Low Accumulation Rates Research Articles

A model framework for atmosphere–snow water vapor exchange and the associated isotope effects at Dome Argus, Antarctica – Part 1: The diurnal changes

Abstract. Ice-core water isotopes contain valuable information on past climate changes. However, such information can be altered by post-depositional processing after snow deposition. Atmosphere–snow water vapor exchange is one such process, but its influence remains poorly constrained. Here we constructed a box model to quantify the atmosphere–snow water vapor exchange fluxes and the associated isotope effects at sites with low snow accumulation rates, where the effects of atmosphere–snow water vapor exchange are suspected to be large. The model reproduced the observed diurnal variations in δ18O, δD, and deuterium excess (d-excess) in water vapor at Dome C, East Antarctica. According to the same model framework, we found that under average summer clear-sky conditions, atmosphere–snow water vapor exchange at Dome A can cause diurnal variations in atmospheric water vapor δ18O and δD of 4.8 ‰ ± 2.6 ‰ and 29 ‰ ± 19 ‰, with corresponding diurnal variations in surface snow δ18O and δD of 0.80 ‰ ± 0.35 ‰ and 1.6 ‰ ± 2.7 ‰. The modeled results under summer cloudy conditions display similar patterns to those under clear-sky conditions but with much smaller magnitudes of diurnal variations. However, under winter conditions at Dome A, the model predicts few to no diurnal changes in snow isotopes, consistent with the stable boundary condition in winter that inhibits effective vapor exchange between the atmosphere and snow. In addition, after 24 h and continuous simulations of 11 d, the model predicts significant enrichments in snow isotopes under summer conditions, while in winter, the depletions also accumulate after each 24 h simulation but with a much smaller magnitude of change compared to the results from summer simulations. If the modeled snow isotope enrichments in summer conditions and the depletions in winter conditions represent the general situation at Dome A, this likely suggests that atmosphere–snow water vapor exchange tends to increase snow isotope seasonality, and the annual net effect would be overall enrichments in snow isotopes since the effects in summer appear to be greater than those in winter. This trend will need to be further explored in the future with more comprehensive model studies and/or field observations and experiments.

Drains in Abdominoplasties: The Less the Better?

Drains are traditionally inserted during surgery for reduction of fluid accumulation in the post-operative period. The appearance of drained fluids and their quantity can be early predictors of complications. Over the years, several studies have been conducted in attempt to determine the optimal number of drains that result in low rates of fluid accumulation with minimal impairment of quality of life. Determine the optimal number of suction drains in abdominoplasty procedures. Retrospective cohort study, analyzing all abdominoplasty patients operated by a single surgeon. Patients were stratified into 3 groups based on number of drains inserted at the end of the procedure. Rate of complications was compared between the groups and a multivariate logistic regression model was computed for the development of complications. Seven-hundred and forty three patients were included in the analysis of this study. No drains were inserted in 355 patients (45%), whereas a single drain was inserted in 153 (20.6%) 2 drains in 255 patients (34.4%). Patients for whom a single drain was inserted intra-operatively, experienced at a statistically significant lower rate, surgical site infections (OR = 0.235), hypertrophic scars (OR = 0.326), wound dehiscence (OR = 0.272), as compared to patients with no drains. On the contrary, insertion of single drain was associated with a statistically significant higher risk for development of seroma (OR = 6.276) and the need for revision surgery (OR = 2.452). Insertion of a single drain is associated with a lower risk of SSI and wound- dehiscence, but a greater risk for seroma development that requires surgical intervention. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.

