[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Chicxulub: Not an impact structure?



Steve wrote:
Just after my post recapping the Chixulub impact crater evidence, I openned my new copy of the The Planetary Report (the Planetary Society magazine) and found a great article entitled, "The Shiva Hypothesis: Impacts, Mass Extinctions and the Galaxy." The article is by MICHAEL RAMPINO*, one of the well-known scientists who study mass extinctions and impact cratering processes (and who, with Stothers, borrowed the term "nuclear winter" to describing an impact aftermath).
 

Hello Chicxulubists!

In Meteoritics 32-2, 1997, pp. 327-328, M.R. RAMPINO* reviews ‘The Great Dinosaur Extinction Controversy’ (by C. Officer and J. Page). Among other things he criticizes, you find the following comments:
Nowhere do they mention:
(1) the persuasive gravity anomaly maps, detailed seismic work, and recent geologic studies that clearly show a large, multi-ringed basin in the Yucatan;
(2) the fact that impact melt at Chicxulub (and that is what it is; it contains silica glass and shocked minerals) has been radiometrically dated at 65 Ma ago (the same age and composition as the Haiti microtektite glass) (see papers in Ryder et al., 1996);
(3) that shocked zircons from the K/T boundary layer in North America have been U-Pb dated and show both an original age of 540 Ma, which is similar to the Pan African basement rocks beneath Chicxulub, and
(4) a shock reset age of 65 Ma (Krogh et al., 1993).
Any book purporting to discuss the "extinction controversy" should have included all of this relevant information.

Regards, Bernd