"Earth In Upheaval" was the book where he gathered the evidence for large death assemblages in the Arctic, particularly Siberia; some of the Arctic islands off Siberia are stuffed with bones (and tusks) of now-extinct animals, clearly they were deposited in one fell swoop.
40 days of worldwide rain would not be within the capacity of the known hydrologic cycle, IOW, it would have to be an unusual event, and that's what is recorded here and there in ancient written sources, and oral traditions -- not great flood stories, although that does happen, but a massive worldwide rain.
I've read that some believe '40' was mistranslated and should just be 'many.' "40 days & 40 nights, wandering in the desert for 40 years, Ali Baba and his 40 thieves", etc
Sixty percent of Bangladesh goes underwater each year. We get an amazing 5' of rain here (Mobile) each year. My jaw dropped when I read about places in Bangladesh that get 50' each year.