Records of Ancient Human-Environmental Interaction from Mayan Southern Petén, Guatemala
Part 1:  A 1300-year record of human activity and climate change from Cancuén

Archaeological and Environmental History at Cancuén

c. 2.70 (?)–2.25 m:  Before Cancuén

The lowermost sediments in this sequence, devoid of any cultural debris, date from the millennia before Cancuén's beginnings in the 17^th century. Sediment chemistry is dramatically different from overlying strata, with phosphorus and calcium concentrations being very low. Plant matter content is low, although this differs very little from overlying sediments. Although the pre-Cancuén sediments have not been sampled extensively, the low plant matter, and lack of any flood deposits from the nearby Pasión, suggests that relatively dry conditions were probably operating at least shortly before the site's beginnings.

2.25–2.10 m:  Early Cancuén

A well-defined layer of sediments from c. 2.25 to 2.10 m depth represents an earlier phase of Cancuén's history, estimated to finish sometime in the late 600s A.D., based on ¹⁴C dating of overlying sediments. Dating of the beginning of this layer may have provided information on when human activity first began in this sector of the city. Unfortunately, no suitable material was recovered from this depth for dating. There is no evidence of human activity below c. 2.10 m depth, below which only sterile buried soils of up to c. 0.5 m thickness are found. No human remains have been uncovered in this stratum to date. A significant amount of ceramic fragments were imbedded in this layer, as were eroded fragments of CaCO₃ material from the upslope structures. These ceramics are presently being analysed by Vanderbilt University researchers for information on their provenance and chronological implications. Chemical and physical indicators show that no major shifts in climate during this time are recorded at Cancuén; no evidence of flooding, nor increases in organic productivity that would accompany wetter conditions.

c. 2.10–1.90 m:  Fire at Cancuén

This well-constrained stratum is entirely composed predominantly of charred material; sediments, organic matter, and some ceramic fragments. The 100 to 200 mm thick band is thought to span the entire gully at this depth, recording a large-scale fire event at the site. Although a series of smaller fires instead may have been responsible, the large fragments of charcoal, up to 100 mm in length, which often span the entire layer, suggest that a single conflagration may have inflicted all of the damage. AMS ¹⁴C dating of this layer places the date of the fire at A.D. 770, occurring sometime toward the end of Cancuén's history between A.D. 690 and 790 (Table 1). Stratigraphically, the fire event would have taken place towards then end of the 0.2 m of deposition; that is, the sediments from 2.10–1.90 m were deposited before the fire.

It is possible that both the fire event in the 'port' area and the termination event recorded in the palace are contemporaneous. Although the age range of each date overlaps, the events responsible for each could be up 100 years apart. However, some support for their close connection comes from the ¹⁴C chemistry of both samples, which is similar. In any case, both events date from the latter period of Cancuén's history, the 700s A.D. It is thought that the dated termination event from the palace may coincide with the ascent of Cancuén's final King, Kan Maax.

1.90–1.50 m:  The last decades of Cancuén

The sediments from 1.90 to 1.50 m depth in the 'port' record the crucial last decades of Cancuén's history. A detailed report on the numerous human remains found in these sediments has been produced by Berryman et al. (2004), and only a brief summary is produced here. Up to 11 human skeletons, partially disarticulated, have been recovered from the stratum immediately above the charred layer. Associated with these were elaborate jade and jaguar-tooth jewellery, suggesting these were the remains of elite inhabitants of the city. A great body of forensic evidence suggests a massacre had occurred; the bodies had been crudely defleshed, some torn apart, and dumped in the gully. More, probably non-elite, human remains were also found towards the top of this stratum. The spatial pattern of these remains, and the level of articulation of the skeletons form the basin of the argument of these bodies having been left in the gully, rather than having eroded in from upslope burials through time. Soil forensic tests, presently being undertaken, will hopefully provide more information on this unique phase of Cancuén's history.

