Northwestern Kyushu Research Articles

Ecology of the Razor ClamSolen gordonisand Fishery Impact on the Population In Sasebo Bay, Kyushu, Japan

ABSTRACT In Sasebo Bay, northwestern Kyushu, Japan, the population of the razor clam Solen gordonis inhabits a coarse sandy substratum at 5- to 20-m water depths. A bundle of long metal rods with cone-shaped tips is used to vertically pierce and harvest clams from fishing boats. Knowledge of the ecological traits of this species and the fishery impact on the population is crucial for sustainable management. In April 2014 to March 2015, quadrat sampling by divers, experimental fishing surveys, and retrieval of clams detached from the fishing gear were conducted monthly. The grand mean individual density at the fishing ground was 555.7 inds/m3. New recruitment occurred in mid-November 2014, and the population excluding the recruits was divided into four cohorts by age according to shell-length-frequency distribution. Individual growth was described based on von Bertalanffy growth function, with L ∞, K, and t0 being 95.7 mm, 0.548/y, and -0.109 y, respectively. The estimated mean shell lengths at the 1+, 2+,...

有明海域下の三池炭田古第三系の地質と北西九州諸炭田の対比

The litho-biostratigraphy of Paleogene coalfields in northwestern Kyushu, Japan is reviewed on the basis of data obtained from the Miike Coalfield below the Ariake Sea. The Miike Coalfield extends over a wide area below the Ariake Sea as far as the west coast. The Paleogene stratigraphy of the coalfield is currently defined as the Ginsui Formation and the Ohmuta and Manda Groups in ascending order. The Manda Group consists of the Kattachi and Yotsuyama Formations in ascending order. The Kattachi Formation contains large quantities of glauconite in the basal part, the base of which has been defined as the base of the marine Manda Group. However, the Kattachi Formation contains coal seams and varies laterally, with glauconite content decreasing westerly. No significant facies variation with the underlying Ohmuta Group can be seen. The Kattachi Formation is, therefore, re-interpreted as the uppermost zone of the underlying coal-bearing Ohmuta Group. Glauconite sandstone of the basal part of the Yotsuyama Formation overlies underlying strata with a clear boundary throughout the coalfield. No significant facies variation exists in the Ohmuta Group. As a result, the Paleogene stratigraphy of the Miike Coalfield is revised into the Ginsui, Miike and Yotsuyama Formations in ascending order. The marine Yotsuyama Formation reaching ca. 800 m in thickness below the Ariake Sea is divided into four lithostratigraphic members: Ia (glauconite sandstone), Ib (shale), IIa (glauconite sandstone), and IIb (shale) Members in ascending order. The Yotsuyama Formation spans the late Middle Eocene (Subzone CP14a of Okada and Bukry, 1980) to the late Late Eocene (Subzone CP15b) age. Marine sequence, biostratigraphically correlative with Ia to IIb Members, is distributed in the Takashima and Amakusa Coalfields, while marine strata correlative with IIb Member are distributed in the Sakito-Mastushima and Isahaya Coalfields. These facts indicate that marine transgression occurred from the south and that a marine environment prevailed in northwestern Kyushu in the late Middle to late Late Eocene and peaked during the Yotsuyama Formation deposition.

Degenerative changes in the appendicular joints of ancient human populations from the Japan Islands

Degenerative changes in six major limb joints were investigated to compare their prevalence among five ancient skeletal populations from the Japan Islands. The populations assessed in this study consisted of the farmers in the northern Kyushu/Yamaguchi area and the foragers from the northwestern Kyushu area from the Yayoi period (5th century BC to 3rd century AD); the Okhotsk (5th to 12th centuries AD) foragers from Hokkaido and Sakhalin; the common people from medieval Kamakura (12th to 14th centuries AD) in Kanto, central Japan; and the early-modern farmers (17th to 19th centuries AD) from Kumejima, in the southernmost island chain (Ryukyu Islands). Crude prevalence comparisons showed that the shoulder and hip joints were principally affected in early-modern Kumejima and medieval Kamakura, which contrasted with the high prevalence of elbow and knee joint changes in the Okhotsk people. The heavy dependence on marine mammals and fish for dietary protein intake probably required flexion and extension movements of the most severely degenerated joints in the Okhotsk people. The northern Kyushu/Yamaguchi and northwestern Kyushu Yayoi peoples were more affected by degeneration in the wrist joints than others, possibly due to their use of innovative tools such as stone or shell knives and harpoons. A multivariate logistic regression analysis, adjusted for age, region, and sex as the predictor variables for degenerative changes in joints, was applied to only the two samples from Kumejima and Kamakura (including previously reported spine data) because of their better preservation. This revealed differences in the prevalence of changes in some joints; for example, age-related changes were recognized. The Kumejima people were more commonly affected by hip and knee joint changes, whereas the Kamakura people were more commonly affected by changes to apophyseal joints. Because a stable isotope analysis indicated that the trophic levels of the two populations were almost the same, the pattern of degenerative changes would have reflected differences in their specific workloads, such as wet rice cultivation using a peculiar hoe by the Kumejima people. This study, combining multivariate logistic regression analysis of degenerative joint changes and stable isotope analyses, uses large skeletal populations to add clarity to the actual rigors of ancient life.

