1. Discuss the various geological events that occurred in the Pacific Northwest region.
2. Describe the various types of rocks that formed due to these geological events.
3. Examine the relationship between the characteristics of these rocks and the geological events.
1.5 billion to 700 million ybp: The Pacific northwest was part of the first supercontinent, Rodinia. The rocks deposited during this era are the oldest in the region. They consist of multicolored sandstone, limestone, and siltstone. These sedimentary rocks demonstrate the action of blue-green algae, which left fossils called stromatolites.
750 to 370 million years ago: This was a tectonically quiet time during which Rodinia was broken apart along the Pacific coast. The earliest known glaciation, from 670 and 600 million years ago, The rocks formed during this time were quartz-rich sandstone, now called the Gypsy and Addy Formations. The limestone of the Metalline Formation also formed at this time, in areas covered by sea water.
370 - 300 million ypb: The ...
Geological history and rock formation in the Pacific Northwest from 1.5 billion years ago to present day.