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It is fitting that our last outdoor stop on the tour of the Ries structure is the place where the Ries story began. This quarry supplied most of the building stone used to construct St. George's Church and other buildings in Nördlingen, beginning in the 15th century. Altenbürg was also the location where suevite was first described and named. Finally, and perhaps most importantly, it was here that suevite was originally interpreted to be a volcanic rock, but also where it was later correctly identified as being the product of a meteorite impact event.
| If we look at the quarry wall, we can see suevite that was deposited from above between two large displaced blocks of limestone, which also form part of the ejecta blanket.
If we look a bit more closely we can see that the contact between the suevite and limestone is vertical. The presence of these vertical contacts and the fact that suevite closely resembles volcanic tuff, led early scientists to interpret the suevite as being a volcanic rock, which meant that the circular Ries structure was also a volcanic crater. However, in 1961, Eugene Shoemaker and Edward Chao discovered the presence of coesite in the suevite from the Otting quarry (stop 9), which indicated a meteorite impact origin for the Ries structure. |
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The suevite at Altenbürg is actually quite weathered compared to other suevite deposits we've seen from earlier in the tour.
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