Late Quaternary slip rates characterize the seismic potential of an active fault in terms of estimating the average expected recurrence period for rupturing episodes. Along the Baikal Rift faults the ...slip rate distributions are poorly understood. This study provides morphotectonic and paleoseismological analyses of the Kichera Fault that stretches within the North Baikal Rift over a length of 100 km. Exposure ages of key displaced terraces of the Neruchanda River from in-situ produced cosmogenic 10Be depth profiles show that the highest terrace T5 is older than 315 ka, intermediate terrace T3 was abandoned 100.0 ± 30 ka ago and the lowest terrace T1 is as old as 48.3 ± 19.9 ka. These exposure ages, coupled with terrace elevation from the actual Neruchanda River bed, allow us to estimate the incision rates for the corresponding time periods which are 0.1 (maximum), 0.16 ± 0.05 and 0.19 ± 0.08 mm yr−1, respectively. Using the cumulated amplitudes of the terrace displacement, we estimate the vertical slip rates along the Kichera Fault are 0.42 ± 0.13 and 0.19 ± 0.08 mm yr−1 over the last ~100 ka and ~48.3 ka, respectively. Paleoseismological studies including morphomertic analyses of the tectonic scarp and trenching across the fault allowed estimating the age (5.4 ka) and minimum magnitude (6.8) of the last Kichera Fault rupture. Using the estimates of short- and long-term slip rates, we propose mean recurrence intervals of 5.3 and 2.4 ka, respectively. The last interval is shorter than the time since the last earthquake, indicating that the future event could be of greater magnitude to maintain the long-term average slip rate.
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•Terraces deformed by the Kichera Fault were dated using In-situ 10Be method.•Vertical slip rates along the Kichera Fault show high variability through time.•Age and magnitude of the last rupture along the Kichera Fault were estimated.•Kichera Fault is the major regional hazard source with a high seismic potential.•Kichera Fault may rupture in the nearest time during the seismic cluster.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The chronology of the most extensive Late Pleistocene glaciation in the eastern Pyrenees is now well established, but climatic variations during the subsequent Last Glacial-to-Interglacial Transition ...(LGIT) are much less well documented. The aim of this research is to fill that gap. We present a new series of 22 10Be exposure ages from a sequence of moraines in the upper Ariège catchment, and update 64 previously published exposure ages from seven other valleys. Based on (i) geomorphological maps of successive generations of ice-marginal deposits and (ii) their age distributions, followed by (iii) glaciological modeling to infer corresponding mass-balance gradients and equilibrium line altitudes (ELAs), we reconstruct glacier behaviour in the eastern Pyrenees during the LGIT and retrieve paleoclimatic parameters for each glacial stillstand. Results document rapid deglaciation involving four relative stillstands, with an ELA rise of ∼410 m and increases in temperature and precipitation of ∼4 °C and ∼40%, respectively, between ∼18 ka (Greenland Stadial GS-2.1b) and ∼14.5 ka (Greenland Interstadial GI-1). A cold and dry environment prevailed from ∼18 ka onward, and deglaciation was almost complete by GI-1. Only small glaciers persisted as late as ∼12.3 ka in cirques where local conditions allowed it. These patterns are compatible with a transient Polar Front Jet Stream repositioning to latitudes of 40–42°N between 18 and 16 ka, with Westerlies-dominated circulation not yet feeding precipitation to the mountain belt abundantly from the northwest, and outbursts of polar air meeting with cool sea waters in the western Mediterranean mostly suppressing precipitation from Mediterranean sources.
