Yusuke Yokoyama

Yusuke Yokoyama
The University of Tokyo | Todai · Atmosphere and Ocean Research Institute

PhD (Australian National Univ)

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458
Publications
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Publications

Publications (458)
Article
Measurement of dissolved organic radiocarbon (DO¹⁴C) in seawater can provide information about the timescale of the dynamics of dissolved organic matter and its sources in the ocean. Despite the development of accelerator mass spectrometry, the DO¹⁴C analysis requires complicated processing techniques such as the use of UV irradiation, which emits...
Article
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The surface of intertidal estuarine sediments is covered with diatom biofilms excreting exopolymeric substances (EPSs) through photosynthesis. These EPSs are highly reactive and increase sediment cohesiveness notably through organo-mineral interactions. In most sedimentary environments, EPSs are partly to fully degraded by heterotrophic bacteria in...
Article
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Massive boulders in landslide and tsunami deposits are prominent geomorphic features in various landscapes. Tracking their movement history is important for reconstructing past geologic dynamics; however, the reworking movements of massive boulders remain unresolved. The boulder field on the Ishigaki Island was formed by repeated tsunamis. Although...
Article
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Plutonium (Pu) has been used as a mid-twentieth century time-marker in various geological archives as a result of atmospheric nuclear tests mainly conducted in 1950s. Advancement of analytical techniques allows us to measure 239Pu and 240Pu more accurately and can thereby reconstruct the Pacific Pu signal that originated from the former Pacific Pro...
Article
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Normal fault scarps, as classical topographic features and geomorphological markers along mountain range-fronts, form in consolidated bedrock due to faulting in extensional settings. They generally preserve more complete records of paleo-earthquakes than fault scarps in unconsolidated sediments. The reconstruction of paleo-seismic history from a be...
Article
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The primary Antarctic contribution to modern sea-level rise is glacial discharge from the Amundsen Sea sector of the West Antarctic Ice Sheet. The main processes responsible for ice mass loss include: (1) ocean-driven melting of ice shelves by upwelling of warm water onto the continental shelf; and (2) atmospheric-driven surface melting of glaciers...
Article
Methane (CH4) associated with marine and terrestrial sites of serpentinization has been proposed to be abiotic in origin. However, the source of carbon and the depth and temperature of CH4 synthesis often remain inconclusive. We measured the radiocarbon (¹⁴C), bulk stable isotope ratios (δ13C and δD) and isotopologue abundance (Δ13CH3D) of CH4, and...
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This Data in Brief paper comprises dataset obtained for sediment cores collected from Lake Selina, located in the West Coast Range of Tasmania, Australia. Datasets include radiocarbon and optically stimulated luminescence age estimates, elemental composition, beryllium isotopes, magnetic properties and the paleomagnetic record measured on the cores...
Article
The Adélie Basin is a relatively small (∼1600 km²), semi-enclosed continental shelf bathymetric depression located adjacent to the Wilkes Subglacial Basin, a basin underlying a sector of the East Antarctic Ice Sheet that contains ∼3–4 meters sea level equivalent of ice. Located within the Adélie Basin is a ∼184 m thick laminated sediment deposit, t...
Article
Corals do not all grow near the sea surface. Different species favour different ranges in depth and can survive at different depths from 0 to 5 m to over 0–100 m. Fossil corals, as markers of sea level, are the preferred choice in radiometric dating. Timing and magnitude of sea-level variations are determined from the location and age of a set of i...
Article
Estimating paleotsunami frequency and size is an important requirement for assessing future tsunami risks. However, several issues such as ground soil erosion by subsequent tsunami waves and the preservation potential of tsunami deposits make it difficult to ascertain the paleotsunami history accurately based solely on tsunami deposits. This study...
Article
Stratigraphic evidence for coseismic subsidence has been documented in active-margin estuaries throughout the world. Most of these studies have been conducted in subduction zone or strike-slip settings; however, the stratigraphic response to coseismic subsidence in other tectonic settings would benefit from further study. Here we show evidence of l...
Article
Full-text available
Speleothems are ideal archives of environmental magnetism and paleomagnetism, since they retain continuous magnetic signals in stable conditions and can be used for reliable radiometric dating using U-series and radiocarbon methods. However, their weak magnetic signals hinder the widespread use of this archive in the field of geoscience. While prev...
