Jun Aizawa

A Combination of Organic Carbon/Total Nitrogen Ratios and Pyrite Contents in Sediments as a Paleoenvironmental Indicator: A Preliminary Study in Northern Kyushu, Japan

Organic carbon (Corg) and total nitrogen (N) contents in Tertiary mudstone samples from four basins in northern Kyushu, Japan, were determined by using a CHN analyzer. A good correlation was observed between the stratigraphic distribution of the Corg/N values and geologically inferred depositional environments. Pyrite contents in carbonaceous sediments from the same basins were also obtained employing a reflecting microscope. Stratigraphic changes of pyrite content in car-bonaceous sediments can be correlated with these depositional environments. Pyrite is expected to play a useful role as an index mineral in estimation of depositional environments in future studies.

Thermal history of selected Mesozoic and Cenozoic sedimentary basins in Kyushu, Japan

Abstract Paleotemperatures of selected Cretaceous and Paleogene sedimentary basins in Kyushu, southwest Japan were measured by means of fluid inclusions in authigenic minerals, and by combined use of vitrinite reflectance of carbonaceous materials and authigenic mineral assemblages. Relationships between vitrinite reflectance and diagenetic minerals were well correlated as previously reported. Paleogeothermal gradients for four sedimentary basins were estimated based on paleotemperatures and overburden thickness. Paleotemperatures and paleogeothermal gradients obtained in this study may be representative of diagentic/low-grade metamorphic thermal conditions in each sedimentary basin.

Regional Patterns of Diagenetic Alteration in the Tertiary of the Kyushu-Korea Region: Implications for Plate Tectonics at the Eastern Asian Continental Margin

ABSTRACT Studies of organic and inorganic diagenesis of Tertiary successions in the Kyushu-Korea region was combined with systematic correlation of the onshore geology. The degree of diagenesis can be attributed to two types of alteration: regional burial diagenesis in each locality was accelerated by additional heat supply from a zone of high paleotemperature in the Sea of Japan. This zone is related to the opening of the Sea of Japan in the Eocene.

AMS Radiocarbon Dating and Pollen Analysis of Core Ks0412-3 from Kashibaru Marsh in Northern Kyushu, Southwest Japan

We performed pollen analysis and accelerator mass spectrometry (AMS) radiocarbon dating on cored sediments (KS0412-3) from Kashibaru Marsh, located in the western part of the Sefuri Mountains in northern Kyushu, southwestern Japan, to investigate environmental change around the marsh. Sediment accumulation began in this marsh around cal AD 1200 and continued with an estimated average sedimentation rate of about 4 mm/yr. Human rice cultivation at this location began around cal AD 1300 and was abandoned due to the deposition of a thick sand layer at around cal AD 1400. Since this event, the area has been maintained as a “natural” marsh.