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Polygonal patterned grounds on the Earth’s surface are typically associated with subsurface-wedge structures in periglacial environments. The presence of such wedges is usually taken as an indicator for cryogenic processes in the subsurface, which form a characteristic vertically laminated sequence. However, similar structures can be found in the subsurface of the Aroma fan in the Central Depression of the Atacama Desert in northern Chile. Within the salt-bearing deposits of the alluvial fan, the calcium-sulphate wedges appear to be preliminary formed by haloturbation and may represent the hyperarid equivalent to periglacial wedge structures. The characteristic vertical lamination of the wedges contains calcium-sulphate phases accompanied by clastic minerals, as found by X-ray diffraction and X-ray fluorescence analyses. Hence, the calcium-sulphate phases in the wedges are assumed to be potential drivers for salt dynamics causing subsurface wedge-growth and surface polygonal patterned ground formation. Due to varying water availability in a generally extremely water-limited environment, these salt dynamics possibly led to significant volumetric changes in the deposits induced by dissolution and (re)precipitation of salts from infiltrating solutions and phase transitions of calcium-sulphate phases.The subsurface-wedge network of the Aroma-fan outcrop is covered by a ~ 20 cm thick calcium sulphate-bearing surface crust, which potentially covered a polygonal patterned ground. The formation and preservation of the surface crust might indicate an amplification of arid conditions leading to the inhibition of wedge growth in the subsurface. To unravel the mechanisms and governing environmental conditions of calcium-sulphate wedge and crust formation at the Aroma site, we present various mineralogical, geochemical, and sedimentological data of wedge and crust material.Furthermore, we applied geochronological methods to resolve wedge-growth phases and episodes of local moisture supply. We tested meteoric 10Be dating and post-infrared infrared stimulated luminescence (post-IR IRSL) dating on wedge material to gain information on the evolution and activity of wedge growth under arid to hyperarid conditions. Such geochronological data is indispensable for using the wedges as terrestrial proxy record for the palaeoclimate in the northern Atacama Desert.

Introduction The treatment of fragility fractures of the pelvis (FFP) is a challenge. The variations of non-operative- and of operative treatment are manifold and a structured treatment algorithm is lacking. The purpose of this study was to evaluate the outcome of elderly patients with a FFP who were treated with a therapeutic algorithm based on the FFP-classification. Patients and Methods In a prospective cohort study 154 patients (mean age: 81.8 ±.61 (65-96); female: (86.8%; 131/154). BMI: 23.7 ±.34 (15-43)) with a FFP after inadequate mono trauma were treated according to a strict therapeutic algorithm between 04/2016 and 12/2018. According to a classification based on CT-scans either a standardized operative treatment or conservative therapy was induced and the outcome regarding objective measurements of mobility, pain, need for analgesics and mortality during hospital stay and after one year was analyzed. Results 82/154 participants (53.2%) were assigned to the conservative treatment group and 72 participants (46.8%) to the operative treatment group. The overall one-year survival rate was 78.1% (118/151). The survival of the operative treatment group was 90.7% (49/54) and significantly higher than the survival of the conservative treatment group (74.7%; 56/75; p=.023). The one-year follow up showed a high dispersion of the pain level in the operatively treated patients and a significantly higher mean in comparison to conservatively treated patients. Both treatment groups showed increasing numbers of patients with unlimited mobilization but also immobile patients. Overall in 31.0% (18/58) of the operative participants and in 14.9% (14/93) of the non-operatively treated participants complications occurred (p=.04). Conclusion The strict compliance to the presented treatment algorithm of FFP with an operative strategy starting from FFP IIc leads to a significantly lower mortality within one year in comparison to the conservatively treated patients. The worst outcome and the highest mortality was seen in patients who refused the recommendation of operative stabilization. The results of this study justify to proceed with the strict classification dependent treatment algorithm and also support the early switch-over to operative treatment of patients with failed conservative therapy in FFP I to FFP IIb.

