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Describing the evolution of the neo-volcanic zone in the spreading ridge is essential for understanding the dynamics and environments of abyssal basins. However, the absolute dating of ocean floor basalts is generally difficult. As a characteristic age indicator, absolute intensity of past geomagnetic field (absolute paleointensity, API) is useful to date ocean floor basalts. In this study, we adopted the Tsunakawa–Shaw method to measure APIs of whole-rock seafloor basalts collected from a conical cone on the Central Indian Ridge and performed rock magnetic experiments. We conducted the experiments on a total of 18 specimens (two or three specimens from each of eight lava sites). Six specimens from two lava sites with different morphologies (pillow and sheet), three for each, passed the acceptance criteria. API means at site level are 33.0 ± 1.0 and 35.8 ± 1.7 μT, respectively. The similarity of API site means suggests that they erupted within a short period. These site-level API means are approximately 0.7 to 0.8 times the present geomagnetic intensity of 46.0 μT at the sampling sites. The accepted specimens show higher Curie temperature, lower initial intensity of natural remanent magnetization, higher ratio of saturation remanence to saturation magnetization (M rs /M s ), and signal of harder magnetic mineral than rejected ones. Our primary comparison between the two site-level API means and the 1590–present high-resolution IGRF-13 + gufm1 model constrains that the eruption timing of the conical cone to be < 1590 CE. When we compared the two site-level API means with the paleointensity curves calculated from the BIGMUDI4k.1 and ArchKalmag14 k.r, we found that they overlap in the period of − 7575 to −1675 CE or − 25 to 1590 CE, which may be the eruption timing of the conical cone. We concluded that timing of recent volcanic eruption in abyssal environment could be investigated by using appropriate rock magnetic selection and carefully examined API. Graphical Abstract

Mass loss from the Antarctic ice sheet, Earth’s largest freshwater reservoir, results directly in global sea-level rise and Southern Ocean freshening. Observational and modeling studies have demonstrated that ice shelf basal melting, resulting from the inflow of warm water onto the Antarctic continental shelf, plays a key role in the ice sheet’s mass balance. In recent decades, warm ocean-cryosphere interaction in the Amundsen and Bellingshausen seas has received a great deal of attention. However, except for Totten Ice Shelf, East Antarctic ice shelves typically have cold ice cavities with low basal melt rates. Here we present direct observational evidence of high basal melt rates (7–16 m yr −1 ) beneath an East Antarctic ice shelf, Shirase Glacier Tongue, driven by southward-flowing warm water guided by a deep continuous trough extending to the continental slope. The strength of the alongshore wind controls the thickness of the inflowing warm water layer and the rate of basal melting. East Antarctic ice shelves typically have cold ice cavities with low basal melt rates. Here the authors direct observational evidence of high basal melt rates beneath Shirase Glacier Tongue in East Antarctica, driven by inflowing warm water guided by a deep continuous trough extending to the continental slope.

The Totten Glacier in East Antarctica, with an ice volume equivalent to >3.5 m of global sea-level rise, is grounded below sea level and, therefore, vulnerable to ocean forcing. Here, we use bathymetric and oceanographic observations from previously unsampled parts of the Totten continental shelf to reveal on-shelf warm water pathways defined by deep topographic features. Access of warm water to the Totten Ice Shelf (TIS) cavity is facilitated by a deep shelf break, a broad and deep depression on the shelf, a cyclonic circulation that carries warm water to the inner shelf, and deep troughs that provide direct access to the TIS cavity. The temperature of the warmest water reaching the TIS cavity varies by ~0.8 °C on an interannual timescale. Numerical simulations constrained by the updated bathymetry demonstrate that the deep troughs play a critical role in regulating ocean heat transport to the TIS cavity and the subsequent basal melt of the ice shelf. The Totten Glacier in East Antarctica is grounded below sea level and vulnerable to ocean forcing. Observations and simulations demonstrate warm water access from offshore to the glacier, facilitated by deep topography off the Sabrina Coast.

