Core

Hello everyone

After referring to dictionaries to find the suitable meaning for the title-word in the following context, I was unable to choose. Can you help?

Quotes from BBC's documentary "incredible human journey" :

'So this is a sedge pollen grain from a marine core?
It's a core taken under 30metres of water in the Hecate Strait.
But what the pollen in his cores proves?'

It likely refers to a core sample. A marine core (sample) would be taken from the sea/ocean floor.

Thank you very much, icecreamsoldier, for this quick accurate answer.