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30 July 2015

Stromatolites of the Helena Formation, Grinnell Glacier Cirque, Montana

My favorite place to have lunch in Montana is at the Grinnell Glacier cirque in Glacier National Park. This is the dining room table: You’re looking at a bedding-plane-parallel exposure of Mesoproterozoic stromatolites here. Every few years, I’m lucky enough to hike up there with motivated students and share food atop this unparalleled view into the shallow seas of more than a billion years ago. Stromatolites are sedimentary structures that …


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