2019 Volume 84 Issue 2 Pages 184-196
This annual excursion has been carried out in every autumn since 2008, visiting the southern Kanto gas field （“Minami-Kanto gas field”）, the largest production field of natural gas dissolved in water in Japan, located in the Boso Peninsula. In the excursion, we have visited the natural gas seepage, the production plant of natural gas and iodine, and outcrops of the Pleistocene Kazusa Group which produces natural gas.
For the first time in the excursion, we have visited the recently very famous outcrop named “Chiba section” along the Yoro River. In this location, we have observed the stratum of the Kokumoto Formation recording the just point of the geomagnetic boundary of Matuyama-Brunhes chrons about 0.77 Ma. It is recently proposed as the Global boundary Stratotype Section and Point （GSSP） of the base of the middle Pleistocene. Next, we have observed the Umegase and Otadai Formations along the Yoro River, which are mainly composed of the turbidite succession and forms the major part of the reservoir rocks in the gas ?eld. After lunch, we have visited the small memorial museum “Otaki-machi natural gas museum” showing the natural gas development in Otaki Town. Then we have observed the natural gas bubbling actively occurring at the surface of the river. After that, we have visited the Nanaido plant of the Kanto Natural Gas Development Co., Ltd. （KNG）, and learned the production system of the natural gas dissolved in water. Finally, we have visited a small outcrop along the road, and observed the shallow marine sediments of the Kasamori Formation, the uppermost part of the Kazusa Group.
