<P> The rocks found in the park are primarily sedimentary rocks of the Belt Supergroup . They were deposited in shallow seas over 1.6 billion to 800 million years ago . During the formation of the Rocky Mountains 170 million years ago , one region of rocks now known as the Lewis Overthrust was forced eastward 50 miles ( 80 km ) . This overthrust was several miles ( kilometers ) thick and hundreds of miles ( kilometers ) long . This resulted in older rocks being displaced over newer ones , so the overlying Proterozoic rocks are between 1.4 and 1.5 billion years older than Cretaceous age rocks they now rest on . </P>
<P> The rocks found in the park are primarily sedimentary rocks of the Belt Supergroup . They were deposited in shallow seas over 1.6 billion to 800 million years ago . During the formation of the Rocky Mountains 170 million years ago , one region of rocks now known as the Lewis Overthrust was forced eastward 50 miles ( 80 km ) . This overthrust was several miles ( kilometers ) thick and hundreds of miles ( kilometers ) long . This resulted in older rocks being displaced over newer ones , so the overlying Proterozoic rocks are between 1.4 and 1.5 billion years older than Cretaceous age rocks they now rest on . </P>
from what time period are most of the rocks in glacier national park
from what time period are most of the rocks in glacier national park
Proterozoic
Proterozoic