The dark-gray mudstone of the Araya Formation distributed in the Tochio area of Nagaoka City, Niigata Prefecture yields various calcareous nodules, such as cylindrical, lenticular, spheroidal and irregularshaped. Some of the cylindrical nodules contain glendonite as the nucleus, which is surrounded by a marly mantle and a rim forming a concentric structure. The carbon and oxygen isotope ratios of the nodules were measured and the genetic link between glendonite and calcareous nodules was studied. The nodules are essentially classified into two types: the glendonite-bearing type and the glendonite-free type. The authigenic mineral composition of the glendonite-bearing type is single-phase calcite, whereas the glendonite-free type is comprised of single-phase calcite and a calcite-siderite mixed phase. There is also a difference in the carbon and oxygen isotopic ratios between the two types. The δ¹³C values increase in the following order: calcite of glendonite-bearing type, calcite of glendonite-free type, calcite of two-phase nodules, siderite of two-phase nodules. In contrast, the δ¹⁸O values of calcite decrease in the same order as above. The isotopic ratios and chemical composition of the nodules represent an almost continuous process of sequeling from sulphate reduction to methane fermentation, following the decomposition of burrowing animals.

Clastic sandy nodules are found on a submerged terrace south of Oki-shima Islet in Lake Biwa, southwest Japan. Vivianite and siderite-rhodochrosite crystals occupy interstitial spaces between the clastic sand grains in the nodules. There are three types of nodules recognised: (1) vivianite only, (2) siderite-rhodochrosite only and (3) coexisting vivianite and siderite-rhodochrosite. The vivianite contains little manganese, and its compositional variation is very small. Some parts of the siderite are enriched with manganese, showing compositions of rhodochrosite. The vivianite and siderite-rhodochrosite in the sediments might be formed during incipient diagenesis in a reduction environment below the oxidative environment of the lake bottom. These interstitial minerals play a role of depositing iron, manganese, phosphorus, carbon and related elements in the sediments.

The Yotsumatayama quartz diorite body exposed at Shimonita Town in Gunma Prefecture, consists of two varieties of rocks, namely, hornblende quartz diorite and two-mica granodiorite. Zircon U-Pb ages of these granitoids are measured.

U-Pb isotope data of zircon grains from hornblende quartz diorite yields an age of 112.7 ± 3.7 Ma, and that from the two-mica granodiorite yields an age of 113.1 ± 3.6 Ma. These values are nearly similar within their respective error limits. The geochronological data time indicates the Early Cretaceous period. The earlier reported K-Ar age of hornblende (105 ± 6 Ma and 110 ± 5 Ma) might represent a cooling age in the Yotsumatayama quartz diorite, whether the U-Pb age of zircon indicates the age of crystallization. U-Pb age of the hornblende quartz diorite indicates also the Early Cretaceous period. However, two-mica granodiorite also included older zircon grains yielding U-Pb age of the Late Jurassic period ~ Early Permian period. We consider these as the inherited zircon grains from possible sedimentary protolith. The difference in the rock facies and the U-Pb age spectrum of the Yotsumatayama quartz diorite possibly support this view.