Burgos, Spain
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Martin-Chivelet J.,Complutense University of Madrid | Munoz-Garcia M.B.,Complutense University of Madrid | Cruz J.A.,Complutense University of Madrid | Ortega A.I.,CENIEH | Turrero M.J.,CIEMAT
Sedimentary Geology | Year: 2017

Carbonate stalagmites have become increasingly attractive to Quaternary paleoclimate research, as they can be accurately dated by radiometric methods and concurrently yield high-resolution multi-proxy records of past climate conditions. Reliable series however require the precise characterization of stalagmite internal micro-stratigraphy, a task too often poorly accomplished despite the recent advances in speleothem research. This weakness is due to the lack of a robust integrative methodological framework capable of integrating the wide range of petrographical and micro-stratigrafical methods currently used in speleothem characterization. For covering this need, this review introduces the Speleothem Architectural Analysis (SAA), a holistic approach inspired in well-established stratigraphic procedures such as the architectural element analysis and the sequence stratigraphy, commonly used by geoscientists for categorizing internal stratigraphic heterogeneities in sedimentary deposits. The new approach establishes a six-fold hierarchy of speleothem architectural elements and their bounding surfaces: individual crystallites (1st order), single growth layers (2nd order), speleothem fabrics (3rd order), stacking patterns sets (4th order), morphostratigraphic units (5th order), unconformity-bounded units and major unconformities (6th order). Each category of architectural element is formed in a different range of time, from intervals as short as a year/season to others of centuries or millennia. The SAA, which has the capability of incorporating any petrographic or stratigraphic classification, provides a useful, systematic, and versatile tool for unraveling the complexities of speleothem growth, and thus for genetically interpreting stalagmites in a multi-temporal scale. A detailed speleothem stratigraphy must be the basis for performing robust reconstruction of paleoclimate series. They should precede and accompany any work focused in absolute age dating or in reconstructing paleoclimate by means of any geochemical proxy. © 2017 Elsevier B.V.

Luetscher M.,University of Innsbruck | Luetscher M.,Swiss Institute for Speleology and Karst Studies SISKA | Hoffmann D.L.,CENIEH | Frisia S.,University of Newcastle | Spotl C.,CENIEH
Earth and Planetary Science Letters | Year: 2011

Mountain glaciers and their sediments are prominent witnesses of climate change, responding sensitively to even small modifications in meteorological parameters. Even in such a classical and thoroughly studied area as the European Alps the record of Holocene glacier mass-balance is only incompletely known. Here we explore a novel and continuous archive of glacier fluctuations in a cave system adjacent to the Upper Grindelwald Glacier in the Swiss Alps. Milchbach cave became partly ice-free only recently and hosts Holocene speleothems. Four coeval stalagmites show consistent petrographic and stable isotopic changes between 9.2 and 2.0ka which can be tied to abrupt modifications in the cave environment as a result of the closing and opening of multiple cave entrances by the waxing and waning of the nearby glacier. During periods of Holocene glacier advances, columnar calcite fabric is characterized by δ18O values of about -8.0‰ indicative of speleothem growth under quasi-equilibrium conditions, i.e. little affected by kinetic effect related to forced degassing or biological processes. In contrast, fabrics formed during periods of glacier minima are typical of bacterially mediated calcite precipitation within caves overlain by an alpine soil cover. Moreover, δ18O values of the bacterially mediated calcite fabrics are consistent with a ventilated cave system fostering kinetic fractionation. These data suggest that glacier retreats occurred repeatedly before 5.8ka, and that the amplitudes of glacier retreats became substantially smaller afterwards. Our reconstruction of the Upper Grindelwald Glacier fluctuations agrees well with paleoglaciological studies from other sites in the Alps and provides a higher temporal resolution compared to traditional analyses of peat and wood remains found in glacier forefields. © 2010 Elsevier B.V.

Turrero M.J.,CIEMAT | Garralon A.,CIEMAT | Sanchez L.,CIEMAT | Ortega A.I.,CENIEH | And 3 more authors.
Environmental Earth Sciences | Year: 2015

Drip-water chemistry in karstic caves can vary at seasonal to interannual scales in response to climatic factors such as temperature, rainfall, and seasonality, which determine changes in the hydrological and hydrochemical processes of the percolating waters in their paths from the atmosphere to the cave. In this paper the characterization of stalagmite forming drip-waters based on longterm (years) time-series data is presented as a key task for understanding the geochemical behavior of a specific system, the Kaite Cave (N Spain). The work focuses on the relationships between rainfall, drip rates, drip-water calcium concentration, and drip-water trace elements amount (e.g., Mg and Sr); as indicators of hydrologic processes defining the karst system and controlling speleothem growth and composition patterns. © Springer-Verlag Berlin Heidelberg 2015.

