Niigata Plain Research Articles

Holocene paleoenvironmental changes inferred from the diatom records of the Echigo Plain, central Japan

The Echigo Plain (=Niigata Plain) located along the Japan Sea (East Sea) is one of the largest coastal plains in the Japanese Islands. The post-Würm glacial sediments are well developed, reaching a thickness over 140 m in the central part of the Echigo Plain. Diatom floral changes of the Holocene borehole cores from the Tsukigata and Shirone areas of the Echigo Plain in Niigata were examined to infer the paleoenvironmental changes in this part of East Asia. Over 290 diatom taxa were identified in the Tsukigata TG-1 and Shirone S9-4 borehole cores, and were divided into nine and 13 provisional diatom units, respectively. Most of the horizons analyzed were characterized by fresh water species, and their environments were inferred as marshes, bogs and small ponds. The major brackish water horizon dated as 10,000–6800 yr BP in the Shirone borehole core was correlated with the Jomon Transgression, which was the Holocene maximum transgression in the Japanese Islands. Several minor sea-level changes in the Echigo Plain were also recognized for the past 6800 yr, which were caused not only by global eustatic changes, but also by the relative subsidence of the basin on account of its location in a tectonically active zone.

Seasonal change of persistent organic pollutant concentrations in air at Niigata area, Japan

The concentrations of persistent organic pollutants (POPs), such as HCB, α-, β-, γ- and δ-HCH, trans- and cis-chlordane ( t-CHL, c-CHL), DDE, DDD and DDT, in ambient air have been measured at five sampling points in Niigata area, Japan (Niigata, Maki, Tsubame, Jouzo and Yahiko) during the period from September 1999 to November 2001. HCB, α-HCH, t-CHL and c-CHL showed higher concentrations than the other chemicals in all locations. All the POPs except t-CHL and c-CHL collected at urban sites of the Niigata Plain was almost the same in their concentration levels. Higher concentrations of t-CHL and c-CHL in residential areas should be attributed to the past usage of the chemical as a termiticide. At Yahiko (remote site), most of the POPs showed lower concentrations than those measured at the other sampling sites, although α-HCH and γ-HCH were comparable with the concentrations found at the other sampling sites. All POPs except α-HCH and γ-HCH tend to decrease 41–80% in their concentrations from 2000 to 2001. The lower POPs concentrations in winter and the higher POPs concentrations in summer at every sampling point can be partly explained by temperature differences. Applying the equation of the logarithm of the POP partial pressure in air versus reciprocal temperature (lnPa= m/ T+ b) to our data, linear relations were observed. HCB gave a poor linearity and the smallest slope, while β-HCH, t-CHL and c-CHL gave good linearities and large slopes in the equation. The results suggest that HCB level is influenced by not only the emission from terrestrial sources but the global-scale background pollution. A peculiar observation is that β-HCH concentration measured in our study showed large temperature dependence, indicating there could be a source of contamination in the surrounding areas.

Tilting movement of Kakuda-Yahiko Mountains, on the west of Niigata Plain, central Japan—appeared in height of Pleistocene terrace and records of leveling—

Tilting movement of Kakuda-Yahiko Mountains, on the west of Niigata Plain, central Japan—appeared in height of Pleistocene terrace and records of leveling—

Identification of active faults in the eastern margin area of Niigata plain, central Japan.

Identification of active faults in the eastern margin area of Niigata plain, central Japan.

基礎試錐のビトリナイト反射率から算定される最高古地温勾配の検討

The following four conclusions were deduced particularly from the examination of vitrinite reflectance (Ro) data from MITI exploratory test wells conducted by the Ministry of International Trade and Industry together with some other data from Japanese oil companies.(1) The regression equation between Ro and maximum burial temperature formulated by disregarding the effective heating time (Barker and Pawlewicz, 1994) is not applicable to the estimation of the temperature gradient of the Tertiary and Quaternary Systems in Japan, because there is significance change of Ro with time within 20-30m.y.(2) Correlation between Ro and maximum paleotemperature was estimated by isomerization of sterane and hopane biomarkers in the MITI Hamayuchi well core (Sakata and Akiyama, 1989). Maximum paleotemperature gradients of 23 wells in Japan were calculated based on the above correlation data. All of the calculated gradient values are much higher than the measured present temperature gradient values (Table 1). This result suggests that the poor correlation is due to too few Ro measurements in the MITI Hamayuchi core, while the estimation method of maximum paleotemperature using isomerization of sterane and hopane biomarkers is reliable.(3) The maximum paleotemperatures estimated from the nomogram of the MITI Shimoigarashi well of Niigata Prefecture (Sekiguchi and Hirai, 1980) show good agreement with the measured present temperature gradient in many wells drilled in the Niigata plain. The area around Mt. Yoneyama in the central part of Niigata Prefecture, which shows marked igneous activity in the Pliocene has a high paleotemperature gradient suggesting much higher heat flow than at the present.(4) The kink in a two-segment vitrinite reflectance profile in MITI Takadaheiya, MITI Kubiki and many other wells in Niigata Oil Field is restricted to the Middle Miocene Nambayama Formation, suggesting perturbation in the thermal gradient caused by heat transfer processes associated with abnormal high-pressures as was discussed by Law et al. (1989) and Hunt (1995).

