THE GEOCHEMISTRY OF THE MAJOR SOURCES OF ARCHAEOLOGICAL OBSIDIAN ON HOKKAIDO ISLAND (JAPAN): SHIRATAKI AND OKETO

The geochemical compositions for obsidian from two of the most important sources on the Japanese island of Hokkaido, Shirataki and Oketo, are presented. This work represents the first systematic study of obsidian geochemistry on Hokkaido from the view of modern methodological standards. The study was performed with the help of neutron activation analysis to determine the concentrations for 28 elements. The results obtained allow us to subdivide both sources into two geochemical groups (Shirataki‐A and ‐B; and Oketo‐A and ‐B), with each representing an individual sub‐source. Obsidian from both Shirataki and Oketo sources is identified at archaeological sites located on Hokkaido, on the neighbouring Sakhalin Island and Kurile Islands, and in the lower course of the Amur River basin. The distance of obsidian transport during the Upper Palaeolithic was up to ～250 km, and in the following Neolithic and Palaeometal periods up to ～1200 km. This testifies to the wide distribution of Hokkaido obsidian to archaeological complexes in North‐East Asia and its active transport/exchange in prehistory. The data presented here should be used as a reference for the obsidian geochemistry of Shirataki and Oketo sources from now on.     

Geochemistry and origin of natural gases dissolved in brines from gas fields in southwest Japan

Previous geochemical studies indicated that most natural gases dissolved in brines in Japan are of microbial origin, consisting of methane produced via carbonate reduction. However, some of those from gas fields in southwest Japan contain methane relatively enriched in ¹³C, whose origin remains to be clarified. To address this issue, chemical and isotopic analyses were performed on natural gases and brines from the gas fields in Miyazaki and Shizuoka prefectures, southwest Japan. Methane isotopic signatures (δ¹³C ≈ ?68‰ to ?34‰ VPDB; δ²H ≈ ?183‰ to ?149‰ VSMOW) suggest that these gases are of microbial (formed via carbonate reduction) or of mixed microbial and thermogenic origin. The relatively high δ²H‐CH₄ values and their relationship with the δ²H‐H₂O values argue against the possibility of their formation via acetate fermentation. The δ¹³C‐CO₂ values (≈?5‰), together with the slope of the correlation between δ²H‐CH₄ and δ¹³C‐CH₄ (Δδ²H‐CH₄/Δδ¹³C‐CH₄ ≈ 1), contradict the possibility of their formation via carbonate reduction followed by partial oxidation by methanotrophs. The ³He/⁴He ratios of the gases from Miyazaki (≈0.11–1.3 Ra) and their low correlation with δ¹³C‐CH₄ values do not support an abiogenic origin. It is inferred therefore that the high δ¹³C‐CH₄ values of natural gases dissolved in brines from gas fields in southwest Japan are indications of the contribution of thermogenic hydrocarbons, although whether abiogenic hydrocarbons contribute significantly to the gases from Shizuoka requires further investigation. This study has clarified that, for the future exploration of natural gases in southwest Japan, we should adopt the strategies for conventional thermogenic gas accumulations, such as checking the content, type and maturity of organic matter in the underlying sedimentary rocks.     

Boats in the rock art of Kanozero and Northern Europe

A comparative analysis of boats depicted in the rock art of Lake Kanozero and Northern Europe suggests that they refer to the same type, which was common in northern cultures and was characterized by a protruding straight keel, an oblique sternpost, and a stem post decorated with an elk head. The design apparently consisted of a broad keel plank to which the sides, bow, and stern were attached. In boats represented at Kanozero, this plank protrudes forward, beyond the nose, and backward, beyond the stern.     

