How can scientists infer past ocean temperatures from sediment cores?

Scientists can infer past ocean temperatures from sediment cores by studying the types of organisms preserved in the sediments. This method relies on the fact that various marine organisms, like foraminifera (a type of plankton), have specific temperature preferences and adaptations. The composition and abundance of these organisms in sediment layers provide valuable clues about the environmental conditions at the time they lived.

For instance, certain species thrive in warmer waters, while others prefer colder climates. By examining the ratios of different species found in sediment cores, researchers can reconstruct a timeline of ocean temperatures over geological epochs. Additionally, some organisms incorporate oxygen isotopes from seawater into their shells, which further enables scientists to estimate historical temperatures through stable isotope analysis.

Other methods mentioned, such as analyzing sediment grain sizes, counting sediment layers, or measuring the weight of sediment cores, do not provide direct insights into past temperatures, making the study of preserved organisms the most reliable approach for this purpose.