Stop 2 at Ries

Panorama of the Unterwilflingen quarry
Photo: G. Osinski, University of Western Ontario
Location: Megablock zone just outside of the structure’s inner ring
Scale: Distance from left to right is approximately 200 meters

This quarry has excavated into a large 1 x 2 kilometer-sized block of crystalline rock within the megablock zone of the Ries structure. A variety of impact breccias are also present, displaying complex relationships. At the east end of the quarry we can see gneiss and granite of the megablock. In the central area, a region of suevite lies between monomict crystalline breccia, composed entirely of heavily fractured and brecciated granite. These suevites have been highly altered to clays and we’ll see much better examples of suevite at later localities. These impact breccias are interpreted to have been injected into this large crystalline megablock during the formation of the Ries crater.

Finally, at the west end of the quarry, Bunte Breccia is present (“Bunte” means multi-colored in German). This type of breccia is composed mainly of sedimentary rock, along with some crystalline rock and is common all around the Ries structure. It represents the ballistic ejecta blanket. We’ll take a closer look at the Bunte Breccia at later stops.

Close-up of Suevite breccias
Photo: G. Osinski, University of Western Ontario
Location: Megablock zone just outside of the structure’s inner ring
Scale: Length of rock hammer is 35 centimeters

Suevites are impact breccias containing fragments and patches of impact glass. At Unterwilflingen, all the glass has been altered to clay (white patches). We’ll see much fresher examples of suevite at other localities, including our next stop.