rainy season. We did look around a bit more, just in case, and one of the project archaeologists (Kike Fernandez) noticed a rather prominent concentration of whole and broken brick fragments on a nearby rise.


Now, we have recovered brick before over at the main component of the site, and even some roof tiles (tejas) but we have never found such large pieces of structural debris anywhere! We quickly decided to sample this area in the short time available to us (we plan on shutting down excavations around the 20-23 of December) in order to get an idea of what exactly is at this part of the site, and what time period it dates too. At the same time we noticed the remains of what seems to be a pyroclastic flow or lahar leading directly to the location of this new site.

Outcrops of pyroclastic flow/lahar with large boulders present just off-camera to the left at the leading edge of this deposit/flow.

Considering the documentary claims that the site was destroyed by eruptions from the Volcan de Fuego, could we be seeing the remains of a part of the site that was directly impacted???

Starting on Monday of last week, a project volunteer (Louise, a Brazilian student in archaeology and history studying in Spain) worked with Angel Mario G., (one of our local community archaeology interns and local coffee farm worker) to open up some exploratory test pits in this area, in the hopes of finding some sort of remains.

Imagine our surprise (considering the lack of cultural features encountered to date at the main site component) when Louise and Angel Mario called us over on Wednesday afternoon with this brick floor/patio feature exposed!

Brick Floor/Patio present in 2x1m Test Unit 18

While this find was quite exciting, we were a little disheartened at the lack of cultural material found above or in association with this feature (Feature 15, officially). Literally nothing else was found, except for lots and lots of brick fragments and some very non-diagnostic ceramic sherds in the top soil strata. Basically, we had nothing to date this feature with (although we asked the farm owner and administrator and they were able to confirm that no modern buildings were present at this site (since at least the mid 20th century. We have a few leads, mainly Kathleen Deagan’s (1987) work with bricks sizes and their correlation to date ranges in the Spanish Americas. Based on the dimensions provided by Deagan, the bricks may date to the 16th century, a finding that would point to the likelihood that this second site may actually be the 1582 town portion of SPA that was destroyed by an eruption! However, as Deagan rightly points out, dating by brick sizes is a very very wobbly endeavor, as the variation in brick sizes (due to their local, variable manufacture) may be so large within time periods that no clear-cut pattern can be deduced.

We decided to open another test unit, about 3 meters to the North of Test Unit 18, to see if we would find more of the brick floor/patio or possibly the remains of a structure associated with it. We found more of the same, namely a (better preserved) brick floor, with little associated material culture (although we DID get some carbon and floatation samples from off the surface!). See below for one of our first attempts at photogrammetry using Autodesk123D Catch Beta software, showing Feature 15 Brick Floor in Test Unit 19. After mapping this floor, we turned to our remaining option: dig more to figure out what exactly we are looking at!

That about gets us to this week: we have new project members coming on board (Eduardo, a project archaeologist) while Kike and Louise have left to start school for the spring/winter semester. Our goal this week is to try and sink 1 or 2 more test units in the second site location in order to find the extent of this patio, diagnostic material culture in association and/or the remains of the structure that likely abutted this patio. We have already set out Test Unit 20 (about 10m East if Test Unit 19) in an area where both bricks and roof tile fragments are found on the surface, in the hopes of hitting other structural remains. More updates coming this week as we explore this part of the site!

Thanks for reading and more soon!


Week 3 Field Update: Partially complete vessel bottom recovered!

Hi all!

Exciting stuff this last week, we will posting on the various developments over the next few days. First things first though, Test Unit 10, located over a concentration of colonial material culture in Sector 1 as well as near a GPR anomaly (see Figure 1) yielded one of the most exciting finds at the site so far.

Figure 1: Black circle indicates location of Test Unit 10 over a prominent GPR anomaly in Sector 1 of SPA.

In general, we have found the uppermost strata of the site to be disturbed by various episodoes of plowing, planting and other coffee farm-related activities. Everything we have found below these strats appear to be community midden deposits, sometimes overlaying floors/work surfaces (and thus fairly broken up from being stepped on and all) and sometimes simply deposited already broken up in secondary contexts.


Considering we are used to this (to the point where we have built our research design and sampling strategy around these types of seconday midden deposits), imagine our surprise when we came across an in-situ (almost complete) ceramic vessel! Of course it worked out in such a way that half of the vessel was outside of the 2x1m unit. We cut a 80x60cm extension to the north of the unit in order to recover the vessel (while avoiding a coffee plant that happened to be right over the ceramic vessel).