Constantin S.,The Emil Racovita Institute of Speleology | Robu M.,The Emil Racovita Institute of Speleology | Munteanu C.-M.,The Emil Racovita Institute of Speleology | Petculescu A.,The Emil Racovita Institute of Speleology | And 9 more authors.
Quaternary International | Year: 2014

The Urşilor Cave (NW Romania) is a famous cave bear paleontological site hosting an important Late Pleistocene faunal assemblage and subject to systematic excavation works. To better understand the origin of fossil assemblages, the sedimentary history of the cave must be reconstructed. We conducted a series of investigations on various cave deposits which included sedimentology and grain-size analyses, U-series dating of speleothems, OSL dating of sediments, and AMS radiocarbon dating of fossil remains. The results allowed for the identification of several major chronological controls for the evolution of the cave during the last 300,000 years. Five evolutionary stages or key-moments were dated, and a tentative speleogenetic scenario is presented. The combined numerical dates and sedimentological study show that the evolution of the cave was more complex than previously thought. In particular, the fossil accumulation was related to a succession of rapid flooding events at ~47-40ka. Alternating depositional and erosional phases have occurred since at least 210ka complicating the sediment structures. The results suggest that the upper and lower levels of the cave may have been functioned occasionally as hydrologically separated karst systems and that the animal populations from what is now a single cave system may not necessarily be synchronous. This case study shows that reconstructing sedimentary history of a given cave is crucial for the correct understanding of its thanatocenosis. © 2013 Elsevier Ltd and INQUA.

Alvarez C.,CENIEH | Pares J.M.,CENIEH | Granger D.,Purdue University | Duval M.,CENIEH | And 2 more authors.
Quaternary International | Year: 2015

Sediments of the Plio-Pleistocene Guadix - Baza basin have provided a wealth of information on the first hominin populations in Western Europe. To better constrain the age of the Fuente Nueva-3 archaeological site within the basin, and to complement previous magnetostratigraphic studies, two vertical boreholes were taken that provide a continuous record of the lower part of the sequence. Results indicate that the sequence is dominated by negative inclinations, but some additional intervals with positive inclination are also identified in the lower part of the sequence. A new cosmogenic nuclide burial age of 1.50 ± 0.31 Ma helps constrain the magnetostratigraphic record. The abundance of normal polarity directions at the bottom of a borehole may indicate proximity to the Olduvai Subchron; however, further analyses are required to confirm this hypothesis. © 2015 Elsevier Ltd and INQUA.

Rodriguez J.,CENIEH | Mateos A.,CENIEH | Martin-Gonzalez J.A.,University of Burgos | Rodriguez-Gomez G.,CENIEH
Quaternary International | Year: 2015

Beneath the hot debate about the tempo and mode of the first human colonization of Europe is the perception that the record of human presence in the Early Pleistocene is sparse and fragmented. As a result, it is often implicitly assumed that hominins, if present, were scarce in the Early Pleistocene European ecosystems. Here we present a quantitative assessment of the rarity and commonness of the European large mammal species during the 1.4-0.8. Ma period, including hominins. Considering the palaeontological record only, Homo was not one of the most common species in Europe, but it may not be considered a rare species. In contrast, taking into consideration the archaeological record, hominins exhibit a wide geographical distribution and a high frequency of occurrence (occupancy) in comparison with other large mammals. It is speculated that hominins were frequent but not abundant in Europe during the late Early Pleistocene. © 2015 Elsevier Ltd and INQUA.