The Atacama Desert (Chile) is one of driest places on Earth, with a hyper-arid climate and less than 2 mm yr−1 precipitation; nevertheless, it has experienced rare periods of sporadic rainfall. These periods shortly enhanced vegetation growth and microbial activity, which must have utilized major nutrients such as phosphorus (P). However, any biological cycling of P involves an oxygen exchange with water, which should now reside in the hyperarid soils as tracer of life. In order to identify such evidences, we performed sequential P fractionation and analyzed the oxygen isotope composition of HCl-extractable phosphate (δ18OHCl–P) in the surface soil (0–15 cm) of a climatic gradient along the rising alluvial fans of the Central Depression to the Precordillera, Chile. At the driest sites, the δ18OHCl-P values were constant with depth and deviated from biologically-driven isotopic equilibrium. In contrast, we observed a considerable increase of δ18OHCl-P values below the soil surface at less arid sites, where some isotope values were even within the range of full isotopic equilibrium with biologically cycled phosphate. For the latter sites, this points to most efficient biological P cycling right below the uppermost surface of the desert. Critically, the absolute concentrations of this biologically cycled P exceeded those of P potentially stored in living microbial cells by at least two orders of magnitude. Therefore, our data provides evidence that δ18OHCl-P values trace not recent but past biological activity, making it a powerful tool for assessing the existence, pathways and evolution of life in such arid ecosystems on Earth and, thus, potentially on other planets such as Mars.

The Atacama Desert is the driest and oldest desert on Earth. Despite the abundance evidence for long-term landscape stability, there are subtle signs of localised fluvial erosion and deposition since the onset of hyperaridity in the rock record. In the dry core of the Atacama Desert, pluvial episodes allowed antecedent drainage to incise into uplifting fault scarps, which in turn generated sinuous to meandering channels. Incision of ancient alluvial fan surfaces occurred during intermittent fluvial periods, albeit without signs of surface erosion. Fluvial incision during predominantly hyperarid climate periods is evident from these channels in unconsolidated alluvium. The absence of dense vegetation to provide bank stability and strength led us to investigate the potential role of regionally ubiquitous CaSO

The Atacama Pediplain (AP) is a major element in the Atacama Desert landscape, commonly used as an indicator of climatic and tectonic stability. We choose the El Salado Canyon area (26°S) that longitudinally exposes the AP to study its relationship with the Andean forearc evolution, combining geomorphologic and stratigraphic observation with new geochronological data (40Ar/39Ar biotite ages on ignimbrites, and 21Ne exposure ages on quartz-clasts). The AP alluvial deposition occurred in two episodes of alluvial backfilling spatially and temporally separated from each other (Early Miocene - Mid Miocene in the Precordillera, and Mid Miocene - Early Pliocene in the Central Depression), and both triggered by semiarid to arid conditions restricted to the higher Precordillera. Both episodes occurred despite the regionally recorded Mid Miocene onset of hyperarid conditions, revealing the local control of the upstream humidity in the downstream sedimentation. Clustered exposure ages from the Pliocene reveal the abandonment of the alluvial plains due to the incision of the El Salado Canyon, whereas younger and individual exposure ages from the Early Pleistocene, explained by minor surficial activity, reveal a climatic control on the surfaces after the incision that ended with the increase of the Pleistocene hyperaridity. Therefore, the development of alluvial deposition despite the regional Mid Miocene hyperaridity, and the development of a deep canyon incision after the last recorded Andean uplift, reveals that the AP has been strongly influenced by local conditions that do not allow its use as a general marker of a single climatic or tectonic event.

Zusammenfassung Zur knöchernen Defektauffüllung wird regelhaft Knochen vom vorderen Beckenkamm entnommen. Typische Komplikationen sind postoperatives Hämatom, Nervenverletzungen, Infektionen oder Schmerzen an der Entnahmestelle. Wir beschreiben einen Fall, in dem es nach Knochenentnahme am rechten Beckenkamm bei einem jungen Patienten als Koinzidenz zu einer akuten Appendizitis kam. Durch die durchgeführte Knochenentnahme kam es zu einer erschwerten Diagnosestellung, die nur durch eine differenzierte klinische Untersuchung und daraufhin eingeleitete laborchemische und apparative Diagnostik möglich war.

