In geology, a key bed (syn marker bed) is a relatively thin layer of sedimentary rock that is readily recognized on the basis of either its distinct physical characteristics or fossil content and can be mapped over a very large geographic area. Marker bed, also called Key Bed, a bed of rock strata that are readily distinguishable by reason of physical characteristics and are traceable over large horizontal distances. Geologic Maps. Strike and dip. Many kinds of rocks form in broad, flat layers, called beds, that stack up like the layers of a cake. In areas like northern Arizona, thick stacks of rock beds that have built up over millions of years remain in their original flat orientation (where they can be viewed as multicolored horizontal layers of rock that make up the spectacular walls of the Grand Canyon).
Lithostratigraphic units are the basic units of geologic mapping. Customarily only distinctive beds (key beds, marker beds) particularly useful for stratigraphic purposes are given proper names and considered formal lithostratigraphic units. There are a number of important principles in geology. Finding the key bed in these situations may help determine whether the fault is a normal fault or a thrust fault. Each geologic map has a map key, which is a table explaining the meanings of all colors and symbols used to represent geologic features in the map. The number accompanying a strike and dip symbol indicates the angle, or tilt, of the rock bed.
Windley Key Fossil Reef Geological State Park, Islamorada: See 166 reviews, articles, and 73 photos of Windley Key Fossil Reef Geological State Park, ranked No. Casa Thorn Bed & Breakfast. A bed of sediment that is coarser at the bottom and finer toward the top (This is called normal graded bedding. Because they are independent of facies, they make excellent key beds for establishing correlations.