What is The calico scallop is an index fossil. It is well documented to have lived 1.8 million years ago. Therefore the approximate age of the rock in which this fossil is found is?

The calico scallop, as an index fossil, indicates that the rock in which it is found is approximately 1.8 million years old. Index fossils are used by geologists to date and correlate the age of rock layers, as they are characteristic of specific geological time periods. Therefore, finding a calico scallop fossil suggests that the surrounding rock formed during the same time frame.