Archaeometric research on production and distribution at the Nakadake Kiln Site Cluster (original) (raw)
The Journal of the Geological Society of Japan
A thick deposit of the muddy Shimajiri Group (Upper Miocene-Early Pleistocene) is overlain by the calcareous sandy Chinen Formation (Pleistocene) in southern Okinawa-Jima, Southwest Japan. The abrupt facies change has been explained by a significant unconformity resulted from subaerial erosion (the Shimajiri disturbance) or the consequence of rapid and regional uplift leading to an abrupt environmental change (the Chinen disturbance). We identified sandy mass transfer deposits (MTD) directly overlying the Shinzato Formation the uppermost part of the Shimajiri Group in the large Urizun outcrop. The Shinzato-Chinen transition zone yields numerous dolomite concretions. The dolomite is strongly depleted in C, with δ δ C values of. to. , suggesting that the concretions were derived from anaerobic oxidation of methane (AOM). Zonation in δ δ O values across the concretions, from. in the centers to. at the rims, suggest that the precipitation temperature increased from. . to. . °°C , corresponding to a shallowing of the water depth from to m. The estimate is consistent with the analysis of benthic foraminiferal assemblage. Given the wide distribution of the Bottom Simulating Reflector (BSR) offshore of Okinawa-Jima, methane hydrates are assumed to have persisted in the Shimajiri Group throughout the Pliocene-Pleistocene. Abrupt uplift and relative sea-level fall during the Chinen disturbance at Ma must have triggered abrupt changes in facies and a massive methane hydrate dissociation. This disturbance resulted in a high methane flux, increased AOM, and the formation of the dolomite concretions in the Shinzato-Chinen transition zone. Methane-derived dolomite concretions are thus a geochemical record of an abrupt tectonic disturbance and hydrate dissociation offshore of Okinawa-Jima.
Journal of the Geological Society of Japan, 2020
We report new uranium-lead (U-Pb) zircon ages for strata in the Sanjakugoshaku Formation in the lower part of the Eocene Nogata Group of the Chikuho Coalfield, Fukuoka, northern Kyushu, western Japan, to provide a better geochronological control for the group than a previously reported fission-track date (.. Ma) from the Uwaishi Formation in the upper part of the Nogata Group. The U-Pb zircon dates were obtained via laser ablation-inductively coupled plasma-mass spectrometry (LA-ICPMS) for four different tuff and tuffaceous layers in the Sanjakugoshaku Formation, yielding ages of. . ,. . ,. . , and. . Ma, in stratigraphic order. These new dates indicate that deposition of the Sanjakugoshaku Formation lasted for more than Myr (including hiatuses), with this period corresponding to most of the chronological interval of the Okinoshiman molluscan Stage (middle middle Eocene to late Eocene?) in Kyushu. Furthermore, the new dates suggest that the basal part of the Sanjakugoshaku Formation and underlying Oyake Formation (the lowest unit of the Nogata Group) are chronologically correlated with the older Takashiman molluscan Stage (early Eocene to early middle Eocene). Therefore, the tectonic processes responsible for the formation of the sedimentary basin of the Chikuho Coalfield appear to have started at latest by the early middle Eocene.
Investigation of the Remains of a Boiler House in Maizuru 3RD Naval Explosives Arsenal
AIJ Journal of Technology and Design
We carried out excavation of the remains of a boiler house in Maizuru 3rd Naval Explosives Arsenal. This investigation consists of measurement of the remains, performance evaluation of concrete, and estimating construction method. As a result, it was estimated that the boiler house was consisted of reinforced concrete foundations/walls, plain concrete floor, and some members from plain or fire bricks. On the other hand, the performance of concrete used for the remains was standard compared with the technical standards during World War II. These results will contribute to the grasp and the evaluation of the then architectural technology and design.