Shimokita Peninsula Research Articles

下北半島東部に分布する下部〜中部中新統の年代層序

下北半島東部に分布する下部〜中部中新統の年代層序

Late Jurassic radiolarians from mudstone near the U–Pb-dated sandstone ofthe North Kitakami Belt in the northeastern Shimokita Peninsula, Tohoku, Japan

Late Jurassic radiolarians from mudstone near the U–Pb-dated sandstone ofthe North Kitakami Belt in the northeastern Shimokita Peninsula, Tohoku, Japan

Eustatic, Climatic and Tectonic Controls on the Evolution of a Middle to Late Holocene Coastal Dune System in Shimokita, Northeast Japan

The Pacific coast of the Shimokita Peninsula, Northeast Japan, is occupied by one of the larger dune complexes in Japan. This coastal aeolian dune complex developed during the Holocene in a monsoon-influenced temperate climatic belt. The stratigraphic and sedimentological characteristics of outcrops, exposures and cores indicate that four generation of aeolian dunes are presented. These dunes developed during eustatic regression following the post-glacial sea-level highstand. Seaward shoreline movement, combined with strong winds from the Pacific Ocean, enhanced aeolian grain transport on the beach, resulting in the onset of dune growth and the consequent shrinkage of the coastal forest. Northeast Japan is located in a transitional zone affected largely by monsoonal circulation from Siberia and Southeast Asia. Thus, the regional climate is responsible for atmospheric changes on a hemispheric scale. Intensified monsoons contributed to flooding produced by rains and snow-melt. Steep increases in annual precipitation at 7200–6300, 4700–3600, 3050–2500, 1850–1100, and 550–200 calendar years before present (cal. yr. BP) increased the amount of surface erosion, causing a large volume of sediment discharge toward the coast. Shimokita has experienced frequent earthquakes and tsunamis, which have reduced dune landform relief by sediment displacement.

Change in slide direction of submarine landslides in the Pliocene‐Quaternary deposits near the Shimokita Peninsula, northeast Japan, using 3D seismic data

AbstractSubmarine landslides constitute a major mass transport process from shallow‐ to deep‐sea and may have catastrophic impacts on both offshore infrastructure and coastal areas. Previous studies on submarine landslides have focused on triggering mechanisms and precondition perspectives, targeting limited numbers of short‐term landslide events. Consequently, few studies have addressed long‐term changes in landslide characteristics, including volume, direction, and timing. The areas studied herein are located on the continental slope facing the Japan Trench off the Shimokita Peninsula, northeast Japan, where a number of large‐scale translational‐type submarine landslide and accompanying unique dike structures have been identified in Pliocene to Recent deposits via 3D seismic data analysis. Here we developed a procedure for recognizing landslide deposits in 3D seismic data from the survey area, then investigated the 3D deposit distributions in detail. Because translational landslides preserve original structures, they can be used to estimate landslide volume. Parallel dike swarm features, which are interpreted as dewatering paths formed soon after landslide events, enable estimation of slide direction in time‐slice images. Such analysis also allows differentiation of landslide deposits from background sediments and estimation of landslide volume. Landslides exceeding 50 km3 in volume have occurred numerous times in the past 6 my. Landslides directions are observed from southwest to northeast over this entire period, whereas slides trending northwest to southeast started at ~ 2 Ma. Although the landslide sizes vary greatly, the average landslide volumes are roughly constant throughout Pliocene and Quaternary time. Such shifts in long‐term trends suggest a change in tectonics in the landslide source region. These unique long‐term records (over 6 my) are enabled by the specific conditions in the study region, which include translational landslides, parallel dike swarms, and monotonous lithology.

An Alternative Approach to Background Radiation Monitoring Using Smartphone-coupled Personal Dosimeter POLISMART in Shimokita Peninsula, Japan

An Alternative Approach to Background Radiation Monitoring Using Smartphone-coupled Personal Dosimeter POLISMART in Shimokita Peninsula, Japan

Feeding habits of larval yellow goosefish Lophius litulon around the Shimokita Peninsula and in Funka Bay, Japan

Feeding habits of larval yellow goosefish <I>Lophius litulon</I> around the Shimokita Peninsula and in Funka Bay, Japan

Comparison of morphological traits of between two typesCommon Crossbills with different calls that were observed in thesame pine forest in Shimokita Peninsula, northern Japan

