An empirical method to predict sediment grain size from inorganic geochemical measurements

Grain size is one of the most fundamental properties of sediments. It is frequently used in paleoclimate, paleoceanographic, and paleoenvironmental research as a proxy for river discharge, current and wind strength, and to identify mass flow deposits. Measuring grain size is, however, time-consuming and destructive. Given the strong influence of grain size on sediment inorganic geochemistry, single-element variations measured by, for example, X-ray fluorescence core scanning are increasingly used to estimate grain-size variations at high resolution in sediment cores. This approach is however limited to a narrow grain-size range since individual elements only monotonically relate to grain size over a narrow size range. Here, we present a simple, code-free, multielement method based on partial least squares regression to predict sediment mean grain size from inorganic geochemical data over the range of sizes commonly encountered in sedimentary basins (clay to sand). The method was first tested using river sediment samples separated in 11 grain-size fractions, and it was later successfully applied to two sediment cores from the Chilean fjords. Our method only requires measuring grain size on a limited number (around 10) of selected training samples, and it allows to predict mean grain size at X-ray fluorescence core scanner resolution. This method has the potential to be applied to any lake or marine sediment core, provided sediment provenance, weathering, and diagenesis remain relatively stable through time, and we anticipate that it will result in a significant increase in the resolution of sediment proxy records of climate and environmental change. Plain Language Summary: Sediment grain size is one of the best indicators of past transport conditions. Here we present a method to predict mean sediment grain size from inorganic geochemical measurements. This method can be applied to geochemical measurements obtained by X-ray Fluorescence core scanning to generate grain-size profiles quickly and at high resolution, and we anticipate that it will result in much improved paleoclimate and paleoenvironmental reconstructions

Geochemistry of surface sediments from the fjords of Northern Chilean Patagonia (44–47°S) : spatial variability and implications for paleoclimate reconstructions

Author Posting. © The Author(s), 2011. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Geochimica et Cosmochimica Acta 76 (2012): 125-146, doi:10.1016/j.gca.2011.10.028.The Patagonian fjords have a clear potential to provide high-resolution sedimentary and geochemical records of past climate and environmental change in the Southern Andes. To improve our ability to interpret these proxy records, we investigated the processes that control fjord sediment inorganic geochemistry through a geochemical, mineralogical and sedimentological analysis of surface sediment samples from the fjords of Northern Chilean Patagonia. A simple terrestrial index based on measurements of salinity and fraction of terrestrial carbon was used to estimate the terrestrial input/river discharge at each site. Our results demonstrate that, under the cold climate conditions of Patagonia, chemical weathering is weak and the inorganic geochemical composition of the fjord sediments is primarily controlled by hydrodynamic mineralogical sorting, i.e., the intensity of river discharge. Our results suggest that the distribution of Fe, Ti and Zr in surface sediments is controlled by their association with heavy and/or coarse minerals, whereas Al is independent of hydrodynamic processes. The elemental ratios Fe/Al, Ti/Al and Zr/Al are therefore well suited for estimating changes in the energy of terrestrial sediment supply into the fjords through time. Zr/Al is particularly sensitive in proximal environments, while Fe/Al is most useful in the outer fjords and on the continental margin. In the most proximal environments, however, Fe/Al is inversely related to hydrodynamic conditions. Caution should therefore be exercised when interpreting Fe/Al ratios in terms of past river discharge. The application of these proxies to long sediment cores from Quitralco fjord and Golfo Elefantes validates our interpretations. Our results also emphasize the need to measure Al-based elemental ratios at high precision, which can be achieved using simultaneous acquisition ICP-AES technology. This study therefore constitutes a strong basis for the interpretation of sedimentary records from the Chilean Fjords.This research was supported by a BAEF fellowship (Belgian American Educational Foundation) and an EU FP6 Marie Curie Outgoing Fellowship to S. Bertrand. J. Sepúlveda was supported by Fundación Andes through the WHOI/University of Concepción agreement, and by a scholarship from the Graduate School of the University of Concepción

