Luminescence Sensitivity of Rhine Valley Loess: Indicators of Source Variability?

Loess provides a valuable terrestrial record of past environmental conditions, including the dynamics and trajectories of air mass circulation responsible for dust transport. Here we explore variations in the luminescence sensitivity characteristics of sedimentary quartz and feldspar as possible tools for identifying changes in source down a loess-palaeosol sequence (LPS). Luminescence sensitivity is a rapidly measurable index which is the product of interplay between source lithology and the history of the quartz or feldspar clasts. Variations in sensitivity of down profile may therefore reflect changes in sediment provenance as well as other factors such as weathering through pedogenesis. We undertake an empirical investigation of the luminescence sensitivity of quartz and feldspar from different grain-size fractions from the Schwalbenberg LPS in the German Rhine valley. We compare samples from a 30 m core spanning the last full glacial cycle with samples of oxygen isotope stage (OIS) 3–2 age exposed within nearby profile. We find an overall inverse relationship between quartz and feldspar sensitivity, as well as variability in sensitivity between different quartz grain sizes. Statistical analyses yield a significant correlation between IR50 sensitivity from unprocessed sediments and clay content, and feldspar sensitivity and Si/Al ratios down the core. Since Si/Al ratios may indicate changes in provenance, the latter correlation suggests that IR50 measurements on unprocessed samples may be used to provide a reliable, rapid scan of source variability over millennial timescales.

Characterizing the taxonomic status of Sphingonotus caerulans in the upper Rhine Valley of Alsace (France) (Orthoptera, Acrididae, Oedipodinae)

Sphingonotus is a genus of grasshoppers that contains species groups with several closely related species, among which Sphingonotus caerulans and an unnamed Sphingonotus that are found in continental France. The exact distribution of both species is still under investigation, but it is believed that S. caerulans might be restricted to the northern part of the country, and that Sphingonotus sp. occurs in the southern half and might reach the north east. We explored the genetic identity of Sphingonotus grasshoppers in the upper Rhine Valley of Alsace (northeastern France) using combined fragments of mtDNA ND5 and cytb genes included with other available samples in ML and Bayesian phylogenetic analyses. The results indicate that the five specimens sampled within this region belong to S. caerulans. The actual distribution of Sphingonotus sp. in France remains to be investigated with wider sampling, especially to get a better knowledge on its northern limit.

Near-surface glaciotectonic structures in the sediments of an overdeepened glacial valley revealed by a shallow 3D seismic survey

<p>Glaciotectonic structures commonly include thrusting and folding, often as multiphase deformation. Here we present the results of a small-scale 3-D P-wave seismic reflection survey of glacial sediments within an overdeepened glacial valley in which we recognise unusual folding structures in front of push-moraine. The study area is in the Tannwald Basin, in southern Germany, about 50 km north of Lake Constance, where the basin is part of the glacial overdeepened Rhine Valley. The basin was excavated out of Tertiary Molasse sediments during the Hosskirchian stage, and infilled by 200 m of Hosskirchian and Rissian glacioclastics (Dietmanns Fm.). After an unconformity in the Rissian, a ca. 7 m-thick till (matrix-supported diamicton) was deposited, followed by up to 30 m of Rissian/Würmian coarse gravels and minor diamictons (Illmensee Fm.). The terminal moraine of the last Würmian glaciation overlies these deposits to the SW, not 200 m away.</p><p>We conducted a 3-D, 120 x 120 m², P-wave seismic reflection survey around a prospective borehole site in the study area. Source/receiver points and lines were spaced at 3 m and 9 m, respectively. A 10 s sweep of 20-200 Hz was excited by a small electrodynamic, wheelbarrow-borne vibrator twice at every of the 1004 realized shot positions. We recognised that the top layer of coarse gravel above the till is folded, but not in the conventional buckling sense, rather as cuspate-lobate folding. The fold axes are parallel to the terminal moraine front. The wavelength of the folding varies between 40 and 80 m, and the thickness of the folded layer is on average about 20 m. Cuspate-lobate folding is typical for deformation of layers of differing mechanical competence (after Ramsay and Huber 1987; µ<sub>1</sub>/µ<sub>2</sub> less than 10), so this tell us something about the relative competence (or stiffness) of the till layer compared to the coarse clastics above. We also detected small thrust faults that are also parallel to the push-moraine, but these have very little offset and most of the deformation was achieved by folding.</p><p>Ramsay, J.G. and Huber, M. I. (1987): The techniques of modern structural geology, vol. 2: Folds and fractures: Academic Press, London, 700 pp.</p>

Millennial-timescale reconstruction of Upper Pleistocene temperature and precipitation derived from earthworm calcite granules in western European loess profiles