Influence of changing water mass circulation on detrital component and carbon burial of late Pleistocene and Holocene sediments in the eastern-central Mid-Adriatic deep

A sediment core was retrieved in the eastern-central Mid-Adriatic Deep (MAD) to study the changes in the water mass circulation and their effect on carbon burial efficiency and the provenance of a detrital sediment component. An age-depth model of the sediment core POS-514-40-11 is based on radiocarbon dating and tephrochronology. Two tephra were correlated to the Neapolitan Yellow Tuff and Pomici di Mercato eruptions, extending the previously known distribution of Pomici di Mercato tephra. Based on the analysis of heavy mineral (HM) assemblages throughout the core, for the first time the occurrence of Eastern Adriatic current (EAC) was estimated at ca. 15 ka BP, i.e., at the beginning of the post last glacial maximum (LGM) transgression. During the late Pleistocene, the detrital component was dominated by Paleo-Po river sediments, which gradually shifted toward the Albanian province as a basin-wide counterclockwise circulation was established. Mass accumulation rates of organic carbon (OC), stable isotopes of carbon (δ 13C) and nitrogen (δ 15N) as well as C/N ratios, showed that carbon burial was affected by sea level rise and climatic changes. Climatic effects are observed during cold periods i.e., the Younger Dryas and the 8.4–7.9 ka cold period when terrestrial OC was dominant. In the latter case dominance of terrestrial carbon was due to the North Adriatic dense water (NAddW) influence. On the other hand, sea level rise increased MAD distance from the main river mouths/deltas, resulting in decreased influx of terrestrial organic carbon and lower accumulation rates of organic carbon in general. This reconstruction of the oceanographic setting is valuable considering that the Adriatic Sea is one of the key locations for the formation of DW and thus affects the overall Mediterranean circulation.

Comparative evaluation of biodegradation of chlorpyrifos by various bacterial strains: Kinetics and pathway elucidation

The present study focused on the isolation and identification of CP and TCP bacteria degrading bacteria from the rhizospheric zone of aromatic grasses i.e. palmarosa (Cymbopogon martinii (Roxb. Wats), lemongrass (Cymbopogon flexuosus) and vetiver (Chrysopogon zizaniodes (L.) Nash.). So that these isolates alone or in combination with the vegetation of aromatic grasses will be used to clean up CP-contaminated soils. The study also explored enzymatic activities, CO2 release, dechlorination potential, and degradation pathways of bacterial strains. A total of 53 CP-tolerant bacteria were isolated on their physical characteristics and their ability to degrade CP. The ten highly CP-tolerant isolates were Pseudomonas aeruginosa Pa608, three strains of Pseudomonas hibiscicola R4–721 from different rhizosphere, Enterococcus lectis PP2a, Pseudomonas monteilii NBFPALD_RAS131, Enterobacter cloacae L3, Stenotrophomonas maltophilia PEG-390, Escherichia coli ABRL132, and Escherichia coli O104:H4 strain FWSEC0009. The CO2 emission and phosphatase activities of the isolates varied from 3.1 to 8.6 μmol mL−1 and 12.3 to 31 μmol PNP h−1, respectively in the CP medium. The degradation kinetics of CP by these isolates followed a one-phase decay model with a dissipation rate ranging from 0.048 to 0.41 d−1 and a half-life of 1.7–14.3 days. The growth data fitted in the SGompertz equation showed a growth rate (K) of 0.21 ± 0.28 to 0.91 ± 0.33 d−1. The P. monteilii strain had a faster growth rate while E. coli ABRL132 had slower growth among the isolates. The rate of TCP accumulation calculated by the SGompertz equation was 0.21 ± 0.02 to 1.18 ± 0.19 d−1. The Pseudomonas monteilii showed a lower accumulation rate of TCP. Among these, four highly effective isolates were Pseudomonas aeruginosa Pa608, Pseudomonas monteilii NBFPALD_RAS131, Stenotrophomonas maltophilia PEG-390, and Pseudomonas hibiscicola R4–721. Illustrations of the degradation pathways indicated that the difference in metabolic pathways of each isolate was associated with their growth rate, phosphatase, dehydrogenase, oxidase, and dechlorination activities.

