Was the 19th century the geologic time scale was based primarily on sequence of fossils in the rock record?

Yes, the 19th century was a pivotal time for developing the geologic time scale, largely based on the sequence of fossils found in the rock record. Paleontologists like Charles Lyell and Richard Owen utilized fossil assemblages to define different geological periods, establishing a framework that correlated rock layers with specific time intervals. This fossil-based approach allowed scientists to understand Earth's history and the evolution of life over time.