[ThinkPlease]

I think what they are saying is not that there wasn't dust created by the impact, but that there wasn't enough dust created of a sufficient particle size to prevent plants from photosynthesizing sunlight.

A subtle difference.

[Scully]

“The original studies of the clay layer found at the K-T boundary assumed much or all of this layer was derived from fine impact dust,” he said. “More recent studies of this layer have shown this not to be the case..."

This makes it sound as if there just simply wasn't enough impact dust to encircle the globe. I doubt that regional fires could have done it either, particularly in view of the clay layer being continuous (with some exceptions) worldwide. Again, I'm left with my original question: Where did the iridium come from?

[Wonder Warthog]

"I think what they are saying is not that there wasn't dust created by the impact, but that there wasn't enough dust created of a sufficient particle size to prevent plants from photosynthesizing sunlight."

If you read closely, this guy's conclusions are based on mathematical models, not measurements. It is probably about as sound as the global warming hypothesis which is also based on modelling. One GLARING supposition is the assumption that large dust particles can be used to model small ones--highly unlikely.

[gleeaikin]

Some time ago I recall reading that the Iridium layer at Gubbio in Italy was several centimeters thick, not milimeters. I believe that other studies indicate that as study sites are farther from the Caribbean athe Iridium layers become thinner. Superheating, dust and soot would have been the seeds for heavy rain. Much destruction of vegetation even without a possible nuclear winter. Then add in thousands of years of sulfate arisols from the Deccan vulcanism, and there are lots of ways that life would have been severly damaged.

Then, we have the additional hypothesis about the Shiva Crater off Mumbai by Chattergee (sp?). It may be 4 to 6 times the size of the Yucatan crater, be of roughly the same age, and perhaps the cause of the Deccan activity. It has been more than a year since I last checked this one out.