ORCID Profile
0000-0002-5270-788X
Current Organisation
Centro Nacional de Investigación sobre la Evolución Humana (CENIEH)
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Publisher: Elsevier BV
Date: 04-2010
Publisher: Elsevier BV
Date: 06-2020
Publisher: Copernicus GmbH
Date: 16-01-2018
Abstract: Abstract. Sediment-routing systems continuously transfer information and mass from eroding source areas to depositional sinks. Understanding how these systems alter environmental signals is critical when it comes to inferring source-area properties from the sedimentary record. We measure cosmogenic 10Be and 26Al along three large sediment-routing systems (~ 100,000 km2) in central Australia with the aim of tracking downstream variations in 26Al/10Be inventories and to identify the factors responsible. By comparing 56 new cosmogenic 10Be and 26Al measurements in stream sediments with matching data (n = 55) from source areas, we show that 26Al/10Be inventories in hillslope bedrock and soils set the benchmark for relative downstream modifications. Lithology is the primary determinant of erosion-rate variations in source areas and despite sediment mixing over hundreds of kilometres downstream a distinct lithological signal is retained. Postorogenic ranges yield catchment erosion rates of ~ 6–11 m/m.y. and silcrete-dominant areas erode as slow as ~ 0.2 m/m.y. 26Al/10Be inventories in stream-sediments reveal overall downstream-increasing minimum cumulative burial terms up to ~ 1.1 m.y. but more generally ~ 400–800 k.y. The magnitude of the burial signal correlates with increasing sediment cover downstream and reflects assimilation from storages with long exposure histories, such as alluvial fans, desert pavements, alluvial plains, and aeolian dunes. We propose that the tendency for large alluvial rivers to mask their 26Al/10Be source-area signal differs according to geomorphic setting. Signal preservation is favoured by i) high sediment supply rates, ii) high mean runoff, and iii) a thick sedimentary basin pile. Conversely, signal masking prevails in landscapes of i) low sediment supply, ii) discontinuous sediment flux, and iii) juxtaposition of sediment storages with notably different exposure histories.
Publisher: Geological Society of America
Date: 2015
DOI: 10.1130/G35856.1
Publisher: Copernicus GmbH
Date: 07-05-2018
Abstract: Abstract. Sediment-routing systems continuously transfer information and mass from eroding source areas to depositional sinks. Understanding how these systems alter environmental signals is critical when it comes to inferring source-area properties from the sedimentary record. We measure cosmogenic 10Be and 26Al along three large sediment-routing systems (∼ 100 000 km2) in central Australia with the aim of tracking downstream variations in 10Be–26Al inventories and identifying the factors responsible for these variations. By comparing 56 new cosmogenic 10Be and 26Al measurements in stream sediments with matching data (n= 55) from source areas, we show that 10Be–26Al inventories in hillslope bedrock and soils set the benchmark for relative downstream modifications. Lithology is the primary determinant of erosion-rate variations in source areas and despite sediment mixing over hundreds of kilometres downstream, a distinct lithological signal is retained. Post-orogenic ranges yield catchment erosion rates of ∼ 6–11 m Myr−1 and silcrete-dominant areas erode as slow as ∼ 0.2 m Myr−1. 10Be–26Al inventories in stream sediments indicate that cumulative-burial terms increase downstream to mostly ∼ 400–800 kyr and up to ∼ 1.1 Myr. The magnitude of the burial signal correlates with increasing sediment cover downstream and reflects assimilation from storages with long exposure histories, such as alluvial fans, desert pavements, alluvial plains, and aeolian dunes. We propose that the tendency for large alluvial rivers to mask their 10Be–26Al source-area signal differs according to geomorphic setting. Signal preservation is favoured by (i) high sediment supply rates, (ii) high mean runoff, and (iii) a thick sedimentary basin pile. Conversely, signal masking prevails in landscapes of (i) low sediment supply and (ii) juxtaposition of sediment storages with notably different exposure histories.
