The preponderance of evidence is, continues to be, and always has been, that the dinosaur die-off was basically immediate and due to the impact of at least one large object. This doesn’t preclude the possibility that the impactor arrived in more than one consecutive chunk, or that it came apart a very short time before impact. There has never been any evidence at all for gradual extinction (which is an oxymoron), and there’s no evidence that some kind of (undocumented, despite claims to the contrary) volcanism played any role at all. The same tired old arguments that were refuted twenty years ago keep getting trotted out by the same tired old unreconstructed Darwinian gradualists in the UK and by their eastern seaboard lackeys.
Impact forensic evidence announced
Jeff Poling
http://www.dinosauria.com/jdp/impact/forensic.html
[snip] When the object from space slammed into the earth, it punched a hole in the ground that, within minutes, rebounded to hurl superheated rock and steam back into the atmosphere. Some of the material was blown into space, while the rest fell to earth creating a parabolic swath of destruction that incinerated North America... Using seismic instruments to measure ballistics more than a kilometer below the Yucatan, the scientists found evidence that the initial crater gouged by the object was around 100 km in diameter. From this, the scientists concluded the object was 10 to 14 km across. They estimate that if the object was an asteroid, it was moving at 20 km/s. If it was a comet, it slammed into the earth going 65 km/s. [/snip]
[snip] 11/19/98 — A meteorite from the Cretaceous/Tertiary boundary (FRANK T. KYTE, Nature 396: 6708): Cretaceous/Tertiary boundary sediments are now widely recognized to contain the record of a large asteroid or comet impact event, probably at the site of the Chicxulub crater on the Yucatan peninsula. After nearly two decades of intensive research, however, much remains unknown about the specific nature of the projectile and of the impact event itself. Here we describe a 2.5-mm fossil meteorite found in sediments retrieved from the Cretaceous/Tertiary boundary in the North Pacific Ocean that we infer may be a piece of the projectile responsible for the Chicxulub crater. Geochemical and petrographic analyses of this meteorite indicate that it probably came from a typical metal- and sulphide-rich carbonaceous chondrite rather than the porous aggregate type of interplanetary dust considered typical of cometary materials. The fact that meteorite survival should be enhanced by impacts at low (asteroidal) velocities also implies that this meteorite had an asteroidal rather than a cometary origin. [/snip]
Researchers Study Ancient Rocks To Test Theory on End of Dinosaurs>
by Halimah Abdullah
July 9, 1997
http://query.nytimes.com/search/article-page.html?res=9C01E6D91239F930A15751C0A9679C8B63&fta=y
[snip] “If there was a major fire after the meteorite hit the earth,” Dr. Wolbach said, “we would see soot in samples from Denmark and around the world. We looked at sedimentary rocks 65 million years old from other geographically distant sites and found soot in them, too. The fire was a global phenomenon.” [/snip]
‘Quick’ demise for the dinosaurs
by BBC News Online’s Jonathan Amos
Thursday, 8 March, 2001, 19:01 GMT
http://news.bbc.co.uk/hi/english/sci/tech/newsid_1209000/1209870.stm
[snip] The evidence comes from a study of rocks in Italy and Tunisia. The work lends support to the idea that a single, giant impact of an asteroid or comet was responsible for the mass extinction of life that occurred 65 million years ago... Sujoy Mukhopadhyay and colleagues studied sedimentary rocks that mark the so-called K-T boundary... 70% of all life, including the dinosaurs, suddenly disappears from the fossil record... They analysed the amount of helium-3 in the rocks of the K-T boundary... The research suggests the K-T boundary was deposited in about 10,000 years. He said the short period lent support to the theory that the dinosaurs were wiped out in a sudden, catastrophic event such as the impact of an extraterrestrial body. The constant rate of accumulation of helium-3 also indicates that the impactor was not part of a comet shower or bombardment... “The Deccan Traps erupted over much longer timescales — over 500,000 years or more. If the recovery of life starts after only 10,000 years, it is hard for us to see how the traps are influencing the mass extinction.” [/snip]
Dino asteroid led to ‘global devastation’
The impact would have shaken the affected planet
By Helen Briggs
BBC News Online
Thursday, 22 November, 2001, 19:32 GMT
http://news.bbc.co.uk/hi/english/sci/tech/newsid_1670000/1670035.stm
[snip] The asteroid thought to have wiped out the dinosaurs destroyed plant life thousands of kilometres from where it struck, say scientists. Fossils uncovered in New Zealand point to major disturbances in climate that led to the death of most trees and flowering plants. Clues from the plant fossil record suggest that even the Southern Hemisphere experienced an artificial winter, acid rain, and raging forest fires. This is the first clear fossil evidence for destruction of plant life so far from the Mexico coast, where the space object is believed to have landed. Dr Timothy Flannery, an expert at the South Australian Museum in Adelaide, told BBC News Online: “The asteroid devastated pretty much everything. This was a case of global devastation rather than North American catastrophe.” [/snip]
Incineration of North America, soot worldwide, plant die-off. All point to a collapse of the food chain, and those organisms not immediately affected by the impact would starve.
Smaller critters can live on less, so the larger ones would tend to be most seriously affected.