Question 12 The most distinctive rock unit i the Theodore Roosevelt NP is: A) sandstone B) lignite C) granite

Option (A)

Explanation:

Sandstone is the main rock of the Theodore Roosevelt National Park. This rocks were formed some 65 million years back, that marked the boundary of the cretaceous mass extinction that wiped out the entire dinosaurs species from earth.

During the Paleocene age, towards the western side of North America, there was continuous folding of beds due to the compressive forces, thereby forming the Rocky mountains. And this mountain over the course of time undergone significant weathering and erosion by wind, water and ice, due to which a huge amount of sediment has been accumulated at the eastern side. These sediments were mostly silt, sand and mud. In addition to that, continuous volcanic eruptions has also taken place in the nearby places, from which the abundant volcanic ashes were released and subsequently got mixed up with the eroded sediments. Therefore, after millions of years, this rocks undergone compaction and lithification, and turned into sandstone.

Thus, the correct answer is option (A).