Final answer:
A large step-like fold in horizontal strata is known as a monocline, an example of which is the Waterpocket Fold at Capitol Reef National Park, which resulted from the Laramide Orogeny.
Step-by-step explanation:
A large, step-like fold in otherwise horizontal strata is called a monocline. These geological structures form when there is a 'step-up' in the rock layers due to movement along a fault.
A classic example can be seen at Capitol Reef National Park where the Waterpocket Fold represents a significant monocline caused by the Laramide Orogeny. It's an event where one side of a fault shifts upwards relative to the other, lifting one side of the sedimentary layers much higher than the other.