Answer :
Final answer:
The oldest sedimentary layer in the Grand Canyon is the Bass Limestone, which is estimated to be about 340 million years old.
Explanation:
The oldest sedimentary layer in the Grand Canyon is the Bass Limestone. It is part of the Redwall Limestone formation, which is found in Group 7 of the cross-section of the Grand Canyon. The Bass Limestone is estimated to be about 340 million years old and is located near the bottom of the canyon.