青森県下北半島において，2017/2018年の冬から春にかけて，2タイプの声をもつイスカが一つの林に同居していた．片方は通年生息し，繁殖もしている下北個体群のイスカ，もう片方は越冬に訪れた繁殖地不明のイスカである．在来集団については2006年以降標識調査を行っており，計測値を蓄積してきた．今回越冬集団と在来集団について計測値を比較したところ，翼長，尾長，ふしょ長は両者で重複が大きかったが，嘴峰長と体重は偏りがみられた．判別分析でも嘴峰長と体重が寄与しており，在来集団は相対的に嘴が短く体重が軽い，越冬集団は嘴が長く体重が重いという特徴があった．嘴峰長の違いはおそらく繁殖地で多く利用している餌資源の違いを反映しているだろう．越冬集団の重い体重は渡り前に体重を増加させていたためかもしれない．

A Study of Variation of the 11-yr Solar Cycle before the onset of the Spoerer Minimum based on Annually measured 14C Content in tree Rings

ABSTRACTProxy-based observations of solar activity in the past have revealed long-term variations, such as the Gleissberg cycle (~88 yr), de Vries cycle (~200 yr), and the Hallstatt cycle (~2000 yr). Such long-term variations of solar activity sometimes cause the disappearance of sunspots for several decades. Currently, solar activity is becoming weaker, and there is a possibility that another long-term sunspot minimum could occur. However, the detailed mechanism of the weakening in solar activity is unknown, and the prediction of solar activity is ambiguous. In this study, we investigate the transitions of solar cycle length before the onset of the Spoerer Minimum, the longest grand minimum in the past 2000 yr. We measured the 14C content in an asunaro tree (Thujopsis dolabrata) excavated at Shimokita Peninsula from 1368–1420 CE using the compact AMS system at Yamagata University. It is found that the solar cycle lengthened to be 14–16 yr from 2 cycles before the onset of the Spoerer Minimum.

下北半島，於法岳火山の岩石記載とK-Ar年代

下北半島，於法岳火山の岩石記載とK-Ar年代

Modelling the Shimokita deep coalbed biosphere over deep geological time: Starvation, stimulation, material balance and population models

AbstractBasin models can simulate geological, geochemical and geophysical processes and potentially also the deep biosphere, starting from a burial curve, assuming a thermal history and utilizing other experimentally obtained data. Here, we apply basin modelling techniques to model cell abundances within the deep coalbed biosphere off Shimokita Peninsula, Japan, drilled during Integrated Ocean Drilling Program Expedition 337. Two approaches were used to simulate the deep coalbed biosphere: (a) In the first approach, the deep biosphere was modelled using a material balance approach that treats the deep biosphere as a carbon reservoir, in which fluxes are governed by temperature‐controlled metabolic processes that retain carbon via cell‐growth and cell‐repair and pass it back via cell‐damaging reactions. (b) In the second approach, the deep biosphere was modelled as a microbial community with a temperature‐controlled growth ratio and carrying capacity (a limit on the size of the deep biosphere) modulated by diagenetic‐processes. In all cases, the biosphere in the coalbeds and adjacent habitat are best modelled as a carbon‐limited community undergoing starvation because labile sedimentary organic matter is no longer present and petroleum generation is yet to occur. This state of starvation was represented by the conversion of organic carbon to authigenic carbonate and the formation of kerogen. The potential for the biosphere to be stimulated by the generation of carbon‐dioxide from the coal during its transition from brown to sub‐bituminous coal was evaluated and a net thickness of 20 m of lignite was found sufficient to support an order of magnitude greater number of cells within a low‐total organic carbon (TOC) horizon. By comparison, the stimulation of microbial populations in a coalbed or high‐TOC horizon would be harder to detect because the increase in population size would be proportionally very small.

Statistical methods to enable practical on-site tomographic imaging of whole-core samples

Statistical methods enable the use of portable industrial scanners with sparse measurements, suitable for fast on-site whole-core X-ray computed tomography (CT), as opposed to conventional (medical) devices that use dense measurements. This approach accelerates an informed first-stage general assessment of core samples. To that end, this novel industrial tomographic measurement principle is feasible for rock-sample imaging, in conjunction with suitable forms of priors in Bayesian inversion algorithms. Gaussian, Cauchy, and total variation priors yield different inversion characteristics for similar material combinations. An evaluation of the inversion performance in rock samples considers, in a discrete form, conditional mean estimators, via Markov Chain Monte Carlo algorithms with noise-contaminated measurements. Additionally, further assessment indicates that this statistical approach better characterizes the attenuation contrast of rock materials, compared with simultaneous iterative reconstruction techniques. Benchmarking includes X-ray CT from numerical simulations of synthetic and measurement-based whole-core samples. To this end, we consider tomographic measurements of fine- to medium-grained sandstone core samples, with igneous-rich pebbles from the Miocene, off the Shimokita Peninsula in Japan, and fractured welded tuff from Big Bend National Park, Texas. Bayesian inversion results confirm that with only 16 radiograms, natural fractures with aperture of less than 2 mm wide are detectable. Additionally, reconstructed images found approximately spherical concretions of 6 mm diameter. To achieve similar results, filtered back projection techniques require hundreds of radiograms, only possible with conventional laboratory scanners.