Decrease in Baiu Precipitation and Heavy Rainfall Days in Late June of the 2000s in Northwestern Kyushu, Western Japan

Decrease in Baiu Precipitation and Heavy Rainfall Days in Late June of the 2000s in Northwestern Kyushu, Western Japan

Progressive Interaction between Dry and Wet Mantle during High-temperature Diapiric Upwelling: Constraints from Cenozoic Kita-Matsuura Intraplate Basalt Province, Northwestern Kyushu, Japan

Intra-plate Cenozoic volcanism in Kita-Matsuura, northwestern Kyushu, Japan, shows systematic spatio-temporal changes in geochemistry that can be explained by partial melting followed by melt segregation in a region of upwelling mantle.We have examined the thermal and melting history of the upwelling mantle by quantitatively estimating melt water contents and melting conditions. The water content of a spectrum of primary melts is estimated to range from 0·5 to 1·5 wt % based on a combination of a plagioclaseliquid and olivine-saturated liquid geohygrometers and MELTS calculations. The estimated melt segregation temperature ranges from 1330 to 15008C, at pressures from 1·7 to 2·8 GPa under hydrous conditions. Melting temperature and pressure decreased with time, whereas the water content of the primary melts increased. Corresponding temporal decreases in high field strength element (HFSE) abundances and HFSE/large ion lithophile element (LILE) ratios require progressive melt extraction and aggregation from a melting mantle with a continuous and gradually increasing input of H2O-rich fluid or melt into the melting system. The estimated isotope composition of influxed fluid lies on a mixing line between the sediment and altered oceanic crust of the Philippine Sea Plate, with strong affinity to the sediment composition. Based on the temporal variation of the magmas and the melting model, we propose small-scale upwelling (c. 70 km in diameter) of a dry mantle peridotite that interacts progressively with the overlying wet mantle wedge. The wet mantle wedge was previously hydrated by fluids from sediments from the subducted Philippine Sea Plate, whereas the deep and dry mantle could have been derived from the mantle beneath the subducted Pacific Plate through a slab window.

長崎市におけるアカイエカとチカイエカの交雑

The occurrence of natural hybridization between the mosquitoes Culex pipiens pallens and Cx. pipiens f. molestus in Northwestern Kyushu, Japan, was confirmed based on morphology and molecular methods. In order to assess the morphological difference in male genitalia of the two forms on the basis of the dorsal/ventral (D/V) ratio, mosquito egg rafts were collected in Nagasaki City using oviposition traps. The morphological parameters of male genitalia from Cx. pipiens f. molestus were discontinuous with those from Cx. pipiens pallens, while intermediate individuals could be found in a single egg raft. These individuals were identified as hybrids using a polymerase chain reaction (PCR)-based assay. The fitness of the family descended from hybrids was lower than that from typical pallens and molestus families, as measured by egg raft size and egg hatchability. The reduced fitness of the hybrids suggested that the genetic introgression between the two forms could be restricted.

Effect of wind stress on the catch of Japanese anchovy Engraulis japonicus off northwestern Kyushu, Japan

Effect of wind stress on the annual catch of Japanese anchovy Engraulis japonicus off northwestern Kyushu for the period between 1963 and 2009 was investigated. Regime shift analysis detected several step changes in catch and environmental variables. Since the mid-1980s, the anchovy catch in the coastal fishery zones has declined, while the catch in the offshore zone has increased. The decline of catch in the coastal zones showed a significant correlation with the long-term variations in prevailing north-northeastward wind stress over the Goto-Nada Sea during spring spawning season. The results indicated that weakened north-northeastward winds caused the recent low recruitment of anchovy through low levels of wind-induced eggs and larval transport from the offshore spawning ground to the coastal nursery areas, resulting in the potential shift of nursery area to the northwestern offshore region. Thus, as well as the growth-favorable ambient temperature, transport process would play a key role on long-term fluctuations in anchovy abundance in these coastal seas.

