I want to know the answer to the following question:
What are used to create geological maps?
All the background I'm provided with is that "These early geologists also proposed a generalized interpretations of Earth history that led James Hutton, Georges Cuvier and Alexandre Brongniart, following in the steps of Steno, to argue that layers of rock could be dated by the fossils they contained: a principle first applied to the geology of the Paris Basin.". Is that enough to answer the question?
Answer: no