Geological records indicate that the hyper-aridity in the Atacama Desert has prevailed since at least the mid-Miocene, with shorter periods of increased humidity punctuating long-term aridity. The 7-m-high accumulation of colluvial sediments at the Salar Grande (21°S/70°W) studied here provides a key palaeoclimate record to understand hillslope dynamics and its relation to humid periods. While 10Be surface exposure ages point to long-term surface stability of the flat upslope surface, a combination of humidity-driven soil creep, overland flow and soil creep related to seismic shaking, caused denudation of the hillslope and accumulation of several metres of colluvium over much shorter timescales during the last 130 ka. A robust chronology for the hillslope sediments has been established by using Infrared Stimulated luminescence (pIR-IR225 protocol) on K-feldspar extracts from nine samples collected within the accumulation. A series of tests has been carried out to confirm the suitability of the method. The estimated ages indicate accelerated sedimentation at 35–80 ka, and 100–130 ka, which are interpreted as periods with more humid climate conditions than present. These findings agree with climate variations in the hyper-arid Atacama indicated by the activity of coastal alluvial fans and river catchments.

We established a new laboratory for noble gas mass spectrometry that is dedicated to the development and application to cosmogenic nuclides at the University of Cologne (Germany). At the core of the laboratory are a state-of-the-art high-mass-resolution multicollector Helix MC Plus (Thermo Fisher Scientific) noble gas mass spectrometer and a novel custom-designed automated extraction line. The mass spectrometer is equipped with five combined Faraday multiplier collectors, with 1012 and 1013 Ω pre-amplifiers for faraday collectors. We describe the extraction line and the automated procedure for cosmogenic neon and the current performance of the experimental set-up. Performance tests were conducted using gas of atmospheric isotopic composition (our primary standard gas), as well as CREU-1 intercomparison material, containing a mixture of neon of atmospheric and cosmogenic composition. We use the results from repeated analysis of CREU-1 to assess the performance of the current experimental set-up at Cologne. The precision in determining the abundance of cosmogenic 21Ne is equal to or better than those reported for other laboratories. The absolute value we obtain for the concentration of cosmogenic 21Ne in CREU is indistinguishable from the published value.

The growth of vertically laminated calcium-sulphate wedges in the Atacama Desert is assumed to be driven by the interaction of moisture supply and salt dynamics in the subsurface. Geochronological data of these wedge laminations is yet sparse but indispensable to resolve wedge-growth phases and episodes of moisture supply and to use these deposits as a palaeoclimate archive in the hyperarid environment. Our pilot study presents a first approach of dating a calcium-sulphate wedge from the Atacama Desert using coarse-grain feldspar luminescence dating. Our results show a widespread and clustered equivalent-dose distribution of two wedge samples from ~20 Gy up to saturation. Optically stimulated luminescence (OSL) of quartz revealed unsuitable properties for dating wedge deposits. Consequently, we applied post-infrared infrared stimulated luminescence (post-IR IRSL) to coarse-grained feldspars. Since feldspar single-grain measurements yielded a low number of luminescent grains, we used 1 mm aliquots as reliable single-grain proxies for genuine single-grain measurements. Data from energy-dispersive x-ray spectroscopy (EDX) showed that the feldspar single grains have large differences in their internal K content, resulting in an averaged internal K content of 3.9 ± 1.0 % for all luminescent grains. This result was subsequently used for dose rate and age calculations. Our results of equivalent-dose distributions and palaeodoses derived from the minimum age model reveal most recent wedge-growth activities at 10.6 ± 2.2 ka and 7.9 ± 1.8 ka for the two wedge samples.

Paleoclimate records from the Atacama Desert are rare and mostly discontinuous, mainly recording runoff from the Precordillera to the east, rather than local precipitation. Until now, paleoclimate records have not been reported from the hyperarid core of the Atacama Desert (

Dating of extensive alluvial fan surfaces and fluvial features in the hyperarid core of the Atacama Desert, Chile, using cosmogenic nuclides provides unrivalled insights about the onset and variability of aridity. The predominantly hyperarid conditions help to preserve the traces of episodic climatic and/or slow tectonic change. Utilizing single clast exposure dating with cosmogenic 10Be and 21Ne, we determine the termination of episodes of enhanced fluvial erosion and deposition occurring at ~19, ~14, ~9.5 Ma; large scale fluvial modification of the landscape had ceased by ~2–3 Ma. The presence of clasts that record pre-Miocene exposure ages (~28 Ma and ~34 Ma) require stagnant landscape development during the Oligocene. Our data implies an early onset of (hyper-) aridity in the core region of the Atacama Desert, interrupted by wetter but probably still arid periods. The apparent conflict with interpretation that favour a later onset of (hyper-) aridity can be reconciled when the climatic gradients within the Atacama Desert are considered.