Drivers of organic carbon distribution and accumulation in the northern Barents Sea

Sedimentary properties and accumulation rates on the continental shelf and in the deep sea reflect temporal oceanographic, biological and chemical processes occurring in the water column and the sediment surface. We used the radionuclides 210Pb, 226Ra, and 137Cs activities to estimate sedimentation rates during the last century at nine stations in the northern Barents Sea region. Elemental (C, N) and stable isotopic composition (δ13C, δ15N) were also analysed from the nine stations sampled in August 2018, and, for five other stations sampled in August and December 2019, and in March and May 2021. Sediment accumulation rates varied between 130 and 1 410 g m−2 y−1. The < 63 μm normalized total organic carbon (TOC63) and the total nitrogen from the sediment surface varied between 0.90–2.56 % and 0.13–0.33 %, respectively. Ice-free shelf stations had higher TOC63 and possibly fresher organic matter (high δ13C, low δ15N) than ice-covered more northern stations. The opposite trend was observed for total inorganic carbon. We found that these trends in biogeochemical parameters were spatially structured by the winter sea ice concentration and biological production differences, and exhibited a south-north separation of the Polar Front region. The low and stable organic carbon accumulation rate (1.7–13.4 g Corg m-2 y−1; ARtoc) is a function of slow sedimentation rates, and high degradation and residence time in the water column and at the sediment–water interface. Overall, the ARtoc has been stable for the past 100 years, with a slight increase from the early 1970s to the present at the shelf and slope stations. Our results highlight that spatial scales of variability of the studied sedimentary parameters are linked to spatial patterns of important environmental variables (e.g., chlorophyll-a, sea ice concentration) in the region. In contrast, no seasonal differences were observed in the sediment parameters of revisited stations, and the dated sediment geochemical profiles did not exhibit substantial longer-term variation. This means that climate-induced changes in variables that modify the sedimentary geochemistry of the environment may affect benthic community activity and structure before leaving a record in ARtoc.

Unearthing the legacy of wildfires: post fire pyrogenic carbon and soil carbon persistence across complex Pacific Northwest watersheds

Wildfires have the potential to dramatically alter the carbon (C) storage potential, ecological function, and the fundamental mechanisms that control the C balance of Pacific Northwest (PNW) forested ecosystems. In this study, we explored how wildfire influences processes that control soil C stabilization and the consequent soil C persistence, and the role of previous fire history in determining soil C fire response dynamics. We collected mineral soils at four depth increments from burned (low, moderate, and high soil burn severity classes) and unburned areas and surveyed coarse woody debris (CWD) in sites within the footprint of the 2020 Holiday Farm Fire and in surrounding Willamette National Forest and the H.J. Andrews Experimental Forest. We found few changes in overall soil C pools as a function of fire severity; we instead found that unburned sites contained high levels of pyrogenic C (PyC) that were commensurate with PyC concentrations in the high severity burn sites—pointing to the high background rate of fire in these ecosystems. An analysis of historical fire events lends additional support, where increasing fire count is loosely correlated with increasing PyC concentration. An unexpected finding was that PyC concentration was lower in low soil burn severity sites than in control sites, which we attribute to fundamental ecological differences in regions that repeatedly burn at high severity compared with those that burn at low severity. Our CWD analysis showed that high mean fire return interval (decades between fire events) was strongly correlated with low annual CWD accumulation rate; whereas areas that burn frequently had a high annual CWD accumulation rate. Within the first year postfire, trends in soil density fractions demonstrated no significant response to fire for the mineral-associated organic matter pool but slight increases in the particulate pool with increasing soil burn severity—likely a function of increased charcoal additions. Overall, our results suggest that these PNW forest soils display complex responses to wildfire with feedbacks between CWD pools that provide varying fuel loads and a mosaic fire regime across the landscape. Microclimate and historic fire events are likely important determinants of soil C persistence in these systems.

Firn air content changes on Antarctic ice shelves under three future warming scenarios