Figure 2: Vessel as we found it: half out of Test Unit 10


Unfortunately the top part of the vessel was broken (likely when the coffee plant was planted 4-5 years ago), and the bottom portion of the vessel was cracked by coffee plant roots. However, the interior of the vessel held a dark, clayey soil that contained 2 obsidian blades (Figure 3, 4).

Figure 3: Vessel bottom with dark, clayey soil inside.

In order to get as much info as possible, we took various samples from this vessel (pollen from inside and underneath the vessel, as well as floting the entire contents of the vessel) and made sure to bag the obsidian separate in order to better isolate potential starch, phytoliths and residues present on the blades.

While the material recovered directly above this vessel indicates that it dates to the colonial period, we are waiting until we can wash/analyze all the material associated with the vessel in

Figure 4: Obsidian blade stuck in clayey fill inside vessel.

order to more securely determine what time period this vessel dates to.  Strangely, this vessel overlay the sterile reddish coarse sand/gravel volcanic strata (see previous blog post), a finding that is odd when compared to nearby Test Unit 4 (excavated in 201o) that contained Late Classic material culture over the sterile coarse sand/gravel strata. Perhaps the West side of the site was only occupied in the colonial period? While other parts of the site were continuously occupied? The more Test Units we excavate, the better idea we get of where the various occupations of the site were located.

Figure 5: Vessel completely excavated, note cracking caused by roots.

Test unit 16 located about 40m to the southeast of Test Unit 10 also shows only a colonial occupation, indicating that the multi-component portion of the site is actually located further to the north, directly abutting the mounds at the site. We’ll see what turns up.

Thanks for reading and keep an eye out for another update in the next day or so on a newly discovered site component 200 or so meters off site! Thanks to a timely tip by a local informant, we have located a concentration of colonial-era bricks, ceramics and what look to be foundation stones. Even more interesting, this site component appears to be right in the path of a possible lahar/pyroclastic flow from the volcano…could it possibly be the early 1582 site component that was destroyed by the Volcan de Feugo (as mentioned by Alonso Ponce in 1584)? More soon!



Searching for Sterile Soil…

Hi all!

Things are moving along, we have opened up a couple more units at the northern and southern extremes of the site (about 150m away from one other) which makes communicating, sharing equipment, getting  new paper work, etc a bit of a hassle. Texting back and forth has helped, as we are now out of yelling distance (thanks to a combo of distance, thickly planted coffee plants and some intense wind).

Anyway, one of the big issues to address this field season is to figure out exactly where some of the deeper cultural deposits are located, and to figure out patterns in the site stratigraphy that would help us figure out what is (capital S!) Sterile soil, meaning the strata under which no cultural material dares dwell. (or something like that).

While it might seem a little strange to be so concerned with finding a strata with NO cultural material in it, finding sterile soil is additionally important in this case because we know that the site contains precolonial remains below the colonial period deposits found closer to the surface (something we determined during preliminary excavations in 2010). Our deepest cultural deposit thus far is at about 150cm, and appears to date to the Late Classic period (AD 800-1000). In one test unit excavated 2010, we found Late Classic material at 150cm, directly under a potential Postclassic (AD 1000-1500) deposit, which was itself below two distinct colonial period occupation strata. However, many of the test units excavated thus far have yielded ONLY colonial period deposits, sometimes down to 130cm. Are we missing something? Do we need to dig deeper to make sure we don’t miss some deeply buried precolonial deposits?

We seem to have hit on something this last week that might help us figure all this out.

We noticed that all the test units opened so far have hit a strata of reddish coarse volcanic tephras (basically volcanic sand and gravel) at between 70-130cm below surface. There is never any cultural material in this strat or below it, although we do find some clayey/silty, dark strats sandwiched between the volcanic gravel strats that seem like they might be occupation layers (appear to actually just be episodes of moderate soil development between volcanic episodes prior to the occupation of the site; see image below of test unit profile for example).

Luckily, we have managed to get some carbon samples from the top, middle and bottom of this strata in a couple of test units this year. If we can carbon date this strat (which is found everywhere at the site, as it appears to have been deposited by a widespread volcanic event) and tie it to an eruption of the Volcan de Fuego, it would go a long ways towards defining the site chronology with absolute dates (complimenting, as well as potentially challenging some of our ceramic-chronology-derived strata dates).

