VARIETIES AND SOURCES OF ARTEFACTUAL OBSIDIAN IN THE MIDDLE STONE AGE OF THE MIDDLE AWASH,ETHIOPIA*

Recent investigation of the geochemical provenance of obsidian artefacts from spatially and temporally variable archaeological sites in Ethiopia has shown the diversity of geological sources and concomitant differences in the transport of raw material to archaeological sites, thus allowing reconstruction of the utilization of raw material by early hominids as well as recent humans. We recognize 30 compositionally different obsidians that were used at the Middle Stone Age (MSA) archaeological sites of Aduma (A8), Halibee Herto, Aladi Springs and Porc Epic in the Middle Awash region. Probable sources of nine of these obsidians are Adokoma, Ayelu, Ida'ale, Assebot, Asboli, Gira‐Ale and Kone. Many compositional types are confined to a single site, but others are shared between sites, although shared obsidians between sites more than 300 km apart are exceptional.     

Reanalysis of in situ permeability measurements in the Barbados décollement

A cased and sealed borehole in the Northern Barbados accretionary complex was the site of the first attempts to measure permeability in situ along a plate boundary décollement. Three separate efforts at Hole 949C yielded permeability estimates for the décollement spanning four orders of magnitude. An analysis of problems encountered during installation of the casing and seals provides insights into how the borehole conditions may have led to the wide range of results. During the installation, sediments from the surrounding formation repeatedly intruded into the borehole and casing. Stress analysis shows that the weak sediments were deforming plastically and the radial and tangential stresses around the borehole were significantly lower than lithostatic. This perturbed stress state may explain why the test pressure records showed indications of hydrofracture at pressures below lithostatic, and permeabilities rose rapidly as the estimated effective stress dropped below 0.8 MPa. Even after the borehole was sealed, the plastic deformation of the formation and relatively large gap of the wire wrapped screen allowed sediment to flow into the casing. Force equilibrium calculations predict sediment would have filled the borehole to 10 cm above the top of the screen by the time slug tests were conducted 1.5 years after the borehole was sealed. Reanalysis of the slug test results with these conditions yields several orders of magnitude higher permeability estimates than the original analysis which assumed an open casing. Overall the results based on only the tests with no sign of hydrofracture yield a permeability range of 10^?14–10^?15 m² and a rate of increase in permeability with decreasing effective stress consistent with laboratory tests on samples from the décollement zone.     

X-RAY FLUORESCENT ANALYSIS OF ANGLO SAXON JEWELLERY

X-ray fluorescence analysis of 30 pieces of Anglo Saxon jewellery, from the Ashmolean Museum, Oxford, is followed by a comparison with similar results obtained from contemporary coinage. The standards of fineness for the coinage are applied to the jewellery and used to date its manufacture. An appendix describes repeatanalyses of some coins which, at first, had widely differing results from XRF and specific gravity methods.     

RAPID CHEMICAL CHARACTERIZATION OF OBSIDIAN ARTIFACTS BY ELECTRON MICROPROBE ANALYSIS

The potential of the electron microprobe to analyse chemically obsidian artifacts for source provenance studies is demonstrated using artifacts from four archaeological sites in Kenya.     

Osteology,DNA and Sex Identification: Morphological and Molecular Sex Identifications of Five Neolithic Individuals from Ajvide,Gotland

Sex identifications are crucial for the understanding of the societies we study. To understand an ancient society we need to have some picture of the roles played by males and females in the society. This knowledge has often been produced by morphological sex identifications in connection with grave goods and burial finds. However, if a morphological sex identification is to be fully trusted, the human remains need to be fairly well preserved. There is also a problem in the fact that morphological traits identified in a modern material are applied on an ancient material. There is a growing difference with time and geographical distance. An alternative to morphological identification is molecular identification based on the presence or absence of a Y chromosome, but such identification has its problems too: the risk of contamination and the fact that the absence of proof is not a good female indicator. In this work we have tried to compare morphological and molecular identifications of five Neolithic individuals from the Ajvide site at Gotland in the Baltic sea. © 1997 by John Wiley & Sons, Ltd.