Article
Full-text available
Past sea-level change represents the large-scale state of global climate, reflecting the waxing and waning of global ice sheets and the corresponding effect on ocean volume. Recent developments in sampling and analytical methods enable us to more precisely reconstruct past sea-level changes using geological indicators dated by radiometric methods....
Article
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We investigated diatom assemblages for the last 19 ka in a piston core KY07-04 PC01 collected from the northern Okinawa Trough, East China Sea. Most of the diatom taxa in the Core KY07-04 PC01 were subtropical to temperate marine species throughout the core. Pronounced turnover of major diatom groups from periphytic to planktonic taxa occurred duri...
Article
License (CC BY 4.0). The quantitative morphology of bedrock fault surfaces combined with aerial surveys and field identification is a useful approach to identify paleoearthquakes, obtain coseismic slips, and evaluate the seismogenic capacity of active faults in bedrock areas where traditional trenching methods are not applicable. Here, we report a...
Article
We quantitatively evaluated the emergence ages of the tectonically uplifted marine terraces, called the Numa terraces, in the southernmost part of the Boso Peninsula, central Japan. The combination of the complete dataset of the geological dating survey and the model inversion method is newly proposed. Along the Sagami Trough, the subduction bounda...
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Antarctic sea-ice extent, primary productivity and ocean circulation represent interconnected systems that form important components of the global carbon cycle. Subdecadal to centennial-scale variability can influence the characteristics and interactions of these systems, but observational records are too short to evaluate the impacts of this varia...
Article
Investigating coastal areas far from tsunami sources can improve the understanding of the magnitude and origin of giant tsunamis. However, distinguishing tsunami deposits from extreme storm deposits is more challenging since the layers are less prominent compared to the those in the locations near a tsunami source. This study reconstructed the Holo...
Article
Lakes are sensitive recorders of anthropogenic activities, as human society often develops in their vicinity. Lake sediments thus have been widely used to reconstruct the history of environmental changes in the past, anthropogenic, or otherwise, and radiocarbon dating provides chronological control of the samples. However, specific values of radioc...
Article
Hydrothermal circulation beneath the spreading axis plays a significant role in the exchange of energy and mass between the solid Earth and the oceans. Deep‐seated hydrothermal circulation down to the crust/mantle boundary in the fast‐spreading axis has been introduced by a number of studies regarding geological investigations and numerical models....
Conference Paper
The dearth of high-resolution climate records for the past millennium has largely limited our understanding of the impacts of natural (e.g., the Little Ice Age: LIA) and anthropogenic climate perturbations (i.e., the ongoing global warming) on the arid regions of West Asia (also referred to as the Middle East). Here, we present multiproxy records i...
Article
Boron isotopes are widely used as a proxy of marine carbonate in paleoclimatology to reconstruct seawater pH and atmospheric pCO2, and precise and accurate boron isotopic analysis is required for this purpose. Determination of boron isotopic composition is susceptible to contamination, especially for sample analyses with small amounts of boron; how...
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Drilling of the eastern Brazilian continental shelf in the 1980’s identified several main factors controlling Holocene reef growth in the South Atlantic. However, this model is limited by few fossil reef cores, sparse uncalibrated dates (< 10) and basic sedimentary and coralgal descriptions. Here we integrate 62 recently published C¹⁴-AMS ages with...
Article
Radiocarbon dating, applied to carbon-containing material such as shells, foraminifers, corals, peats, and bulk organic matter, is an essential method for constraining Late Quaternary age models. However, selection of appropriate material requires paleoenvironmental knowledge because past climate and sea-level variability may affect depositional pr...
Article
In contrast to the detection and resolution of Late Pleistocene interstadials (Marine Isotope Stages; MIS 5c, 5a and 3) in marine and ice core-based oxygen isotope records, accurately defining palaeosea-levels for these events from sea level indicators remains a challenge. Commonly, such investigations have been undertaken in tectonically active, s...
Article
Full-text available
To study the influence of different ocean currents on the trophic spectra found in a sympatric fish community, we analyzed the radiocarbon contents (Δ14C) and stable carbon (δ13C) and nitrogen (δ15N) isotopic compositions in their bulk muscle tissues and the δ15N of individual amino acids in 26 species of demersal fish collected from off Tohoku (Pa...
