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The sand spike occurrence near Mount Signal in southern California, USA a Typical sand spike from Mount Signal, California. The sand spikes occurs within a horizon with convolute bedding, dikes, and sills (image: Mila Zinkova, USRA Earth Science Picture of the Day, 24 November 2013; https://epod.usra.edu/blog/2013/11/sand-spike-concretions.html). b Sand spike from Mount Signal described by Garner (1936; redrawn after his Fig. 4). c Simplified geological situation in the Imperial Valley, California, with the sand spike occurrence at Mount Signal and the most prominent faults of the San Andreas transform fault system indicated. Apices of the sand spikes are orientated away from the San Andreas fault system and perpendicular (or even opposite) to the general drainage system in the Imperial Valley.
Source publication
Sand spikes, pin-shaped, carbonate-cemented sandstone bodies of variable size widely
interpreted as sedimentary concretions, have been enigmatic for nearly two centuries. We
here present a high-energy mechanism for their formation. Two classic sand spike occurrences are found in the North Alpine Foreland Basin of Central Europe and at Mount Signal...
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Citations
... Despite a large number of publications on the Ries event, it is striking that, except for the so-called Brockhorizont (brock horizon) and the moldavites, the remote effects of the impact have received only little attention in the literature until recently. Only in the last years, some papers have been published that also consider seismic and resulting sedimentological effects in the Molasse Basin (Buchner et al., 2021Lange & Suhr, 2022;Schmieder et al., 2022). One of the significant problems is the difficulty in identifying synchronous deposits across different facial zones. ...
... Buchner et al. (2020) succeeded in detecting seismites immediately below the Brock horizon in outcrops 110 km (Biberach and Ochsenhausen), 140 km (Ravensburg), and 180 km (Bernhardzell) from the Ries center. These are slip folds, convolute beddings, ball-andpillow structures, flame structures, clastic dikes, and sand spikes in sandy and silty sediments of the Upper Freshwater Molasse (Buchner et al., , 2021. However, some clastic (Hurtig, 2017;Lange, 1993). ...
The Ries impact is the most important cosmic event in the younger geological history of Europe. Its effects reach far beyond the area considered so far and are documented in manifold evidence. In this paper, the widely scattered reports in the literature are compiled and supported with investigations by the authors. Besides well-known ejecta features like the Brockhorizont, Reuter's blocks, and moldavites, little known or forgotten indications, like a lechatelierite and β-cristobalite occurrence in Bavaria and unusual sedimentation phenomena in northern Germany, are presented. The paleogeographic reconstruction shows that the Ries impact occurred on the southern side of the Neogene Central European mainland. Large parts of this erosional area were devastated by the impact. Pressure waves and thermal radiation had a lasting effect on the landscape within hundreds of kilometers around the impact site. Destruction of the vegetation cover by impact-induced storms, wildfires, and heavy rainfall generated intense erosion. The adjacent sedimentation area to the north (Paleo-North Sea) experienced an increased and short-term supply of terrestrial debris to the marine environment. The stratigraphic coincidence of these exceptional sediments with the Ries event leads us to conclude that the distal effects of the impact are present here, which have so far received little or no attention in this context. The paper considers the different indications and sets them in a large-scale context.
For decades, the Nördlinger Ries and Steinheim Basin in southern Germany have been regarded as a textbook example of a terrestrial impact crater doublet, although the oldest crater lake deposits in both craters suggest a biostratigraphic age difference of ~ 0.5 to 1 Myr. We previously presented stratigraphic arguments that challenged the double impact scenario and favoured a model of two temporally independent impact events in the Mid-Miocene. We here present, for the first time, four localities within a distance of ~ 50–100 km from the Ries and ~ 50–70 km from the Steinheim crater that expose two independent seismite horizons, together unique within the Upper Freshwater Molasse of the North Alpine Foreland Basin, each one featuring impressive water escape structures. The seismite horizons are separated by ~ 10 to 15 m of undisturbed Molasse deposits and, biostratigraphically, by an entire European Land Mammal Zone, thus providing evidence for two independent major seismic events within a time span of ~ 0.5–1 Myr. Both the lower and the upper seismite horizons can be correlated litho- and biostratigraphically with the basal crater lake sediments at the Ries and Steinheim craters, respectively, deposited immediately after the impacts. From a biostratigraphic point of view, the impact event that formed the Steinheim Basin probably occured around 14 Ma, some 0.8 Myr after the ~ 14.81 Ma Ries impact event.
