A record of changing redox conditions in the northern Peru Basin during the Late Quaternary deduced from Mn/Fe and growth rate variations in two diagenetic manganese nodules

Two diagenetic manganese nodules from the Peru Basin were investigated by thermal ionization mass spectrometry and high resolution alpha spectrometry for uranium and thorium. The TIMS concentrations for nodule 62KD (63KG) vary as follows: 0.12–1.01 ppb (0.06–0.59) ²³⁰Th, 0.51–1.98 ppm (0.43–1.40) ²³²Th, 0.13–0.80 ppb (0.09–0.49) ²³⁴U, and 1.95–13.47 ppm (1.66–8.24) ²³⁸U. Both nodules have average growth rates of 110 mm per million years. However, from the variations of excess ²³⁰Th with depth we estimate partial accumulation rates which range from 50 to 400 mm per million years. The δ²³⁴U dating method cannot be applied due to remobilization of U from the sediment and subsequent incorporation into the nodules' crystal lattice, reflected by decay corrected δ²³⁴U values far above the ocean water value. Sections of fast nodule growth are related to those layers having high Mn/Fe ratios (up to 200) and higher densities. As a possible explanation we develop a scenario that describes similar glacial/interglacial trends in both nodules as a record of regional changes of sediment and/or deep water chemistry.     

Tertiary Tsondab Sandstone Formation: preliminary bedform reconstruction and comparison to modern Namib Sand Sea dunes

The Tertiary Tsondab Sandstone Formation, which underlies much of the present Namib Sand Sea, is a key element in understanding the Cenozoic evolution of the Namib Desert. Outcrops of the aeolian facies of the Tsondab Sandstone at Elim and Diep Rivier consist of two sequences of bioturbated cross-strata separated by likely formation-scale surfaces of stabilisation. Cross-strata consist of scalloped sets about 200 m in width and separated by southeast dipping bounding surfaces. Internally, sets contain reactivation surfaces of probable seasonal origin. The north to south-southeast dipping foresets define crescent shapes with a trough axis trending northeast. Although additional data are needed to define the Tsondab bedform, the outcrop data is best satisfied in computer simulations by north trending, east migrating main bedforms, which had relatively large and slow-moving dunes superimposed upon their eastern flanks and migrated to the north. Foresets dipping to the south to south-southwest at Elim suggest that superimposed dunes also occurred on the western flanks of the main bedform and migrated to the south, but that their record was largely lost with net eastward migration of the main bedform. This preliminary Tsondab model shares attributes such as trend, scale of cross-strata, and presence of scalloped sets with reactivation surfaces with computer models of the modern linear dunes in which large-scale sinuosity migrates alongcrest to the north. Differences emerge in the overall set architecture and the orientation of cross-strata and bounding surfaces, as well as the degree of vegetation that must have characterised Tsondab dunes.     

The American Crocodile in Florida Bay

The American crocodile was declared endangered in the United States in 1975. At that time 75% of the remaining crocodile nests were in Everglades National Park, in Florida Bay. In 1980, the National Park Service established a crocodile sanctuary in northeastern Florida Bay to protect nesting and nursery habitat. In 1985, a monitoring program, focused on nesting, growth, and survival, was established to evaluate the effects of modified water deliveries on crocodiles in Florida Bay. The number and range of crocodile nests increased between 1970 and 1995, but nesting success decreased slightly. Nests on artificial substrates in the Greater Flamingo-Cape Sable area accounted for most of the increase in nests. Nests on artificial substrates were more prone to predation by raccoons. At least 1.5% of marked hatchlings survived for more than 12 mo, and growth rates were variable. Detailed information on growth and survival of crocodiles is still lacking. It is no longer a question of whether crocodiles with survive in Florida Bay, but how ecosystem restoration and management can be applied to improve conditions for crocodiles.     

Evidence for MTBE in Heating Oil

"Contamination of heating oil with MTBE could result in increasing the environmental impact of subsurface heating oil releases."     

Substorm observations in the early morning sector with Equator-S and Geotail

Data from Equator-S and Geotail are used to study the dynamics of the plasma sheet observed during a substorm with multiple intensifications on 25 April 1998, when both spacecraft were located in the early morning sector (03–04 MLT) at a radial distance of 10–11 R_E. In association with the onset of a poleward expansion of the aurora and the westward electrojet in the premidnight and midnight sector, both satellites in the morning sector observed plasma sheet thinning and changes toward a more tail-like field configuration. During the subsequent poleward expansion in a wider local time sector (20−04 MLT), on the other hand, the magnetic field configuration at both satellites changed into a more dipolar configuration and both satellites encountered again the hot plasma sheet. High-speed plasma flows with velocities of up to 600 km/s and lasting 2–5 min were observed in the plasma sheet and near its boundary during this plasma sheet expansion. These high-speed flows included significant dawn-dusk flows and had a shear structure. They may have been produced by an induced electric field at the local dipolarization region and/or by an enhanced pressure gradient associated with the injection in the midnight plasma sheet.     

