By: magic-gigapans
Image: Callan Bentley, Mid-Atlantic Geo-Image Collection
License: Creative Commons Non Commercial ⧉

Uploaded: 6 May 2020
Last Updated: 19 May 2020

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The Antietam Formation (Cambrian, Sauk sequence) is brecciated in many (but not all) places along its outcrop belt in the western Blue Ridge. The nature of these breccias is enigmatic, though the traditional story is that they are "fault breccias" related to the thrusting of Blue Ridge rocks over younger strata of the Valley & Ridge. The breccias are sometimes cemented with quartz, sometimes with iron oxides, sometimes with manganese oxides.