The existence of missing geomagnetic reversals has been proposed, with potential for new magnetostratigraphic age controls. We estimate geomagnetic reversal frequency from 0 to 155 Ma using adaptive‐bandwidth kernel density estimation (AKDE) to evaluate data sparseness and to assess how reversal frequency changes when recently identified geomagnetic reversals are incorporated into the geomagnetic polarity time scale (GPTS) data set. AKDE is a two‐stage procedure that uses an initial density estimator based on an initial (pilot) bandwidth. We found that the pilot bandwidth determined using cross‐validation is stable with respect to data set length. The AKDE results obtained based on the cross‐validated pilot bandwidth reveal four troughs after the Cretaceous Normal Superchron, spaced 13.5–15.0 Myr apart and corresponding to relatively long chrons (>0.8 Myr). One trough near 32 Ma becomes less distinct after the four recently identified reversals are added to the data set. This sensitivity suggests that troughs in the frequency curve may indicate missing geomagnetic reversals.

We recently found a markedly lower prevalence of vascular complications, including kidney disease, in diabetic patients with Gilbert syndrome, a congenital form of hyperbilirubinemia, suggesting a beneficial effect of bilirubin (BIL) on diabetic nephropathy. To directly examine this, we determined whether hereditary hyperbilirubinemic Gunn j/j rats and biliverdin (BVD)-treated diabetic db/db mice were resistant to the development of renal disease. Both rodent models had less albuminuria and complete protection against the progression of mesangial expansion accompanied by normalization of transforming growth factor-β1 and fibronectin expression. Simultaneously, there was normalization of urinary and renal oxidative stress markers, and the expression of nicotinamide adenine dinucleotide phosphate (NAD(P)H) oxidase subunits in the kidney. In cultured vascular endothelial and mesangial cells, BIL and BVD significantly inhibited NADPH-dependent superoxide production, and both high glucose- and angiotensin II-induced production of reactive oxygen species. Collectively, our findings suggest that BIL and BVD may protect against diabetic nephropathy and may lead to novel antioxidant therapies for diabetic nephropathy.

BackgroundAnastomotic leakage (AL) after gastrointestinal surgery remains a challenging complication that requires surgical or non-surgical treatment. Although various therapeutic endoscopic techniques are available, no definitive interventions exist. We developed a therapeutic endoscopic submucosal injection method using novel gel-forming mixed solutions to close AL and evaluated the elasticity of the developed hydrogel. The safety and efficacy of the injection method were explored in porcine AL models.MethodsWe developed a novel gel-forming solution, and the formed gel lasted approximately one week within the gastrointestinal wall. An indentation test evaluated the elasticity of the novel hydrogel. After the confirmation of AL on porcine anterior gastric walls, sodium alginate was endoscopically injected into the submucosal layer around the leakage site circularly, followed by a calcium lactate/chitosan-based solution. After that, the outcomes data were collected, and histopathological effectiveness was evaluated.ResultsThe increased sodium alginate elasticity with the addition of calcium lactate/chitosan-based solution facilitated long-lasting gel formation. Four pigs with AL underwent this intervention consecutively. Each endoscopic injection was completed in less than 5 min. No significant complications were observed for 3 weeks after the intervention. All AL sites were macroscopically healed. Histopathologic findings at 3 weeks showed that the wall defect was filled with collagen fibers that had grown around the site of the muscle layer tear. No tissue necrosis was observed.ConclusionThis preclinical study demonstrated that the therapeutic injection method for gastroenterological AL using gel-forming solutions could be an alternative endoscopic treatment, especially in patients with severe conditions or comorbidities. The optimal target of this treatment is small size and early AL without poor blood flow or intense hypertrophic scar lesions.

The Kairei (KHF) and Yokoniwa hydrothermal fields (YHF) are hosted in mafic as well as ultramafic rocks distributed at an off-axis volcanic knoll of the Central Indian Ridge. Despite intensive investigations, their geological and geophysical background is still debated. Here, we show the results of near-seafloor magnetic anomaly surveys conducted using a submersible. We investigated the bulk magnetization of the hydrothermally altered zone and the surrounding lava flows and evaluated their intensities compared with previously reported values at axial areas of seafloor spreading environments. The KHF is characterized by low coherence between observed and modeled anomalies and low values of magnetization. This result suggests that magnetic minerals within basaltic lava flows were likely altered by hydrothermal fluid circulation. The variation pattern in the observed magnetic anomalies above the lava flows is in phase with that of the modeled magnetic anomalies for the simple assumption that the magnetization direction is parallel to the geomagnetic field. This result suggests that these lava flows preserve normal magnetic polarity corresponding to the Brunhes Chron. The estimated magnetic-anomaly-derived absolute magnetizations show a reasonable correlation with the natural remanent magnetizations of rock samples collected from the seafloor of the same region; their relationship is consistent with previously reported datasets from the Mariana Trough and Mid-Atlantic Ridge. The estimated magnetization intensity reaches 20 A/m in the study area, which is clearly greater than those of previously reported off-axis areas, suggesting that recent volcanic eruption may have occurred in these off-axis areas. The high magnetization distributions are commonly observed at the bottoms of the western slope from the KHF and YHF. This finding provides new insight into the distribution of highly magnetized lava flows in the off-axis areas and indicates the distribution of recent off-axis volcanic activities, which is potentially linked to the sub-seafloor hydrothermal circulation.

