Deep to shallow lacustrine evaporites in the Libros Gypsum (southern Teruel Basin, Miocene, NE Spain): an occurrence of pelletal gypsum rhythmites

ABSTRACT A number of non‐marine evaporite units composed of primary gypsum were deposited in saline lakes that developed in the southern Teruel Basin (NE Spain) during the Miocene. In the basin depocentre, a continuum of lacustrine evaporite lithofacies influenced by the activity of organisms is displayed. The Libros Gypsum was deposited in a deep lake, in which water stratification became unstable with progressive shoaling. Rhythmites, composed of laminae of pelletal gypsum and laminae of very fine lenticular gypsum crystals mixed with siliceous microorganisms, formed in addition to gypsum turbidites, intraformational gypsum breccias and slump structures. The pelletal laminae originated from the faecal activity of animals (crustaceans?) ingesting gypsum crystallites in the lake water during episodes of maximum evaporation, whereas the laminae of very fine lenticular gypsum mixed with microorganisms accumulated during episodes of relative dilution. In the wide marginal zones of the basin, the Libros Gypsum unit consists of massive to thin‐bedded bioturbated gypsum and thin‐bedded clotted gypsum, which formed in intermediate to very shallow (palustrine) water depths. The bioturbated gypsum lithofacies were produced by the action of diverse organisms, presumably worms and coleopterans, and chironomid larvae to a lesser extent; the massive lithofacies precipitated in very shallow water; and the thin‐bedded lithofacies formed in shallow to deeper settings. The thin‐bedded clotted gypsum is a relatively deep facies that may have diverse origins (e.g. bioturbation, compaction, disruption of soft sediments and early diagenesis). There is a well‐developed metre‐scale cyclicity in the marginal lake sequences, which is not observed in the inner lake deposits. This suggests a depth control in the various lacustrine subenvironments to record cyclic evaporitic processes. The isotopic composition of the gypsum indicates early sulphate‐reducing bacterial activity in the bottom of the lake and suggests that the sulphate was derived from the chemical recycling of Triassic evaporites of the country rocks.     

Use of targets to track 3D displacements in highly vegetated areas affected by landslides

Monitoring landslides with terrestrial laser scanning (TLS) is currently a well-known technique. One problem often encountered is the vegetation that produces shadow areas on the scans. Indeed, the points behind a given obstacle are hidden and thus occluded on the point cloud. Thereby, locations monitored with terrestrial laser scanner are mostly rock instabilities and few vegetated landslides, being difficult or even impossible to survey vegetated slopes using this method with its classical non-full wave form. The Peney landslide (Geneva, Switzerland) is partially vegetated by bushes and trees, and in order to monitor its displacements during the drawdown of the Verbois reservoir located at its base, an alternative solution has been found. We combined LiDAR technique with 14 targets made of polystyrene placed at different locations inside and outside the landslide area. The obtained displacements were compared with classical measurement methods (total station and extensometer), showing good resemblance of results, indicating that the use of targets in highly vegetated areas could be an efficient alternative for mass movements monitoring.     

MedFlux: Investigations of particle flux in the Twilight Zone

The MedFlux project was devised to determine and model relationships between organic matter and mineral ballasts of sinking particulate matter in the ocean. Specifically we investigated the ballast ratio hypothesis, tested various commonly used sampling and modeling techniques, and developed new technologies that would allow better characterization of particle biogeochemistry. Here we describe the rationale for the project, the biogeochemical provenance of the DYFAMED site, the international support structure, and highlights from the papers published here. Additional MedFlux papers can be accessed at the MedFlux web site (http://msrc.sunysb.edu/MedFlux/).     

Mineralogy,petrology, chronology,and exposure history of the Chelyabinsk meteorite and parent body

Three masses of the Chelyabinsk meteorite have been studied with a wide range of analytical techniques to understand the mineralogical variation and thermal history of the Chelyabinsk parent body. The samples exhibit little to no postentry oxidation via Mössbauer and Raman spectroscopy indicating their fresh character, but despite the rapid collection and care of handling some low levels of terrestrial contamination did nonetheless result. Detailed studies show three distinct lithologies, indicative of a genomict breccia. A light‐colored lithology is LL5 material that has experienced thermal metamorphism and subsequent shock at levels near S4. The second lithology is a shock‐darkened LL5 material in which the darkening is caused by melt and metal‐troilite veins along grain boundaries. The third lithology is an impact melt breccia that formed at high temperatures (~1600 °C), and it experienced rapid cooling and degassing of S₂ gas. Portions of light and dark lithologies from Chel‐101, and the impact melt breccias (Chel‐102 and Chel‐103) were prepared and analyzed for Rb‐Sr, Sm‐Nd, and Ar‐Ar dating. When combined with results from other studies and chronometers, at least eight impact events (e.g., ~4.53 Ga, ~4.45 Ga, ~3.73 Ga, ~2.81 Ga, ~1.46 Ga, ~852 Ma, ~312 Ma, and ~27 Ma) are clearly identified for Chelyabinsk, indicating a complex history of impacts and heating events. Finally, noble gases yield young cosmic ray exposure ages, near 1 Ma. These young ages, together with the absence of measurable cosmogenic derived Sm and Cr, indicate that Chelyabinsk may have been derived from a recent breakup event on an NEO of LL chondrite composition.     

