Çatalhöyük 1998 Archive Report

ÇATALHÖYÜK 1998 ARCHIVE REPORT

Collection of Soil and Sediment Samples for the Chemical Identification of Activity Areas at Çatalhöyük

William D Middleton

During the 1998 excavation season, a team from the Laboratory for Archaeological Chemistry at the University of Wisconsin- Madison (T. Douglas Price and William D. Middleton) began a program of sample collection for the chemical identification of activity areas at Çatalhöyük. Over 900 soil and sediment samples were collected from floors, fill deposits and features at the site, as well as from present-day mud-brick houses and off-site contexts in the vicinity of Çatalhöyük. These samples will be used to characterize the archaeological deposits and identify activity areas on occupied surfaces.

On-site, samples were collected from all areas currently under excavation (West, North, BACH, and Mellaart), with the most intensive sampling at Mellaart, North, and Bach. Off-site samples were collected from three present-day households in the villages of Turkmencamili and Süleymanhaci and a trench excavated by the KOPAL project. The samples have been shipped to the Laboratory for Archaeological Chemistry for analysis and interpretation.

Analysis of the samples will be conducted at the Laboratory for Archaeological Chemistry following the laboratory's established methodology. Samples are dried at 105°C for 48 hours, pulverized in a Coors porcelain mortar, screened with a 2 mm geological sieve, and extracted at room temperature for two weeks with 1 N HCl. The extract is then scanned with an Inductively Coupled Plasma Atomic Emission Spectrometer (ICP/AES) for aluminum (Al), barium (Ba), calcium (Ca), iron (Fe), potassium (K), magnesium (Mg), manganese (Mn), sodium (Na), phosphorus (P), strontium (Sr), titanium (Ti), and zinc (Zn) (see Middleton 1998; Middleton and Price 1996). Up to 150 samples can be scanned in a single day. Because soil properties such as organic matter content, pH, and texture (grain size composition) can impact the concentrations of extracted elements, these properties will be determined as needed.

A non-aggressive extraction procedure is utilized for two reasons. First, anthropogenic chemical residues are deposited, and subsequent pedogenic alterations of the sediment chemistry take place, within a comparatively narrow temperature and Ph range and have relatively little impact on the mineral composition/chemistry of the sediment. More aggressive procedures (i.e. hot extraction/digestion and stronger acids) are more heavily influenced by the mineral chemistry of the sediment and therefore not as sensitive to anthropogenic chemical residues. The mineral composition of the Çatalhöyük sediments will be determined through soil micromorphology. Second, many aggressive techniques, particularly hot extraction, are more sensitive to method based variation in time and temperature (e.g. slight variations in heating temperature and time). The two week, room temperature extraction period yields highly reproducible results (Burton and Simon 1993).

Following the analyses, the elemental data are surface plotted and visually screened for any observable patterning and statistically analyzed using principal component analysis, numerical classification, and discriminant analysis for known (i.e. ethnoarchaeologically documented) activity signatures (see Middleton 1998; Middleton and Price 1996). Specific activity areas are defined primarily on the basis of their chemical composition, but other excavation data (architecture, artifacts, microdebitage, and the other soils data) will be utilized to test and corroborate the observed chemical patterning. Micromorphology will be a particularly useful complement to elemental characterization because physical remains of specific residues can be visually identified (e.g. a distinction can be made between wood ash and coprolites). Samples whose inorganic chemistry indicate a high potential for the preservation of organic residues (i.e. high concentrations of P and Ca) will be tested with more intensive analytical techniques (e.g. GC/MS, C-H-N-O, immunochemical analysis, etc.).

The samples collected during the 1998 season are currently being analyzed at the Laboratory for Archaeological Chemistry, and further sampling at Çatalhöyük is planned for the 1999 season.