The Middle Pleistocene Negoya Formation in the Udo Hills (Shizuoka, central Japan) consists of marine deposits and three gravelly wedges, i.e., Ago (AGM), Furuyado (FGM) and Nakahiramatsu (NGM) Gravel Members in ascending order. The first appearance datum of the nannofossil Emiliania huxleyi {marine isotope stage (MIS) 8} was reported at horizon just above the top of the AGM. The overlying Kunosan Formation is known to have been deposited during MIS 6.5. Therefore, sediments above the AGM is expected to be sediments deposited during three glacial-eustatic sea-level fluctuations from MIS 8 to 6.6, although only two transgressive-regressive cycles have been recognized. To solve this problem, we examined sedimentary facies and molluscan fossils of the upper part of the Negoya Formation as well as the Kunosan Formation. As a result, we successfully identified a total of three transgressive-regressive cycles that can be correlated with oxygen isotope stages.

抄録全体を表示

The Anazawa Limestone is one of the largest methane-seep carbonate mounds intercalated in massive siltstone of the lower Middle MioceneBessho Formation, Northern Fossa Magna Region, central Japan. In August 2007, boring core samples were obtained in order to make clear the subbottom structure of the Anazawa Limestone. The drilling direction (N57°W, 35°S) is normal to the bedding, and the core samples were recovered continuously from the outcrop surface to 50.5 m in core depth. This is the first data report on its lithological succession and fossil occurrences in the core samples. The Anazawa Limestone is mainly composed of muddy micrite yielding abundant chemosynthetic bivalve fossils, such as vesicomyids (Adulomya uchimuraensis) and bathymodiolins (“Bathymodiolus” akanudaensis). In the core succession, the muddy micrite was intermittently confirmed in the upper part of the core (above 20.8 m in core depth), intercalating about 1-m thick beds of calcareous siltstone and massive siltstone. Chemosynthetic bivalve shells commonly occur from both micrite and siltstone in the upper part of the core. Almost all of the muddy micrite and calcareous siltstone are characterized by auto brecciated or fractured fabrics, which contain intraformational breccias of variably cemented micrite-intraclasts exhibiting both brittle and ductile deformation. Below the depth of 20.8 m grey massive siltstone is continuously distributed, but above 39.5 m core depth the siltstone contains abundant irregular-shaped small calcareous granules, less than 1 cm in diameter.

抄録全体を表示

We measured the major element composition of volcanic glass shards and plagioclase of Daidokutsu pumice which was deposited from 40 BC to AD 240 within a submarine cave named Daidokutsu at Ie Island, Japan. The results show that volcanic glass shards have a rhyolitic composition and plagioclase was identified as andesine. In addition, wollastonite and grossular-andradite series garnet were associated with volcanic glass shards.

抄録全体を表示