Pleistocene intraplate magmatism in the Goto Islands, SW Japan: Implications for mantle source evolution and regional geodynamics

We present geochemical, Sr, Nd and Pb isotopic data for the youngest back-arc tholeiitic and alkali basalts in the southern tip of Goto Islands along the Taiwan–Shinji Folded Belt in northwestern Kyushu, SW Japan. The data are compared with those more-or-less contemporaneous back-arc basalts elsewhere in the region and interpreted accordingly. Our sampling loci included Ukujima (ca. 1Ma), Ojikajima and Kamigoto (from 0.6Ma to 0.14) and six locations in the Fukue island area (ages between 0.7 and 0.02Ma). The Ukujima tholeiites show the highest SiO2 (ca. 52.5wt%), FeO* (13wt%), TiO2 (>2.5wt%) and lowest MgO (4wt%) and CaO (7.5wt%) contents whereas the alkali Kamigoto and most Ojikajima magmas show lower SiO2 (48wt%) and higher MgO (8.5wt%) and CaO (11wt%). The Ukujima tholeiites also show the least radiogenic lead with closely similar 87Sr/86Sr and 143Nd/144Nd ratios ranging between 0.7038 and 0.7042, and between 0.51280 and 0.51285, respectively. Mantle-normalized incompatible element distributions are of alkali basalt-type exhibiting, along with the major element, significant spatio-temporal variations. Regardless of such differences the younger basalts, as compared with older 6–15Ma eruptive products in Hirado (and those in Kita-Matsuura), northeastward along the belt, are the least radiogenic. The 15Ma volcanics were erupted during episodes of lithospheric extension and show effects of crustal contamination. The 6–9Ma tholeiites and alkali basalts appeared as regional extension gave way to compression and show hybrids of depleted mid-ocean ridge basalt-like (N-MORB) mantle and heterogeneous EM2 (enriched mantle type 2) (Uto et al., 2004). As extension diminished, deeper asthenospheric sources were tapped producing a range of enriched mantle type 1 (EM1)-contaminated N-MORB-like magmas in the younger (<1Ma) Ukujima, Ojikajima-Kamigoto and Fukue volcanoes. This composition is believed to present throughout East and Southeast Asian asthenosphere.

Age, growth and habitat use of the topmouth gudgeon,Pseudorasbora parvain irrigation ditches on northwestern Kyushu Island, Japan

Summary In Japan, Pseudorasbora parva has not been negatively affected by artificial changes in its habitat. Ecological traits of the species may explain this easy adaptation to artificial habitats. An ecological investigation of P. parva inhabiting irrigation ditches was conducted monthly for approximately two years on northwestern Kyushu Island, Japan. Measurements of 1927 individuals revealed two size classes, maturation age (1 year), and lifespan (1–2 years). Results of this study and previous studies show that the species exhibits life history plasticity. In addition, habitat use of ditches indicates that abundances correlated positively with water temperature and negatively with current velocity in the crop-growing season, and positively with water depth and negatively with current velocity in the fallow season. Structural factors such as ditch revetment conditions and aquatic macrophyte cover were unimportant for this species. The study shows that the gudgeon adapts to artificial ditches easily and successfully because of both life history plasticity and wide-scale use of the habitat.

Examination of out-of-hospital cardiac arrest patients with the Utstein style in Saga prefecture, Japan

Saga Prefecture is a small prefecture with an area of 2,439 km2 (place-of-residence 1,339 km2), a population of 849,709, and is located in northwestern Kyushu in the western part of Japan. Saga University has the only medical department in Saga Prefecture, Japan, and it is in charge of both the online and offline medical control of Saga. This report examined the present status of OHCA in Saga, which should be improved, and it aimed at exploring policies that can contribute to the improvement in a ROSC rate.

Discovery of Halicyclops continentalis (Cyclopidae, Halicyclopinae) from Estuaries and Salt Marshes on the West Coast of South Korea

A cyclopoid species from several salt marshes and estuaries on the west coast of South Korea were identified as Halicyclops continentalis Ueda and Nagai, 2009, recently described from Ariake Bay at northwestern Kyushu, Japan. Detailed examination on the Korean specimens justifies Ueda and Nagai's proposition that the H. sinensis sensu Tai and Chen, 1979 formerly known from the Chinese coast of the Yellow Sea should be identical to H. continentalis. Furthermore, this report reinforces their assumption on the geographical distribution of H. continentalis, that is, the Ariake Bay population is a continental relict of the East Asia continent. Herein, a redescription of the species is provided on the basis of the Korean specimens, with a comment on the morphological comparison among three populations around the Yellow Sea.