Aggregatilinea lenta gen. nov., sp. nov., a slow-growing, facultatively anaerobic bacterium isolated from subseafloor sediment, and proposal of the new order Aggregatilineales ord. nov. within the class Anaerolineae of the phylum Chloroflexi.

A novel slow-growing, facultatively anaerobic, filamentous bacterium, strain MO-CFX2T, was isolated from a methanogenic microbial community in a continuous-flow bioreactor that was established from subseafloor sediment collected off the Shimokita Peninsula of Japan. Cells were multicellular filamentous, non-motile and Gram-stain-negative. The filaments were generally more than 20 µm (up to approximately 200 µm) long and 0.5-0.6 µm wide. Cells possessed pili-like structures on the cell surface and a multilayer structure in the cytoplasm. Growth of the strain was observed at 20-37 °C (optimum, 30 °C), pH 5.5-8.0 (pH 6.5-7.0), and 0-30 g l-1 NaCl (5 g l-1 NaCl). Under optimum growth conditions, doubling time and maximum cell density were estimated to be approximately 19 days and ~105 cells ml-1, respectively. Strain MO-CFX2T grew chemoorganotrophically on a limited range of organic substrates in anaerobic conditions. The major cellular fatty acids were saturated C16 : 0 (47.9 %) and C18 : 0 (36.9 %), and unsaturated C18 : 1ω9c (6.0 %) and C16 : 1ω7 (5.1 %). The G+C content of genomic DNA was 63.2 mol%. 16S rRNA gene-based phylogenetic analysis showed that strain MO-CFX2T shares a notably low sequence identity with its closest relatives, which were Thermanaerothrix daxensis GNS-1T and Thermomarinilinea lacunifontana SW7T (both 85.8 % sequence identity). Based on these phenotypic and genomic properties, we propose the name Aggregatilinea lenta gen. nov., sp. nov. for strain MO-CFX2T (=KCTC 15625T, =JCM 32065T). In addition, we also propose the associated family and order as Aggregatilineaceae fam. nov. and Aggregatilineales ord. nov., respectively.

Phylogeographic diversification and postglacial range dynamics shed light on the conservation of the kelp Saccharina japonica.

Studies of postglacial range shifts could enhance our understanding of seaweed species’ responses to climate change and hence facilitate the conservation of natural resources. However, the distribution dynamics and phylogeographic diversification of the commercially and ecologically important kelp Saccharina japonica in the Northwest Pacific (NWP) are still poorly surveyed. In this study, we analyzed the evolutionary history of S. japonica using two mitochondrial markers and 24 nuclear microsatellites. A STRUCTURE analysis revealed two partially isolated lineages: lineage H, which is scattered along the coast of Japan; and lineage P, which occurs along the west coast of the Japan Sea. Ecological niche modeling projections to the Last Glacial Maximum (LGM) revealed that the southern coasts of the Japan Sea and the Pacific side of the Oshima and Honshu Peninsulas provided the most suitable habitats for S. japonica, implying that these regions served as ancient refugia during the LGM. Ancient isolation in different refugia may explain the observed divergence between lineages P and H. An approximate Bayesian computation analysis indicated that the two lineages experienced post‐LGM range expansion and that postglacial secondary contact occurred in Sakhalin. Model projections into the year 2,100 predicted that S. japonica will shift northwards and lose its genetic diversity center on the Oshima Peninsula in Hokkaido and Shimokita Peninsula in Honshu. The range shifts and evolutionary history of S. japonica improve our understanding of how climate change impacted the distribution range and diversity of this species and provide useful information for the conservation of natural resources under ongoing environmental change in the NWP.