Article
Leads, lags, or synchronies in climatic events among different regions are key to understanding mechanisms of climate change, as they provide insights into the causal linkages among components of the climate system. The well-studied transition from the Lateglacial to early Holocene (ca. 16–10 ka) contains several abrupt climatic shifts, making this...
Article
Full-text available
Sea-level proxies for Marine Isotopic Stage 5e (MIS 5e, ca. 124 ka) are abundant along the Japanese shoreline and have been documented for over at least the past 60 years. The bulk of these sea-level proxies are identified in Japan as marine terraces, often correlated by stratigraphic relationships to identified tephra layers, or other chronologica...
Article
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The solid earth plays a major role in controlling Earth’s surface climate. Volcanic degassing of carbon dioxide (CO 2 ) and silicate chemical weathering are known to regulate the evolution of climate on a geologic timescale (> 10 ⁶ yr), but the relationship between the solid earth and the shorter (< 10 ⁵ yr) fluctuations of Quaternary glacial–inter...
Article
Constraining East Antarctic Ice Sheet (EAIS) evolution during the Holocene is important for exploring the forcing mechanisms behind ice sheet retreat and to constrain numerical ice sheet models that aid predictions of future sea-level rise. Beryllium (Be) isotope analysis of bedrock and marine sediments have offered unparalleled insight into Antarc...
Article
Rationale Precise and accurate determination of the ratio of the cosmogenic nuclide ¹⁰Be to the stable isotope ⁹Be (¹⁰Be/⁹Be) is needed across multiple fields of research within the Earth Sciences. Current techniques used to measure the ⁹Be content of geological materials generally require a large amount of sample or solution aliquot and present a...
Article
Lake sediment archives covering several glacial cycles are scarce in the Southern Hemisphere and they are challenging to date. Here we present the chronostratigraphy of the oldest continuous lake sediment archive in Tasmania, Australia; a 5.5 m and 270 ka (Marine Isotope Stage 8) sediment core from Lake Selina. We employ radiometric dating (radioca...
Article
Full-text available
We performed coenzyme factor 430 (F430) analysis and radiocarbon measurements to identify deep microorganisms, including methanogenic archaea, and assess the origin of methane in a deep organic- and iodine-rich aquifer in a forearc basin at the Southern Kanto gas field, Boso Peninsula, Japan. We detected high concentrations of native F430 (approxim...
Preprint
Full-text available
Sea-level proxies for Marine Isotopic Stage 5e (MIS 5e, ca. 124 ka) are abundant along the Japanese shoreline, and have been documented for over at least the last 60 years. The bulk of these sea-level proxies are identified in Japan as marine terraces, often correlated by stratigraphic relationships to identified tephra layers, or other chronologic...
Article
Full-text available
The NE‐trending Hinagu fault zone, length 81 km, is one of the major active faults in Kyushu, Japan. From north to south, it is divided into three segments based on geomorphic features and paleoseismic behavior: the Takano‐Shirahata, Hinagu, and Yatsushiro Sea segments. The 2016 Kumamoto earthquake produced a 6‐km‐long surface rupture with a dextra...
Article
Full-text available
Abstract We investigated an alkenone-based sea surface temperature (SST) and the hydrographic change records of the subarctic Northwestern (NW) Pacific from the last glacial to interglacial. The core we investigated is a piston core (LV 63-41-2, 52.56° N, 160.00° E; water depth 1924 m) retrieved from the southern offshore east coast of the Kamchatk...
Article
Full-text available
Organic matter in lake sediments contains information that can be used to reconstruct lake environmental histories over decades or centuries. In this study, we used organic geochemical proxies (i.e., total organic carbon [TOC], TOC/total nitrogen [TN] atomic ratios [C/N], stable carbon isotope ratios of TOC [δ13CTOC] and palmitic acid [δ13CC16:0],...
Article
On the Pacific coast of Hokkaido, historical documents and seismic detections spanning the last 200 years show that large earthquakes (magnitude 7–8) have occurred every 50–100 years along the Kuril Trench. Geological reconstructions of past earthquakes in the region show extend records to the last 6000 years and show that unusually large (>M8) ear...
