Excavations followed one of two basic methods, one for stratigraphic investigations, the other for extensive exposures.
Stratigraphic investigations were small test pits (generally 1 x 2 m) or trenches (generally in sections of 1 x 2 or 1 x 3 m) excavated in arbitrary 20 cm levels and usually screened top to bottom through a 5 mm mesh. Levels were sometimes excavated to conform to natural stratigraphy if stratigraphic changes were identified during excavation.
For the extensive excavations, a grid of 2 x 2 m units was laid out over the surface of the mound. Excavation proceeded by natural stratigraphic units. Excessively deep natural units were sometimes subdivided arbitrarily for more refined stratigraphic control.
Units thus defined stratigraphically and/or arbitrarily were referred to as lots, and each was given a unique number.
Lots had no preassigned size or shape but rather were defined by the excavator in accordance with each new stratigraphic situation encountered. In abbreviated provenience designations, lots or levels are preceded by a slash. Thus Md. 12 P5/13 refers to Level 13 of Test Pit 5, Mound 12, while Md. 12 E4/15 refers to Lot 15 in Grid Unit E4 at Mound 12 Since both arbitrary and natural criteria were used in defining levels (in the stratigraphic investigations) and lots (in the extensive exposures), these two forms of provenience designations sometimes resembled each other.
Levels, however, were always defined solely within individual test pits or trenches. As a result, levels with the same number in different test units are not necessarily correlated.
Lots, in the 1992–1993 excavations at Mounds 1 and 12, were not confined to the boundaries of individual excavation units but were defined within each excavation locale as a whole. Samples from the same lot number but different grid units are therefore from the same stratigraphic deposit. In 1997, during excavations of Mound 32 and Mz-250, a new system was introduced: lots were uniquely designated proveniences.
See Chapter 5 for further discussion of that system and how it differs from that used in 1992–1993.
A single, arbitrary, primary datum was established for each mound or off-mound excavation locale. The datum was generally 10 to 20 cm above the highest ground in each locale so that all depths could be expressed in centimeters below datum (cm bd). We used line levels and string to set up datum stakes near each excavation unit based on this primary datum. Beginning and ending depths for each lot or level, as well as depths of features or significant artifacts, were measured by line levels from these datum stakes.
Screening
Stratigraphic excavations were generally screened top to bottom through a 5 mm mesh. Selected units of the extensive excavations (and some of the trench sections at Mound 32) were not screened. Unscreened lots included deposits of slope wash or platform construction. All culturally significant lots, including occupation surfaces, floors, post holes, features, and midden deposits, were screened. All materials remaining in the screen, including ceramics, obsidian, jade, magnetite, bone, ground stone, fire-cracked rock, pumice fragments, burnt daub, and even pebbles, were retained for analysis in the laboratory. Burials, floors, structures, and post holes were numbered separately. Units that did not fall into one of those categories but that appeared to have cultural significance were labeled feature. The term floor was used to designate all living surfaces identified in the excavations, regardless of whether those were structure floors or simply patio or activity areas. We numbered cultural units of each class sequentially either within the site as a whole (burials) or within each mound or off-mound excavation locale (floors, post holes, and features). The remains of perishable buildings were numbered in reverse chronological order in each excavation locale (for example, Structure 1 is later than Structure 2). In these data records and the associated chapters, we refer to structures either by their full formal designation (for example, Mound 6 Structure 4) or in abbreviated form, with the mound number, a hyphen, and the structure number (Mound 6 Structure 4 becomes Structure 6-4, and Mound 1 Structure 2 becomes Structure 1-2). From 1990 through 1993, when we assigned numbers to features in the field, we usually did not also assign them lot or level numbers if they were removed as single units. Large or complicated features, however, were divided into multiple lots or levels. Thus Mound 12 Feature 19, a trash pit, was removed as a single unit and therefore does not also have any associated lot number, whereas Mound 12 Feature 2, a complex trash- and sediment-filled ditch, is divided into Lots 12, 13, 15, 19, and 22 where it appears in Units E3 and E4. The lack of a lot or level number associated with some features proved annoying as we worked with the data, and in the 1997 excavations, all features were assigned at least one lot number.
Most features were completely excavated upon identification. We took 2- to 4-liter sediment samples from trash-filled pits and midden deposits for flotation. Human burials were exposed using ice picks and paintbrushes. Bone preservation was fair to very poor. In several instances we applied a solution of Duco cement and acetone to the bones before removal in an attempt to keep them intact. Basic processing of the cultural materials was carried out concurrent with the excavations in a field laboratory. Artemio Villatoro of the New World Archaeological Foundation (NWAF) supervised the washing, sorting by material type, counting, and weighing of all materials. After the ceramics from each lot had been counted and weighed, they were sorted again to identify all rims, diagnostic body sherds, and slipped body sherds. Unslipped, non-diagnostic body sherds were then typically discarded. As of 2019, materials are still curated at the NWAF laboratory in San Cristóbal de Las Casas, Chiapas.
Naming
Several systems for designating excavation units have been employed. Ceja Tenorio (1985) excavated test pits, which he numbered sequentially irrespective of where they were located. Test Pits 1 through 3 were in Mound 1, while Test Pits 15 through 19 were in Mound 5, and so on. In 1990 a second system was initiated. In this system, test units were numbered sequentially, starting from 1, in each new mound investigated. Thus Michael Ryan excavated Mound 7 Test Pits 1, 2, and 3, while Lesure excavated Mound 12 Test Pit 1. At the same time, we retained Ceja’s sequential numeration for isolated off-mound tests, excavating Test Pits 27, 28, 29, and 30. In these data records and the associated book, test pits are referred to simply as pits, sometimes abbreviated as P. Thus P29 is Test Pit 29 and Md. 12 P5 is Test Pit 5 at Mound 12. Trenches at Mounds 12 and 32 were numbered and divided into lettered sections. Md. 12 T1E is Section E of Trench 1 at Mound 12, while Md. 32 T4F is Section F of Trench 4 at Mound 32. For the large, horizontal exposures at Mounds 1, 6, and 12, a grid of 2 x 2 m units was established on each mound. Rows along one axis were designated by letters, rows along the other axis by numbers. Each grid unit can thus be uniquely described by a letter and number combination, such as Unit E4, G7, and so forth.
Discovery of midden deposits in the off-mound Test Pit 32 prompted a gradual expansion of this test to 12 adjacent units covering 36.5 m2. The adjacent units were labeled with letters and sometimes numbers: Unit 32A, Unit 32B2, etc. (See Figure 6.11.) That excavation as a whole will be referred to as the Pit 32 excavation. The other off-mound location that saw significant excavation will be referred to as Mz-250. It was originally identified as a small site adjacent to Paso de la Amada, with the site code Mz-250 (Clark 1994a:163). Clark (2004a:Figure 2.5a) now includes this area as part of “greater Paso de la Amada.” The 11 units excavated in 1997 were numbered 1 through 11 in the order in which they were opened (Figure 6.16). The excavation as a whole is referred to with the original site designation, Mz-250, though we treat it as part of Paso de la Amada.