Final answer:
During the intrusion of the Palisades Sill, sandstone and shale were transformed into hornfels through the process of contact metamorphism, which involves heat from an igneous intrusion.
Step-by-step explanation:
During the intrusion of the Palisades Sill, the heat from the igneous intrusion resulted in contact metamorphism, which changed sandstone and shale into hornfels. Hornfels are formed during contact metamorphism, which is the process of the baking by heat of intrusive igneous masses. These rocks are often nonfoliated or massive, and in some cases very durable, making them distinct from those created in regional metamorphism or by other processes. While marble also forms through contact metamorphism, it evolves from limestone under heat and pressure, not from sandstone or shale. Therefore, the correct answer is (d) hornfels.