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oh fun, more geology.
UL is the Purcell Sill (igneous rock) that you normally see up high as a black band along the top layer of some of the mountains in Glacier Park. Sills are formed when magma forces its way in between layers of sedimentary rock and then hardens. Throughout most of the park, the sill stands out as a 130 to 300 ft. dark layer of diorite sandwiched between strips of white, low-grade marble that formed as heat from the cooling magma baked the limestonehttp://formontana.net/purcell.html
UR Part of this Purcell Sill diorite has been altered to make the green mineral epidote.
LL is a Stromatolite: This 1.1-billion-year-old limestone unit contains the abundant remains of stromatolites and stromatolite rip-up clasts. Mound, conical and dome-shaped stromatolites are abundant, and often found in bioherms. Many of these bioherms (also called “zones” and “cycles”) are laterally persistent and traceable for miles, and can be seen at the foot of Grinnell Glacier, along the Highline Trail leading to Granite Park Chalet, as you drive on the upper western section of Going-to-the-Sun Road, under the Logan Pass Visitor Center.
LR I can't remember what he said causes those dimples in the rock but it was really cool. I don't know that it was raindrops. I've left a message for him on Facebook so hopefully I can touch base with him.
UL is the Purcell Sill (igneous rock) that you normally see up high as a black band along the top layer of some of the mountains in Glacier Park. Sills are formed when magma forces its way in between layers of sedimentary rock and then hardens. Throughout most of the park, the sill stands out as a 130 to 300 ft. dark layer of diorite sandwiched between strips of white, low-grade marble that formed as heat from the cooling magma baked the limestonehttp://formontana.net/purcell.html
UR Part of this Purcell Sill diorite has been altered to make the green mineral epidote.
LL is a Stromatolite: This 1.1-billion-year-old limestone unit contains the abundant remains of stromatolites and stromatolite rip-up clasts. Mound, conical and dome-shaped stromatolites are abundant, and often found in bioherms. Many of these bioherms (also called “zones” and “cycles”) are laterally persistent and traceable for miles, and can be seen at the foot of Grinnell Glacier, along the Highline Trail leading to Granite Park Chalet, as you drive on the upper western section of Going-to-the-Sun Road, under the Logan Pass Visitor Center.
LR I can't remember what he said causes those dimples in the rock but it was really cool. I don't know that it was raindrops. I've left a message for him on Facebook so hopefully I can touch base with him.
Aug 11 2021