Amino acid and amino sugar yields and compositions as indicators of dissolved organic matter diagenesis

Microbial decomposition experiments were used to characterize changes in the amino acid and amino sugar yields and compositions of natural marine substrates during early diagenesis in seawater. On average, 63% of added carbon and 68% of added nitrogen were removed within the first 30 days of decomposition. In all cases, amino acid utilization accounted for a substantial fraction of the removed C and N. Carbon-normalized amino acid yields decreased to less than 50% of their starting values and most of this change occurred within the first 10 days of decomposition. Increases in the concentrations of amino sugars and decreases in the GlcN:GalN ratio in particulate organic matter (POM) illustrated the significance of microbial production during the decomposition of added substrates. Changes in the mol % composition of amino acids during early diagenesis were substantial but highly variable with substrate. Previous survey data collected from the same region were used in conjunction with the experimental data to investigate the utility of several established amino acid-based indices of organic matter diagenesis. This comparison showed that a combination of these degradation indexes is most effective for describing the diagenetic state of dissolved organic matter (DOM). Carbon-normalized amino acid yields were found to be the most effective indicator for early diagenesis. Relative abundances of amino acids were effective indicators of intermediate stages of diagenesis and the mol % composition of the non-protein amino acid γ-Aba (γ-aminobutyric acid) was an effective indicator of advanced DOM diagenesis.     

Vertikal-Bewegungen der Makaronesen

Zusammenfassung Die Bildung der Sockel der makaronesischen Inseln erfolgte durch vulkanotektonischen Zusammenschub geschichteter Vulkan-Gesteine (+ Sedimente auf Maio), die dabei steil aufgerichtet wurden und (auf den Inseln mit heute anstehendem Tertiär) bis in den Bereich abtragender Kräfte (der Brandung) gelangten. Die Hebung ging weiter. Bald lagerten sich randlich um die Inselkerne tertiäre Sedimente (Tuffite, Kalke) ab, die ihrerseits wieder gehoben wurden; und zwar en bloc, wo der Vulkanismus erloschen war; zerstückelt, wo er weiter dauerte. - Ursachen der Vertikalbewegungen sind vulkanische Intrusionen.Von den Canaren werden mehrere Hebungen und Senkungen angegeben, auf den portugiesischen Makaronesen sind nur Hebungen mit Sicherheit nachweisbar.Vertikalbewegungen des Festen und eustatische Bewegungen des Meeres-Spiegels interferieren; es ist daher nicht möglich, Strand-Linien nur nach ihrer Höhe über dem Meeres-Spiegel zu korrelieren.6: N. Jahrb. Min. Abh.96, 31–47. 1961.     

Cross-shore distribution of longshore sediment transport rates on a barred non-tidal beach

This study was conducted to relate the cross-shore distribution of longshore sediment transport and grain size characteristics to cross-shore and longshore current velocities on a sandy low-energy beach in a non-tidal embayment of the Baltic Sea. Simultaneous measurements of current velocities and amount of sand caught in streamer traps were made on 31 sampling runs on 6 d in April 1999 at three fixed sites including the swash zone on the upper foreshore, the lower foreshore, and the crest of the most landward of four bars. Spilling waves broke frequently on the bar but rarely on the lower foreshore, even during onshore wind speeds up to 11.0 m s⁻¹. Waves always broke as plunging waves at the step at the base of the upper foreshore and were converted directly into swash. The greatest longshore current velocities in the swash occurred when wind speeds and water levels were greatest, but wind direction was nearly directly onshore. Longshore velocities were greater in the swash zone than at other sites except when relatively strong winds blew nearly parallel to the shoreline, causing a pronounced wind-induced current at the other two sites. Calculated longshore shear stress and rate of sediment trapped were highly correlated on the bar (r=0.90), less highly correlated in the swash zone, and least highly correlated (r=0.66) on the lower foreshore. Mean trapping rates in the swash were 14.6 times greater than on the lower foreshore and 7.2 times greater than on the bar. Greater trapping rates in the swash are attributed to the greater turbulence mobilizing sediments in the uprush and backwash. Little of the finer-grained sediment on the offshore sites was reworked under low energy conditions. The study reveals the dominance of swash transport on steep, reflective, low-energy beaches where wave energy dissipation takes place over small distances on the upper foreshore.     