Cosmogenic nuclide exposure dating of ancient shoreline terraces of the Quillagua-Llamara Soledad Lake in the central Atacama Desert of northern Chile provides new insights in the paleohydrology of the driest desert on Earth. The lake developed in a paleo-endorheic drainage system in the Central Depression prior to draining into the Pacific due to incision of the Rio Loa canyon. The durations of lake stages were sufficiently long to form wave-erosion induced shoreline terraces on the wind-exposed slopes of former islands. Successively younger shoreline levels are preserved over an elevation range of 250 m due to progressive uplift of the islands coeval with the lake stages. Cosmogenic 10Be- and 21Ne-derived exposure ages of the shorelines reveals that the hyperarid conditions in the Rio Loa catchment were interspersed by several pluvial stages during the Pliocene and Pleistocene, which generated a large and persistent lake in the Quillagua-Llamara basin. The exposure ages of the final lake stage provide the maximum age for the incision of the Rio Loa canyon (274 ± 74 ka) and the subsequent breaching of the Coastal Cordillera.

The hyperarid parts of the Atacama Desert, N Chile, are among the driest places on Earth, and a number of studies have emphasized the remarkable slowness of Earth surface processes since the late Tertiary. Despite episodic overland flow or flash flood activity, salt-driven shrink-swell processes, dust deposition, and seismic shaking have significantly contributed to the formation of the characteristic landscape. The enigmatic and Atacama-specific zebra stripes are contour-parallel, thin lateral bands of rather angular gravels on hillslopes, characterized by grain sorting, a lateral succession of 1-3 m-wide frontal lobes, and specific wavelengths, occurring generally in areas with lowest rainfall and low to no fog occurrence. While previous investigations suggest that zebra stripes represent fossil evidence of overland flow, a recent study challenged their water-related evolution and emphasized the role of seismicity in their formation, and in shaping the Atacama landscape in general. Similar landforms may also be found on Mars, although related processes may be different to those on Earth.We use UAV-derived orthophotos and digital elevation models, geomorphological surveys and sediment sampling, as well as OSL rock surface dating and cosmogenic nuclide (21Ne, 10Be) analysis of surface clasts to provide new insights into zebra stripe activity and stability in the Atacama Desert. Our investigations show that zebra stripes are found in numerous areas in the hyperarid core of the Atacama, implying a wider distribution of zebra-striped hillslopes than previously suggested. Inter-site comparison illustrates considerable differences between individual zebra stripe sites, and geomorphological characteristics suggest that zebra stripes may be active or inactive forms, depending on their location. Active forms are indicated by well-developed frontal lobes, reduced dust contents, and clearly developed downslope sorting trends with a high percentage of freely floating clasts, whereas inactivity seems to be indicated by poorly visible frontal lobes, high dust contents, poor sorting trends and a high proportion of clasts embedded into the underlying vesicular soil horizon. At the same time, preliminary chronological data based on OSL rock surface dating suggests that active stripes contain clasts with active bleaching fronts at top and bottom sides, pointing to late Pleistocene to Holocene activity and clast overturning. Inactivity, in contrast, is indicated by similar IR50 and pIR225 bleaching curves (equilibrium of bleaching and dosing) in upper clast surfaces and the lack of a bleaching front at the bottom side, pointing to long exposures without clast overturning. Combined with cosmogenic nuclide concentrations, our results allow for inter-site comparisons and a better understanding of (relative) stripe chronologies and activity-stability patterns. Alongside further investigations on the significance of fog, wind, rain and seismicity, future work will aim at constraining time scales on which active/young and inactive/old forms have developed. If these forms are seismicity-related, our study contributes important information on the paleoseismic evolution of the central Atacama.

