How was the age of the limestone layers in Niagara Cave determined?

The age of the limestone layers in Niagara Cave was primarily determined through fossil records. This method relies on the presence of various fossils found within the limestone, which provide clues about the age of the rock layers. Fossils can indicate the period in which the organisms lived, allowing geologists to correlate layers of rock with known timeframes in the geological record. The fossilized remains of marine creatures found in the limestone suggest that these layers were formed in a particular geological epoch when those species thrived, thus providing a relative age for the rocks.

Other methods mentioned, such as radiometric dating and carbon dating, are typically used for dating igneous rocks or organic materials, not limestone. Volcanic ash can be useful for dating certain rock strata, but this is less applicable to limestone formations unless they are directly associated with volcanic activity, which is usually not the case in typical limestone deposits like those found in Niagara Cave. Thus, using fossil records offers a more direct and relevant means of determining the age of the limestone layers in this specific context.