Gifts from the cliffs
Thirty miles south of Copenhagen a dark layer runs through the chalk sea cliffs. It dates to about 66 million years ago and occurs in sedimentary rocks of that age all over the world. Stevns Klint is one of the best exposures in Europe. Below it dinosaur fossils are abundant, above it they’re absent, and many years above mammal fossils appear. The layer itself contains high levels of iridium, an element rare on earth but common in asteroids.
You’ve guessed. This is the c[K]retaceous-tertiary (K-T) boundary, caused by an asteroid hit on the coast of Mexico; global winter, mass extinction and the Chicxulub crater the result.
Hojerup, with car park, museum and an excellent restaurant, a bit south of the red arrow on the map above, is the best access spot. Descend the steps by the old church on the cliff edge; legend says it never falls into the sea despite the eroding cliffs, because every night, when no-one’s looking, it hops inland a bit! A few yards south along the shingle, scramble up to see and touch the boundary layer. So many people have done so that there is a large overhang, so don’t stay long. Have a swim instead.
I’ve been twice, and collected quite a few bits of the boundary layer. I often award visiting speakers to our department with a piece, but I rarely get round to adding a note to remind them why their gift of crumbly grey rock is interesting. Now I can print off this post.