Early Pleistocene age of fluvial sediment in the Stará Garda Cave revealed by 26Al/10Be burial dating: implications for geomorphic evolution of the Malé Karpaty Mts. (Western Carpathians)

Assessment of vertical movements of tectonically boundedblocks is crucial for determination of geohazards in denselyinhabited zones, such as the border zone of western Slovakiaand eastern Austria. The morphostructure of the Malé KarpatyMts. divides the Vienna and Danube basins in the WesternCarpathian – Eastern Alpine junction, and its neotectonicactivity is of high importance. This study was focused on26Al/10Be burial dating of fluvial sediment in the Stará GardaCave, located in the central part of the mountains. The structuralresearch revealed predisposition of forming of horizontalpassages in low angle to subhorizontal bedrock stratificationtogether with low-grade metamorphic foliation. Fluvial originof the passages was inferred from mezoscale erosional featureson the bedrock as well as from facies character of the well preservedsedimentary profile. Cave sediment was according topetrographic analysis derived from a watershed comparableto recent one of the Stupavský Potok Stream. Three analyseddating samples provided low values of isotopic concentrations,allowing us only to calculate the minimum burial age of thedeposit of 1.72 Ma. Assuming the low position of the caveabove recent surface streams, resulting maximum incision rateof 26 m/Ma indicates very low uplift of the mountains horstduring the Quaternary. The slow incision of the river network is in good agreement with a widespread preservation of theplanation surface called "Mid-mountain level". In contrast arerelatively high values of palaeodenudation rates inferred fromisotopic concentrations. Generally, our results indicate that theMalé Karpaty Mts. horst underwent relatively intense but shortuplift in the Early Pleistocene, followed by very moderate upliftup to the recent.Key words: Western Carpathians, Malé Karpaty Mts., fluvialcave sediment, burial dating, Early Pleistocene, neotectonics.Zgodnja pleistocenska starost fluvialnihsedimentov v jami Stará Garda, ki jo je dala 26Al/10Be datacija:uporabnost za geomorfni razvoj Nizkih Karpatov (ZahodniKarpati)Ocena vertikalnih premikov tektonsko omejenih blokov jeključna za določitev geohazardov v gosto naseljenih območjih.Morfostruktura Malih Karpatov deli Dunajski in Donavski bazenna stičišču Zahodnih Karpatov – Vzhodnih Alp in njegovaneotektonska aktivnost je zelo pomembna. Študija se je posvetila26Al/10Be dataciji fluvialnih sedimentov v jami Stará Gardav osrednjem delu gorovja. Strukturna raziskava je razkrilapredispozicijooblikovanja vodoravnih jamskih rovov pod nizkimkotom v odvisnosti od subhorozontalne stratifikacije kamnineter tudi z nizko stopnjo metamorfne foliacije. Na fluvialnoporeklo rovov smo sklepali iz srednje velikih erozijskih oblik nanjihovih stenah kot tudi iz lastnosti faciesov dobro ohranjenegasedimentnega profila. Glede na petrografske analizejamskisediment izhaja iz povodja, ki je primerljiv z recentnim povodjempotoka Stupavský. Trije analizirani vzorci so nam dalinizke vrednosti koncentracij izotopov, ki so nam omogočilele izračun najnižje pokopne starosti sedimenta, ki je znašala1,72 Ma. Če upoštevamo, da leži jama nizko nad recentnimivodnimi tokovi, dobimo maksimalno hitrost vrezovanja dolinsamo 26 m/Ma, kar kaže na zelo majhen tektonski dvig v časukvartarja. Počasno vrezovanje rečne mreže se dobro ujema sširoko ohranjenim uravnanim površjem, imenovanim »Srednjegorskauravnava«. V nasprotju pa so sorazmerno visoke vrednosti hitrosti paleodenudacije, ki izhajajo iz koncentracijizotopov. Na splošno naši rezultati kažejo, da je bil horst NizkihKarpatov podvržen relativno močnemu, toda kratkemu dvigovanjuv spodnjem pleistocenu, ki mu je sledil zmeren dvig dosedanjosti.Ključne besede: Zahodni Karpati, Nizki Karpati, fluvialnijamski sedimenti, pokopna datacija, starejši pleistocen, neotektonika.

Cosmogenic burial dating of in cave-deposited alluvium: unravelling long-term incision rates and complex speleogenesis in multi-level cave systems