Embryo dune development drivers: beach morphology,growing season precipitation,and storms

For development of embryo dunes on the highly dynamic land–sea boundary, summer growth and the absence of winter erosion are essential. Other than that, however, we know little about the specific conditions that favour embryo dune development. This study explores the boundary conditions for early dune development to enable better predictions of natural dune expansion. Using a 30 year time series of aerial photographs of 33 sites along the Dutch coast, we assessed the influence of beach morphology (beach width and tidal range), meteorological conditions (storm characteristics, wind speed, growing season precipitation, and temperature), and sand nourishment on early dune development. We examined the presence and area of embryo dunes in relation to beach width and tidal range, and compared changes in embryo dune area to meteorological conditions and whether sand nourishment had been applied. We found that the presence and area of embryo dunes increased with increasing beach width. Over time, embryo dune area was negatively correlated with storm intensity and frequency. Embryo dune area was positively correlated with precipitation in the growing season and sand nourishment. Embryo dune area increased in periods of low storm frequency and in wet summers, and decreased in periods of high storm frequency or intensity. We conclude that beach morphology is highly influential in determining the potential for new dune development, and wide beaches enable development of larger embryo dune fields. Sand nourishment stimulates dune development by increasing beach width. Finally, weather conditions and non‐interrupted sequences of years without high‐intensity storms determine whether progressive dune development will take place. Copyright © 2017 John Wiley & Sons, Ltd.     

Late Pleistocene outburst floods from Issyk Kul,Kyrgyzstan?

Elevated shorelines and lake sediments surrounding Issyk Kul, the world's second largest mountain lake, record fluctuating lake levels during Quaternary times. Together with bathymetric and geochemical data, these markers document alternating phases of lake closure and external drainage. The uppermost level of lake sediments requires a former damming of the lake's western outlet through the Boam gorge. We test previous hypothesised ice or landslide dam failures by exploring possible links between late Quaternary lake levels and outbursts. We review and recompile the chronology of reported changes in lake site, and offer new ages of abandoned shorelines using ¹⁴C in bivalve and gastropod shells, and plant detritus, as well as sand lenses in delta and river sediments using Infrared Stimulated Luminescence. Our dates are consistent with elevated lake levels between ~45 ka and 22 ka. Cosmogenic ¹⁰Be and ²⁶Al exposure ages of fan terraces containing erratic boulders (>3 m) downstream of the gorge constrain the timing of floods to 20.5–18.5 ka, postdating a highstand of Issyk Kul. A flow‐competence analysis gives a peak discharge of >10⁴ m³ s^–1 for entraining and transporting these boulders. Palaeoflood modelling, however, shows that naturally dammed lakes unconnected to Issyk Kul could have produced such high discharges upon sudden emptying. Hence, although our data are consistent with hypotheses of catastrophic outburst floods, average lake‐level changes of up to 90 mm yr^–1 in the past 150 years were highly variable without any outbursts, so that linking lake‐level drops to catastrophic dam breaks remains ambiguous using sedimentary archives alone. This constraint may readily apply to other Quaternary lakes of that size elsewhere. Nonetheless, our reconstructed Pleistocene floods are among the largest reported worldwide, and motivate further research into the palaeoflood hydrology of Central Asia. Copyright © 2017 John Wiley & Sons, Ltd.     

Strömgren CCD photometry of Globular Clusters

We present results from Strömgren uvby photometry forthe globular clusters M3 and M13, obtained from the Nordic Optical Telescope and the Danish 1.54 m telescope on La Silla obtained as part ofa larger program to investigate cluster ages.     

Dating lava flows of tropical volcanoes by means of spatial modeling of vegetation recovery

The age of past lava flows is crucial information for evaluating the hazards and risks posed by effusive volcanoes, but traditional dating methods are expensive and time‐consuming. This study proposes an alternative statistical dating method based on remote sensing observations of tropical volcanoes by exploiting the relationship between lava flow age and vegetation cover. First, the factors controlling vegetation density on lava flows, represented by the normalized difference vegetation index (NDVI), were investigated. These factors were then integrated into pixel‐based multi‐variable regression models of lava flow age to derive lava flow age maps. The method was tested at a pixel scale on three tropical African volcanoes with considerable recent effusive activity: Nyamuragira (Democratic Republic of Congo), Mt Cameroon (Cameroon) and Karthala (the Comoros). Due to different climatic and topographic conditions, the parameters of the spatial modeling are volcano‐specific. Validation suggests that the obtained statistical models are robust and can thus be applied for estimating the age of unmodified undated lava flow surfaces for these volcanoes. When the models are applied to fully vegetated lava flows, the results should be interpreted with caution due to the saturation of NDVI. In order to improve the accuracy of the models, when available, spatial data on temperature and precipitation should be included to directly represent climatic variation. Copyright © 2017 John Wiley & Sons, Ltd.     

Sorption and Chemical Reactions of PAHs with Dissolved Humic Substances and Related Model Polymers

Sorption coefficients measured for PAHs on dissolved humic substances by SPME and FQT were found to be inevitably different and method‐dependent – SPME provides activity‐based and FQT concentration‐based sorption coefficients. Poly(acrylic acid) esters as well‐defined model polymers were used in sorption experiments, leading to the conclusion that short aliphatic chains are more effective in binding PAHs than aromatic moieties. FQT was inappropriate to measure sorption coefficients for the interaction of pyrene with poly(acrylic acid) esters but the experiments revealed a characteristic shift in the fluorescence spectrum. Using pyrene as a probe for the molecular environment in the sorbed state, the observed spectral shift indicated a highly hydrophobic microenvironment. The empirical relationships between lg K_DOC and lg K_OW were generalized on the basis of a modified Flory‐Huggins concept. Introducing only one sorbent‐specific parameter, the solubility parameter δ_DOM, the calculation of sorption coefficients became possible for a wide range of HOCs using fundamental data readily available from the literature. Long‐term experiments showed that reactive PAHs (such as acenaphthylene and 9‐methylanthracene) are able to react with HAs under strictly abiotic and anoxic conditions, whereas less reactive PAHs (such as naphthalene and dihydroanthracene) do not form bound residues. The HA reveals two functions in the interaction, behaving as a reaction partner and as a protecting ligand.