Understanding the age and dynamics of the overriding plates allows an assessment of competing subduction initiation hypotheses. The Izu‐Bonin‐Mariana margin in the Western Pacific is a key example of initiation and hence it is important to constrain the age and origin of the oldest igneous crust of the supra‐subduction Philippine Sea Plate. We present geochronological and geochemical data of igneous rocks from the oldest ocean basins of the Philippine Sea Plate: the West Philippine and Palau Basins. Basalts from these basins have enriched geochemical characteristics similar to the EM‐2‐like mantle component found in OIB‐like basalts associated with the Oki‐Daito mantle plume. Ages of basalts from the northernmost West Philippine Basin (WPB) and the Palau Basin range from 43.5 to 50.5 Ma, which is similar to the oldest samples associated with the Oki‐Daito mantle plume (48–50 Ma). This implies that the plume contributed to magmatism from the onset of basin formation. It also provides support for the proposition that rifting of the Mesozoic arc terrane and subsequent seafloor spreading of the WPB was triggered by the arrival of the Oki‐Daito mantle plume at the base of the lithosphere. The age of these Philippine Sea Basins implies that only the Mesozoic Daito Ridge Group and the Gagua Ridge existed as Philippine Sea Plate crust before subduction initiation. A major fault activity after 37 Ma in the northernmost WPB demonstrates that careful reconstruction of the Eocene Philippine Sea Plate is critical to understanding plate dynamics during subduction initiation in the Western Pacific. Plain Language Summary This study investigates the formation of the crust beneath the Philippine Sea Plate. An outcome of this research is a clearer understanding of the plate tectonic configuration in the Western Pacific at the point when volcanic activity started. We collected rock samples from what is thought to be the oldest sections of the West Philippine Basin and the Palau Basin, and determined their age and chemical composition. These rocks were erupted between 43.5 and 50.5 million years ago, and are of a similar age and composition to the volcanic rocks known to be associated with the Oki‐Daito mantle plume (48–50 million years old). These similarities imply that the initial volcanism on the Philippine Sea Plate was triggered by the arrival of the upwelling Oki‐Daito mantle plume. A consequence of the hot and buoyant mantle plume was to stretch the existing crust and develop a new ocean basin by volcanic activity. The new ages for the oldest ocean basins in the Philippine Sea Plate reveal that only the Mesozoic arc terrane existed as the Philippine Sea Plate crust before subduction initiation. This provides new constraints on the conditions under which subduction can initiate between the two plates. Key Points New dating indicates that a major part of the oldest Philippine Sea Plate basins formed after c. 51 Ma Ocean crust of the oldest Philippine Basins is affected by the Oki‐Daito mantle plume Onset of spreading of the West Philippine Basin could have been triggered when the Oki‐Daito plume hit the base of preexisting lithosphere

We conducted magnetotelluric measurements to investigate a large serpentinite complex in the northern Kamuikotan Zone that intruded a Cretaceous–Paleocene forearc sedimentary sequence. The resistivity model we derived by three-dimensional inversion clearly shows a low-resistivity zone beneath the outcrop of the serpentinite complex. We interpret the low-resistivity zone to represent aqueous pore fluid within a serpentinite mélange derived from the subducting Pacific plate or mantle wedge. Previous geological studies in the area have shown that the serpentinite mélange had uplifted during the early Pleistocene. They indicate that the ultramafic rocks and aqueous fluids have continued to rise in the area. The uplifting serpentinite body might have formed a zone enriched in pore fluid that promoted the occurrence of a previously identified intra-plate slow slip event. These results demonstrate the important role of fluid transport during tectonic processes related to uplift in subduction zones.