Abstract. The Antarctic firn layer provides pore space in which an estimated 94 % to 96 % of the surface melt refreezes or is retained as liquid water. Future depletion of firn pore space by increased surface melt, densification and formation of low-permeability ice slabs can potentially lead to meltwater ponding, hydrofracturing and ice-shelf disintegration. Here, we investigate the 21st-century evolution of total firn air content (FAC) and accessible FAC (i.e. the pore space that meltwater can reach) across Antarctic ice shelves. We use the semi-empirical IMAU Firn Densification Model (IMAU-FDM) with an updated dynamical densification expression to cope with changing climate forcing. The firn model is forced by general circulation model output of the Community Earth System Model version 2 (CESM2) for three climate emission scenarios (SSP1-2.6, SSP2-4.5 and SSP5-8.5), dynamically downscaled to a 27 km horizontal resolution by the Regional Atmospheric Climate Model version 2.3p2 (RACMO2.3p2). To estimate accessible FAC, we prescribe a relationship between ice-slab thickness and permeability. In our simulations, ice shelves on the Antarctic Peninsula and the Roi Baudouin Ice Shelf in Dronning Maud Land are particularly vulnerable to total FAC depletion (&gt; 50 % decrease by 2100), even for low-emission (SSP1-2.6) and intermediate-emission (SSP2-4.5) scenarios. In the high-emission (SSP5-8.5) scenario in particular, the formation of ice slabs further reduces accessible FAC on ice shelves with low accumulation rates (current rates of &lt; 500 mmw.e.yr-1), including many East Antarctic ice shelves and the Filchner–Ronne, Ross, Pine Island and Larsen C ice shelves. These results underline the potentially large vulnerability of low-accumulation ice shelves to firn air depletion through ice-slab formation.

Organic carbon accumulation in British saltmarshes

Saltmarshes are a crucial component of the coastal carbon (C) system and provide a natural climate regulation service through the accumulation and long-term storage of organic carbon (OC) in their soils. These coastal ecosystems are under growing pressure from a changing climate and increasing anthropogenic disturbance. To manage and protect these ecosystems for C and to allow their inclusion in emissions and natural-capital accounting, as well as carbon markets, accurate and reliable estimates of OC accumulation are required. However, globally, such data are rare or of varying quality. Here, we quantify sedimentation rates and OC densities for 21 saltmarshes in Great Britain (GB). We estimate that, on average, saltmarshes accumulate OC at a rate of 110.88 ± 43.12 g C m−2 yr−1. This is considerably less than widely applied global saltmarsh averages. It is therefore highly likely that the contribution of northern European saltmarshes to global saltmarsh OC accumulation has been significantly overestimated. Taking account of the climatic, geomorphological, oceanographic, and ecological characteristics of all GB saltmarshes and the areal extent of different saltmarsh zones, we estimate that the 451.65 km2 of GB saltmarsh accumulates 46,563 ± 4353 t of OC annually. These low OC accumulation rates underline the importance of the 5.20 ± 0.65 million tonnes of OC already stored in these vulnerable coastal ecosystems. Going forward the protection and preservation of the existing stores of OC in GB saltmarshes must be a priority for the UK as this will provide climate benefits through avoided emissions several times more significant than the annual accumulation of OC in these ecosystems.

Profits and capital accumulation in the Mexican economy

Abstract The paper studies the long-run disconnection between a rising profit share of income and a constant rate of capital accumulation in Mexico since the early 1990s. According to stylized facts based on the Cambridge accumulation equation, the disconnection reflects two factors: first, a flat trajectory of the investment share of profits, and second, a gap between a rising profit share and a constant or even falling profit rate due to a decline in the output/capital ratio. In manufacturing—where the disconnection was particularly sharp—econometric estimates show that the accumulation rate was negatively affected not only by the decline in the output/capital ratio but also by a fall in the relative Mexican/US profit rate. The estimates show in addition that, among financialization indicators, a rise in interest payments as a share of profits may have contributed to the low accumulation rate.

Depositional characteristics of fine-grained sedimentary rocks and the links to OAE-3 and PETM of the Upper Cretaceous-Paleogene Madingo Formation, lower Congo Basin, West Africa