Identification of sea bass species (Pisces, Percichthyidae) by PCR·RFLP analysis and differences in habitat use of the larvae and juveniles in the surf zones of sandy beaches in northwestern Kyushu Island

Identification of sea bass species (Pisces, Percichthyidae) by PCR·RFLP analysis and differences in habitat use of the larvae and juveniles in the surf zones of sandy beaches in northwestern Kyushu Island

Seasonal Variation of Sulfate Scavenging Ratio Around the Northwestern Kyushu Region

Seasonal Variation of Sulfate Scavenging Ratio Around the Northwestern Kyushu Region

3-B10 新生代ユーラシア大陸東縁部背弧域の上部マントル : 北西九州および韓国の玄武岩からの岩石学的制約(マグマの発生と移動2,口頭発表)

3-B10 新生代ユーラシア大陸東縁部背弧域の上部マントル : 北西九州および韓国の玄武岩からの岩石学的制約(マグマの発生と移動2,口頭発表)

Growth Inhibiting Factors for Edible Brown Alga, Sargassum fusiforme, along Coast of Nagasaki Prefecture, Northwestern Kyushu, Japan

Growth Inhibiting Factors for Edible Brown Alga, Sargassum fusiforme, along Coast of Nagasaki Prefecture, Northwestern Kyushu, Japan

新生代北部九州のテクトニクス史と火山活動史―背弧火山岩区研究における重要性―

Cenozoic western Pacific is characterized by numerous subduction volcanisms, opening of back arc basins, and within-plate volcanisms in backarc regions. These phenomena suggest that thermal disturbances induced by mantle flow caused mantle melting and eruption of magmas in back-arc regions, although diverse modes have been proposed for the mantle condition. To constrain the origin of the magmatism, it is important to clarify both the geodynamics and physicochemical conditions of the mantle in the arc-back arc system. Cenozoic back-arc volcanisms and tectonics in northern Kyushu are key objectives. This paper focuses on the dynamics of the upper mantle in relation to the tectonics of the area. Cenozoic volcanism of the northern Kyushu district is characterized by eruptions of a number of alkaline volcanisms. This volcanic province extends some one hundred kilometers along the Japan Sea coast and includes the Chugoku area. Although the volcanism has been regarded as a large single volcanic province, the northern Kyushu activity is distinguishable from that in Chugoku by geochemical characteristics. Cenozoic basalt volcanism in northern Kyushu occurred mainly in the Tertiary sedimentary basins, which is common to Cenozoic volcanism in the Japan Sea Basin. The sedimentary basin deposits underwent intensive folding with extensive inversion tectonics occurring mainly around the end of Miocene. Studies on dykes and thrust faults also indicate a compressional stress field dominated in northwestern Kyushu during the late Miocene. Initiation of the basaltic activity took place in Kita-Matsuura area and expanded outwards. Basaltic rocks from the Kita-Matsuura are mostly hypersthene-normative and sub-alkalic, whereas rocks from peripheries, such as North Kyushu and Goto Islands, are predominantly less normative-hypersthene and thus are alkalic. From spatial and temporal variations and genetic conditions of basalt magmas, a most plausible source was a small-scale mantle diapir with a potential temperature of more than 1400°C. Combined with an inversion tectonic background after the Japan Sea opening event, the origin of the back-arc magmatism was unrelated to large-scale mantle upwelling. Fluid-fluxed melting of the mantle is not supported by the chemistry. My proposal is active upwelling of a small-scale mantle diapir, probably from the depth of stagnant slab or mantle transition zone.