•Pyrenean paleoclimates are inferred from cosmogenic dating and glaciological modeling.•Full deglaciation in the eastern Pyrenees occurred between 19.2 ± 0.7 and 14.5 ± 0.6 ka.•Small cirque glaciers persisted until ∼12 ka in a few sheltered, elevated valleys.•The earlier period (∼20–14 ka) was colder and drier than all subsequent intervals.•A cool Mediterranean and cold Atlantic (Polar Front ∼42°N) impeded precipitation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The chronology of the late Pleistocene glaciation in the Massif Central, France, is not well documented and there are divergent hypotheses regarding the timing of glacial events in this area. This ...study aims at reconstructing the chronology of late Pleistocene glacial fluctuations in the Aubrac Mountains. We present a new set of Be-10 and Al-26 exposure ages from twenty erratic boulders embedded in six glacial landforms. Glacial landforms were sampled to determine the timing of three glacial stades and the deglaciation of the Aubrac Mountains. These new data allowed us to constrain the timing of: (i) the Local Last Glacial Maximum, which is coeval with the early Marine Isotopic Stage 2 (MIS 2) (28–24 ka), and (ii) the Grandvals and Bouquincan stades, which are both coeval with the late MIS 2 (24–16 ka). Deglaciation occurred during Heinrich Stadial 1 (18–15.6 ka). This new direct glacial chronology is supported by regional paleoenvironmental proxies and it updates the chronostratigraphic framework available for the southwestern Massif Central. Western European atmospheric circulation changes (i.e., a southward shift in North Atlantic storm tracks and Mediterranean influences) during MIS 2 were identified as significant factors controlling glacier growth in the Aubrac Mountains as well as other glaciated mountains within the southwestern Massif Central, such as the Cantal, Margeride and Lozère mountains.
•The Aubrac icefield fluctuations (Marine Isotopic Stage 2) were used as significant climatic proxies in the Massif Central.•Timing of three distinct glacial stades were inferred from cosmogenic exposure dating (n = 20).•The Local Last Glacial Maximum was coeval withthe early Marine Isotopic Stage 2 (28–24 ka).•Minor glacier advances were recorded during the late Marine Isotopic Stage 2 (24–16 ka).•The Heinrich Stadial 1 (18–15.6 ka), characterized by an arid climate, was coeval with the Aubrac Mountains deglaciation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Abstract We perform a systematic and detailed study of the 14 C and 14 C‐ 10 Be dating systems for meteorite terrestrial ages. Physical model calculations indicate that neither the 14 C production ...rates nor the 14 C/ 10 Be production rate ratios are constant enough to be reasonably approximated by average values. By using simple averages, one introduces a significant size‐dependent bias into the database for meteorite terrestrial ages. By combining modeled 14 C production rates and 14 C/ 10 Be production rate ratios with ( 22 Ne/ 21 Ne) cos ratios and assuming ~80% ablation losses, relatively easy to use correlations of 14 C production rates and 14 C/ 10 Be production rate ratios as a function of ( 22 Ne/ 21 Ne) cos are established. The new correlations enable the determination of terrestrial ages that are more accurate than ages based solely on average values for 14 C and/or 14 C/ 10 Be. We validate the model predictions by measuring 14 C activity concentrations, 14 C/ 10 Be production rate ratios, 21 Ne cos concentrations, and ( 22 Ne/ 21 Ne) cos ratios in four recently fallen meteorites: Mt. Tazerzait, Boumdeid (2011), Bensour, and SaU 606. The experimental data confirmed the model predictions, although the available data are insufficient to be conclusive. More data from freshly fallen meteorites are needed for validating the model predictions for different chondrite sizes and chondrite types.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The migration of Homo erectus in Southeast Asia during Early Pleistocene is cardinal to our comprehension of the evolution of the genus Homo. However, the limited consideration of the rapidly ...changing physical environment, together with controversial datings of hominin bearing sites, make it challenging to secure the robust timeline needed to unveil the behavior of early humans. Here, we reappraise the first appearance datum of Javanese H. erectus by adding the most reliable age constraints based on cosmogenic nuclides Formula: see textBe and Formula: see textAl produced in situ to a compilation of earlier estimates. We find that H. erectus reached Java and dwelled at Sangiran, Java, ca. 1.8 Ma. Using this age as a baseline, we develop a probabilistic approach to reconstruct their dispersal routes, coupling ecological movement simulations to landscape evolution models forced by reconstructed geodynamic and climatic histories. We demonstrate that the hospitable terra firma conditions of Sundaland facilitated the prior dispersal of hominins to the edge of Java, where they conversely could not settle until the Javanese archipelago emerged from the sea and connected to Sundaland. The dispersal of H. erectus across Sundaland occurred over at least tens to hundreds kyr, a time scale over which changes in their physical environment, whether climatic or physiographic, may have become primary forcings on their behavior. Our comprehensive reconstruction method to unravel the peopling timeline of SE Asia provides a novel framework to evaluate the evolution of early humans.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Relict rock glaciers are well-preserved features of high-elevated valleys in the Western Tatra Mts., Western Carpathians, but their chronology remained poorly constrained with numerical dating ...methods. We present the first robust set of 10Be exposure ages for eight rock glaciers with front elevation of 1376–1819 m asl. The results suggest that the rock glaciers stabilized throughout the Weichselian Lateglacial from ∼16.5 ka to 11 ka. This timing is consistent with the period of rock glacier stabilization in European mountain regions, but it extends the age span previously determined for rock glaciers in the Tatra Mts. There are differences between north- and south-facing valleys in the elevation and time of the stabilization of the rock glaciers, which were probably caused by contrasts in potential incoming solar radiation that affected the retreat of former glaciers and the subsequent formation of the rock glaciers. The initiation altitude of ∼1610 and ∼1830 m asl determined for the oldest and youngest dated rock glaciers is generally consistent with previous estimates of the glacier equilibrium line altitude during the Greenland Stadials 2.1 and 1, respectively. However, the lower limit of the rock glaciers is well above regional paleopermafrost features from the same periods, which suggests that rock glaciers may underestimate past permafrost extents and temperature declines disputing their regional validity for paleoenvironmental reconstructions.