<p>Loess-Palaeosol Sequences (LPS) represent the most extensive Quaternary terrestrial archives. Although researchers have long been able to identify short-lived climatic changes in LPS through stratigraphy, until recently we have lacked the tools to 1) identify how continuous loess archives may be, and to what extent short-lived, millennial-timescale climatic events were recorded in loess sediments, and to 2) quantitatively reconstruct past climate parameters from loess proxies. Stratigraphically, the impact of short-lived climatic cycles can be observed in the form of primary loess deposits reflecting cold stadial conditions, intercalated with arctic and boreal brown soils and tundra gley horizons indicating milder interstadials. Short-term establishment and subsequent degradation of an active permafrost layer can also be identified in temperate-latitude loess such as that found in the Rhine Valley of central-western Europe. Recently developed proxy methods can now be used to quantify climatic parameters such as temperature and precipitation in these regions <sup>1,2</sup>. Associated with radiocarbon dating, these new approaches will vastly improve our understanding of continental environmental changes through the Upper Pleistocene, which can now be compared at high temporal resolution with marine and ice core records. In particular, the quantity and stable isotope ratios of crystalline calcite granules (> 0.8 mm), secreted by earthworms (<em>Lumbricus sp.</em>)  at the soil surface, preserve climate information contemporaneous with deposition of the loess sediment.</p><p>In this study, we assess the utility of the earthworm calcite granules (ECG) approach by reconstructing temperature and precipitation at high resolution between 50 and 15 ka from two temporally overlapping loess sequences, Schwalbenberg and Nussloch, situated approximately 200 km apart in the German Rhine Valley. ECG counts down the two profiles reveal millennial-timescale climatic variations; high ECG concentrations associated with pedogenetic horizons suggest milder climatic with increasing biological activity and vegetation cover. Using empirical equations based on 1) observations of modern earthworm response to temperature and 2) the linear relationship between ∆<sup>13</sup>C values of plants and precipitation, the stable oxygen and carbon isotope compositions from ECGs can be used as direct proxies for warm season temperature and annual soil moisture, respectively. We embed our climate reconstructions within Bayesian age models based on radiocarbon dating of ECG in order to establish precise correlations between the two sequences and with other climatic archives. We find that ECGs provide valuable proxies able to meaningfully quantify palaeoclimate variations from terrestrial deposits over millennial timescales. Our results further show periods of quasi-simultaneous climatic change in the Northern Hemisphere, closely linking the climatic signatures recorded in the Upper Pleistocene of Schwalbenberg and Nussloch to the Greenland ice core records.</p><p>References: </p><p>1. Prud’homme, C. <em>et al.</em> Palaeotemperature reconstruction during the Last Glacial from δ<sup>18</sup>O of earthworm calcite granules from Nussloch loess sequence, Germany. <em>Earth Planet. Sci. Lett.</em> <strong>442</strong>, 13–20 (2016).</p><p>2. Prud’homme, C. <em>et al.</em> δ<sup> 13</sup>C signal of earthworm calcite granules: a new proxy for palaeoprecipitation reconstructions during the Last Glacial in Western Europe. <em>Quat. Sci. Rev.</em> <strong>179</strong>, 158–166 (2018).</p>

Prey, management and landscape requirements of an endangered population of the Woodlark Lullula arborea in Southwest Germany

Vineyards can be valuable habitats for biodiversity conservation. For example, in Rhineland-Palatinate (Germany) over a third of the state’s critically endangered Woodlark (Lullula arborea) population breeds in vineyards along the western margin of the Upper Rhine Valley. We here aim to elucidate how local ground cover management, food availability and the proximity to settlements affect territory selection by this bird species in the region. As climate, site conditions and management differ greatly from more continental or Mediterranean wine-growing areas, conditions for Woodlark conservation may differ as well.We compared 26 Woodlark territories in vineyards with 26 nearby reference areas from which Woodlarks were absent. We recorded vineyard ground cover in the inter-rows (% cover) as well as vegetation height and composition (forbs vs. grasses). Arthropods were sampled using pitfall traps, since they are the main food resource of Woodlarks during the breeding season. In addition, the distance to built-up areas was measured. The vegetation in Woodlark territories was shorter (mean 14.2 vs. 19.6 cm) and more dominated by forbs (39% vs. 27% cover) than in absence areas. The vegetation cover in the inter-rows had no effect on Woodlark territory presence or absence. Woodlarks also favoured areas with a higher abundance of arthropods (mean abundance 69.1 vs. 57.5) and a greater distance to built-up areas (mean distance 554 vs. 373 m). We conclude that to promote the Woodlark in wine-growing areas, short, forb-rich swards should be created, facilitating arthropod detectability. This is likely to require low levels of nitrogen fertilization since fertilizers favour tall-growing grasses that outcompete forbs. Pesticide applications should be kept at a minimum to enhance arthropods as the main food source for Woodlarks and their chicks. In addition, the expansion of settlements into breeding areas of Woodlarks should be avoided.

The δ13C, δ18O and Δ47 records in biogenic, pedogenic and geogenic carbonate types from paleosol-loess sequence and their paleoenvironmental meaning

Paleoenvironmental reconstructions are commonly based on isotopic signatures of a variety of carbonate types, including rhizoliths and land-snail shells, present in paleosol-loess sequences. However, various carbonate types are formed through distinct biotic and abiotic processes over various periods, and therefore may record diverging environmental information in the same sedimentological layer. Here, we investigate the effects of carbonate type on δ13C, δ18O, and clumped isotope-derived paleotemperature [T(Δ47)] from the Quaternary Nussloch paleosol-loess sequence (Rhine Valley, SW Germany). δ13C, δ18O, and T(Δ47) values of co-occurring rhizoliths (-8.2‰ to -5.8‰, -6.1‰ to -5.9‰, 12–32°C, respectively), loess dolls (-7.0‰, -5.6‰, 23°C), land-snail shells (-8.1‰ to -3.2‰, -4.0‰ to -2.2‰, 12–38°C), earthworm biospheroliths (-11‰, -4.7‰, 8°C), and “bulk” carbonates (-1.9‰ to -0.5‰, -5.6‰ to -5.3‰, 78–120°C) from three sediment layers depend systematically on the carbonate type, admixture from geogenic carbonate, and the duration of formation periods. Based on these findings, we provide a comprehensive summary for the application of the three isotopic proxies of δ13C, δ18O, and Δ47 in biogenic and pedogenic carbonates present in the same sediment layer to reconstruct paleoenvironments (e.g., local vegetation, evaporative conditions, and temperature). We conclude that bulk carbonates in Nussloch loess should be excluded from paleoenvironmental reconstructions. Instead, pedogenic and biogenic carbonates should be used to provide context for interpreting the isotopic signature for detailed site- and time-specific paleoenvironmental information.