Clouds and Strata
Clouds hang against the strata exposed on the cliffs above the Going-To-The-Sun Highway in Glacier National Park, Montana. Theses sedimentary rocks were deposited in a shallow sea during the Proterozoic Eon between 1.6 to 1.8 billion years ago. The youngest of these rocks are the limestones and dolomites of the Shepard Formation which make up the massive beds at the top of the cliff. The next set of strata are partially hidden by the clouds and vegetation. If you look close at the right side, in the middle of the photo, you can make out the reddish to buff argillites (slightly metamorphosed shale), siltites (slightly metamorphosed siltstones) and quartzites (slightly metamorphosed sandstones) of the Snowslip Formation. These sediments were deposited on land in streams and mudflats adjacent to the ancient sea. The cliffs at the bottom of the photo are composed of thinly bedded limestones and dolomites with minor beds of argillite that composed the Helena or Siyeh Formation. These beds formed on the floor of the shallow sea. Some of the limestone beds are composed of beds formed of calcium carbonate precipitated by beds of cyanobacteria. The fossil cyanobacteria (called stromatolites) can be seen in the limestone. Glacier National Park has fascinating geology.
Clouds and Strata
Clouds hang against the strata exposed on the cliffs above the Going-To-The-Sun Highway in Glacier National Park, Montana. Theses sedimentary rocks were deposited in a shallow sea during the Proterozoic Eon between 1.6 to 1.8 billion years ago. The youngest of these rocks are the limestones and dolomites of the Shepard Formation which make up the massive beds at the top of the cliff. The next set of strata are partially hidden by the clouds and vegetation. If you look close at the right side, in the middle of the photo, you can make out the reddish to buff argillites (slightly metamorphosed shale), siltites (slightly metamorphosed siltstones) and quartzites (slightly metamorphosed sandstones) of the Snowslip Formation. These sediments were deposited on land in streams and mudflats adjacent to the ancient sea. The cliffs at the bottom of the photo are composed of thinly bedded limestones and dolomites with minor beds of argillite that composed the Helena or Siyeh Formation. These beds formed on the floor of the shallow sea. Some of the limestone beds are composed of beds formed of calcium carbonate precipitated by beds of cyanobacteria. The fossil cyanobacteria (called stromatolites) can be seen in the limestone. Glacier National Park has fascinating geology.