Publisher: Copernicus GmbH
Date: 04-03-2021
DOI: 10.5194/EGUSPHERE-EGU21-9165
Abstract: & & The Finke River in central Australia is counted among the world& #8217 s oldest drainage systems, raising the prospect that it holds a geomorphic record relevant to testing ideas about the role of sub-lithospheric mantle flow in shaping the Australian landscape. The Finke& #8217 s upper reaches preserve an enigmatic set of intertwined active and relict gorges that suggest a complex history of incision, aggradation and re-incision. We measured cosmogenic & sup& & /sup& Be and & sup& & /sup& Al in fluvial gravels stored in the gorges, and we applied a Markov chain Monte Carlo-based inversion model to test two limiting-case hypotheses about the timing of the gravel deposition and exhumation. Our results suggest that the nuclide memory contained within the gravels was essentially erased during protracted sediment storage. Previous studies attribute landscape evolution to the intensified post-Miocene aridity in tune with the perception that central Australia experienced limited deformation during the Cenozoic. However, the close correlation between drainage network patterns and the gravity field leads us to propose, instead, that incision/aggradation phases in the upper Finke are driven by a flexural response (at ~10& sup& & /sup& km length scales) to extreme uncompensated loads embedded in the crust. Further, we suggest that dynamic mantle processes have deformed the central Australian topography over longer (~10& sup& & /sup& km) wavelengths via the in-situ stress field, with horizontal stress variations of order 1& #8211 MPa. Acting together, these crustal and sub-lithospheric structures have imposed to-and-fro tilting on the Finke, triggering the phases of incision/aggradation on a million-year timescale that created the unusual intertwined bedrock gorges. The litude of topographic responses in the upper Finke to inferred variations in end-loading on the plate helps resolve an ongoing debate about the effective elastic thickness of the central Australian lithosphere to no more than 35 km.& &
Publisher: Elsevier BV
Date: 03-2022
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-8547
Abstract: & & & span& & span& In the 60& #8217 s, the formulation of the plate tectonic theory changed our understanding of the Earth dynamics. Aiming at explaining the earth first order kinematics, this primary theory of plate tectonic assumed rigid plates, a necessity to efficiently transfer stress from one boundary to another.& & /span& & /span& & & & & & span& & span& If successful to explain, at first order, the plate-boundary evolutions, this theory fails when compared to the unpredicted but identified deformation located inside the plate-domains: the intraplate orogens. Indeed, the intraplate regions are thought to be slowly, if at all, deforming. Therefore, it is expected that intraplate regions do not show important finite deformation, that is to say, no mountains. Some intraplate regions, however, have important relief: the Snowy Mountains (Australia), the Ural Mountains (Russia) or the Massif Central (France) for ex les. Traditionally, such regions are interpreted as old structures that are slowly eroded, interpretations that are most of the time weakly constrained.& & /span& & /span& & & & & & & & & & & span& & span& Our study is aiming at providing stronger constraints and then a better understanding of such challenging area that are the intraplate orogen domains. Because direct measurements of deformations (e.g. GNSS: Global Navigation Satellite System or InSAR: Interferometric Synthetic Aperture Radar) are most of the time below the precision level, it is necessary to derive this information from the landscape evolution. To do so, terrestrial cosmogenic nuclide (TCN) technics are a key method, allowing to constraint the temporal landscape evolution. Classically, two TCN-based approaches are used to quantify the landscape evolution rate: burial ages and watershed-wide denudation rates, based on measurement in quartz sediment of 10Be and 26Al concentrations, two radioactive cosmogenic isotopes.& /span& & /span& & & & & & & & & & & span& & span& Using the Massif Central (France) as study area, we show that this region is currently deforming.& /span& & /span& & & & & & span& & span& From new geochronological constraints and a geomorphometric study, we propose that the region undergoes an active uplift encompassing the last c.a. 4 Ma. It can be explained by the combination of at least two phenomena: the first one is the uplift triggering event, that has yet to be clearly identified, and the second one: the erosional isostatic adjustment enhancing the first one and possibly continuing after the end of the first one.& & /span& & /span& & &
Publisher: Copernicus GmbH
Date: 31-01-2023
DOI: 10.5194/TC-2022-252