Expression of the Toarcian Oceanic Anoxic Event: New insights from a Swiss transect

A sedimentological, biostratigraphical and geochemical (stable isotopes and Rock‐Eval parameters) analysis was performed on four Swiss successions, in order to examine the expression of the Toarcian Oceanic Anoxic Event along a north–south transect, from the Jura through the Alpine Tethys (Sub‐Briançonnais and Lombardian basins). The locations were selected to represent a range of palaeoceanographic positions from an epicontinental sea to a more open marine setting. The Toarcian Oceanic Anoxic Event was recognized by the presence of the characteristic negative carbon‐isotope excursion in carbonate (ca 2 to 4‰) and organic matter (ca 4 to 5‰) at the base of the falciferum ammonite Zone (NJT6 nannofossil Zone). The sedimentary expression of the Toarcian Oceanic Anoxic Event varies along the transect from laminated mudstone rich in total organic carbon (≤11 wt.%) in the Jura, to thin‐bedded marl (≤5 wt.% total organic carbon) in the Sub‐Briançonnais Basin and to hemipelagic reddish marly limestone (total organic carbon <0·05 wt.%) in equivalent levels from the Lombardian Basin. The carbon‐isotope excursion is thus independent of facies and palaeoceanographic position. The low nannofossil abundance and the peak in Calyculaceae in the Jura and the Sub‐Briançonnais Basin indicate low salinity surface waters and stratified water masses in general. Sedimentological observations (for example, obliquely‐bedded laminae and homogeneous mud layers containing rip‐up clasts) indicate the presence of dynamic conditions, suggesting that water mass stratification was episodically disrupted during the Toarcian Oceanic Anoxic Event. The proposed correlation highlights a stratigraphic gap and/or condensed interval between the Pliensbachian–Toarcian boundary and the Toarcian Oceanic Anoxic Event interval (most of the tenuicostatum ammonite Zone is missing), which is also observed in coeval European sections and points to the influence of sea‐level change and current dynamics. This transect shows that the sedimentary expression of the Toarcian Oceanic Anoxic Event is not uniform across the Alpine Tethys, supporting the importance of local conditions in determining how this event is recorded across different palaeoceanographic settings.     

Widespread distribution of some estuarine crustaceans (Cyathura polita,Chiridotea almyra,Almyracuma proximoculi) in the limnetic zone of the lower Hudson River,New York

From June through September 1983, a survey was conducted to document the occurrence, abundance and distribution of benthic macroinvertebrates in the main channel, Hudson River Estuary. The survey was restricted to a 118-km reach of the limnetic zone from just below Albany to New Hamburg, New York. Results indicated that two crustacean species,Cyathura polita (Stimpson) andChiridotea almyra Bowman, are widely distributed and common throughout the limnetic zone, including areas more than 100 km upstream from the northernmost(=most upstream) intrusion of ocean-derived brackish water.Almyracuma proximoculi Jones and Burbanck was much less common, but also was found in areas well removed from any brackish-water influences. All three species previously have been thought to occur primarily in estuarine waters with at least some salinity. We could find no evidence to suggest that non-ocean derived sources were supplementing the levels of dissolved ions in the river water or sediments. Therefore, it appears that all three species have established permant populations in a truly freshwater habitat.     

New data on the age of the installation of Urgonian-type carbonates along the northern Tethyan margin: biostratigraphy of the Chopf Member (Helvetic Alps,eastern Switzerland)

The Chopf Member is a glauconitic, phosphate-bearing succession that occurs in the distal part of the Helvetic Alps (eastern Switzerland). The recent discovery of age-diagnostic ammonites within this horizon allows for its attribution to the lower part of the Gerhardtia sartousiana zone (middle Late Barremian). This new age corresponds to a maximal age for the onset of the Schrattenkalk Fm. in this area, and is coeval with the onset of the Urgonian facies in other parts of the western Tethyan realm. This new age allows also for a more precise dating of Late Barremian ${\delta }^{13}\text{C}$ curves. To cite this article: S. Bodin et al., C. R. Geoscience 338 (2006).     

High‐resolution study of Icelandic tephras in the Kangerlussuaq Trough,southeast Greenland,during the last deglaciation

Tephra abundance data and geochemistry in Late‐glacial and Holocene sediments on the East Greenland shelf are presented. Two well‐known tephras were identified from electron microprobe analysis of tephra shards picked from ash peaks in the cores. These are the Vedde Ash and Saksunarvatn Ash, which probably were deposited on the shelf after transport on drifting ice. The radiocarbon dates (marine reservoir corrected by −550 yr) that constrain the timing of deposition of the tephra layers compare well with the terrestrial and ice‐core ages of the tephras without requiring additional reservoir correction to align them with the known tephra ages. Several prominent tephra layers with a composition of Ash Zone 2 tephra punctuate the deglacial sediments. These tephra peaks coincide with significant light stable isotope events (signifying glacial meltwater) and fine‐grained sediments poor in ice‐rafted detritus. We interpret the Ash Zone 2 tephra peaks as sediment released from the Greenland Ice Sheet during strong melting pulses of the deglaciation. Copyright © 2002 John Wiley & Sons, Ltd.     

