Archaeological Chronometry

Radiocarbon and Tree-Ring Models and Applications from Black Mesa, Arizona

Francis E. Smiley

Richard V.N. Ahlstrom

All archaeologists face chronometric interpretive problems in developing and refining chronology. This volume, Archaeological Chronometry, addresses such problems in terms of radiocarbon and tree rings. The work described here provides both data sets and models for the interpretation of radiocarbon and tree-ring information. We hope it can serve at various levels as a guide and sounding board for interpreting chronological data from archaeological contexts.

We describe two studies that took place as part of the Black Mesa Archaeological Project (BMAP) in northeastern Arizona. The first concerns the chronometry of early agricultural villages and associated sites on Black Mesa. These sites date to Basketmaker II times, about 1900-1600 B.P., and belong to the Lolomai phase. Part Il of this study interprets a large body of radiocarbon dates from the early villages and, in so doing, refers to research on tree-ring materials from historic period Navajo sites occupied between A.D. 1800 and 1980 in the Black Mesa project study area. The second study (Part III) consists of research on tree-ring and other chronometric data of the Pueblo I through early Pueblo III periods (A.D. 800-1150).

This volume results from 17 years of field research that has involved a significant focus on both chronology and chronometry. The early work of the Black Mesa project produced the initial prehistoric chronology that provided the impetus and point of departure for the concentrated studies in chronometry that took place during the later years of the project. The chronometric studies have sought to develop, refine, and delineate methods for precisely and accurately placing archaeologically observed events and processes in time. The studies include investigations involving various tree-ring, radiocarbon, ceramic, archaeomagnetic, and stratigraphic dating techniques. We provide detailed examinations of the histories, databases, and interpretive findings for each of these dating techniques as they were employed in the course of the Black Mesa project. In addition, we provide basic data for the radiocarbon and tree-ring dating research that underlie the interpretation of the other techniques.

The volume follows from the survey, collection, and mapping of more than 2,000 prehistoric and historic archaeological sites and the excavation of more than 200 of those sites. The long-term, intensive archaeological research on Black Mesa provided unparalleled amounts of information of unusually high quality for doing chronometry. Artifactual assemblages aside, a primary Black Mesa project contribution consists of three basic data sets. The first is the large body of tree-ring determinations from prehistoric contexts in the 100-square-mile study area. The second consists of the large suite of radiocarbon dates from pre-Ceramic sites, all of them sites that could not be dendrochronologically dated. The third data set is composed of thousands of tree-ring samples and dates from modern-day and historic period Navajo occupations in the Black Mesa study area.

The luxury of access to modern-day tree-ring materials provides the basis for evaluating the radiocarbon data in ways that have important implications for radiocarbon date interpretation in many other archaeological situations. The large treering database from prehistoric sites enables an extremely high-resolution examination of the prehistoric chronology and provides a means for evaluating the numerous efforts at ceramic chronology and other techniques for dating.

Given the Black Mesa project's more than 20-year history, as well as the variety in approaches to dating employed by project researchers, it is not surprising that there has been disagreement among the project's participants over issues relating to dating and chronology. The present study is in part a summing up and evaluation of Black Mesa project chronology, and it does not always agree with earlier chronological analyses and interpretations. Debates have arisen among Black Mesa researchers in other realms as well -see, for example, Plog's and Powell's 1984 disagreement over the seasonal versus year-round use of the many small Puebloan period sites located on Black Mesa. Far from being a sign of weakness, such scholarly debates indicate intellectual vitality in long-term projects.

We intend this volume to be useful to archaeologists interested in practical solutions to problems of chronometric interpretation. In addition, we aim to provide a compendium of the methods, data, and conclusions of the numerous chronometric and chronological studies made possible by the Black Mesa project.