Abstract: Abstract. During the interglacial and interstadials of Marine Isotope Stage 5 (MIS 5e, 5c, 5a), outlet and alpine glaciers in the Dry Valleys region, Antarctica, appear to have advanced in response to increased precipitation from enhanced open ocean conditions in the Ross Sea. We provide further evidence of this antiphase behaviour through retreat of a peripheral lobe of Taylor Glacier in Pearse Valley, a region that was glaciated during MIS 5. We measured cosmogenic 10Be and 26Al in three granite cobbles from thin, patchy drift (Taylor 2 Drift) in Pearse Valley to constrain the timing of retreat of Taylor Glacier. Assuming simple continuous exposure, our minimum, zero erosion, exposure ages suggest Taylor Glacier partially retreated from Pearse Valley no later than 65–74 ka. Timing of retreat after 65 ka and until the Last Glacial Maximum (LGM) when Taylor Glacier was at a minimum position, remains unresolved. The depositional history of permafrost sediments buried below Taylor 2 Drift in Pearse Valley was obtained from 10Be and 26Al depth profiles to ~3 metres in permafrost in proximity to the cobble s ling sites. Depth profile modelling gives a depositional age for near-surface ( 1.65 m) permafrost at Pearse Valley of 180 ka +20/−40 ka, implying deposition of permafrost sediments predate MIS 5 advances of Taylor Glacier. Depth profile modelling of deeper permafrost sediments ( 2.09 m) indicates a depositional age of 180 ka. The cobble and permafrost ages reveal Taylor Glacier advances during MIS 5 were non-erosive or mildly erosive, preserving the underlying permafrost sediments and peppering boulders and cobbles upon an older, relict surface. Our results are consistent with U/Th ages from central Taylor Valley, and suggest changes in moisture delivery over Taylor Dome during MIS 5e, 5c and 5a appear to be associated with the extent of the Ross Ice Shelf and sea ice in the Ross Sea. At a coastal, lower elevation site in neighbouring Lower Wright Valley, 10Be and 26Al depth profiles from a second permafrost core exhibit near-constant concentrations with depth, and indicate the sediments are either vertically mixed after deposition, or are sufficiently young and post-depositional nuclide production is negligible relative to inheritance. 26Al/10Be concentration ratios for both depth profiles range between 4.0 and 5.2 and are all lower than the nominal surface production rate ratio of 6.75 indicating that prior to deposition, these sediments experienced a complex exposure-burial history. Assuming a single cycle exposure-burial scenario, the observed 26Al/10Be ratios are equivalent to a total minimum exposure-burial history of ~1.2 Ma. Our new data corroborates antiphase behaviour between outlet and alpine glaciers in the Dry Valleys region and ice extent in the Ross Sea. We suggest a causal relationship of cold-based glacier advance and retreat that is controlled by an increase in moisture availability during retreat of sea ice and perhaps the Ross Ice Shelf, and conversely, a decrease during times of sea ice and Ross Ice Shelf expansion in the Ross Sea.
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-9099
Abstract: & & Although more and more processes are discussed and discovered on the genesis and evolution of cave systems, the tiered karsts are often explained by a control of the base level evolution. In this classical model, the horizontal galleries are explained by a stability of the base level elevation. To the contrary, the shafts and network segments with steep slopes are related to incision periods with a base level lowering.& & & & We use Terrestrial Cosmogenic Nuclide Geochronology to estimate burial ages of alluvium trapped in several caves of the Larzac plateau in Southern France. All the s les are collected in horizontal cave levels, sometimes located between steeper segments. Some caves are opened in river gorge walls, while others are located below the Larzac plateau not farther than 5km away from the river gorges.& & & & The burial ages for the caves opening in the gorges are consistent with the incision rates given for the area and could be interpreted using the classical model. However, the cave within the plateau show a horizontal level with alluvium deposited 200m above the caves in the gorge with the same burial ages (~1 Myr). Since then, new shafts have been opened without alluvium and are hydrologically connected to the river by deeper[jfr1]& hypogenic galleries. The cave morphologies and the geochronological data suggest that the classical model fails to explain the horizontal levels in cave below the plateau. We postulate that the geometry of the caves in these limestone and dolomite plateaus are related to a previous period of ghost-rock and alteration roots formations. Without the opening of an efficient connection between this primokarst and the valley, no alluvium can flow through the cave. Therefore, we think that our burial ages constrain the emptying of the ghost-rocks leading to the genesis of the cave where water and possibly alluvium can flow through. Furthermore, these new finding explain why the horizontal levels in the caves are not clearly related to horizontal markers in the surface geomorphology and why large shafts (& m) exist in the area without evidences of long periods of base level stability followed by large drop of the regional base level.& & & & & & & & & & / & & / & & / &
Publisher: Geological Society of America
Date: 02-01-2018
DOI: 10.1130/B31767.1
Publisher: Copernicus GmbH