Fine-grained sedimentary rocks of the Madingo Formation in the Lower Congo Basin (LCB), are significant targets for Upper Cretaceous–Paleogene depositional system analysis in West Africa. Six types of fine-grained sedimentary rocks of the Madingo Formation were identified based on integrated analyses of petrographic characteristics, geochemical element analysis and electron back-scattered diffraction of thin sections, including (1) siliceous mudstone, (2) claystone, (3) marlstone, (4) radiolarian-rich mudstone, (5) foraminifera-rich mudstone, and (6) phosphatic mudstone. Geochemical indexes (U/Th, V/(V + Ni), V/Cr, and Ni/Co) indicate that the Madingo Formation on the deep-water slope was characterized by typical oxygen-poor and even anaerobic environment, preserving organic matter and thus preserving sediments with relatively high TOC, abundant marine fossils and framboidal pyrite. The LCB experienced two different marginal marine environments during the deposition of the Madingo Formation. The lower Madingo Formation was characterized by a radiolarian-rich mudstone (the first stage of upwelling) deposited in a marginal semi-restricted sea bay environment (correlated with the Coniacian–Santonian Oceanic Anoxic Event 3; OAE-3), with up to 4.0% TOC, and types II2 and II1 organic matter. The upper Madingo Formation was characterized by foraminifera-rich and phosphatic mudstone (the second stage of upwelling) deposited in a marginal open marine environment (correlated with the Paleocene-Eocene Thermal Maximum; PETM), with up to 4.83% TOC and 5.0 mg/g phosphate that is rich in types I and II1 organic matter. The whole Madingo deposition is estimated to have spanned a 52-Myr period, and the low sediment accumulation rate of approximately 9 μm/yr can lead to a high TOC content. The three identified condensed sections include radiolarian-rich, foraminifera-rich or phosphatic mudstones that deposited in the deep-water slope, were probably marine source rocks for post-salt exploration in West Africa.

Why does western Makran have a low seismicity rate?

The Makran Subduction Zone is segmented into western and eastern Makran where all instrumentally recorded megathrust earthquakes happened in eastern Makran. To find out how the lack of megathrust earthquakes and the observed low seismicity rate in western Makran is related to a combination of long interseismic quiescence, aseismic creep, or low rate of interseismic strain accumulation within the megathrust zone, we have complemented the five existing GPS vectors along the coasts of Makran by nine new GPS vectors and an extra eight new GPS vectors across the width of the Makran megathrust zone. Our block modeling shows that the coupling of the subducting Arabian oceanic plate with the overriding plate in western Makran is more than four times smaller than that of eastern Makran. Additionally, the maximum interseismic strain rate accumulation within the onshore part of the megathrust zone of western Makran is >7 times smaller than that in eastern Makran. We found a right-lateral motion of about ∼16 mm across the transfer zone between Zagros and Makran. We consider a much lower earthquake hazard for western Makran relative to that of eastern Makran because the overriding Lut block is moving northward causing much less strain accumulation within the megathrust zone, and because of the lower seismic coupling between the subducting and overriding plates. Our findings show a large strain rate across the transfer zone between Zagros and Makran and thus imply a much higher earthquake hazard for the transfer zone.

Stratigraphic noise and its potential drivers across the plateau of Dronning Maud Land, East Antarctica

Abstract. Stable water isotopologues of snow, firn and ice cores provide valuable information on past climate variations. Yet single profiles are generally not suitable for robust climate reconstructions. Stratigraphic noise, introduced by the irregular deposition, wind-driven erosion and redistribution of snow, impacts the utility of high-resolution isotope records, especially in low-accumulation areas. However, it is currently unknown how stratigraphic noise differs across the East Antarctic Plateau and how it is affected by local environmental conditions. Here, we assess the amount and structure of stratigraphic noise at seven sites along a 120 km transect on the plateau of Dronning Maud Land, East Antarctica. Replicated oxygen isotope records of 1 m length were used to estimate signal-to-noise ratios as a measure of stratigraphic noise at sites characterised by different accumulation rates (43–64 mm w.e. a−1), snow surface roughnesses and slope inclinations. While we found a high level of stratigraphic noise at all sites, there was also considerable variation between sites. At sastrugi-dominated sites, greater stratigraphic noise coincided with stronger surface roughnesses, steeper slopes and lower accumulation rates, probably related to increased wind speeds. These results provide a first step to modelling stratigraphic noise and might guide site selection and sampling strategies for future expeditions to improve high-resolution climate reconstructions from low-accumulation regions.

