I think that we can all agree that a comet is an accumulation of primordial dust assembled normally out of the dust halo surrounding our solar system. This halo of dust is kept at bay by the Sun’s radiative out flow and is reasonably formed from generally lighter materials. Once such dust agglomerates into a sufficiently large enough mass, it becomes vulnerable to perturbation that can send it into a close orbit toward to sun as a comet.
We can also agree that this comet carries water in particular. Unfortunately, this has leaned heavily on the thinking of theorists and it has been supposed that as the comet approaches the sun that the increased warmth helped create a cloud. I do not think it has much to do with warming at all. Much more likely, the dust mass progressively charges up because of increased radiation from the sun. This induces charge accepting particles to separate, and of course the comet is an accumulation of dust.
I suspect that the main charge accepting particle is carbon soot. Thus a comet is a mass of fine condrite dust, water and ammonia vapor and lots of free carbon soot.
This means that is is plausible that a comet strike on Earth will also inject a huge amount of carbon into the atmosphere. So we can assert that the principal signature of a comet strike will be an atmosphere full of carbon soot and a layer of soot associated with the event.
Tunguska had a carbon soot signature observed downwind around the world. This also makes it clear that what arrived at ground zero for the Tunguska event was mostly the shock wave after the high altitude explosion. Any actual debris would mostly be concentrated on the approach path and may have decelerated enough to simply be falling out of the sky at that point. Good luck on finding any of it. The explosion would have filled the atmosphere with carbon soot along the same path, but wind would have taken it all hugely down wind. In fact, the evidence suggests that a lot stayed aloft for days.
This means that the extensive soot layer associated with the Pleistocene Nonconformity of 12,900 years ago is convincing proof of the involvement of a massive comet likely striking the ice cap at the then location of the North Pole and inducing the noted crustal shift and the ending of the Ice Age. If you do not understand those assertions, please read my posts on the subject.
It always is pleasing to make a good working conjecture and to then see fresh evidence march in to support the conjecture. We have added here the conjecture that the principal reason for the growth of a comet’s tail is charge acceptance of carbon soot. However we are actually replacing an unconvincing explanation with a very convincing one. I do not know is carbon soot has been fingered by researchers prior to this but it seems simple enough that it should have been. If my readers come across a good reference to this, I would welcome it.
We already knew that the object hitting the Ice Cap was huge in kinetic energy content. We also knew that for it to be placed on a bulls eye collision course, the perturbation needed to take place in the Kuiper belt were an atomic bomb could do the job. What arrived was a broken up comet whose center of mass was still focused on the pole itself. The sky would have been full of Tunguska like explosions caused by smaller pieces of debris. A huge amount of ice would also have been lofted south ward by the impact as the comet was coming in flat into the ice. These sent debris into the Eastern US and created the signature keys in the Carolinas. That a layer of carbon soot appeared through out the US is no surprise although concentration may be affected by proximity to air burst from debris.
What we can take from all this is that Siberia and the North America suffered a huge shock wave that flattened forests and slaughtered game everywhere. However, the expectation that heat was also associated is likely quite wrong in general. So it is no surprise that mass extinctions took place as it took some time for game to recover and the climate was also then radically changing and reshaping the ecology.