The latest date for occupation at Cancuén is May 12^th, A.D. 800, based on the epigraphic record. Results from the site's ceramic chronology place the end of Cancuén about the same time (end of the Tepeu 2 and beginning of the Tepeu 3 ceramic phase). All available evidence suggests that Cancuén was rapidly abandoned after this time. No record of the massacre is preserved in any other archaeological source to date, including the epigraphic record. It is not inconceivable then, that the massacre probably post-dates May 12^th, A.D. 800. During these final decades, the 'port' area of Cancuén was very active. The geochemical record suggests significant numbers of people and possibly animals were still active in the immediate area during these final years. High phosphorus levels, most likely the product of human and/or animal waste, record substantial human activity, while additional calcium being eroded into the basin gave rise to the highest levels recorded during the site's history, suggesting significant activity upslope of the gully in the final decades. The sediments during this phase, the early 800s A.D., are dominated by significant hillslope erosion, with no visual evidence of flooding from the nearby Pasión River. With some 0.4 m of sediment deposited between the fire event and the site's end, a crude estimate places eroded soil material being deposited as rapidly as 40 mm a year. Plant organic matter is also low during this period. These separate lines of evidence suggest relatively dryer climatic conditions prevailed during the 700-800s A.D.

1.50–0.00 m:  Post-Cancuén, the last 1000 years

A well-defined boundary separates those sediments above c. 1.50 m from those below this depth. The sediments above this depth are considered to date from after Cancuén's abandonment. The most convincing evidence of this comes from the geochemical and archaeological record. Phosphorus, a strong indicator of human activity, decreases dramatically by nine times above 1.50 m. In fact, the sediment chemistry above this depth is very similar to that of the sterile soils of >2.3 m depth. Although some ceramic and bones are found in the top 1.5 m of sediment (mainly towards the base of the unit), their occurrence is rarer than in the sediments below. Typically, only individual bones or fragments are found above 1.50 m, and it is thought that these, in contrast to the in situ remains found below, have been eroded into the port over time from shallow burials above. The rapid end of Cancuén, in what increasingly seems to be tumultuous conditions, leads to rapid, shallow burials taking place on patio floors surrounding the 'port' area (Alvarado et al., 2003). Ceramic remains in these sediments are in poor condition, with rounded edges, again suggesting transportation from the surrounding former occupation area's post-abandonment.

The top c. 1.50 m of sediments in the 'port' records the environmental history of over 1000 years after Cancuén. What information is preserved about environmental conditions from the mid 800s to today? The sharp boundary observed at c. 1.50 m depth is suggestive of a discontinuity in sedimentation. If dry conditions continued past the 800s A.D., then without human activity in the area to generate erosion, sedimentation in the gully would have been significantly reduced, and possibly halted. Climate records from the nearby northern Petén suggest that extremely dry conditions prevailed in the Terminal Classic, between A.D. 800 and 900 (Rosenmeier et al., 2002). Such conditions eventually shifted at Cancuén, and hillslope erosion recommenced, bringing in soil and cultural debris from the surrounding area. Based on palaeoclimate records from the Yucatán, the driest period of the last 10,000 years roughly corresponds to the Late Classic period, leading to causative associations with the Maya 'collapse' (Metcalfe et al., 2000). Wetter conditions at least in the Yucatán appear to have recommenced shortly after this time.

Click on image to enlarge.

Solid evidence of a shift in climate is recorded from a depth of 0.90 m in the 'port' in the form of several thick bands of flood deposits from the nearby Pasión (Figure 7, shown above), the only such features identified anywhere in this sequence. These are found from 0.90-0.80 m, 0.74-0.68 m and 0.48-0.45 m depth. The most recent of these was dated as being deposited post A.D. 1950. It is at this depth that lead levels in the sediments first rise above background levels, recording the atmospheric input industrial lead, firmly placing this stratum in the 20^th century in age. Chemically, these flood-born sediments are characterised by very high potassium concentrations, and levels of phosphorus above background. These deposits also have distinctly more clay than those soils eroded from the surrounding hills.

Although there is little chronological information from these upper sediments at present, we can say that in the last 1000 years in this region climatic conditions were different from those that existed in the Late Classic. Although the flood deposits themselves have low plant organic content, those slope-derived sediments from this era recorded very high values, which imply wetter climatic conditions. These conditions that began at some stage in the last millennia were wetter than at any period during Cancuén's occupation from c. A.D. 600-800. A coarse estimate of when the Río Pasión began periodically flooding the gully, based solely on a linear interpolation between ¹⁴C dates, is the 15/16^th century A.D. What we do know is that these new conditions began relatively quickly; there is a sharp boundary between the lowest flood deposits and the underlying slope-derived sediments. Modern observations of the Pasión suggest that occasional over-bank flow into the 'port' area can occur. These flood deposits therefore may record the beginning of environmental conditions not too different to those at Cancuén today. More detailed palaeoenvironmental information for the millennia post-Cancuén cannot, at present, be identified due to the course chronological resolution. Future research on the dating of these sediments will aim to refine when these shifts in environmental conditions post-A.D. 800 took place.

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