The Upper Cretaceous petroleum system of the East Beni Suef Basin, Egypt: an integrated geological and 2D basin modelling approach

We integrated geological and 2D basin modelling to investigate the tectonostratigraphic evolution of the East Beni Suef Basin (EBSB) of north central Egypt and its implications for the Upper Cretaceous petroleum system. Two intersecting seismic sections and three exploration wells were used for this study. The geological model defines the structural and geometrical framework of the basin, which formed the basis for subsequent 2D basin modelling. The developed basin models were calibrated and fine-tuned using vitrinite reflectance and corrected temperature data. Modelling results indicate that the Abu Roash ‘F’ source-rock maturity ranges from the early oil window at the basin margins to the main oil window in the centre. The main phase of hydrocarbon generation occurred during the Eocene after trap formation in the Late Cretaceous. Generated hydrocarbons have migrated both laterally and vertically, most likely from the central part of the basin towards the basin margins, particularly eastwards to the structural traps. The model predicts low accumulation rates for the EBSB, which are caused by the ineffective sealing capacity of the overburden rocks and normal faults. In addition to the proven kitchen for the charging of the Abu Roash ‘E’ reservoirs, an additional kitchen area to the NW of the basin is suggested for the Abu Roash ‘G’ reservoirs.

Comparison of carbon and nitrogen accumulation rate between bog and fen phases in a pristine peatland with the fen-bog transition.

Long-term carbon and nitrogen dynamics in peatlands are affected by both vegetation production and decomposition processes. Here, we examined the carbon accumulation rate (CAR), nitrogen accumulation rate (NAR) and δ13 C, δ15 N of plant residuals in a peat core dated back to ~8500 cal year BP in a temperate peatland in Northeast China. Impacted by the tephra during 1160 and 789 cal year BP and climate change, the peatland changed from a fen dominated by vascular plants to a bog dominated by Sphagnum mosses. We used the Clymo model to quantify peat addition rate and decay constant for acrotelm and catotelm layers during both bog and fen phases. Our studied peatland was dominated by Sphagnum fuscum during the bog phase (789 to -59 cal year BP) and lower accumulation rates in the acrotelm layer was found during this phase, suggesting the dominant role of volcanic eruption in the CAR of the peat core. Both mean CAR and NAR were higher during the bog phase than during the fen phase in our study, consistent with the results of the only one similar study in the literature. Because the input rate of organic matter was considered to be lower during the bog phase, the decomposition process must have been much lower during the bog phase than during the fen phase and potentially controlled CAR and NAR. During the fen phase, CAR was also lower under higher temperature and summer insolation, conditions beneficial for decomposition. δ15 N of Sphagnum hinted that nitrogen fixation had a positive effect on nitrogen accumulation, particular in recent decades. Our study suggested that decomposition is more important for carbon and nitrogen sequestration than production in peatlands in most conditions and if future climate changes or human disturbance increase decomposition rate, carbon sequestration in peatlands will be jeopardized.

Dating pelagic sediments from the northwestern Pacific Ocean by integration of Multi-geochronologic approaches

As the largest promising rare earth elements and yttrium (termed as REY) resource in the world, pelagic sediments enriched in REY (REY-rich sediments) have gained extensive attention. However, the mechanism responsible for the enrichment of REY in pelagic sediments remains unknown, primarily due to the challenge of obtaining robust geochronology. Despite previous attempts, integration of multi-geochronologic approaches seems better suited to determine robust geochronology for pelagic sediments. Here, we present a continuous chronostratigraphic framework for a pelagic sediment core collected from the northwestern Pacific Ocean, integrating authigenic 10Be/9Be dating, 230Thex dating, and magnetostratigraphy. Our results indicate that the REY-rich sediments deposited prior to ∼ 2.5 Ma, and a highly REY-rich sediment layer deposited at ∼ 11.5–9.5 Ma in the study area. We suggest that a low sedimentation accumulation rate (SAR) was necessary for REY enrichment in pelagic sediment, while the deposition of highly REY-rich sediments should be attributed to the additional contribution from active bottom currents. Our study proposes that the enrichment of bioapatite fossils and micronodules related to enhanced bottom currents under a low SAR sedimentary environment could promote the widespread highly REY-rich sediments in the study region.