Article
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The Great Barrier Reef (GBR) is an internationally recognized and widely studied ecosystem, yet little is known about its sea surface temperature (SST) evolution since the Last Glacial Maximum (LGM) (~20 kyr BP). Here, we present the first paleo-application of Isopora coral-derived SST calibrations to a suite of 25 previously published fossil Isopo...
Article
Recent studies have revealed that the Holocene climate was not stable, but has varied on a centennial-to-millennium scale. The abrupt global climate shifts that occurred in ~8.2ka and ~4.2 ka had received much attention in the form of a tripartite subdivision of the Holocene, with the terms ‘Early’, ‘Middle’, and ‘Late’ Holocene applied in the Quat...
Article
Full-text available
Observations of coral reef losses to climate change far exceed our understanding of historical degradation before anthropogenic warming. This is a critical gap to fill as conservation efforts simultaneously work to reverse climate change while restoring coral reef diversity and function. Here, we focused on southern China’s Greater Bay Area, where...
Article
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Magnitude 8 megathrust earthquakes that have generated large tsunamis with wave heights of >5 m in coastal areas of southwestern Japan have occurred every 100–150 years along the Nankai–Suruga Trough, which marks the convergent boundary between the Eurasian and Philippine Sea plates. Using sedimentological, geochemical, and paleontological analyses...
Article
Full-text available
This study aimed to reconstruct temperatures experienced during the larval period by adult Pacific bluefin tuna Thunnus orientalis using high-resolution otolith stable oxygen isotope (δ18O) analysis. A novel otolith sample preparation protocol for secondary ion mass spectrometry (SIMS) analysis developed in this study reduced the background noise o...
Article
Reconstructing the history of Holocene relative sea levels around Tonga provides essential constraints on the recent geological evolution of this region and paleoenvironmental context for archaeological studies. However, few sea level records are currently available in the region, and no quantitative paleoenvironmental studies using geochemical or...
Article
Full-text available
Significance North Atlantic cold events in the past have been shown to cause large-scale atmospheric reorganizations. Results of our dust record from southeastern Iran, which is highly susceptible to capture dust storms from North Africa and the Arabian Peninsula—the largest dust source on Earth—show a direct link between North Atlantic cooling and...
Article
Full-text available
Past major changes in sea level have had a significant influence on global and shelf sea tidal dynamics. Some of these changes are preserved in sedimentary records from the shelf seas, and so appropriate proxy data have the potential to constrain tidal model outputs over the recent geological past. Tidal models which simulate the evolution of tide-...
Article
Full-text available
1. Ocean acidification by anthropogenic carbon dioxide emissions is projected to depress metabolic and physiological activity in marine calcifiers. To evaluate the sensitivity of marine organisms against ocean acidification, the assimilation of nutrients into carbonate shells and soft tissues must be examined. 2. We designed a novel experimental p...
Article
Full-text available
Rapid sea-level rise caused by the collapse of large ice sheets is a threat to human societies. In the last deglacial period, the rate of global sea-level rise peaked at more than 4 cm yr−1 during Meltwater Pulse 1A, which coincided with the Bølling warming event some 14,650 years ago. However, the sources of the meltwater have proven elusive, and...
Article
Deltas host large urban centers and expanses of coastal wetlands worldwide. As such, their future will play an important role in the economic and ecological health of many coastal communities. Although threats to deltas from drowning due to subsidence and accelerating sea-level rise are well-studied, far less is known about the physical effects of...
Article
The study of bedrock fault scarps is a useful approach to identify paleo-earthquakes and acquire the faulting history in bedrock areas where traditional trench techniques are not applicable. Here, we report a study on the Luoyunshan piedmont fault (LYSPF), southwestern Shanxi Rift, China. Although several studies have analyzed the LYSPF, its faulti...
Preprint
Full-text available
Speleothems can be an ideal archive of paleomagnetism because they retain continuous geomagnetic records in stable conditions and can be used for reliable radiometric dating using U-series and radiocarbon methods. However, their weak magnetic signals hinder the widespread use of this archive in the field of geoscience. While previous studies succes...
Preprint
Full-text available
Speleothems are an ideal archive of paleomagnetism since they retain continuous geomagnetic records in stable conditions and can be used for reliable radiometric dating using U-series and radiocarbon methods. However, their weak magnetic signals hinder the widespread use of this archive in the field of geoscience. While previous studies successfull...