Physical factors influencing immature-fish communities in the surf zones of sandy beaches in northwestern Kyushu Island, Japan

We aim to understand the relationships between physical conditions and characteristics of the immature-fish community in surf zones of sandy beaches. Therefore, we obtained fish samples between March 2007 and February 2008 and analyzed certain physical conditions in the surf zones of 21 sandy beaches on the coastline of the northwestern Kyushu Island, Japan. We collected a total of 83 species and 6458 immature individuals. In a BIO-ENV analysis, the highest correlation was observed between fish assemblage and S20 (i.e., the slope from the shoreline to the sites where the depth was 20 m) and current velocity (CV) values. Stepwise multiple linear regression analyses revealed that the number of species and individuals decrease with an increase in the S20 and CV values. These results show that species richness and the abundance of immature-fish increase under shelving and calm conditions. Thus, immature-fish assemblages are strongly influenced by the prevailing physical conditions. Moreover, in six of the 10 dominant species, a negative correlation was observed between CV and abundance. On the other hand, S20 was found to be the explanatory variable only in the case of the most dominant species, i.e., Gymnogobius breunigii. Furthermore, a positive correlation was observed between S1 (i.e., the slope from the shoreline to the sites where the depth was 1.0 m at the mean tidal level) and median particle size (i.e., MPS of the sediments) and the abundances of Sillago japonica and Favonigobius gymnauchen, respectively, and a negative correlation with salinity, in the case of Acanthogobius lactipes. We conclude that the characteristics of the fish community in surf zones on sandy beaches are determined by not only the shelving and calm conditions, which influence fish assemblages and abundances, but also the habitat diversity, which influences the diversity of fish species.

累進的減圧融解によるマグマ生成： 北西九州、北松浦玄武岩からの制約

累進的減圧融解によるマグマ生成： 北西九州、北松浦玄武岩からの制約

Progressive Melt Extraction from Upwelling Mantle Constrained by the Kita-Matsuura Basalts in NW Kyushu, SW Japan

Systematic petrological, geochemical, and chronological studies of Cenozoic intra-plate volcanism in southwesternJapan, in the KitaMatsuura area in northwestern Kyushu, reveal temporal and spatial changes in mantle melting processes on a time scale of 2 5 Myr and a horizontal scale of 35 km.The most extensive basaltic activity in the area occurred between 8 5 and 6 0 Ma. Four vertical sections through the volcanic sequence from the underlying basement to the top flows were studied to encompass the distribution of the KitaMatsuura basalt. In the central and western sections (Hirado, Senryu, and Ishimori) there is a temporal variation in the chemical composition of the basalts: volcanism initiated eruption of mildly alkaline basalts (lowto medium-SiO2 group) followed by major flows of sub-alkaline basalt (mediumto high-SiO2 group). The eastern section (Kunimi section) is characterized by mildly alkaline basalts (low-SiO2 group). Each SiO2 group has a distinctive phenocryst assemblage and major element composition. The Zr/Y, Nb/Th, and Nb/Y ratios of the Kita-Matsuura basalts are positively correlated, which cannot be explained by assimilation of crustal materials but instead is linked to melting processes in the mantle. The average segregation depth of the inferred parental magmas of the three groups decreases in the order of SiO2 enrichment, indicating a temporal decrease in melt segregation depth in the central and western sections.The correlation between Zr/Yand Nb/Y can be reproduced by a series of instantaneous melts resulting from decompressional critical melting of a primitive mantle source with 2% trapped melt. In each section, both Zr/Yand Nb/Y decrease upwards, which implies an increase in the degree of melting with time. The temporal and spatial variations in basalt chemistry are most plausibly accounted for by progressive melt extraction during mantle upwelling, which started in the garnet stability field ( 3 0 GPa) and ended in the spinel field ( 1 5 GPa). Upwelling was centred beneath the Hirado section, in the westernmost area in KitaMatsuura, with a diameter inferred to be greater than 70 km.

Calcareous nannofossil and planktic foraminiferal biostratigraphy of the Paleogene Iojima Group in the Takashima Coalfield, Nagasaki Prefecture, southwest Japan

The Paleogene Iojima Group is exposed in the Takashima coalfield of northwestern Kyushu, southwest Japan. The group is divided into four formations: the Okinoshima, Magome, Funazu, and Daimyoji formations (in ascending stratigraphic order). Among these strata, mudstone and muddy sandstone of the Okinoshima and Funazu formations contain a number of common age-diagnostic calcareous microfossils, nannofossils, and planktic foraminifers.Our biostratigraphic study of the Paleogene Iojima Group indicates that the Okinoshima Formation corresponds to calcareous nannofossil Zone CP14 and planktic foraminiferal Zones E10-E13; the Funazu Formation is assigned to Zones CP14-CP16. The Okinoshima and Funazu formations are assigned to the late middle Eocene and late middle Eocene to early Oligocene, respectively, suggesting that 1) the Okinoshiman molluscan Stage correlates with the middle Eocene, as proposed in previous studies; and 2) the Magome Formation, which includes coal-bearing strata, correlates with the Onga marine regression.