Luminescence modulation in liquid crystalline phases containing a dispiro[fluorene-9,11′-indeno[1,2-b]fluorene-12′,9′′-fluorene] core

International audienceA luminescent liquid crystalline compound containing a bulky dispiro[fluorene-9,11′-indeno[1,2-b]fluorene-12′,9′′-fluorene] has been designed and synthesized by di-substitution of a bromo derivative with N-(4-ethynylphenyl)-3,4,5-tris(hexadecyloxy)benzamide fragments. This di-substituted 3π-2spiro derivative forms stable and well-organized mesophases over large temperature ranges. Combination of DSC, POM and SAXS analyses has revealed the formation of a lamellar mesophase between 60 and 150 °C followed by another mesophase with a 2-dimensional lattice of rectangular symmetry that remains up to the isotropization point near 225 °C. In the original molecular packing model deduced from SAXS, the tert-butyl terminal groups fill the centre of hollow columns constituted by both the dihydro(1,2-b)indenofluorene and benzamide fragments and separated from each other by the surrounding aliphatic tails. The merging of the columns yielding the lamellar phase turned out to be governed by the dynamics of both, the micro-phase segregation process and the network of hydrogen bonds. In the various mesomorphic states and in solution, a strong luminescence was observed. The emission spectrum however depends on temperature and drastically changes between both mesophases and the isotropic liquid. In particular, a strong modulation of the emission wavelength occurs at the isotropic to 2D phase transition. This luminescence modulation results from an enhanced contribution of the vibronic peaks at higher energies in the emission profile. The compound was also found to be soluble in 5CB and was integrated in a guest-host LC cell, allowing efficient modulation of the photoluminescence polarization, in the presence or absence of an electrical field

Modern sedimentary processes at the heads of Martínez Channel and Steffen Fjord, Chilean Patagonia

Chilean fjord sediments constitute high-resolution archives of climate and environmental change in the southern Andes. To interpret such records accurately, it is crucial to understand how sediment is transported and deposited within these basins. This issue is of particular importance in glaciofluvial Martinez Channel and Steffen Fjord (48 degrees S), due to the increasing occurrence of Glacial Lake Outburst Floods (GLOFs) originating from outlet glaciers of the Northern Patagonian Icefield. Hence, the bathymetry of the head of Martinez Channel and Steffen Fjord was mapped at high resolution and the grain-size and organic carbon content of grab sediment samples were examined. Results show that the subaquatic deltas of Baker and Huemules rivers at the head of Martinez Channel and Steffen Fjord, respectively, are deeply incised (up to 36 m) by sinuous channels. The presence of sediment waves and coarser sediments within these channels imply recent activity and sediment transport by turbidity currents. Although several triggering mechanisms are possible, we argue that elevated river discharge and the associated relatively high suspended sediment loads is the main cause of the occurrence of turbidity currents at the head of these fjords and are of key importance in shaping the fjord's subaquatic morphology. This study shows that the heads of Martinez Channel and Steffen Fjord are dynamic sedimentary environments with rapidly migrating channels. It highlights the importance of site selection and multi-coring in any future project aimed at reconstructing environmental change using the sediments of either fjord

Sediment provenance in the Baker-Martínez fjord system (Chile, 48°s) indicated by magnetic susceptibility and inorganic geochemistry

