Simulation of trajectories and maximum reach of distal impact ejecta under terrestrial conditions: Consequences for the Ries crater, southern Germany

Moldavites from the Cheb Basin, Czech Republic

“…Such a distribution does not follow the usual radial size trend observed among ordinary proximal and distal ejecta (Melosh, 1989, and references therein). Yet, as pointed out by Buchner et al (2007), moldavites were not ejected and transported in a solid phase but as a vapor-melt mixture with extreme ejection velocities. Indeed, Artemieva et al (2002) and Stö ffler et al (2002) were able to numerically model not only the melt formation and ejection process during and shortly after the Ries-forming impact, but also the ballistic trajectories for molten moldavites, which reflect the actual observed size distribution over the entire strewn field.…”

The Steinheim Basin impact crater (SW-Germany) – Where are the ejecta?

“…In contrast to the enormous amount of proximal continuous impact ejecta in the surroundings of the Ries crater within a distance of 30-40 km and distal ejecta boulders in a distance of up to 200 km from the crater rim (e.g., Buchner et al, 2007;Sturm et al, 2013), impact ejecta outside the Steinheim Basin impact crater have never been described in the literature or mapped in the local geological charts. Generally, the lack of an ejecta blanket around the Steinheim crater could be explained in the following ways: 1. it has been eroded away; 2. it exists but has not been recognized; 3. it never formed.…”

“…On Earth, interaction with the atmosphere and/or fluids in target rocks are responsible for multiphase ejecta formation, transfer of 1.5-2 crater radii for a continuous ejecta blanket (e.g., Barlow, 2005), and on the order of 2-3 crater diameters for distal ejecta (e.g., Melosh, 1989). Sturm et al (2013) recently demonstrated that the Ries ejecta blanket in southern Germany contains a massive and continuous, dual-layer rampart structure at 1.45-2.12 crater radii from the crater center, whereas the most distal coarse-grained ejecta (the lithic ejecta clasts of the ''Ries-Brockhorizont'') was identified in fluvial sandy deposits of the North Alpine Foreland Basin in northern Switzerland nearly 200 km ($8 crater diameters) away from the Ries crater rim (Hofmann and Gnos, 2006;Buchner et al, 2007;Alwmark et al, 2012). Crucial factors for the acceleration and distribution of impact ejecta such as velocity, angle and property of the impacting body have been discussed in detail (e.g.…”

“…Conspicuous palustrine oncoids deposited chronologically close to the impact event, along with post-impact sandy Molasse deposits, indicate that the regional sedimentary succession stratigraphically brackets the time of impact; however, no medial or distal ejecta horizon has so far been detected within these deposits. In contrast, distal Ries ejecta components (Brockhorizonte) are embedded within fluvial and lacustrine Middle Miocene sediments deposited synchronous with the Ries impact (e.g., Buchner et al, 2007;Alwmark et al, 2012).…”

“…The $24 km Nördlinger Ries (Shoemaker and Chao, 1961;von Engelhardt, 1997;Osinski, 2004;Buchner et al, 2007) and the $3.8 km in diameter Steinheim Basin impact craters (e.g., Dietz, 1959;Grieve and Shoemaker, 1994; are situated on the Upper Jurassic limestone plateau of the Swabian and Franconian Alb (SW Germany; Fig. 1).…”