Having defined our sterile soil (for the moment) is helping us get a handle on the natural and cultural deposits we have encountered at SPA. However, just in case, after we reach this sterile volcanic gravel strat we auger down an additional 150cm in two locations in each unit to make sure we do not miss a buried cultural layer, meaning we get down to between 250-275cm in each test unit. So far, no luck finding anything in the augers, so it seems we may have just found our sterile!

More info on all this as soon!

Week 2 Field Update: Floor Feature Found!

Hi all!

We are finally back on again, after having some issues with the site (updates to site content, more on the way!) and being knocked offline the last week or so due to internet connection trouble at the field house.

Quick Field Update:

Excavations are in progress (and have been since the second week of November). As part of this season’s work, we have focused on the colonial site core at San Pedro de Aguacatepeque. Twelve 2×1 meter test units have been placed to sample different areas of the known extent of the site. The exact location of test units within the different areas of the site was determined by work completed in 2010, namely geophysical prospecting, collection of artifacts on the surface of the site and preliminary test excavations.

So far we have wrapped up three test units in the northern portion of the site that we clustered around a ground penetrating anomaly detected in July of this year. One of these test units (Test Unit 15) yielded one of the first intact subsurface features found at the site(thank you GPR and Stanford Community Engagement Grant)! At about 50-60cm below surface, we encountered a very hard compact floor surface, with colonial period artifacts, mainly lead glazed redware and Guatemalan majolica sherds above it and directly on it.

Profile of Feature 6, compact floor surface.

This floor was only visible in about half of the unit, but continues out to the east and south beyond the limits of excavation. The soil underneath the artifacts lying on the surface of the floor was sampled for pollen, and parts of the floor and soil above it was taken as a flot sample. However, we did not find much below the level of the floor, a rather strange finding considering that all test units excavated in 2010 had multiple strata from temporally distinct occupations of the site. Seems that we may have found a portion of the site that was occupied ONLY in the colonial period…pretty exciting! Photo below shows some of the artifacts that are showing up over the Feature 6 floor that are part of a colonial period community midden at the site.

Colonial Artifact Concentration over Feature 6 Floor

We have left the floor intact for the time being (minus the back end that was sampled while we profiled the feature) and will come back to it at the end of the season after we have finished the other 7-9 test units planned for this season. More soon!

July 2011 GPR Survey Recap

Summer 2011 Guatemala GPR Work

Field research at the site of San Pedro de Aguacatepeque (SPA) has been ongoing since the summer of 2010. As part of this research, considerable effort and expense has been expended on locating the remains of the colonial period Kaqchikel Maya (apprx. AD 1521-1820) occupation of the site. While the colonial period settlement remains the focus of this project, the 2010 excavations have forced us to expand the temporal scope of the project to the earliest observed occupation at the site, which dates to the Late Classic period (apprx. 800-1000AD)  and stretches through the Postclassic (1000-1500AD) and into the Late Colonial Period. The multiple stratified occupations at the site have pushed us to embrace a diachronic framework of analysis (drawing on Lightfoot 1995) for investigating the changes in daily life and material traditions at SPA catalyzed by the challenges and opportunities of the colonial encounter

Common archaeological practice would call for a widespread systematic subsurface survey of the site, wherein test units of 50x50cm would be dug at regular intervals over the area of interest, with the intent of locating buried remains and defining the limits of archaeological deposits at the site. Complicating things at SPA is the most recent use of the land where the site is located, namely as a plantation for high-altitude, primo Guatemalan coffee. An important part of the field work at SPA has centered on a collaborative relationship with multiple stakeholders at the site, namely the landowner, plantation workers that are drawn from local communities, the Instituto de Antropologia e Historia de Guatemala which oversees the management of archaeological resources in Guatemala and Stanford University/my dissertation committee. In 2009 we began consultations with the landowner in the hopes of starting up a project in a region notorious for declining archaeological research on private lands (for a variety of reasons, most prominent of which are safety/security concerns, worries over access to sites and misinformation regarding government land grabs where archaeological resources are encountered). In 2010 we were able to secure permission to undertake preliminary research at the site, on the condition that the coffee plants were not damaged or destroyed in the process. As a result, research carried out over the summer of 2010 thanks to a National Geographic Waitt Grant, centered on geophysical prospecting as a rapid, non-invasive set of techniques for locating subsurface deposits at the site. Electromagnetic Induction, Magnetometry and Ground Penetrating Radar were all used (see Field Work section of the site for more details) to various degrees of success. The latter technique, GPR, yielded the most promising results for the type of silty sand substrate found at SPA.