Geophysical constraints on microbial biomass in subseafloor sediments and coal seams down to 2.5\xa0km off Shimokita Peninsula, Japan

To understand the ability of microbial life to inhabit a deep subseafloor coalbed sedimentary basin, the correlation between fluid transport properties and the abundance of microbial cells was investigated based on core samples collected down to about 2.5 km below the seafloor during the Integrated Ocean Drilling Program Expedition 337 off the Shimokita Peninsula, Japan. The overall depth profiles for porosity and permeability exhibited a decreasing trend with increasing depth. However, at depths greater than 1.2 km beneath the seafloor, the transport characteristics of the sediments were highly variable, with the permeability ranging from 10−16 to 10−22 m2 and the pore size ranging from < 0.01 to 100 μm. This is mainly attributed to the diversity of the lithology, which exhibits a range of pore sizes and pore geometries. Fracture channels in coal seams had the highest permeability, while shale deposits had the smallest pore size and lowest permeability. A positive correlation between permeability and pore size was confirmed by the Kozeny-Carman equation. Cell abundance at shallower depths was positively correlated with porosity and permeability, and was less strongly correlated with pore size. These findings suggest that one of the factors affecting the decrease in microbial cell abundance with increasing depth was a reduction in nutrient and water supply to indigenous microbial communities as a result of a decrease in porosity and permeability due to sediment compaction. Anomalous regions with relatively high cell concentrations in coal-bearing units could be explained by the higher permeability and larger pore size for these units compared to the surrounding sediments. Nutrient transport through permeable cleats in coal layers might occur upwards toward the upper permeable sandstone layers, which are well suited for sustaining sizable microbial populations. Conversely, impermeable shale and siltstone with small pores (< 0.2 μm, which is smaller than microbial cell size) may act as barriers to water and energy-yielding substrates for deep microbial life. We propose that the pore size and permeability govern the threshold for microbial habitability in the deep subseafloor sedimentary biosphere.

Detrital zircon U–Pb age of sandstone within the Jurassic accretionary complex in the Omori area, northeastern Shimokita Peninsula, Northeast Japan.

Detrital zircon U–Pb age of sandstone within the Jurassic accretionary complex in the Omori area, northeastern Shimokita Peninsula, Northeast Japan.

Distribution and Speciation of Bromine and Iodine in Volcanic Ash Soil Profiles

Core Ideas Concentration and speciation of Br and I in volcanic ash soils are determined. Br and I were enriched in soils with andic properties, mainly as organic form. Br and I accumulated in surface soils during Andosol formation process. Bromine and iodine are halogens with similar chemical properties. Distributions of Br and I in the soil profile provide insights for understanding of their biogeochemical cycles and fate of these elements derived from artificial origin. Although generally not abundant in parent rock materials, they are often found in higher concentrations in soils, particularly volcanic ash soils in Japan. However, the process of Br and I accumulation in soils during soil formation remains unclear. We investigated the vertical distribution of Br and I to characterize the processes of Br and I accumulation in volcanic ash soils. Soils were collected from three pedons in the southern Shimokita Peninsula, Japan. Bromine (1.4 to 253 mg kg–1) and iodine concentrations (1.2 to 90 mg kg–1) in the soils were significantly correlated. Nondestructive speciation analysis by X‐ray absorption near edge structure spectroscopy showed that both Br and I mainly exist in their organic forms in soils enriched in those elements. Indices of the degree of Andosol formation (oxalate‐extractable Al and Fe, pyrophosphate‐extractable Al and Fe, phosphate absorption coefficient, and soil pH [NaF]) were significantly correlated with both Br and I concentrations in the soils. These results suggest that Br and I, derived from atmospheric deposition, were retained in surface soils after transformation to organic form and accumulated during Andosol formation from their parent tephra deposits.

Authigenic carbonate formation influenced by freshwater inputs and methanogenesis in coal-bearing strata offshore Shimokita, Japan (IODP site C0020)

Abstract Authigenic carbonate chemistry and mineralogy provide key insights into diagenetic pathways and microbial processes in sedimentary records. We characterize the mineralogy, elemental composition, and isotopic composition of 28 authigenic carbonate nodules recovered from coal-bearing forearc sediments offshore Shimokita Peninsula (Japan) to better understand fluid sources, diagenetic environments, and biogeochemical processes associated with subsiding sediments containing high organic carbon content. The carbonate nodules were collected at Integrated Ocean Drilling Program (IODP) Site C0020 from sediment cores between 1604 and 2460 m below seafloor (mbsf) spanning a transition from terrestrial to marine depositional environments. These carbonates range from

23A. 下北半島の新第三紀水中火山岩類 : とくにPillow lobeとLava lobeについて(日本火山学会1988年春季大会)

23A. 下北半島の新第三紀水中火山岩類 : とくにPillow lobeとLava lobeについて(日本火山学会1988年春季大会)

地球深部探査船「ちきゅう」の下北半島沖慣熟航海コア試料の年代モデル

地球深部探査船「ちきゅう」の下北半島沖慣熟航海コア試料の年代モデル

地球深部探査船「ちきゅう」の下北半島沖慣熟航海コア試料 : 物性変動から予測される古環境変動

地球深部探査船「ちきゅう」の下北半島沖慣熟航海コア試料 : 物性変動から予測される古環境変動