This photo displays a pretty spectacular unconformity—an erosional/non-depositional surface where rock units deposited during different intervals of time appear to be continuous.
In the bottom half of the image, you can see Paleoproterozoic pink quartzite ~1.7 Ga in age, while in the top half of the image—directly overlying the quartzite—is Cambrian sandstone conglomerate ~540 Ma in age.
That means that there’s a missing gap of over one billion years between the time when these two rock units were deposited!
Location: Devil’s Lake State Park // Baraboo, Wisconsin
Image by author
Emily Zawacki, Ph.D. 