You are likely thinking of Nicholas Steno, a Danish scientist and priest who lived in the 17th century. He is considered one of the founding fathers of geology for his groundbreaking contributions:

* Principles of Stratigraphy: Steno formulated the principle of superposition, which states that in undisturbed rock layers, the oldest layers are at the bottom and the youngest are at the top. He also proposed the principle of original horizontality, suggesting that sedimentary layers are originally deposited horizontally. These principles are fundamental to understanding the sequence of geological events and the age of rocks.

* Fossil Origins: Steno made significant observations about fossils, arguing that they were the remains of once-living organisms and not just naturally occurring shapes. He also proposed the principle of lateral continuity, suggesting that rock layers extend laterally in all directions until they thin out or encounter an obstacle.

* Early Geological Maps: While not as extensive as later maps, Steno created some of the earliest geological maps based on his observations of rock formations and fossils.

While not a single person, it's important to remember that Steno built upon the work of previous naturalists and his ideas helped set the stage for the development of geology as a formal science.