Dear stales: In the past year there have been quite a few papers about possible role of methane hydrate in the KT catastrophe. I saw a paper describing massive sediment slump off Norway 8,000 years ago that must have sent a huge tsunami towards British Isles. And I have seen a couple papers saying deposits off North Carolina could slump, and tsunami could devastate large part of east coast US.
But if I remember right, the presence of iridium at KT boundary cannot be attributed to volcanism.