Fjord sediments are increasingly used as high-resolution archives of climate and environmental change, including variations in glacier mass balance and terrestrial hydrology. To accurately interpret such sediment records, it is crucial to comprehend sediment transport processes and determine sediment provenance. With this in mind, our main objective is to identify cost-effective parameters that can be used to reconstruct relative variations in the origin of sediments deposited in the Baker-Martínez fjord system, which is located between the Northern (NPI) and Southern (SPI) Patagonian Icefields. We focus on estimating the proportions of sediment derived from each icefield, taking advantage of the clearly distinct lithologies that underlie NPI (Patagonian Batholith) and SPI (Eastern Andean Metamorphic Complex) glaciers. The magnetic susceptibility and inorganic geochemistry of 21 surface sediment samples collected along the fjord system and that of suspended sediment samples from the four main rivers that discharge at its heads were investigated. Results indicate that sediments derived from the NPI are characterized by higher magnetic susceptibility and log(Ti/Al) values than those from the SPI, reflecting the mafic nature of the batholith. In fjords that receive contributions from both the NPI and SPI, magnetic susceptibility and log(Ti/Al) primarily reflect sediment provenance. In fjords receiving sediment from only one icefield, however, these parameters are positively correlated with grain size and reflect the progressive settling of particles from the surficial plume. Our results suggest that magnetic susceptibility and log(Ti/Al) can be used to reconstruct sediment provenance within the Baker-Martínez fjord system, but that only log(Ti/Al) can provide quantitative estimates of the proportions of sediment derived from each icefield. Ultimately, applying these provenance indicators to long sediment cores from the Baker-Martínez fjord system could allow reconstructing relative variations in sediment input from each icefield, which may in turn be interpreted as changes in river discharge and/or glacier mass balance

Geochemical evidence (C, N and Pb isotopes) of recent anthropogenic impact in south-central Chile from two environmentally distinct lake sediment records

Author Posting. © The Author(s), 2009. This is the author's version of the work. It is posted here by permission of John Wiley & Sons for personal use, not for redistribution. The definitive version was published in Journal of Quaternary Science 25 (2010): 1100-1112, doi:10.1002/jqs.1364.In this paper, we compare the elemental and isotopic (C, N, Pb) geochemistry of lake sediments from two contrasted environments in South-Central Chile. The first lake, Laguna Chica de San Pedro (LCSP), is situated in the urbanized area of the Biobio Region (36°S). The second lake, Lago Puyehue (40°S), is located 400 km to the southeast of LCSP and belongs to an Andean national park. Our aim is to identify environmental impacts associated with increasing industrial activities and land-degradation during the last 150 years. In LCSP, shifts in C/N atomic ratios, δ13C and δ15N from 1915–1937 to the late 80’s are attributed to successive land-degradation episodes in the lake watershed. Based on a Pb isotopic mixing model, we estimate that up to 20% of lead in LCSP sediments is supplied from urban atmospheric pollution. By contrast, human impact in the watershed of Lago Puyehue is very limited. We observe no change in organic geochemistry during the last 150 years and lead contamination remains lower than 5%, even during the last decades. Although contamination levels are much higher in LCSP than in Lago Puyehue, a peak in anthropogenic Pb is recorded during the same period (1974–1976) at both sites. This maximum contamination level is consistent with increased industrial activity in the vicinity of Concepción.This research was partly supported by the Belgian OSTC project EV/12/10B "A continuous Holocene record of ENSO variability in southern Chile", by the Scientific Co-operation Exchange Program between University of Concepción (Chile) and University of Liège (Belgium) funded by the Belgian CGRI (Commissariat Général aux relations internationales de la Communauté Française de Belgique), and by Fondecyt project Nº 1070508. S.B. is supported by a BAEF fellowship (Belgian American Educational Foundation), and by an EU Marie Curie Outgoing Fellowship under the FP6 programme

Intrascrotal Testicular and Extratesticular Epidermoid Cysts: About Two Cases

Painless solid testicular masses on ultrasonography are commonly malignant. However, if the lesion is well demarcated, rounded, and hypoechoic with alternating hyperechoic and hypoechoic layers, and no internal vascular flow, the possibility of an epidermoid cyst should be considered. Epidermoid cysts are uncommon benign testicular lesions and are extremely rare in the intrascrotal extratesticular region. Including these cysts in the differential diagnosis may allow the urologist to perform testis-sparing surgery. Teaching Point: The possibility of an epidermoid cyst should be considered when a scrotal mass shows an ‘onion ring’ appearance on sonography and no vascularity on Doppler

Sediment provenance indicated by magnetic susceptibility and inorganic geochemistry in the Baker-Martínez fjord system (Chile, 48°S)

