You've seen how isotopes in microfossils indicate changes
in ocean chemistry over time. Now you'll look at another
piece of evidence from microfossils.
Layers of sediments from as far back as six million
years ago have been extracted from drilling sites in
both the Caribbean and the Pacific. The inset images
show fossils of microorganisms called foraminifera.
This species of foraminifera has been found in sediment
cores from drilling sites on both sides of the Isthmus.