Rodriguez J.,CENIEH | Martin-Gonzalez J.A.,CENIEH | Goikoetxea I.,CENIEH | Rodriguez-Gomez G.,CENIEH | Mateos A.,CENIEH
Quaternary International | Year: 2013

The first human settlement of Europe occurred around 1.6 Ma, although human populations were unable to cross parallel 45°N until 1.2 Ma We analyse the distribution of mammalian species during the early Pleistocene to evaluate the possible existence of a climatic or ecological barrier that prevented the northern expansion of those early colonisers. Differences in the composition of the Mediterranean and northern species pools existed during the early Pleistocene, but the differences attained were maximal during the 1.6-1.2 Ma time period. The two regional pools were more similar in species composition during the Galerian (1.2-0.8 Ma), coinciding with the expansion of early Homo northward. The two regional pools also differed in ecological structures during the early Pleistocene, although the northern pool became more similar to the southern pool during the Galerian. © 2011 Elsevier Ltd and INQUA.

Pares J.M.,CENIEH | Duval M.,CENIEH | Arnold L.J.,CENIEH
Quaternary International | Year: 2013

Current knowledge of hominin migration into Eurasia is severely biased by poor age constraints at many Lower Pleistocene sites. This contribution analyzes the current status of the chronology for the most important sites in the Circum-Mediterranean region, with an emphasis on those sites for which the archaeological remains (fossils and/or artifacts) are found in an unambiguous stratigraphic context. Taken together, current data shows an apparent occupation window of between 0.9 and 1.8 Ma for the bulk of Lower Paleolithic Sites in Western Eurasia. Noticeably, the oldest known sites, Dmanisi and Atapuerca TE9 (1.8 and 1.2 Ma respectively), are among the most geographically disparate sites in Eurasia. The time gap between these sites could be an artifact of the incomplete archaeological record, but it might also relate to distinct pulses of hominin migration into Eurasia. The uncertainty in existing ages prevents ascertaining whether the main climatic events in the Plio-Pleistocene match migration pulses of human dispersal into Eurasia. © 2011 Elsevier Ltd and INQUA.

Pares J.M.,CENIEH | Miguens L.,CENIEH | Saiz C.,CENIEH
Journal of Petroleum Science and Engineering | Year: 2016

We describe and test a method to determine the directional properties of pore fabric in siliciclastic rocks using magnetic techniques. The approach is based on injecting into rock specimens a ferrofluid, a stable colloidal suspension of sub-domain magnetic particles in a liquid carrier, and measuring the magnetic susceptibility in different directions. Because the magnetic susceptibility after impregnation increases thirty times, the rock susceptibility can be neglected and therefore the anisotropy of magnetic ferrofluid susceptibility (AMFFS) provides an image of the 3D fabric and porosity in the rock. Our results on Triassic red sandstones suggest that both interparticle and intraparticle pores, which are measurable via AMFFS, are present and are largely determined by the micas and clays. Interparticle pores are most likely found between clay platelets, whereas intraparticle pores correspond to cleavage-plane pores within clay aggregates. Overall this study highlights that magnetic methods can be readily applied to siliciclastic rocks to characterize pore networks and more important, to determine the preferred orientation of the pores assemblage. © 2016 Elsevier B.V.

Scholz D.,University of Mainz | Hoffmann D.L.,CENIEH | Hoffmann D.L.,University of Bristol | Hellstrom J.,University of Melbourne | Bronk Ramsey C.,University of Oxford
Quaternary Geochronology | Year: 2012

Speleothems, such as stalagmites and flowstones, can be dated with unprecedented precision in the range of the last 650,000 a by the 230Th/U-method, which is considered as one of their major advantages as climate archives. However, a standard approach for the construction of speleothem age models and the estimation of the corresponding uncertainty has not been established yet.Here we apply five age modelling approaches (StalAge, OxCal, a finite positive growth rate model and two spline-based models) to a synthetic speleothem growth model and two natural samples. All data sets contain problematic features such as outliers, age inversions, large and abrupt changes in growth rate as well as hiatuses.For data sets constrained by a large number of ages and not including problematic sections, all age models provide similar results. In case of problematic sections, the algorithms provide significantly different age models and uncertainty ranges.StalAge, OxCal and the finite positive growth rate model are, in general, more flexible since they are capable of modelling hiatuses and account for problematic sections by increased uncertainty. The spline-based age models, in contrast, reveal problems in modelling problematic sections.Application to the synthetic data set allows testing the performance of the algorithms because the 'true' age model is available and can be compared with the age models. OxCal and StalAge generally show a good performance for this example, even if they are inaccurate for a short section in the area of a hiatus. The two spline-based models and the finite positive growth rate model show larger inaccurately modelled sections. © 2012 Elsevier B.V.

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