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Plio-Quaternary incision rates in the Meuse catchment vs long-term uplift rates of the Ardennes (E Belgium): new insights from 26Al/10Be burial dating of in cave-deposited alluvium

peer reviewe

Toward the feldspar alternative for cosmogenic 10Be applications

The possibility of quantifying surface processes in mafic or volcanic environment using the potentialities offered by the in situ-produced cosmogenic nuclides, and more specifically by the in situ-produced 10Be, is often hampered by the rarity of quartz minerals in the available lithologies. As an alternative to overcome this difficulty, we explore in this work the possibility of relying on feldspar minerals rather that on quartz to perform in situ-produced 10Be measurements in such environments. Our strategy was to cross-calibrate the total production rate of 10Be in feldspar (P10fsp) against the total production rate of 3He in pyroxene (P3px) by measuring 3He and 10Be in cogenetic pyroxene (3Hepx) and feldspar (10Befsp). The samples were collected from eight ignimbritic boulders, exposed from ca 120 to 600 ka at elevations ranging from 800 to 2500 m, along the preserved rock-avalanche deposits of the giant Caquilluco landslide (18°S, 70°W), Southern Peru. Along with data recently published by Blard et al. (2013a) at a close latitude (22°S) but higher elevation (ca. 4000 m), the samples yield a remarkably tight cluster of 3Hepx - 10Befsp total production ratios whose weighted-mean is 35.6 ± 0.5 (1s). The obtained weighted-mean 3Hepx - 10Befsp total production ratio combined with the local 3Hepy total production rate in the high tropical Andes published by Martin et al. (2017) allows to establish a total SLHL 10Be in situ-production rate in feldspar mineral (P10fsp) of 3.57 ± 0.21 at.g-1.yr-1 (scaled for the LSD scaling scheme, the ERA40 atm model and the VDM of Lifton, 2016). Despite the large elevation range covered by the whole dataset (800–4300 m), no significant variation of the 3Hepx - 10Befsp total production ratios in pyroxene and feldspar was evidenced. As an attempt to investigate the effect of the chemical composition of feldspar on the total 10Be production rate, major and trace element concentrations of the studied feldspar samples were analyzed. Unfortunately, giving the low compositional variability of our dataset, this issue is still pending

Toward the feldspar alternative for cosmogenic 10Be applications in mafic environment

In situ-produced 10Be is one of the most commonly used TCN in quantitative geomorphology due to the fact that its production rate is relatively well constrained in the ubiquitous quartz mineral whose integrity minimizes the possibility of contamination by meteoric 10Be. Easily decontaminated from meteoric 10Be, it is in addition reliably measured using the Accelerator Mass Spectrometry technique for which its detection limit is lower than 104 at.g-1. However, volcanic or mafic areas are generally quartz free, which hamper the routine use of 10Be. In the case of a quartz poor lithology, an alternative possibility is to rely on 10Be - feldspars. Two preliminary studies (Kober et al., 2005 and Blard et al., 2013a) already provided promising results, demonstrating that (1) the decontamination protocol classically applied to quartz (Brown et al., 1991) efficiently removes all the meteoric 10Be contamination from the feldspar grains and (2) the total production rate of 10Be in feldspar is 8 to 10 % lower than that in quartz. However, only two samples were analyzed in both studies. In order to better constrain the 10Be in situ-production rate within feldspars, the number of samples analyzed needs to be increased. In this study, we developed a new chemical protocol for the 10Be extraction from feldspar matrices, and to cross-calibrate the total 10Be in situ-production rate in feldspar (P10fsp) against the total 3He production rate in pyroxene (P3px). The cosmogenic 3He and 10Be concentrations were measured, respectively, in pyroxene and feldspar extracted from eight samples of ignimbrite boulders from a giant landslide located between 800 and 2500 m in the high central Andes of Southern Peru. This area is ideally located, since two studies have already determined the local total 3He production rate in pyroxene on the nearby Altiplano (Blard et al., 2013b; Delunel et al., 2016)

Teleconnections between boreal cooling and tropical glaciers in the Cordillera Blanca (Peru)

30 samples have been collected for the cosmogenic dating of expanding and shrinking glacial phases southwesternward of Nevado Hualcán (9º, 12'S; 77º, 31'W, 6122 m), in the Cordillera Blanca (Peru).The set includes 28 moraine boulder surface samples and 2 polished bedrock surface samples. The resistivity of 3 samples of moraine boulder surfaces, measured in the AMS facility ASTER, did not allow us to estimate the accumulation of 10Be. Therefore, it was not possible to estimate the exposure age of these samples. However, it was possible to obtain 27 10Be glacial ages: 25 boulder ages from 5 moraine sets (M5-M1) and 2 polished bedrock ages (between M2-M1). 5 boulder ages seem too high, probably because of cosmogenic inheritance. Nevertheless, despite the uncertainties, the remaining 22 ages seem consistent with their geomorphological context. Nowadays, the oldest moraines (M5) are higher than younger moraines, because they define a glacial paleo-valley cut by the current valley in which the other groups of moraines (M4-M1) are becoming younger and younger and in higher altitudes. M5 ages (~132-61 ka) suggest the existence of at least two glacial phases long before the Last Glacial Maximum (LGM). The oldest phase could be traced back to the beginning of the Last Glacial Cycle (LGC). The M4-M1 moraines chronologies seem to correlate with paleolake transgressions in the Bolivian Altiplano. They can be interpreted as a reflection of wetter paleoclimatic phases than the current phase, and are linked to cooling periods in the Northern Hemisphere (Placzek et al., 2013). This link suggests the existence of a boreal/tropical teleconnection through a large shift towards the south of the Inter-Tropical Convergence Zone (Kelly et al., 2012) and/or of the Bolivian High (Martin et al., 2018). The M4 moraines define the maximum glacier advance on the south-west area of Nevado Hualcán. Their ages (~32-24 ka) are consistent with the early LGM, shown by various proof around the world (Clark et al., 2009). The M3 and M2 moraines show smaller and thinner readvances than previous moraines. Their ages (~20-12 ka and ~13-11 ka) are contemporaneous to Tauca (~18-14 ka) and Coipasa transgressions (~13-11 ka; Blard et al., 2011). The deglaciation after M3 could be the results of a weakening of tropical circulation related to boreal heating Bølling-Allerød. In that period (ages ~3-1 ka), the glaciers retreated to above their current limit. The M1 moraines pinpoint the last glacier advances, whose exposure ages without cosmogenic inheritance (~1.0-0.3 ka) are consistent with lichenometry-based dating in nearby valleys (Jomelli et al., 2008) and the ITCZ southward shift during the Little Ice Age (Sachs et al., 2009)

