The Toarcian (Early Jurassic) Posidonia Shale Formation is a possible unconventional gas source in Northern Europe and occurs within the Cleveland Basin (United Kingdom), the Anglo-Paris Basin (France), the Lower Saxony Basin and the Southwest Germany Basin (Germany), and the Roer Valley Graben, the West Netherlands Basin, Broad Fourteens Basin, the Central Netherlands Basin and the Dutch Central Graben in The Netherlands. Outcrops can be found in the United Kingdom and Germany. Since the Posidonia Shale Formation does not outcrop in the Netherlands, sample material suitable for experimental studies is not easily available. Here we have investigated lateral equivalent shale samples from six different locations across Northern Europe (Germany, The Netherlands, The North sea and United Kingdom) to compare the microstructure and composition of Toarcian shales. The objective is to determine how homogeneous or heterogeneous the shale deposits are across the basins, using a combination of Ion Beam polishing, Scanning Electron Microscopy and X-ray diffraction. The work presented here shows that the Toarcian shales of Northern Europe display considerable homogeneity in mineralogy and microstructure in the different investigated samples and formations, where the largest variability is the carbonate content ranging from almost zero up to 80%. We conclude that the outcrop locations in Germany and the United Kingdom are suitable analogues with respect to their mineralogy and microstructure for experimental studies on the Posidonia Shale in the Dutch subsurface.@en

Recognition of terrestrial dust in geological records is essential for reconstructing paleoenvironments and quantifying dust fluxes in the past. However, in contrast to eolian sands, silt-sized dust is difficult to recognize in pre-Quaternary records due to a lack of macroscopic features indicating eolian transport and mixing with alluvial sediments. Windblown dust deposits are commonly identified by comparing their sedimentological and petrological features with Quaternary examples of dust known as loess. Here, we review the characteristics of terrestrial dust deposits and conclude that most of these features are not exclusively windblown and may be formed by alluvial deposits as well. We therefore synthesize a set of criteria which enable a reliable identification and quantification of dust while acknowledging potential contributions of alluvial components. These methods include quartz-grain surface morphology analysis to distinguish eolian and alluvial transport modes, provenance studies to identify local and extrabasinal sources, grain-size-shape end-member modelling to quantify the various sedimentary contributions to the record, and a basin-scale stratigraphic approach to derive regional patterns and avoid interpretation of local phenomena. We reassess the Eocene to Pliocene records of the Chinese Loess Plateau and conclude that these strata represent both alluvial and eolian sediments deposited in extensive mudflat systems. Quaternary loess, by contrast, is almost exclusively composed of windblown dust. The early Pleistocene shift from mudflat to loess deposits is associated with a significant increase in accumulation rates, likely due to increased dust production upwind, overwhelming and blanketing the local mudflat systems in central China.@en