Two geologic processes in the northernmost area of the Kashiwazaki-Choshi Line were extracted from thick and deformed Plio-Pleistocene strata. 1) The eastward-dipping Ukawa submarine slope contributed to the long-distance transportation of the collapse debris from the Paleo-Yoneyama volcanic island (2.4-2.3 Ma) to accumulate the Hachikokusan Formation at the slope foot. 2) A horizonal compressive stress field of WNW-ESE trend formed the Sabaishi quasi-ductile shear zone (of N10°W strike, ca. 5 km wide) in the middle to lower Sabaishi River area.

Large numbers of Gastrochaenolites were found from the ravinement surface of the Lower Pleistocene Bushi Formation, western Kanto Plain, central Japan. These are classified into four types based on their morphology: Types 1 and type 2 are Gastrochaenolites ornatus which have different sizes, and Types 3 and type 4 are Gastrochaenolites isp. which have egg shaped cross section and have different sizes. Fossil of Barnea (Umitakea) japonica, the producer, occurred from types 1 and type 4. Fossil of Petricola aequistriata, the producer, occurred from type 3. The producers of type 3 and type 4 bored only downward, while producers of type 1 and type 2 used two methods: downward boring and rotational boring. The formation of the substrate containing these Gastrochaenolites and the boring into the substrate were events during the transgression stage of the glacio-eustasy of approximately 40,000-year cycle of the Early Pleistocene. The substrate is judged to be a firmground because of borings and bioglyph formed in the substrate. The upper parts of most of Gastrochaenolites were lost. This is related to shoreface erosion during the formation of the ravinement surface after boring into the substrate by the producers.

Late Early to middle Pleistocene gravelly fan-delta deposits of the Ogasa Group crop out widely in the Iwatahara Plateau, Enden Hills, Kasui Hills, Ogasa Hills, and Minamiyama Hills in the western part of Shizuoka Prefecture, central Japan. The Ogasa Group divided into the Soga, Osuga, Kasui and Fukuroi Formations in ascending order. On the basis of microfossils, volcanic ash layers and paleomagnetic polarity data, depositional ages of these formations are estimated to be 1.78-1.19 Ma (Soga Formation), 1.19-0.91 Ma (Osuga Formation), 0.91-0.77 Ma (Kasui Formation), and after 0.77 Ma (Fukuroi Formation). The depositional processes and paleogeographical changes of the Ogasa Group can be divided into four stages as follows. Stage A: during the depositional stage of the Soga Formation, sand and mud were deposited on the seafloor from the shore face to the continental slope, and at the late of this depositional stage, the northwestward seafloor channel was buried by coarse-grained sediments from the Tenryu River. Stage B: during the depositional stage of the Osuga Formation, the formation of a large fan-delta by the Oi River from the northeast, which successively advanced to the southwest, expanding the fan and extending offshore. Therefore, an inner bay was formed on its northwestern side, and sand and gravel from the Tenryu River were deposited. Stage C: during the depositional stage of the Kasui Formation, a lake was formed by sandbars formed offshore duo to the transgression. Stage D: during the subsequent deposition of the Fukuroi Formation, the fan formed by the Tenryu and Oi Rivers was thought to have expanded to the south.

We carried out geological and radiolarian studies in the Tateishi Formation of the Kumage Group in the South Shimanto Belt, distributed in and around the Hamatsuwaki district of the Tanegashima Island. The Tateishi Formation in the study area consists mainly of black mudstone and sandstone rich alternating beds of sandstone and mudstone with minor amount of varicolored mudstone. As a result of the radiolarian study, Late Eocene to Early Oligocene and Late Eocene radiolarian fossils were obtained from a sample of black mudstone and two samples of varicolored mudstones, respectively. Therefore, it is concluded that the depositional age of the Tateishi Formation is Late Eocene to Early Oligocene.