Ist der Kreuznacher Sandstein des Rotliegenden äolisch oder fluviatil entstanden?

The Kreuznach Sandstone belongs to the youngest Rotliegend sediments in the Bad Kreuznach area, northeastern Nahe Syncline. Because of its large-scale crossbedding — the thickness of sets of cross-strata can exceed — it has been interpreted as a typical aeolian dune sandstone, and has been placed to the Upper Rotliegend/ Zechstein boundary. To find out the origin of the Kreuznach Sandstone, it was examined by various sedimentological methods: petrography, granulometry, bedding and frame of crossbedding, sedimentary structures, facies associations, and quartz grain morphoscopy by scanning electron microscope. Although most of the results do not permit a clear decision between aeolian and fluvial origin, there are some arguments speaking well for fluvial sedimentation of the Kreuznach Sandstone. The very large-scale crossbedding — which is uncommon for river sands — is the sedimentological projection of the tectonic rise of the Kreuznach Rhyolitic Massif. Between the latter and the alluvial fans at the southern edge of the Hunsrück uplift the floods of an (ephemeral ?) stream coming from E/SE were narrowed. Thus water depth, stream velocity and concentration of sands grew rapidly so that megaripples, dunes and giant ripples could be built up. In the East before and in the West behind this narrow pass (as to stream direction) the stream spread out over a large plain, as a system of braided channels. Sand- and mudstones with laminated and small-scale ripple bedding were deposited there instead of the Kreuznach Sandstone.     

Schätzungen über die Dauer des Quartärs,insbesondere auf der Grundlage seiner paläoböden

Zusammenfassung 1. Die Dauer des Quartärs alter Gliederung (ab Günz) war mit grö\enordnungsmä\ig rd. 400 000 Jahren wesentlich kürzer als ursprünglich angenommen. 2.Die Gesamtdauer des Quartärs kann mit rd. 1,2 Mill. Jahren und evtl. darüber veranschlagt werden. 3. Das älteste Pleistozän war zumindest in seinen warmen Abschnitten anders geartet als das jüngere.

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1. The length of the Quaternary period in the classical sense (i. e. since Günz) is about 400 000 years, much shorter than previously assumed. 2. The length of the whole Quaternary period can be assumed to be approximately 1,2 million years or, perhaps, a little longer. 3. The climate of the oldest Pleistocene (at least in its warmer divisions) was of different nature than the younger Pleistocene.

     

Aeolian transport rates across raked and unraked beaches on a developed coast

Wind characteristics and aeolian transport were measured on a naturally evolving beach and dune and a nearby site where the beach is raked and sand‐trapping fences are deployed. The beaches were composed of moderately well sorted to very well sorted fine to medium sand. The backshore at the raked site was wider and the foredune was more densely vegetated and about 1 m higher than at the unraked site. Wind speeds were monitored using anemometers placed at 1 m elevation and sand transport was monitored using vertical traps during oblique onshore, alongshore and offshore winds occurring in March and April 2009. Inundation of the low backshore through isolated swash channels prevented formation of a continuously decreasing cross‐shore moisture gradient. The surface of the berm crest was dryer than the backshore, making the berm crest the greatest source of offshore losses during offshore winds. The lack of storm wrack on the raked beach reduced the potential for sediment accumulation seaward of the dune crest during onshore winds, and the higher dune crest reduced wind speeds and sediment transport from the dune to the backshore during offshore winds. Accretion at wrack seaward of the dune toe on the unraked beach resulted in a wider dune field and higher, narrower backshore. Although fresh wrack is an effective local trap for aeolian transport, wrack that becomes buried appears to have little effect as a barrier and can supply dry sand for subsequent transport. Aeolian transport rates were greater on the narrower but dryer backshore of the unraked site. Vegetation growth may be necessary to trap sand within zones of buried wrack in order to allow new incipient foredunes to evolve. Copyright © 2010 John Wiley & Sons, Ltd.