Date: 04-03-2021
DOI: 10.5194/EGUSPHERE-EGU21-14132
Abstract: & & Cosmogenic production rates (PRs) are the essential conversion factor between AMS cosmogenic concentrations and absolute exposure ages. The accuracy of cosmogenic glacial chronologies and reliability in their comparison to other paleoclimate systems & is largely contingent on the precision and accuracy of the adopted production rate. This is particularly critical in determining past glacial geochronologies at the scale of millennial temporal resolution. Most PR calibrations are carried out at deglaciation sites where radiocarbon provides the independent chronometric control usually based on 14C ages in basal sediments or varves& from lake or bog cores which is assumed to represent the minimum age for glacial retreat. Under these conditions and hence provide PRs as maximum values. Given that today most AMS facilities can deliver 10-Be, 26-Al and 36-Cl data with total analytical errors less than 2% ( for 10 ka exposure), the precision of a PR remains largely dependent & on the error in the independent chronology and accuracy of AMS standards. The history over the past 20 years of the ever-decreasing value of & SLHL 10-Be cosmogenic spallation PRs & from initial estimates of about 7 atoms/g/a to the current& & #8216 accepted& #8216 (global average) values of ~4 atoms/g/a,& & is an interesting story in itself and demonstrates the complexity in such determinations. & & & & & Over the past few years new web-based calculators are now available to calculate uniformly new production rates from either new data or combinations of any set of published data (CRONUS-Earth, CRONUS-UW, CosmoCalc, ICE-D, CREp). This delivers a means by which new production rates can be seamlessly integrated and compared using identical constants, methods and statistics that were used to generate (currently accepted) global average or regional production rates.& & & & & For the British Isles, there are a number of 10-Be reference sites that give PRs (Lm scheme) between 3.89& #177 % & atoms/g/a & (Putnam, QG, v50, 2019) to 4.20& #177 % atoms/g/a (Small, JQS, v30, 2015) which convert to 3.95 and 4.28, respectively, using datasets in the ICE-D calculator). This difference in 10-Be spallation PRs has recently raised some debate and challenges for the timing of the local-LGM and demise of the British Ice Sheet. This work provides a new & British Isles site specific 10Be PR from the & Arenig Mountains in North Wales where radiocarbon dating of basal sediments from a bog core associated with a series of nearby cirque moraines provides independent age control.& Similarly in the South Island of New Zealand, the current accepted 10Be PR is 3.76& #177 % (Putnam, QG 2009 converts to 3.94& #177 % using ICE-D) and is the only available PR that is used for these southern hemispheric glacial sites. This work provides a new Australasian site specific 10Be PR from Arthurs Pass retreat moraines where radiocarbon dating of basal sediments from three cores extracted from a bog impounded by the moraine provides independent age control.& & &
Publisher: Copernicus GmbH
Date: 15-12-2020
DOI: 10.5194/GCHRON-2-367-2020
Abstract: Abstract. Northern New Zealand is an important location for understanding Last Glacial Interval (LGI) palaeoclimate dynamics, since it is influenced by both tropical and polar climate systems which have varied in relative strength and timing. Sediments from the Auckland Volcanic Field maar lakes preserve records of such large-scale climatic influences on regional palaeo-environment changes, as well as past volcanic eruptions. The sediment sequence infilling Orakei maar lake is continuous, laminated, and rapidly deposited, and it provides a high-resolution (sedimentation rate above ∼ 1 m kyr−1) archive from which to investigate the dynamic nature of the northern New Zealand climate system over the LGI. Here we present the chronological framework for the Orakei maar sediment sequence. Our chronology was developed using Bayesian age modelling of combined radiocarbon ages, tephrochronology of known-age rhyolitic tephra marker layers, 40Ar∕39Ar-dated eruption age of a local basaltic volcano, luminescence dating (using post-infrared–infrared stimulated luminescence, or pIR-IRSL), and the timing of the Lasch palaeomagnetic excursion. We have integrated our absolute chronology with tuning of the relative palaeo-intensity record of the Earth's magnetic field to a global reference curve (PISO-1500). The maar-forming phreatomagmatic eruption of the Orakei maar is now dated to 132 305 years (95 % confidence range: 131 430 to 133 180 years). Our new chronology facilitates high-resolution palaeo-environmental reconstruction for northern New Zealand spanning the last ca. 130 000 years for the first time as most NZ records that span all or parts of the LGI are fragmentary, low-resolution, and poorly dated. Providing this chronological framework for LGI climate events inferred from the Orakei sequence is of paramount importance in the context of identification of leads and lags in different components of the Southern Hemisphere climate system as well as identification of Northern Hemisphere climate signals.