The Early Acheulean technology of Barranc de la Boella (Catalonia, Spain)

Since 2007, excavations at Barranc de la Boella (Tarragona, Catalonia, Spain) have revealed three localities with rich archaeo-paleontological assemblages: La Mina, El Forn and Pit 1. Palaeontology, palaeomagnetism and cosmogenic analyses have dated these localities to close to 1 Ma. The presence of Mammuthus meridionalis, Hippopotamus antiquus, Stephanorhinus cf. hundsheimensis, Mimomys savini and Victoriamys chalinei stand out in the sample of macro and micro-mammals. The lithic assemblages from the three sites are made up of percussion cobbles, choppers, chopper-cores, cores, simple flakes, and some retouched flakes: mainly denticulates and notches. In the case of the El Forn and Pit 1 localities, two large cutting tools have been recovered: a cleaver-like tool and a pick made of hard-wearing schist. The lithic assemblage of Pit 1, which includes several refitting lithic sets, is closely associated with the remains of a young-adult Mammuthus meridionalis, in a clear butchering site context. This evidence suggests that Barranc de la Boella is the oldest European Early Acheulean site, and one of the oldest butchering site on the subcontinent during the late Early Pleistocene. The study of the variability among these three localities in similar environmental conditions, together with information from other sites, are discussed in order to gain further knowledge about the appearance of the Acheulean in Europe, and its continuity or discontinuity in relation to pre-existing technologies.Since 2007, excavations at Barranc de la Boella (Tarragona, Catalonia, Spain) have revealed three localities with rich archaeo-paleontological assemblages: La Mina, El Forn and Pit 1. Palaeontology, palaeomagnetism and cosmogenic analyses have dated these localities to close to 1 Ma. The presence of Mammuthus meridionalis, Hippopotamus antiquus, Stephanorhinus cf. hundsheimensis, Mimomys savini and Victoriamys chalinei stand out in the sample of macro and micro-mammals. The lithic assemblages from the three sites are made up of percussion cobbles, choppers, chopper-cores, cores, simple flakes, and some retouched flakes: mainly denticulates and notches. In the case of the El Forn and Pit 1 localities, two large cutting tools have been recovered: a cleaver-like tool and a pick made of hard-wearing schist. The lithic assemblage of Pit 1, which includes several refitting lithic sets, is closely associated with the remains of a young-adult Mammuthus meridionalis, in a clear butchering site context. This evidence suggests that Barranc de la Boella is the oldest European Early Acheulean site, and one of the oldest butchering site on the subcontinent during the late Early Pleistocene. The study of the variability among these three localities in similar environmental conditions, together with information from other sites, are discussed in order to gain further knowledge about the appearance of the Acheulean in Europe, and its continuity or discontinuity in relation to pre-existing technologies

Cronologías glaciales de los Andes Centrales occidentales de Perú estimadas por el Proyecto FONDECYT 144-2015

Este trabajo presenta edades de exposición a la radiación cósmica (berilio-10) de fases de avance y retroceso de glaciares en montañas de altitud decreciente, alineadas en un transecto norte-sur de la cordillera occidental de los Andes Centrales. Las muestras se recogieron en valles comprendidos por grandes morrenas de avances glaciares, al suroeste del Nevado Hualcán (región Ancash), al suroeste del Nevado Pariacaca (región Lima) y al sur del Nevado Chila (región Arequipa). Los resultados reflejan máximos avances glaciares (M5) hace 120-130 ka; 60-70 ka y 40-50 ka, anteriores al Last Glacial Maximum global (LGM; ~30-19 ka). También hay edades LGM (M4; 32-24 ka), 2 fases posteriores de reavances menores (M3-M2) y una última pulsación M1 de la Pequeña Edad del Hielo (PEH). Los avances glaciares parecen bastante bien correlacionados con transgresiones de los paleolagos en Bolivia y eventos fríos en el hemisferio norte. Ese hecho sugiere la existencia de una teleconexión enfriamiento boreal-humedad tropical a través de un desplazamiento hacia el Sur de la Zona de Convergencia Inter-Tropical (ZCIT)