Figure: Graph showing oxygen isotope ratio in planktonic foraminifera shells at

Question

Figure: Graph showing oxygen isotope ratio in planktonic foraminifera shells at ODP Site 677 (tropical Pacific Ocean), for the last 500,000 years.

1- Do odd or even isotope stages best represent glaciations based on the oxygen isotope data?

2- Of the isotope stages known on your graph, four display the greatest ice volume. What stages are these?

3- Based on the last 12 isotope stages, when was the maximum extent of the ice sheet (in Kyr)?

4- How long did it take to form ice during the Pleistocene glacial period? How long did it take for the ice to decay? Are the glacial or interglacial steps shorter?

5- What three potential problems can you think of that could be involved with measuring the oxygen isotope ratios in foraminifera shells? (HINT: planktic forams live in the surface ocean: think about how they are preserved in sediment).

Explanation / Answer

1) from the given graph we can see that the isotopes on the left vertical coordinates and the ages in the horizontal coordinates having the data. so if we talk about the odd or even which is best representing the glacial based data then it is even isotope stages. it is due to the fact that it have great magnitude as compred to the odd.

2) it is the oxyge isotops stage which is display the greatest ice volume in this.

3) based on the last 12 isotopes stages the maximum extent of the ice sheet was at the Kyr scale of 340.

4) it take the long time to form the ice during the pleistocean glacial period of the about 2 to 3 month time if we take it on the normal time period on the monthly basis scale.the decay time is shorter as compared to the formation time that is about 2 month.yes the interglacial steps are shorter.

5) => this will imbalance the oxygen cycle in the water bodies.

=> there may be create the fall in the value of the shell density.

=> the ratio may not be remain same and the value may change during the setup of this.

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