Publisher: Wiley
Date: 21-11-2017
DOI: 10.1002/ESP.4273
Publisher: Copernicus GmbH
Date: 28-03-2022
DOI: 10.5194/EGUSPHERE-EGU22-12056
Abstract: & & Centro Nacional de Investigaci& #243 n sobre la Evoluci& #243 n Humana (or National Research Centre on Human Evolution, CENIEH) is located in Burgos, northern Spain. The centre is dedicated to human evolution research worldwide, including Atapuerca, a world heritage archaeological site where the oldest human fossil in Europe to date have been discovered. To support the needs of characterising geological and sedimentological context of archaeological sites, the institute also features a wide range of geological analysis (e.g., Laser diffraction grain size analyser, XRD, XRF, Raman Spectroscopy, SEM, Micro CT, Digital mapping and 3D analysis) and geochronology laboratories (including palaeomagnetism, OSL, ESR and U-series). In 2020, a new cosmogenic nuclide dating research line has initiated to strengthen the existing geochronological capabilities in the centre, particularly, at timescales of early-mid Pleistocene and beyond. To date, we have established a procedure for routine quartz separation and & sup& & /sup& Be-& sup& & /sup& Al extraction. Current projects include & sup& & /sup& Be-& sup& & /sup& Al burial/isochron dating of cave deposits, fluvial terraces and artefacts in the context of archaeological and landscape evolution research. In this paper, we present a general setup of the laboratory, its capacity and current projects as well as future prospective.& &
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-20252
Abstract: & & The mantle convection accompanying plate motion causes vertical movements of up to a few hundred metres at Earth& #8217 s surface over wavelengths of 10& sup& & /sup& & #8211 & sup& & /sup& km. This & em& dynamic topography& /em& appears to come and go at ~ 1& #8211 Myr timescales in areas that are often well away from plate margins, although its spatial and temporal characteristics are subject to ongoing debate. Since such motions are small and transient, discriminating convective signals from other drivers of relief generation and/or sediment dispersal remains tricky. An outstanding challenge is to detect these elusive, transient undulations from a tell-tale geomorphic imprint preserved in either drainage patterns or the stratigraphic record.& & & & In the intra-plate setting of central Australia, a 30 km long sinuous gorge is developed where the major regional drainage, Finke River, dissects a band of low hills. Remarkably, this gorge is intertwined with an abandoned and less deeply incised gorge that forms hanging junctions and shares similar width and sinuosity. This unusual overprinting of the two gorges remains unexplained.& & & & With an aim to investigate the history of the intertwined gorges, we measured cosmogenic & sup& & /sup& Be and & sup& & /sup& Al in fluvial gravels stored in the palaeovalley cutoffs. The gravels are remnants of major alluviation episodes that we surmise result from ongoing vertical motions associated with dynamic topography. We use a Markov chain Monte Carlo-based inversion model to test two hypotheses to explain the nuclide inventory contained within the stored fluvial gravels. In the first case, rapid alluviation and erosion since 1 Ma preserves the nuclide memory of the source area in the second, the nuclide memory is erased during long-term fluvial storage (& 5 Myr) and is restored during exhumation of the palaeovalley gravel-pile. The two hypotheses are therefore limiting-case scenarios that constrain overall fast versus slow landscape evolution, respectively. Our model results suggest that long-term burial decouples the source-area signal from nuclide abundances measured in the palaeovalley gravels. This casts events into a Miocene timescale.& &
Publisher: Elsevier BV
Date: 12-2017
Publisher: Geological Society of London
Date: 2010
DOI: 10.1144/SP346.8
Publisher: Elsevier BV
Date: 04-2022
Publisher: Copernicus GmbH
Date: 23-06-2023
DOI: 10.5194/EGUSPHERE-2023-765
