When Were the Atlantic and Pacific Oceans Oceans Separated by Land?
ES2307  Pulleniatina as an Indicator of Change

The image below shows another kind of foraminifera called Pulleniatina. Unlike other microfossils, Pulleniatina is not found on both sides of the isthmus through time. In the graphic below, you’ll determine which layers have Pulleniatina fossils.

  !   Click the red dots on the map to see cross sections of cores from the Caribbean and Pacific drilling sites. Move your cursor over the layers of each core to see assemblages of microfossils present in the layers of different ages. Look for Pulleniatina in each assemblage.

6. In which layers was Pulleniatina present? Complete the chart on your student answer sheet.

7. How would you explain the presence or absence of Pulleniatina only on the Pacific Ocean side?


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