Archaeological Geology
As the recognition of archaeological geology as a formal subdiscipline has increased, so have discussions about it nature and boundaries. In early 1979 Fekri Hassan published a short article, ‘Geoarchaeology: the Geologist and Archaeology’ (American antiquity). In this article Hassan defined 9 district areas where geological work is necessary for contemporary archaeological investigation. Earlier, I discussed the role of geologist on the archaeological field staff (Journal of field archaeology, 1975) and B.G. Gladfelter detailed the role of the geomorphologist and the sedimentary petrologist in archaeological research (American antiquity, 1977). Such presentations will continue as more interdisciplinary research is done on the relationship between the myriad of earth sciences - paleontology, petrology, stratigraphy, geomorphology, mineralogy, geophysics, geochemistry, geochronology - and archaeology.
A minor difference of views at present concerns whether geoarchaeology or archaeological geology is the most adequate title for the range of problems studies and research methods used. In naming the Archaeological Geology Division of the Geological Society of America, I accepted the rationale of Reuben Bullard that the practitioners would be geologists doing geology of a very special kind that is solving problems that involved both geological and archaeological materials, structures and strata. Hence, using archaeology as the adjectival modifier on the noun geology seed appropriate.
Papers continued to appear this year on the identification of geological/geographic sources of lithic and metal artifacts. Usually these assignments are based on trace elements signatures (fingerpoints). For chert, the earlier dependence on physical characteristics, particularly color, has been shown to be grossly misleading. Chert, which is much less chemically homogenous than obidian, requires more chemical information to make relatively unambiguous determinations of provenance. Increasing emphasis is now being placed on discriminant analysis to assessing unknowns to source localities.
Extensive geological field work is now providing the framework for understanding the stratigraphy and paleoenvironmental setting of early hominid sites. Large - and small-scale geological processes have shaped the course of human evolution. Dynamic geological and climatological conditions provided the impetus for major environmental change. The geological contexts affected the lifeways as well as the burial and preservation conditions. Although the east African sites at Olduvai, Laetolil, Omo, and Hadar are household words in the lexicon of early man, major field work is also under way in southeast Asia. D. Ninkovich and L.H. Burkle are working in Java, Gary Johnson is studying the Ramapithecus - bearing sediments of the Siwalik group in Pakistan, and the group from Iowa State University (Carl Vondra, Mark Mathisen, Dan Burggraf and Erik Kvale) are investigating the field evidence for early man in the central Cagayan valley of northern Luzon, the Phillippines.
In east Africa, Jim Aronson has surveyed 50 square km of the Hadar Formation. Sheet-like major sands with fluvial structures bear most of the fossils. Frank Brown reports that here is no geological evidence for altitudinal changes in the important lower Omo basin during or since the deposition of the Shungura Formation between about 3.5 and 0.8 million years ago. Remains of about 100 vertegrate genera, two-thirds of which are still extant, have been recovered from the Shungura Formation. Dick Hay has determined the paleoenvironment of the Laetolil beds that contain a rich vertebrate fauna, including hominids. These beds have been dated by K-Ar at 3.6 to 2.8 million years old. The ancient environment was a semiarid grassland savannah with Acacia trees, rather like that of the same area today.
Archaeological geologists have joined soil scientist and archaeologist sin the study of plant opal phytoliths to determine the potential of this biogenic opal in providing evidence for the paleoecology of archaeological sites. Phytoliths were first discovered more than a century ago in windblown dust, but their systematic typology has never become a major research concern of botanists. A geologist, Page Twiss, provided the beginnings of a systematic genetic classification a decade ago. Adequate taxonomic keys for the identification of phytoliths from soil or archaeological strata do not yet exist but are being developed in several laboratories. If enough individual phytolith types or phytolith assemblages prove to be diagnostic they will supplement the palynological data on which most of our paleoenvironmental reconstructions depend.