Coprophilous fungal spores: NPPs for the study of past megaherbivores

Spores from coprophilous fungi are some of the most widely used non-pollen palynomorphs. Over the last decades, these spores have become increasingly important as a proxy to study the Pleistocene and Holocene megafauna. Although the number of types used in palaeoecology is relatively small, there is a wide range of coprophilous fungal taxa whose utility in palaeoenvironmental reconstruction remains under-researched. However, environmental and taphonomic factors influencing preservation and recovery of these spores are still poorly understood. Furthermore, our understanding of whether and how spores are transported across the landscape is limited.Dung fungal spore presence appears to correlate well with megaherbivore presence. However, depending on the site, some limitations can remain to quantitative reconstructions of megaherbivore abundance from dung fungal spore records. The presence of dung fungal spores is often more significant than their absence and variation in in abundance with time should be interpreted with caution. Correlation with other proxies may provide a promising way forward.The majority of studies using dung fungal spores as an indicator for large herbivore abundance are of records of Late Pleistocene and Holocene age, with a focus on Late Quaternary megafaunal extinction. However, more research could potentially extend records further back in time.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5240664

Belemnite geochemistry from Albstadt-Pfeffingen (Middle Jurassic, Baden-Württemberg, Germany)

Belemnite calcite is an important source of stable isotope (18O, 13C) and element (Fe, Mg, Mn, S, Sr) proxies with potential for high-resolution quantitative reconstructions of palaeoenvironments and seasonality since Urey et al (1951). Belemnites are also a very important archive for environmental reconstructions of the early Toarcian; it is important, however, to study their calcite over intervals of comparative environmental stability to assess the meaning of proxy data extracted from their calcite. Here, we report on recent developments on geochemical proxies derived from belemnite rostra from Albstadt-Pfeffingen, a potential GSSP for the base of the Callovian, in Baden-Württemberg.

Belemnite geochemistry from Albstadt-Pfeffingen (Middle Jurassic, Baden-Württemberg, Germany)

Belemnite calcite is an important source of stable isotope (18O, 13C) and element (Fe, Mg, Mn, S, Sr) proxies with potential for high-resolution quantitative reconstructions of palaeoenvironments and seasonality since Urey et al (1951). Belemnites are also a very important archive for environmental reconstructions of the early Toarcian; it is important, however, to study their calcite over intervals of comparative environmental stability to assess the meaning of proxy data extracted from their calcite. Here, we report on recent developments on geochemical proxies derived from belemnite rostra from Albstadt-Pfeffingen, a potential GSSP for the base of the Callovian, in Baden-Württemberg.

Eliminating incident subtraction in diffraction tomography

Diffraction tomography is a powerful algorithm for producing high-resolution quantitative reconstructions across a wide range of applications. A major drawback of the method is that it operates on the scattered field, which cannot generally be directly measured, but must instead be calculated by subtracting the incident field, i.e. the equivalent field with no scatterer present. Unfortunately, often the incident field is not measurable and hence must be estimated, causing errors. This paper highlights an important, but not widely recognized, result: for particular widely used formulations of the algorithm, the subtraction of the incident field is unnecessary, and the algorithm can actually be applied directly to measured signals. The theory behind this is derived, showing that the incident field will vanish under far-field conditions, and the result is demonstrated in practice. Tests with subsampled arrays show that aliasing artefacts can appear, but can be removed with a filter at the expense of resolution. The incident field also has no effect for a variety of array configurations tested. Finally, the performance in the presence of both correlated and uncorrelated errors is confirmed, in all cases demonstrating that the incident field has a negligible effect on the final reconstruction.