[Abstract] The Atacama Desert in northern Chile is one of the driest deserts on Earth. Hyperaridity persists at least since the Miocene and was punctuated by pluvial phases. However, very little is known about the timing, regional spread and intensities of precipitation changes. Here, we present a new precipitation record from a sedimentary sequence recovered in a tectonically blocked endorheic basin that is located in the hyperarid core of the Atacama Desert. The chronostratigraphic framework of the record is given by a multi-disciplinary dating approach, suggesting an age of ca. 68 ka BP for the core base. The sequence consists of three sediment types, whose sedimentological and geochemical characteristics suggest different depositional processes that reflect different degrees in humidity. First, particularly fine-grained sediments with high clastic but low calcium sulfate and carbonate contents reflect a particularly dry climate with only sporadic precipitation events and fluvial supply via channel systems. Second, more coarse-grained sediments with lower clastic and higher calcium sulfate and carbonate contents reflect more moist conditions with stronger precipitation events that lead to fluvial activity not restricted to the channels but involving the slopes and plains in the catchment. Third, normally graded layers with an equally high proportion of calcium sulfate and carbonate reflect occasional high-precipitation events that caused sediment supply also from most distant parts of the catchment via severe flash floods. The sedimentary succession suggests that precipitation changes took place on orbital but also on millennial time scales. Rather moist periods occurred during most of MIS 2, several shorter periods within MIS 3 and parts of MIS 4. Comparison of the findings from the Huara record with selected climate records from continental and marine sites in South America suggests a strong precipitation heterogeneity across the Atacama. This heterogeneity is caused by pronounced differences in the dominating climate patterns and a shift from predominant summer rain in the north to winter rain in the south. Precipitation supply to the Huara clay plan is controlled by the atmospheric circulation rather than the surface temperature of the adjacent ocean.

Unicellular eukaryotes, also called protists, are potentially fast evolving organisms. The small size of protists, their fast reproduction rate and ability to form cysts as well as their adaptability to extreme conditions allow them to associate to endemic animals, plants, saline lakes and soil even in extremely arid systems. These properties make unicellular eukaryotes ideal model organisms to combine studies on evolutionary processes of very different groups of organisms and across very different time scales comprising even geological ones. The hyperarid Atacama Desert offers a study area unique on Earth, where a predominantly arid climate was present for millions of years. A comprehensive analysis of the diversity of unicellular eukaryotes in different habitats (endemic desert plant phyllosphere, the gut of endemic darkling beetles, isolated hypersaline waters) revealed a dataset distinct and divergent from other regions on Earth. We used standard isolation and cultivation protocols to elucidate divergence patterns for a variety of very different and independent taxonomic groups of protists such as gregarines and ciliates among alveolates, placidids among stramenopiles and choanoflagellates among opisthokonts. The ability to rapidly adapt to extreme environments, which enhance a fast divergence rate at high UV radiation, has only been reported for prokaryotes up to now. The establishment of arid to hyperarid conditions in the Atacama Desert about 20 Ma ago has obviously led to an isolation of protist populations followed by a radiation of species. There are only a few regions on Earth with similar extreme salinity conditions reducing the chance of an exchange between protist populations. Divergence patterns in unicellular eukaryotes in very different phylogenetic groups independently mirror the effect of geological evolution and climate variability during the Neogene.

Atmospheric circulation over the North Atlantic has undergone significant fluctuations during the Holocene. To better constrain these changes and their impacts on the Fennoscandian subarctic, we investigated molecular and inorganic proxies as well as plant wax D/H isotopes (I´DC28) in a Holocene sedimentary record from Lake TornetrA¤sk (Sweden). These data indicate a thermal maximum c. 8100 to 6300Â cal. a BP with reduced soil organic matter input, followed by a long-term cooling trend with increasing soil erosion. I´D data suggest a stable atmospheric circulation with predominance of westerly flow and North Atlantic moisture sourcing during the Early and Middle Holocene. AÂ substantial depletion in I´D followed by increased flood frequency starting at c. 5300Â cal. a BP and intensifying c. 1500Â cal. a BP suggests a reorganization of the atmospheric circulation from zonal towards meridional flow with predominantly Arctic Ocean and Baltic Sea moisture sourcing.