GPR Basics and 2010 GPR Survey

Ground penetrating radar (GPR) is an active geophysical prospection method that operates by introducing an electromagnetic pulse into the ground, and analyzing the resulting reflections of the wave against buried strata and features.  GPR can provide detailed profiles of the stratigraphy of an area, as well as identify the location and relative depth of archaeological objects and features.  However, while acquiring GPR data is itself a much slower process than acquiring magnetometry data, the processing and interpretation of the data is itself even more time consuming.  As a result, GPR surveys are usually undertaken after initial small scale tests have shown the efficacy of the method in the conditions of the site and region, in order to avoid investing substantial time into the processing of data that may indeed show nothing (if the conditions on the ground are not conducive to the GPR method).  For this reason, the other prospection methods were carried out at the site in 2010 at a greater scale, and the GPR work was undertaken mainly as a small scale preliminary test to evaluate the potential of the method at SPA.

The ground penetrating radar work at the site in 2010 was limited to two 50 meter long transects through parts of the site that with large concentrations of colonial material culture on the surface.  Nigel Crook, of the Stanford Shared Measurement Facility performed the GPR prospection using a Sensors & Software Pulse-Ekko Pro system with 200Mhz antenna.  More GPR transects were planned for the 2010 field season, however

Figure 1: 2010 GPR Survey lines at SPA

issues related to the failure of the GPR batteries as a result of rain and moisture at the site limited the GPR work to two transects (Figure 1). Despite these technical difficulties, the GPR work was quite successful and it was determined that this methods may be the best one for SPA.  The GPR work provided a detailed rendering of stratigraphy to a depth of between 3-4 meters and helped identify certain anomalies in the stratigraphy (i.e. possible archaeological features dug into strata) as well as possible archaeological materials within each strata (Figure 2). An excavation unit was placed on GPR transect 2 in an area that showed a depression in a strata possibly related to cultural activity.  The excavation confirmed the presence of many artifacts as well as confirming that the GPR’s representation of the stratigraphy in the area was indeed

Figure 2: 2010 GPR Survey Profiles

accurate. While no clear archaeological features were detected, GPR survey has great potential to do so when used on a larger scale and may facilitate the rapid evaluation of magnetic and electromagnetic anomalies detected across the site.

These conclusions led to the planning of a large-scale GPR survey in the 2011 field season (which was made possible by a Stanford University Community Engagement Grant) using a mobile GPR system that will allow for faster collection of data and a higher frequency antenna (400Mhz) that will allow for more detailed images of the substrate closer to the surface (1-2meters from surface) where the majority of archaeological material has been encountered.

2011 GPR Survey 

Over the course of the first week of July 2011, I carried out a large scale GPR survey at SPA over the areas of the site containing the remains of the colonial occupation. In total almost 8500 square meters (or .85 hectares) of area were surveyed with a GSSI SIR-3000 using a 400mhz antenna and survey wheel. This setup facilitated the rapid collection of good resolution data on subsurface deposits to a depth of about 150-175cm (more than adequate considering that most archaeological materials were located within 2m of the surface). Conditions were less than ideal for the GPR survey, as the coffee plants restricted the survey to within the coffee rows separating plants. While the rows are fairly regularly spaced; we were unable to very accurately and closely space the GPR transects as is ideal for this type of survey. GPR transects were placed at 1.5m intervals, which is the spacing of the coffee rows. The survey was carried out in several episodes, with survey blocks of different lengths and widths due to the specific obstacles obstructing the GPR in the different areas of the site (tree lines, ledges, rock outcrops, etc). In general, the coffee rows were filled with leaf litter and branches from the coffee plants and their associated shade-giving trees. These rows had to be cleared by hand (thanks to Walter, the plantation worker in charge of the area where the site is located, for helping Luisa and I clear!) before the GPR could pass through, a task complicated by nightly rains that made the entire area quite soggy and difficult to navigate in.

Once the survey was completed, the next task consisted of processing the raw GPR data into a variety of profile and plan images. Dr. Dean Goodman graciously provided the project with a short term license of  GPR-Slice software; a critical contribution as this software allowed us to create plans of the GPR data (at various depths) to then overlay on aerial images of the site. In addition, this software facilitates 3D modeling of the GPR data that provides another perspective on the anomalies detected by the GPR as well as animations showing time slices that roughly correlate to depth.

