1.6 billion year old ripples.Stop and think about that headline for a second, isn’t it remarkable? T

1.6 billion year old ripples.Stop and think about that headline for a second, isn’t it remarkable? The casts on the surface of this rock layer preserve patterns made by the ocean flowing over sediment nearly 2 billion years ago.These rocks come from Montana’s Glacier National Park. 1.6 billion years ago a large rift zone opened on what is today the western side of North America. The ocean flowed into that growing basin and huge piles of sediments were deposited along the edges. Those sediments were much richer in iron than the typical sediments deposited in the ocean today as the ocean chemistry was still adapting to the presence of oxygen in the atmosphere. Iron that today would rust in the air made it all the way to the ocean and into these rocks, staining them red as we find them today.The ripples are a couple centimeters across (plant leaf at lower right gives some scale). Just like ripples today, they were created by water flowing over loose sediment, likely in shallow water. Preserving them would require burying this sediment with another layer before the waves could rework the dirt, maybe during a storm. The preservation of these ripples is also helped by the fact that they are so old; there were no burrowing animals or plants in the Precambrian, so once the ripples were buried there was nothing else to churn them up. Many of the rocks in Glacier National Park are sediments from the Belt Supergroup that have been thrust upwards during subsequent mountain building in Montana.-JBBImage credit: Glacier NPShttps://flic.kr/p/7RFpxY -- source link

More pics about