Magnetostratigraphy of the Mercia Mudstone Group (Devon, UK): implications for regional relationships and chronostratigraphy in the Middle to Late Triassic of Western Europe

Global synchronization of environmental change in terrestrial successions in deep time is challenging owing to the paucity of dating methods, a case also applicable to the Middle to Upper Triassic Mercia Mudstone Group in Britain. Using coastal cliff sections, magnetostratigraphy was evaluated at 263 horizons, defining 53 magnetozones. Magnetozones from the lower 140 m of the group demonstrate correspondence to those from the mid-Ladinian to early Carnian polarity timescale, dating that is compatible with magnetostratigraphy from the underlying Sherwood Sandstone Group. Magnetostratigraphy of the Dunscombe Mudstone Formation, and associated palynological data, suggest a late Carnian to earliest Norian age, and a dramatically lower accumulation rate than for adjacent formations. The polarity record demonstrates coeval flooding events, evaporite deposits and intervals of sand supply between the Wessex Basin and the Central European Basin in the Carnian. This is the result of linked climatic and eustatic changes between these separate basins, related to aeolian dust supply and the shrinkage of hyper-arid source regions for the fine material. Magnetostratigraphy from the Branscombe Mudstone and Blue Anchor formations demonstrates their Norian and early Rhaetian age. These and other data suggest an alternative synchronization of marine and non-marine polarity records for the Norian polarity timescale. Supplementary material : Section details and detailed logs of the sampled sections and inferred sequence boundaries, magnetic mineralogy data, demagnetization behaviour and mean directions, summary of virtual geomagnetic pole data and a comparison with other European poles, construction of other composite reference sections and revised polarity scales, an Excel sheet of magnetic data, statistically evaluated correlation models and age models are available at https://doi.org/10.6084/m9.figshare.c.6613788

Occurrence of Multiple Glyphosate-Resistant Weeds in Brazilian Citrus Orchards

Glyphosate is the most widely used herbicide for weed control in citrus orchards in Brazil; therefore, it is likely that several species have gained resistance to this herbicide and that more than one resistant species can be found in the same orchard. The objective was to identify weeds resistant to glyphosate in citrus orchards from different regions of the São Paulo State (SP) and determine how many resistant species are present within the same orchard. Seeds of Amaranthus deflexus, A. hybridus, Bidens pilosa, Chloris elata, Conyza bonariensis, Digitaria insularis, Solanum Americanum, and Tridax procumbens, which, as reported by growers, are suspected to be resistant to glyphosate, were collected from plants that survived the last application of this herbicide (&gt;720 g of acid equivalent [ae] ha–1) in sweet orange and Tahiti acid lime orchards. Based on dose–response and shikimic acid accumulation assays, all populations of A. deflexus, A. hybridus, B. pilosa, and T. procumbens were sensitive to glyphosate. However, populations of B. pilosa from the Olimpia region (R-NS, R-PT and R-OdA) showed signs of resistance based on plant mortality rates by 50% within a population (LD50 = 355–460 g ae ha−1). All populations of C. bonariensis, C. elata, and D. insularis were resistant to glyphosate, presenting resistance ratios from 1.9 to 27.6 and low shikimate accumulation rates. Solanum americanum also showed resistance, with resistance ratios ranging from 4.3 to 25.4. Most of the citrus orchards sampled presented the occurrence of more than one species resistant to glyphosate: Nossa Senhora—one species; Olhos D’agua and Passatempo—two species; Araras—four species; and Cordeiropolis and Mogi-Mirim—up to five species. The results reported in this paper provide evidence of multiple species in citrus orchards from São Paulo that have exhibited resistance to glyphosate. This underscores the difficulties in managing glyphosate-resistant weeds which are prevalent throughout the country, such as C. bonariensis and D. insularis. The presence of these resistant species further complicates the control of susceptible species that may also develop resistance. In addition, the glyphosate resistance of S. americanum was identified for the first time.

