Some time in the 1980's I read a novel that involved a protagonist discovering that the ancient Minoan practice of "jumping the bull" was actually a metaphor for an effect produced by some ancient artifact. As I recall the artifact(s) are a pair of micro black holes, one "negative" and one "positive" embedded in ancient rock. They are some distance apart on the Earth. One is in Crete and the other somewhere else in the Mediterranean. They are attracted to each other but if they meet the Earth will be destroyed. When the protagonist finds one of the artifacts it warps gravity in its vicinity.

I have tried googling all manner of search terms without success. Perhaps it was a novella or short story instead of a novel.