LEGRI instrument health. A historical review

LEGRI has been operating successfully on MINISAT-01 since its switch-on the 22nd of May 1997. HouseKeeping (HK) data have been continuously receivedfor nearly two years by LEGRI SOC in Valencia, and subsequently checked on adaily basis and then stored for long term monitoring analysis.LEGRI HouseKeeping data include three critical operating parameters:temperature, power and polarisation voltages. Six temperature sensors arespread over the different LEGRI units: Detector Unit, Data Processing Unit,High Voltage Unit and Star Sensor. Voltages are measured at eight differentpoints. Detector Unit temperature and polarisation voltage are thecritical parameters for LEGRI operation. Solid state detectors aresensitive to changes not only in polarisation but also in temperature.Around one and a half million of measurements for each of the HK fourteen parameters have been recorded and analysed. The data show a very remarkablestability, within the expected margins, and the averages are very close to theoptimal design values. Special attention has been paid to the detectorpolarisation voltages analysis with a mean value of 286 ± 2 V when the detectors are operating. Thermal control over all the LEGRI units shows a remarkable stability in their temperatures.On the detector plane a mean value of T _det = 13 ± 2 ^°C has been found.We can therefore conclude that LEGRI as a system has been operating withinits optimal design conditions. We also want to point out the excellentperformance of the MINISAT-01 thermal control system.     

Progressive failure leading to the 3 December 2013 rockfall at Puigcercós scarp (Catalonia,Spain)

A detailed analysis of the pre-failure behavior of the 3 December 2013 rockfall (1,012 m³) occurred on Puigcercós pilot study area (Catalonia, Spain) is presented. The exact date of failure was obtained based on a photographic monitoring performed every 4 h. The long-term monitoring (2,217 days) of the rock slope carried out by a Terrestrial LiDAR allowed the early detection of both pre-failure deformation and precursory rockfalls preceding the final failure. By means of the analysis of the pre-failure deformation, four different deformed areas were detected and the tertiary creep phase was observed in three of them. An attempt to predict the time to failure was performed using the Fukuzono’s (1985) method. Furthermore, the temporal evolution of the precursory rockfalls occurred in those four areas during the progressive failure showed a close resemblance with the exponential pattern of the cumulated displacements at tertiary creep stage. Finally, the study of the meteorological conditions did not show any single triggering factor associated with the final failure. Reversely, the increase in the occurrence of precursory rockfalls on several areas of the slope together with the observed acceleration on the deformation pattern reinforce the role of a progressive degradation of the stability conditions, which ultimately leaded to the 3 December rockfall event.     

Constraining albedo,diameter and composition of near-Earth asteroids via near-infrared spectroscopy

We present a method to constrain the albedo and diameters of near-Earth asteroids (NEAs) based on thermal flux in their near-infrared spectra (0.7–2.5 μm) using the Standard Thermal Model. Near-infrared spectra obtained with the SpeX instrument on NASA Infrared Telescope Facility are used to estimate the albedo and diameters of 12 NEAs (1992 JE, 1992 UY4, 1999 JD6, 2004 XP14, 2005 YY93, 2007 DS84, 2005 AD13, 2005 WJ56, 1999 JM8, 2005 RC34, 2003 YE45, and 2008 QS11). Albedo estimates were compared with average albedo for various taxonomic classes outlined by Thomas et al. (Thomas, C.A. et al. [2011]. Astron. J. 142(3)) and are consistent with their results. Spectral band parameters, like band centers, are derived and compared to spectra of laboratory mineral mixtures and meteorites to constrain their composition and possible meteorite analogs. Based on our study we estimate the albedos and diameters of these NEAs and compare them with those obtained by other techniques such as ground-based mid-infrared, Spitzer thermal infrared and Arecibo radar. Our results are broadly consistent with the results from other direct methods like radar. Determining the compositions of low albedo asteroids is a challenge due to the lack of deep silicate absorption features. However, based on weak absorption features and albedo, we suggest possible meteorite analogs for these NEAs, which include black chondrites, CM2 carbonaceous chondrites and enstatite achondrites. We did not find any specific trends in albedo and composition among the asteroids we observed.