Abstract: Numerical Aspects of Chemical Variation and Texture--Contribution from Maya Archaeology

Ronald L. Bishop, Frank G. Ethridge, Robert L. Rands

An interdisciplinary investigation of ancient Maya (600-900 A.D.; Chiapas, Mexico) socioeconomics involved a detailed analysis of pottery fragments by instrumental neutron activation and petrographic techniques. The combination of analytic procedures provided data related not only to ceramic trade, but to the effects of texture on sedimentary geochemistry as well. Petrographic examination revealed generalized paste-textural classes of pottery. Classes included varying amounts of fine and medium sand which may have been temper-added to an originally fine-grained matrix or which simply may represent utilization of naturally occurring mixed sediments. As conducted, the ceramic-paste-activation analysis made no allowance for chemical variations resulting from textural differe ces. Identification and removal of grain-size effects were possible when textural and chemical data were considered jointly using a combination of cluster, principal-components, and factor analyses. Sc, Th, and Ti increase in abundance as sediment size decreased. Examination of samples by electron microscopy and X-ray fluorescence revealed that titanium was dispersed primarily though-out the clay matrix rather than being carried by inclusions. Quartz sand essentially displaced the matrix and lowered the titanium concentration. Recognition of size effects allowed for compensation by proportional measures and ordination procedures. Once variations related to size were removed, the remaining chemical variations were explained in terms of geologic source areas and/or patterns relating to tra e. Thus, when it is impractical to analyze samples of similar grain size by chemical methods, the size effects should be removed if textural data are available.

AAPG Search and Discovery Article #90972©1976 AAPG-SEPM Annual Convention and Exhibition, New Orleans, LA