If the lithology and fossil content of two bodies of rock on opposite sides of a canyon are identical, then these remaining outcrops were likely physically connected at one time and formed part of an extensive, sheet-like layer of rock. This idea summarizes the principle of .
A. superposition
B. original continuity
C. original horizontality
D. uniformitarianism

Option (B)

Explanation:

The law of Original continuity was contributed by Nicolas Steno. This law says that in an undisturbed sedimentary basin, the sediments and other fragments of rocks were initially deposited and were extended in all directions, covering a large geographical area. These rocks are now being cut or separated by the presence of rivers, valleys, and other geological erosional features.

In the given condition, the two rock bodies on either side of a canyon are comprised of similar lithology and the fossil assemblage, and this describes the principle of original continuity.

Thus, the correct answer is option (B).