424. 新潟平野における海面上昇の影響予測 : 海没する地域について

424. 新潟平野における海面上昇の影響予測 : 海没する地域について

Changes in the concentrations of chlornitrofen (CNP) and CNP-amino in river and faucet water in Niigata, Japan

It has been reported that the standardized mortality ratios (SMRs) of biliary tract cancer (BTC) (female gallbladder cancer (GBC) in particular) are high in the Niigata plain and low in other parts of Niigata Prefecture. Based on epidemiological studies, the presence of environmental water pollution by agricultural chemicals is likely to be associated with the occurrence of GBC, and one of the most suspected of these is a diphenylether herbicide, chlornitrofen (CNP). The purpose of the present study was to investigate whether or not there was a difference in concentrations of CNP and its reduction product (CNP-amino) in river and faucet water between Niigata and Joetsu Cities, which are located in the Niigata plain and another part of Niigata, respectively. By employing a new method for CNP and CNP-amino extraction, the detection of CNP and CNP-amino was undertaken by using a gas-chromatograph with an electron-capture detector. The maximum levels of CNP concentrations were 871 and 554 ng/l in river and faucet water, respectively on May 6, 1992 in Niigata City. The concentration of CNP in faucet water was well correlated with that in river water. In Joetsu City, the maximum concentration in river water was 183 ng/l on May 6 and had decreased rapidly towards the background level on July 29, 1992. As to the concentrations of CNP in faucet water in Joetsu City, they fluctuated between the levels of 2 and 9 ng/l. In the case of CNP-amino concentrations in faucet water, a clear-cut difference was evident between the two cities; 384 ng/l in Niigata and under the quantity limit in Joetsu.(ABSTRACT TRUNCATED AT 250 WORDS)

Quaternary stratigraphy and tectonic movement of the northeastern marginal area of Niigata Plain, Japan

Quaternary stratigraphy and tectonic movement of the northeastern marginal area of Niigata Plain, Japan

新潟平野北東縁の活しゅう曲地域にみられる隆起量と侵食様式・削剥強度の関係

This paper discusses the relationships between relief energy and types and intensity of erosional processes in an active folding zone in the northeastern margin of the Niigata plain. It is recognized that there is a positive correlation among relief energy, magnitude of erosional processes and intensity of denudation in areas that have relief energy less than 150 m and are underlain by the upper Miocene mudstones. This relationship suggests that the intense areal denudation in the higher relief zone provides an upper limit of relief energy in the areas of less resistant rocks.In the study area, where denudation is not yet in the equilibrium with uplifting, the relief energy will reflect the amount of uplift. Large amount of uplift is expected to produce large relief energy, and mountainous landscape characterized by large-scale landslide and lack of crest-flats in the southern part of the surveyed area. In contrast with the southern part, in the northern part of the surveyed area, where the amount of uplift is smaller than the southern part, the hilly landscape characterized by the broad crest-flats and numerous gullies are formed in the low relief area.

完新世における新潟平野北東部の地形発達史

完新世における新潟平野北東部の地形発達史

秋田および新潟油田地域に発達する西黒沢期玄武岩 基礎試錐「仁賀保」・「新潟平野」で認められた玄武岩のもつ意義

Thick basaltic piles of Nishikurosawa stage of early to middle Miocene age are widely distributed from Akita through Yamagata to Niigata oil fields along the Japan Sea side. Recently, MITI Nikaho Well and MITI Niigata-heiya Well were drilled at the foot of Mt. Chohkai in the southern part of Akita, and at the central part of the Niigata plain, respectively. Both wells encountered a thick basaltic layer ranging up to 1, 400 meters of the Nishikurosawa stage. We studied micropaleontological features and petrochemical characters about the basaltic layers from the wells and their surrounding areas.The basaltic piles, described collectively as the Nishikurosawa stage in Akita and Niigata areas, are divided into two groups erupted in substages of NN 4 Zone (eary Nishikurosawa age) and NN 5 Zone (middle Nishikurosawa age) of Martini's zonation. The basalt of the midde Nishikurosawa age consists of relatively undifferentiated type in FeO*/MgO ratio with less than 1.4% of TiO2 content. On the other side, the basalt in early Nishikurosawa age is slightly differentiated and rich in TiO2 content compared with the above.In the present paper, we discuss the volcanostratigraphy of the Nishikurosawa stage in Akita and Niigata oil fields.