Abstract: Abstract. We present 27 new burial ages based on 26Al / 10Be ratios of terrestrial cosmogenic radionuclides measured in clasts and sediments deep within 12 caves in the southern Massif Central, France. Our results together with previously published burial ages, verifies that cave morphogenesis has been continuously active in this region for at least the past ~6 Myrs. Combining s le burial ages with their associated cave elevation above modern stream bed gives a mean regional incision rate of 88 ± 5 m/Ma for the Grands Causses area. South of the Cevennes Fault zone bordering the Grands Causses, the incision rate is 43 ± 5 m/Ma, suggesting that this difference might be accommodated by the fault zone. Sediment burial ages from caves which are not located on river valley flanks or cliff walls are surprisingly too young relatively to the expected age calculated using this regional average river incision rate. This suggests that the classical epigenic speleogenesis model that presumes a direct correlation between cave level development and regional base level lowering does not apply for the study area. Therefore, we propose that regional speleogenesis is mainly controlled by removal of ghost-rocks by regressive erosion from river canyons to central parts of the plateaus, emptying incipient primokarst passages to create cave systems. Our results suggest a continuum process from hypogene primokarst composed of ghost-rocks filled passages to epigene karst dynamic emptying these passages and creating cave networks. We propose this is a major process in the southern Massif Central that initiates the speleogenesis and control the geometry of the networks. In this region tiered karst cannot be associated with major incising rivers but must be explained by former ghost-rocks (or hypogene) processes.
Publisher: Copernicus GmbH
Date: 31-01-2023
Publisher: Elsevier BV
Date: 04-2010
Publisher: Elsevier BV
Date: 2019
Publisher: Elsevier BV
Date: 30-09-2005
Publisher: Elsevier BV
Date: 11-2012
Publisher: Elsevier BV
Date: 11-2012
Publisher: Copernicus GmbH
Date: 05-08-2020
Abstract: Abstract. Northern New Zealand is an important site for understanding Last Glacial Interval (LGI) paleoclimate dynamics, since it is influenced by both tropical and polar climate systems which have varied in relative strength and timing of associated changes. The Auckland Volcanic Field maar lakes preserve these climatic influences on the regional paleoenvironment, as well as past volcanic eruptions, in their sedimentary infill. The sediment sequence infilling Orakei maar lake is continuous, laminated, high-resolution and provides a robust archive from which to investigate the dynamic nature of the northern New Zealand climate system over the LGI. Here we present the chronological framework for the Orakei maar sediment sequence. Our chronology was developed combining Bayesian age modelling of combined radiocarbon ages, tephrochronology of known-age rhyolitic tephra marker layers, 40Ar/39Ar-dated eruption age of a local basaltic volcano, luminescence dating (using post infrared-infrared stimulated luminescence, or pIR-IRSL), and the timing of the Lasch paleomagnetic excursion. We also investigated the application of meteoric (cosmogenic) Beryllium-10 variability to improve the age-depth model by complementing relative paleointensity measurements. However, the results were apparently influenced by some unaccounted catchment process and unable to reach satisfactory interpretation, apart from confirming the presence of the Lasch excursion, and therefore the 10Be data are not used in the production of the final age model. We have integrated our absolute chronology with tuning of the relative paleointensity record of the Earth’s magnetic field to a global reference curve (PISO-1500). The maar-forming phreatomagmatic eruption of the Orakei maar is now dated to 130,120 yr (95 % confidence range 128,665 to 131,560 yr). Our new chronology facilitates high-resolution paleoenvironmental reconstruction for northern New Zealand spanning the last ca. 130,000 years for the first time as most NZ records that spall all or parts of the LGI are fragmentary, low-resolution and poorly dated. Providing this chronological framework for LGI climate events inferred from the Orakei sequence is of paramount importance in the context of identification of leads and lags in different components of the Southern Hemisphere climate system as well as identification of Northern Hemisphere climate signals.