The Atacama Desert in western South America is considered as one of the driest places on earth, but is nevertheless characterized by surprisingly high species richness and levels of endemism. The plant genus Cristaria (Malvaceae), with ca. 21 species, is one of the most diverse genera of the Atacama Desert, while the much less diverse sister genus Lecanophora (7 species) is found east of the Andes. Here, we use DNA sequence data and divergence time estimates in order to investigate the biogeographical history of the Atacama species of Cristaria. We further investigate a possible influence of Andean uplift and the subsequent onset of hyperaridity in the Atacama Desert on diversification times in Cristaria. We sequenced three plastid markers (ndhF, trnK(matK) & rpl16) for 19 species of Cristaria and two species of Lecanophora from the Atacama Desert and Argentina, respectively. Further, we included sequences of the same plastid regions from GenBank in order to get a comprehensive dataset of Malvoideae. Phylogenetic relationships were inferred using maximum likelihood and Bayesian analyses, and divergence times were estimated with BEAST2. Our results place the monophyletic genera Cristaria and Lecanophora as sister groups in a clade sister to the rest of Malveae. The split between these two lineages (~20 Ma) correlates with Andean uplift during the early Miocene, indicating a vicariant event. During the late Miocene, two Mediterranean members of Cristaria separated from the major Atacama clade. The subsequent diversification of the latter one correlates with the onset and subsequent temporal expansion of hyperarid conditions in the Atacama Desert since the late Miocene and during the Quaternary climate oscillations.

The 3.6 Ma sediment record of Lake El'gygytgyn/NE Russia, Far East Russian Arctic, represents the longest continuous climate archive of the terrestrial Arctic. Its elemental composition as determined by X-ray fluorescence scanning exhibits significant changes since the mid-Pliocene caused by climate-driven variations in primary production, postdepositional diagenetic processes, and lake circulation as well as weathering processes in its catchment. During the mid- to late Pliocene, warmer and wetter climatic conditions are reflected by elevated Si / Ti ratios, indicating enhanced diatom production in the lake. Prior to 3.3 Ma, this signal is overprinted by intensified detrital input from the catchment, visible in maxima of clastic-related proxies, such as K. In addition, calcite formation in the early lake history points to enhanced Ca flux into the lake caused by intensified weathering in the catchment. A lack of calcite deposition after ca. 3.3 Ma is linked to the development of permafrost in the region triggered by cooling in the mid-Pliocene. After ca. 3.0 Ma the elemental data suggest a gradual transition to Pleistocene-style glacial–interglacial cyclicity. In the early Pleistocene, the cyclicity was first dominated by variations on the 41 kyr obliquity band but experienced a change to a 100 kyr eccentricity dominance during the middle Pleistocene transition (MPT) at ca. 1.2–0.6 Ma. This clearly demonstrates the sensitivity of the Lake El'gygytgyn record to orbital forcing. A successive decrease of the baseline levels of the redox-sensitive Mn / Fe ratio and magnetic susceptibility between 2.3 and 1.8 Ma reflects an overall change in the bottom-water oxygenation due to an intensified occurrence of pervasive glacial episodes in the early Pleistocene. The coincidence with major changes in the North Pacific and Bering Sea paleoceanography at ca. 1.8 Ma implies that the change in lake hydrology was caused by a regional cooling in the North Pacific and the western Beringian landmass and/or changes in the continentality. Further increases in total organic carbon and total nitrogen content after ca. 1.6 Ma are attributed to reduced organic matter decay in the sediment during prolonged anoxic periods. This points to more extensive periods of perennial ice coverage, and thus, to a progressive shifts towards more intense peak glacial periods. In the course of the Pleistocene glacial–interglacial sequence eight so-called "super-interglacials" occur. Their exceptionally warm conditions are reflected by extreme Si / Ti peaks accompanied by lows in Ti, K, and Fe, thus indicating extraordinary high lake productivity.