Patagonian fjord sediments are increasingly used as high-resolution archives of past climate and environmental change, including variations in glacier mass balance, flood frequency, and seismic activity. To accurately interpret these proxy records, it is crucial to comprehend modern day sedimentation processes and determine the provenance of the sediments. With this in mind, the main objective of this study is to identify parameters that can be used to reconstruct sediment provenance in the fjords of Chilean Patagonia. We focus on the Baker-Martínez fjord system, which is located between the Northern and Southern Patagonian Icefields and seems particularly sensitive to climate change. This fjord system connects the terrestrial ecosystems of Patagonia with the SE Pacific Ocean, and most of its sediment originates from glacier-fed rivers draining either the Patagonian Batholith (PB; Baker and Huemules rivers) to the north, or the Eastern Andes Metamorphic Complex (EAMC; Bravo and Pascua rivers) to the south. Eighteen surface sediment samples from across the Baker-Martínez fjord system and 44 suspended sediment samples from two sequential (Baker fjord) and one continuous (Steffen fjord) sediment trap were investigated. In addition, we analyzed suspended sediment samples collected at the mouths of the four main rivers that drain the PB and EAMC to define end-members. We focus on mass-specific magnetic susceptibility (MS) and inorganic geochemistry, which seem to be particularly promising in this fjord system dominated by lithogenic sediments (97–85 wt%). Our results indicate that sediments derived from the PB are characterized by high MS, Ti/Al, and Fe/Al values, reflecting the granodioritic nature of the batholith (rich in pyroxene and amphibole). In contrast, sediments from the southern EAMC-derived rivers have significantly lower MS, Ti/Al, and Fe/Al values. The sediment trap results reveal MS values that increase with increasing Baker river discharge, either during the summer melt season, or during high precipitation events (rain-on-snow) in winter. Likewise, the MS, Ti/Al and Fe/Al values of the fjord surface sediments are also directly related to sediment provenance. In fjords fed by only one river (e.g., Martínez channel), however, the MS is significantly correlated with mean grain size (r = 0.90; p < 0.01) and with the proportion of lithogenic particles (r = 0.73; p < 0.05). The latter observation means that future research is needed to correct the MS and geochemical data for grain-size before using them as quantitative provenance indicators. This study suggests that, after grain-size correction, MS and inorganic geochemistry (Ti/Al and Fe/Al) can be used to reconstruct sediment provenance within the Baker-Martínez fjord system. Ultimately, applying these provenance indicators to long sediment cores from the same fjord system will allow us to reconstruct variations in the behavior of outlet glaciers from both icefields independently

Synchronisation of sedimentary records using tephra : a postglacial tephrochronological model for the Chilean Lake District

Well-characterised tephra horizons deposited in various sedimentary environments provide a means of synchronising sedimentary archives. The use of tephra as a chronological tool is however still widely underutilised in southern Chile and Argentina. In this study we develop a postglacial tephrochronological model for the Chilean Lake District (ca. 38 to 42 degrees S) by integrating terrestrial and lacustrine records. Tephra deposits preserved in lake sediments record discrete events even if they do not correspond to primary fallout. By combining terrestrial with lacustrine records we obtain the most complete tephrostratigraphic record for the area to date. We present glass geochemical and chronological data for key marker horizons that may be used to synchronise sedimentary archives used for palaeoenvironmental, palaeoclimatological and palaeoseismological purposes. Most volcanoes in the studied segment of the Southern Volcanic Zone, between Llaima and Calbuco, have produced at least one regional marker deposit resulting from a large explosive eruption (magnitude >= 4), some of which now have a significantly improved age estimate (e.g., the 10.5 ka Llaima Pumice eruption from Llaima volcano). Others, including several units from Puyehue-Cordon Caulle, are newly described here. We also find tephra related to the Cha1 eruption from Chaiten volcano in lake sediments up to 400 km north from source. Several clear marker horizons are now identified that should help refine age model reconstructions for various sedimentary archives. Our chronological model suggests three distinct phases of eruptive activity impacting the area, with an early-to-mid-Holocene period of relative quiescence. Extending our tephrochronological framework further south into Patagonia will allow a more detailed evaluation of the controls on the occurrence and magnitude of explosive eruptions throughout the postglacial