The GPR data are still being processed, evaluated, and interpreted however numerous subsurface anomalies were detected. In particular, a circular/cone shaped anomaly was found starting at approximately 70 cm below surface and extending to Sector 1 (Figure 3,4,5).


Figure 3: Vertical and Horizontal GPR Slices of Sector 1 2011 Survey at SPA; showing top of circular anomaly.

Feature 4: Horizontal GPR slice of Sector 1 2011 GPR survey at SPA; showing bottom of circular anomaly and modeled anomalies.






Figure 5: Sector 1 2011 GPR Survey, showing circular anomaly; overlaid on site topography.


The anomaly appears to be at least 15-20m in diameter at its top, and narrows to approximately 5m at the bottom. In addition, this anomaly is associated with dense concentrations of colonial period artifacts encountered in the 2010 surface collection (Figure 6), an elevated magnetic anomaly detected by the magnetometer (Figure 7) and near anomalies detected by the EM survey (Figure 7).

Figure 6: Sector 1 2011 GPR Survey showing anomaly overlaid by surface collection points (blue points represent points where colonial period artifacts were found, with point size representing number of colonial artifacts recovered).

Figure 7: Showing Sector 1 of SPA, with overlays of (top to bottom): 1) Topo contours of the site, 2) 2011 GPR survey, 3) EM survey Sensor 1, 4) EM Survey Sensor 2, 5) Magnetometer survey.














These correlations indicate that what the GPR has identified is in fact an anomaly of some sort (likely cultural, due to the association with artifacts) and not an artifact of the survey process or the GPR. Needless to say, we have decided to excavate three test units on or near this anomaly in order to determine what it is (the shape indicates a trash pit of some sort, dug in the early colonial period down into previous occupation strata, but this is only speculation).

A set of linear anomalies were encountered in the southern most portion of the site (Figure 8). These anomalies were also associated with EM and Magnetometer anomalies (Figure 9), as well as some linear features observed on the surface of the site in a high-resolution satellite image taken when the site was cleared of coffee plants. However, the magnetometry in this area did detect large magnetic anomalies likely associated with magnetic volcanic material, and thus excavations are necessary to determine the nature of the anomalies detected in this area. The results of the GPR survey have pushed us to excavate at least two test units on and near these anomalies.

Figure 8: 2011 Sector 2 GPR Survey, with linear anomalies circled.

Figure 9: 2011 Sector 2 GPR Survey, overlaying Magnetometer survey; linear anomalies circled for both GPR and Mag surveys).















In short the GPR work undertaken in 2011 has served to focus the Nov-Dec of 2011 excavation of the site. The location of numerous anomalies, and their observed association with other lines of evidence have allowed us to survey large swaths of the archaeological sites (and its subsurface) and reveal promising areas of the site to excavate, while minimally disturbing the coffee plants on the surface. Excavations have started this week (with 2 units in progress directly over the circular GPR anomaly!) and the final phase of the GPR work -groundtruthing identified anomalies- will commence!

Please check the project website at for updates.



Lightfoot, K. G.

1995    Culture Contact Studies: Redefining the Relationship between Prehistoric and Historical Archaeology. American Antiquity 60:199-217.

Field work starts this week!

Hi all,

Things are moving along and the 2011 field season at San Pedro de Aguacatepeque is starting this week! Luisa Escobar and I made it out to the field site on Thursday to check in with the landowners, workers and community members and to take a peek at the site. We had not yet seen the site during the dry season (Nov-May) and it sure looks different! The coffee plants have lost a lot of leaves, and workers are busy harvesting the coffee berries off the plants in these months.

A bonus for us is the lack of leaves on the plants, as we can actually see from row to row and get a better sense of the topography of the site and more easily see artifacts on the surface. In addition, digging between the coffee rows will be SO much easier with out huge, leafy plants pushing in on us from all sides…

Just a couple of pics from our visit to give an idea of how nice it’s looking out there:

More posts coming soon, we are laying in test units and starting excavations this week, and I am putting the finishing touches on the recap of GPR work carried out in July 2011.

Thanks for reading!


Volcanology Section Up!

Hi all!

Quick update: Rudiger Escobar Wolf, a PhD candidate in Volcanology at Michigan Tech University (who works on the impact of volcanic activity on historic and modern communities near the Volcan de Fuego) has graciously provided a write-up and content on the impact of volcanic activity on the historic site/community of San Pedro de Agucatepeque. Click the Volcanology tab above this post to go to it.

Check it out and stay tuned for more posts later this week on the preliminary results of the July GPR survey at the site. Thanks for reading!