Devolatilization‐induced pressure build‐up: Implications for reaction front movement and breccia pipe formation

Generation of fluids during metamorphism can significantly influence the fluid overpressure, and thus the fluid flow in metamorphic terrains. There is currently a large focus on developing numerical reactive transport models, and with it follows the need for analytical solutions to ensure correct numerical implementation. In this study, we derive both analytical and numerical solutions to reaction‐induced fluid overpressure, coupled to temperature and fluid flow out of the reacting front. All equations are derived from basic principles of conservation of mass, energy and momentum. We focus on contact metamorphism, where devolatilization reactions are particularly important owing to high thermal fluxes allowing large volumes of fluids to be rapidly generated. The analytical solutions reveal three key factors involved in the pressure build‐up: (i) The efficiency of the devolatilizing reaction front (pressure build‐up) relative to fluid flow (pressure relaxation), (ii) the reaction temperature relative to the available heat in the system and (iii) the feedback of overpressure on the reaction temperature as a function of the Clapeyron slope. Finally, we apply the model to two geological case scenarios. In the first case, we investigate the influence of fluid overpressure on the movement of the reaction front and show that it can slow down significantly and may even be terminated owing to increased effective reaction temperature. In the second case, the model is applied to constrain the conditions for fracturing and inferred breccia pipe formation in organic‐rich shales owing to methane generation in the contact aureole.     

A Paleolithic Cache at Tolbor (Northern Mongolia)*

This study presents analyses of a unique assemblage of lithic artifacts, 57 large flakes, discovered in the Ikh Tulberiin Gol River valley of Northern Mongolia. The assemblage represents the first Paleolithic cache ever discovered in Mongolia and is an isolated find, not directly associated with a habitation or logistic activity site. Results of use-wear analysis suggest most of the flakes were unused, with only a few minimally used for processing wood. GIS analyses of the local landscape indicate that the placement of the artifacts was likely symbolic, rather than utilitarian or for storage, lying in an east-west linear viewshed of the primary mountain pass to an adjacent river basin. Based on the context of the discovery as an isolated find and technical-typological features of the artifacts, the assemblage is interpreted as a cache of tool blanks that was purposefully and symbolically positioned on the landscape relative to the primary mountain pass by Upper Paleolithic hunter-gatherers.     

A Micro Computerized Tomography (X-RAY MICROSCOPY) of the Hand Phalanx of the Denisova Girl*

In 2010, the complete mitochondrial genome of a fossil hominin from Denisova Cave, Altai was sequenced on the basis of mtDNA extracted from the hand phalanx of a girl. Modern micro tomographic techniques mark a new stage in the morphological study of extant and fossil hominins, offering opportunities to work with fragmentary material. We have used the nondestructive method of micro computerized tomography for a comparative histological assessment of the Denisova girl's biological age. The diaphyseal and metaphyseal parts of the phalanx, reflecting different ontogenetic stages, were undergoing rapid growth. The histological pattern of the walls of the diaphysis, specifically the lamellar structure with rare osteons, indicates a stage corresponding to 6–7 years in modern children. An altogether different pattern, resembling that of adults, was earlier observed in a Neanderthal child from Okladnikov Cave, Altai. The resemblance between the Denisova individual and extant humans in certain features of growth and skeletal maturation may point to the very early origin of the modern skeletal growth pattern. The Neanderthal pattern is quite distinct and may have originated after these hominins had branched off from the common stem.     

A 6000‐Year‐Old Hand Amputation from Bulgaria—The Oldest Case from South‐East Europe?

A skeleton from Tell Yunatsite in Bulgarian Thrace shows evidence of amputation of the right hand. The individual dates back to the end of the fifth millennium, connecting it to the Late Copper Age of that region. The Chalcolithic settlement on the tell ended immediately after a bellicose assault. Therefore, the question arose if the loss of the hand may be connected with this incidence. Anthropological studies in close collaboration with the archaeologists on site made clear that the abscission took place at an earlier time. This result led to a series of complex questions. These are described in this work. We will show that a congenital origin for the loss of the hand can be excluded, and that the individual survived this severe injury for a certain time span. Several possible explanations for an amputation are discussed. It turns out that a surgical intervention seems to be the most likely reason. It becomes clear that there must have been an excellent medical knowledge in the Copper Age concerning surgery and wound treatment. Furthermore, the survival of the handicapped individual documents a certain social cohesion. Copyright © 2011 John Wiley & Sons, Ltd.