What is the unique geological feature at the tip of Michigan’s Northern Lower Peninsula?

The unique geological feature at the tip of Michigan’s Northern Lower Peninsula is the Old Mission Point Lighthouse. This lighthouse, located at the tip of the Old Mission Peninsula, serves not only as a functional structure to assist maritime navigation but also as a significant landmark that reflects the region's historical and geological heritage.

While Lake Michigan Sand Dunes are stunning natural formations along the coastline and the Mackinac Bridge is a prominent engineering marvel linking the Lower and Upper Peninsulas, neither is specific to the very tip of the Northern Lower Peninsula. Similarly, Petoskey Stone, a fossilized coral found in the area, is renowned but does not represent a geological feature in the way that the Old Mission Point Lighthouse does, which symbolically and physically marks the endpoint of the peninsula. Thus, the lighthouse is the correct answer as it embodies a unique aspect of the region's landscape.