Asked by Edward
Hello Edward! Great question.
Fossils can be very useful in understanding past environmental change; this can be linked to past glacier fluctuations so that we can understand what the environment or climate was like when glaciers in the past grew larger or smaller.
For example, fossil pollen from plants can be found in cores from lake sediments or peat bogs. This can tell us about past vegetation, which is linked to regional climate. Chironomids, which are a kind of non-biting midge, can tell us about past temperatures. In the ocean, tiny animals like foraminifera can tell us about past ocean conditions.
When glaciers are in equilibrium with climate and are therefore maintaining their position, they can make landforms like moraines (a pile of rocky and muddy debris) at their terminus. Sometimes, organic material like plant material or shells may be picked up by the glacier and deposited in the moraine. We can can then use techniques like radiocarbon dating to understand the date when the moraine was formed.
Why are fossils important figuring out ice ages?
Good question!
Fossils are very important for working out ice ages.
Fossils of ocean dwelling species (e.g. corals, clams, Foraminifera) can inform us of temperature variations by the proportions of oxygen-18 and oxygen-16 within their shells. Oxygen-16 is lighter, therefore evaporates more readily and makes up a higher proportion of precipitation. So, during cold periods like an ice age, more oxygen-16 is locked up in ice sheets and glaciers and the shells of ocean creatures contain higher proportions of oxygen-18, the heavy isotope of oxygen. During warmer periods the ice melts and oxygen-16 is returned to the oceans and incorporated into the shells. So, looking at the proportion of oxygen in the shells of fossilised species within an ocean core can help determine whether the environment was warm or cold!
Flora and fauna fossils (plants and animals) can also help work out past environments, as each will be adapted to survive in certain conditions, so the presence and distribution of their fossils can be used to indicate changes in climate too.