Today we are on the east coast of the North Island in New Zealand at a place called Tora,
and I'm with Chris Hollis who's a geologist who has studied the rocks of this area
for many many years. Now there's something about these rocks which is quite unique, so
Chris what's the big story of this piece of rock that we've got in front of us?
So the interesting thing about these rocks is that we have
recently established that they were deposited in the deep sea as part of a submarine
fan or submarine channel. But a lot of these grains are rounded as if they were formed on the
beach so the question that we've asked is: "How did this these rounded rocks get into the deep
sea?" - And - just a question: how deep when you say deep sea? Probably 500 to 1000 meters water
depth. Okay and normally at that depth you'd expect to find very fine silty rocks rather
than big gravelly rocks? Exactly - well you might find big gravelly rocks, but you wouldn't normally
find them rounded in the form that you get on beaches or in rivers, and so the fact that we've
got rounded pebbles in this deposit immediately causes us to think something weird is going on.
And the the extra added interest factor with these rocks is that they sit exactly at the time that we
know the dinosaurs died out. So work we've done to date these rocks has shown that they are dated
at 66 million years ago which is the end of the Cretaceous Era the end of the the dinosaur era.
So that's what we call the K-T Boundary? That's what we call the K-T Boundary. For a long time
we've been interested in finding K-T boundary sites around New Zealand and this site had been
relatively uninteresting because we hadn't found the K-T boundary layer that we try and find at
many of the other sites to pinpoint the boundary. But now a new theory has developed from the
the K-T boundary scenario which proposes the idea that the dinosaurs were wiped out by an asteroid
that blanketed the earth in a dust cloud and and killed all plants and then killed half of the rest
of life on earth and as well as that the impact would have caused a huge magnitude 12 earthquake
and would have generated a huge tsunami around the impact site, possibly a hundred meters high.
And where was the impact site compared to New Zealand? The impact was in present-day Mexico,
so on the other side of the Pacific Ocean. But modeling has shown that the tsunami would have
followed along two trajectories - one across the Atlantic and one into the South Pacific and
so now we're wondering is this deposit at Tora an indicator of the mega-tsunami generated by the the
meteorite impact hitting New Zealand? And so what would have happened would be the impact would have
hit New Zealand, swept up the coast and then swept all the debris back out into the submarine
channel that's present here, so that's how we get beach rock into the deep sea.
Brilliant! So this tiny little patch of gravel that's below us here is representing a global
impact, a massive event that affected all of life on planet earth 66 million years ago.
A small thing to look at has a huge story behind it. So Chris one more question is: Can we see
any more of this rock around where we are? It's not just here of course. Down here you can see
the Cretaceous / Tertiary boundary here and so limestone below, greensand above and within
the greensand you see all these rounded pebbles and dislocated beds of various sorts, and rip-up
clasts of various sorts. And so this is clearly a turbulent event that's caused this deposition.
And over here we have another interesting thing to look at: So these are
burrows on the top Cretaceous bed, so on the top of the Cretaceous seafloor prior to
the tsunami coming in. The intensity of these burrows suggests that perhaps some of them are
escape burrows and perhaps the organisms living on the sea floor shuffled off pretty quickly
as soon as they felt the rumblings of the tsunami. And again above these burrows you can see
the the pebbles, the coarse sediments that came in with the presumed tsunami deposit.
Is this the first time a possible tsunami deposit from the K-T boundary has been found in anywhere
or just in New Zealand? What's the story? It's not the first time, there's been tsunami deposits
identified close to the source in Mexico and North America but this is the first time we've found any
convincing evidence so far away, so this is the further most reach of the of the tsunami
that we know about. So this is showing us a new idea for the K-T boundary in New Zealand and I
believe that very few people up to now even know of this location, probably a handful or
less is that correct? That's right - just a few people. So you've been let in on a big secret,
somewhere on the Tora coast is a possible tsunami deposit from the event - from the massive
catastrophe - that impacted planet earth many many millions of years ago and wiped out the dinosaurs.