Publisher: Copernicus GmbH
Date: 04-03-2021
DOI: 10.5194/EGUSPHERE-EGU21-10398
Abstract: & & Cosmogenic & sup& & /sup& Be and & sup& & /sup& Al exposure ages from 20 erratic s les collected from Cadair Idris (893 m), a mountain in southern Snowdonia, Wales, provide evidence for the timing of deglaciation from summits to cirques at the end of the Late Pleistocene. The summit of the mountain is characterised by intensely modified frost-shattered surfaces that have long been identified as a representing a former nunatak. Numerous glacially-transported quartz boulders on the highest ground indicate that ice overran the summit at some point in the Pleistocene. Two quartz boulders, one with preserved striations, s led at c. 856 m near the summit of Cadair Idris yielded consistent & sup& & /sup& Be and & sup& & /sup& Al paired exposure ages of 75 ka to 60 ka (using a high-latitude sea level & sup& & /sup& Be spallation production rate of 4.20 at/g/y, scaled by the Lal/Stone scheme). A glacially polished bedrock quartzite outcrop at 735 m gave an age of 17.5 ka. Immediately below this, cirque and down-valley recessional moraine ages, covering an elevation of 480 m to 350 m ranged from 10 to 15 ka respectively.& & & & These results confirm that Cadair Idris was overridden by the Welsh Ice Cap during marine isotope stage (MIS) 4, when ice was thicker than at the global last glacial maximum (LGM) in MIS 2. This is consistent with findings from northern Snowdonia. The highest Welsh summits, including Cadair Idris, emerged above a thinning Welsh Ice Cap (British Irish Ice Sheet) during the transition from MIS 4 to 3. The summit area above ~800 m then stood as nunataks above the LGM ice sheet surface in MIS 2. The Welsh Ice Cap then rapidly thinned over Cadair Idris at& ~20-17 ka& based on ages from high-level ice-moulded bedrockThis is supported by more new ages from high-level paired erratics and bedrock s les on several other mountains throughout Snowdonia,& leading to a phase of alpine-style deglaciation. Valley glaciers initiated their retreat up-valley from ~17 to 14 ka after Heinrich Event 1. A later phase of glacier stabilisation or still stand formation produced classic cirque moraines near the rim of a present cirque lake basin (480 m elevation) yielding & sup& & /sup& Be ages of 13-10 ka during the Younger Dryas.& &
Publisher: Elsevier BV
Date: 11-2012
Publisher: American Association for the Advancement of Science (AAAS)
Date: 19-06-2020
Abstract: Reworking of old sediment in the Murray-Darling implies alteration of environmental signals traveling from source to sink.
Publisher: Geological Society of America
Date: 2009
DOI: 10.1130/G25042A.1
Publisher: Elsevier BV
Date: 10-2015
Publisher: Elsevier BV
Date: 03-2013
Publisher: Elsevier BV
Date: 09-2019
Publisher: Elsevier BV
Date: 02-2018
Publisher: Elsevier BV
Date: 05-2018
Publisher: Elsevier BV
Date: 10-2011
DOI: 10.1016/J.JENVRAD.2010.06.010
Abstract: A study has been carried out to assess the potential of using fallout plutonium (Pu), which originated from atmospheric nuclear-weapons tests, as a tool to investigate recent erosional processes within the lower Cotter water-supply catchment in the Australian Capital Territory. This catchment, which was predominantly pine plantation, was severely affected by a major bush fire in 2003. Accelerator mass spectrometry has been used to measure Pu in soil s les collected from a number of sites across the catchment. The results indicate that less than 1cm of surface soil had been lost since the early 1960s over much of the catchment. Areas of more erodible soil have, however, lost 2-4cm of topsoil, and a loss of ∼6cm of soil was identified at one particular site.
Publisher: Geological Society of America
Date: 2005
DOI: 10.1130/G21746.1
Publisher: Elsevier BV
Date: 2018
Publisher: Elsevier BV
Date: 11-2011
Publisher: Elsevier BV
Date: 04-2022
Publisher: Copernicus GmbH
Date: 23-06-2023
Publisher: Copernicus GmbH
Date: 16-01-2018
Publisher: Elsevier BV
Date: 10-2019
Publisher: Elsevier BV
Date: 2013
Publisher: Wiley
Date: 05-12-2019
DOI: 10.1002/ESP.4744
Location: Australia
Location: Australia
Location: Spain
No related grants have been discovered for Toshiyuki Fujioka.