Active Structures in the Northeast Marginal Area of Niigata Plain, Central Japan

In the northeast margin of the Niigata Plain, many active structures are distributed. Author investigated them to clarify the features, especially their activities in the late Quaternary. The results are summarized as follows.1. The Murakami Hills and the Kushigata Mountains which are situated eastern margin of the Niigata Plain have folded and uplifted. But the rate of uplift of them are not equal. The average rate of uplift in the Murakami Hills is 0.1-0.2mm/yr, and that of the Kushigata Mountains, south of the Murakami Hills is 1-2mm/yr.2. At the western foot of the Kushigata Mountains, active reverse faultings have occured with a sense discordant to the uplifting of the Mountains. The vertical slip rate of them are about 0.3-0.5mm/yr.Around the Murakami Hills, there is no active faultings with a such sense.3. The summit level of Mountains and hills are accordant to the rate of uplift.4. In the eastern margin of the Niigata Plain, the active faults have acted with left-lateral sense. This sense is not according to the regional stress field.These facts represent the regional differences of crustal movement along the Shibata-Koide tectonic line which have played the important role for the reduction of Niigata sedimentary basin. And, it is suggested that active faulting in the eastern margin of the Niigata Plain has occured under the secondary stress field.

The Quaternary System of the Kamo Hills in the Eastern Marginal Area of the Niigata Plain

The Quaternary System of the Kamo Hills in the Eastern Marginal Area of the Niigata Plain

新潟平野の形成史

新潟平野の形成史

新潟平野の上部更新統・完新統 とくに沈降現象との関係について

新潟平野の上部更新統・完新統 とくに沈降現象との関係について

新潟平野東縁の活断層と山地の隆起

In the eastern marginal area of the Niigata Plain, the Kaj igawa Fault, the Tsukioka Fault and the Muramatsu Fault are distributed. Each fault has a sense discordant with the uplift of the Tide and Echigo Mountains. In order to examine the tectonic features of the active faulting and mountain building, (1) distribution and deformation of river terrace surfaces in the eastern margin of the Niigata Plain, and (2) gradients of river terrace surfaces distributed along the Kaji River and the Agano River, were investigated. The results are summerized as follows. The western part of the Tide and Echigo Mts. has been tilted and uplifted since early Pleistocene, and the middle part has been uniformly uplifted. A large amount of gravel derived frcm the mountains were deposited, forming the ST surface (alluvial fan surface), at the western foot of the mountains. Since the formative period of the ST surface, active reverse faultings have occurred with westerly upthrown sense and left lateral slip. They are presumably the rej uvenations of pre-existing normal fault beneath the Niigata Plain, under compressional field.

Observation of 1- to 5-second microtremors and their application to earthquake engineering. Part II. Evaluation of site effect upon seismic wave amplification due to extremely deep soil deposits

abstractThe usefulness of long-period microtremor observation for earthquake engineering problems at extremely deep soil deposit site was examined in this study. Microtremor observations were made in the Niigata Plain, Japan, and in Los Angeles, California, where depths to the basement rock are several kilometers. These two locations were selected because strong-motion records obtained during the Niigata earthquake of 1964 and the San Fernando earthquake of 1971 contain large long-period amplitudes. Understanding why these predominate long-period motions were recorded is important for the evaluation of seismic input motions for large-scale structures.Long-period microtremor observations were carried out in both areas in order to evaluate the characteristics of deep soil. Observations were performed simultaneously at a number of stations to distinguish the nature of deep soil deposit. The result of Fourier analysis showed that amplitude of microtremors in long-period range increases systematically from the point of basement rock outcrop to deep deposit site, with the increase corresponding to the depth-to-basement rock. This relationship coincides with that observed in the strong-motion earthquake records. These analyses indicated that simultaneous observation of long-period microtremors at a number of stations can provide insight to the characteristic of deep soil amplification and, therefore, permit estimation of seismic input motions for large-scale structures.

Estimation of organic maturity in Niigata Plain

Estimation of organic maturity in Niigata Plain

Quaternary stratigraphy of Sasagami Hills, to the east of Niigata Plain, Japan

Quaternary stratigraphy of Sasagami Hills, to the east of Niigata Plain, Japan

Gravity exploration in the eastern margin of the Niigata Plain

Gravity exploration in the eastern margin of the Niigata Plain