And that alternates with a sediment that looks like this.

This sediment is 100 percent made up of the shells of microscopic plants.

By means of a super high pressure water spray practically all the sediment is removed.

Lots of evidence from sediment cores and the pollen types, oxygen isotopes and so on.

Rivers washed sediment into the seas, until the organic remains of the algae were buried.

And the black rock is the sediment on the sea bottom in the absence of plankton.

And these plants need sunlight, so we know when we find that sediment there's no ice overhead.

And all the sediment is then put through these screens, and where we go again through it very carefully,

It doesn't matter what kind of sediment you're using to grind up, whether it's bacteria or any other plants or animals.

Well, an excavation was begun immediately, and more and more little bits of skull started to be extracted from the sediment.

It's a basin, and rivers flow down from the highlands into the basin, carrying sediment, preserving the bones of animals that lived there.

And we take samples of the sediment, and it tells us the CO2 level of the ocean, and therefore the CO2 level of the atmosphere.

And if you look north here, there's a big river that flows into the lake that's been carrying sediment and preserving the remains of the animals that lived there.

They take the sediment itself, they extract the oil from it, and from that they can produce compounds which turn out to be very specific to particular microbial groups.

It's because lipids are so tough, they can get preserved in sediment and last the hundreds of millions of years necessary, and be extracted and tell us who was there.

That signal was so strong, it could only have been produced by 10 trillion tons of water buried in the sediment, collected over millions and billions of years by the impact of asteroids and comet material.

The chalk itself's composed by plankton which has fallen down from the sea surface onto the sea floor, so that 90 percent of the sediment here is skeleton of living stuff, and then you have that millimeter thick red layer, and then you have black rock.