When Were the Atlantic and Pacific Oceans Separated by Land?
ES2307  Identifying Microfossils in Caribbean and Pacific Cores

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.

Map: "From Glaciation to Gateways", Ocean Drilling Program;
Microfossils: Top left: Ronny G. Thomas Research Associates
Department of Chemistry Texas A&M University - Kingsville;
Bottom right: The Astrobiology Institute,
Marine Biological Laboratory, Woods Hole

5. How do you think this marine species could have spread to both sides of the isthmus?

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