•10Be exposure ages for rock glaciers in the Western Tatra Mts. are presented.•Rock glaciers stabilized from ∼16.5 ka to 11 ka.•Initiation altitude of rock glaciers is close to glacier equilibrium line altitude.•Lower limit of rock glaciers is well above regional paleopermafrost features.•Rock glaciers may underestimate past permafrost extents and temperature declines.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
South Asia is rich in Lower Paleolithic Acheulian sites. These have been attributed to the Middle Pleistocene on the basis of a small number of dates, with a few older but disputed age estimates. ...Here, we report new ages from the excavated site of Attirampakkam, where paleomagnetic measurements and direct ²⁶Al/¹⁰Be burial dating of stone artifacts now position the earliest Acheulian levels as no younger than 1.07 million years ago (Ma), with a pooled average age of 1.51 ± 0.07 Ma. These results reveal that, during the Early Pleistocene, India was already occupied by hominins fully conversant with an Acheulian technology including handaxes and cleavers among other artifacts. This implies that a spread of bifacial technologies across Asia occurred earlier than previously accepted.
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BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
The aim of this work is to build a new chronology of the Late Pleistocene glacial fluctuations in the Cantal Mountains and on the Cézallier Plateau (western Massif Central, France). The study of ...glacial landform-sediment assemblages is supported by the production of new exposure ages (n = 48) from (i) forty-three erratic boulders (36Cl and 10Be) spread over twelve glacial landforms, (ii) two ages from polished bedrocks (10Be) and (iii) three ages from depth profiles (10Be and 26Al) in tills. The results indicate that the majority of glacial deposits are attributed to Marine Isotopic Stage 2 (29 to 11 ka). From this dataset, four glacial stadials are discriminated: the Early-Local Last Glacial Maximum at 29–24 ka, (ii) Late-Last Glacial Maximum at 24–20 ka, (iii) a glacial still stand at approximately 17 ka, during a general deglaciation phase between 20 and 16 ka and finally (iv) a cirque stadial localized only in the Cantal Mountains at <16 ka. This new chronology strengthens the chronostratigraphy of the western Massif Central and highlights the sensitivity of the area to atmospheric circulation changes.
•Revisions of glacial landform-sediment assemblages define four distinct glacial events.•Glacial fluctuations are dated to the MIS 2 with surface exposure ages using 10Be, 26Al and 36Cl (n = 48).•Two major glacier advances occurred during the Last Glacial Maximum, at 29–24 and 24–20 ka.•The paleoglacier is limited to the Cantal cirques from ~16 ka.•Paleoglacier from the western Massif Central are sensitive to north Atlantic paleoclimatic changes.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Following the installation and acceptance test of the French 5
MV AMS facility ASTER, the focus has been on improving the capability for routine measurements of
10Be and
26Al. Quality assurance has ...been established by the introduction of traceable AMS standards for each nuclide, by self-monitoring through participation in round-robin exercises and proficiency testing, and by surveillance of long- and short-time variability of blank and reference materials. A background level of 3
×
10
−14 makes ASTER well-suited for measuring
41Ca/
40Ca in the10
−12 region, which is sufficient for a wide range of applications. Routine AMS measurements of volatile elements like
36Cl and
129I will most likely become feasible in the very near future as the result of significant improvements in the ion source design.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