How old is too old? Implications of averaging 14C-Based estimates of ventilation age to assess the Pacific Ocean's role in sequestering CO2 in the past

Compilations of benthic foraminiferal 14C-based ventilation age estimates from the deep North Pacific have been used to argue the average age of bottom waters during the last glacial maximum was 3000 years, or about 1000 years older than modern. If true, glacial bottom waters would have accumulated additional respired carbon and contributed to the drop in atmospheric CO2. By the same reasoning, ventilation ages that were 1000 years older, would have lost dissolved oxygen and become anaerobic and thereby unable to support epibenthic fauna. The current study re-analyzed the Pacific 14C data and finds the glacial ventilation age average is biased by inclusion of data from low sediment accumulation rate cores that have been affected by bioturbation and contaminated with older specimens. Removal of data from cores with sedimentation rates less than 10 cm/ky reduces the old-bias and results in an average ventilation age that is close to the modern ocean.

The 2021 Mw 5.2 Baicheng Earthquake: Implications for the Hazards of Extremely Shallow Earthquakes

Abstract On 23 March 2021, an Mw 5.2 earthquake struck Baicheng city at the southern foreland of the Tian Shan mountains and produced unexpected severe damages. Based on Interferometric Synthetic Aperture Radar observations, geological investigations, petroleum seismic-reflection profiles, and available seismological results, we found that (1) the earthquake rupture was sinistral-slip dominated and mostly concentrated at ≤2 km depth, suggesting an extremely shallow earthquake; (2) the earthquake produced a 4.1-km-long surface rupture zone, along which the lateral slip ranged from 0 to 135 cm and showed a significant short-wavelength variation; and (3) the causative fault is poorly developed (i.e., has low slip accumulation and slip rate) and cuts through a shallow-buried salt dome. These findings, along with those of previous studies, document some unique characteristics of moderate earthquakes at extremely shallow depths (≤3 km) relative to those at greater depths. First, shallow earthquakes occur on faults that are poorly developed and bracketed by rocks being able to behave as velocity weakening at shallow depth (including crystalline basement rocks, carbonites, volcanic rocks, or evaporites). Second, the surface rupture produced by shallow earthquakes has abnormally large length and slip, and possibly includes an abrupt slip variation. These characteristics highlight potential severe damages of the shallow moderate earthquake but enhance the challenge of identifying the earthquake causative fault (the earthquake source) prior to the event using traditional methods (e.g., geomorphic mapping, geophysical imaging surveys, and paleoseismic trenching).

Trends of legacy and emerging organic contaminants in a sediment core from Cienfuegos Bay, Cuba, from 1990 to 2015

Legacy and emerging organic pollutants pose an ever-expanding challenge for the marine environment. This study analysed a dated sediment core from Cienfuegos Bay, Cuba, to assess the occurrence of polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), polybrominated diphenyl ethers (PBDEs), alternative halogenated flame retardants (aHFRs), organophosphate esters (OPEs), and phthalates (PAEs) from 1990 to 2015. The results evidence the continuing presence of historical regulated contaminants (PCBs, OCPs, and PBDEs) in the southern basin of Cienfuegos Bay. PCB contamination declined since 2007, likely in response to the gradual global phasing out of PCB containing materials. There have been relatively consistent low accumulation rates for OCPs and PBDEs at this location (in 2015 approximately 1.9 and 0.26ng/cm2/year, respectively, with 2.8ng/cm2/year for Σ6PCBs), with indications of recent local DDT use in response to public health emergencies. In contrast, sharp increases are observed between 2012 and 2015 for the contaminants of emerging concern (PAEs, OPEs, and aHFRs), and in the case of two PAEs (DEHP and DnBP) the concentrations were above the established environmental effect limits for sediment dwelling organisms. These increasing trends reflect the growing global usage of both alternative flame retardants and plasticizer additives. Local drivers for these trends include nearby industrial sources such as a plastic recycling plant, multiple urban waste outfalls, and a cement factory. The limited capacity for solid waste management may also contribute to the high concentrations of emerging contaminants, especially plastic additives. For the most recent year (2015), the accumulation rates for Σ17aHFRs, Σ19PAEs, and Σ17OPEs into sediment at this location were estimated to be 10, 46 000, and 750ng/cm2/year, respectively. This data provides an initial survey of emerging organic contaminants within this understudied region of the world. The increasing temporal trends observed for aHFRs, OPEs, and PAEs highlights the need for further research concerning the rapid influx of these emerging contaminants.