Some thoughts on what happened at the end of the Cretaceous!

Most recent:
Dinosaur Demise from a Collision: A Theory in the Making (2008): Dinosaur Demise From a Collision.pdf
(From the Connecticut Journal of Science Education, V. 47 No. 1, Fall - Winter 2008 2009, A publication of the Connecticut Science Teachers Association, CSTA - Join Now).

From MS Defense (1992):
By Kurt Zeppetello

Amino acids exist in Cretaceous-Tertiary sediments from the Raton Basin, northcentral New Mexico, southcentral Colorado, U.S.A. Alpha-aminoisobutyric acid (α- aminoisobutyric acid), an amino acid common in meteorites but having a rare terrestrial occurrence, is associated with the Cretaceous-Tertiary boundary (KTB). The distribution of α-
aminoisobutyric acid as well as more common biogenic amino acids such as aspartic acid, glutamic acid, glycine, alanine, valine, isovaline, isoleucine, and leucine were measured using ion exchange chromatography. Results of analyzing samples from 40 centimeters above the KTB to 20 centimeters below the KTB indicate that α-aminoisobutyric acid is obtained in the largest amounts from KTB samples by leaching the amino acid with water. It was not detectable after leaching with hydrochloric acid.

α-Aminoisobutyric acid concentration in KTB clay at Starkville (an outcrop in the Raton Basin) is 15.8 pmol/g S20WH). The next highest concentration is 4.2 pmol/g at 16 centimeters above the KTB in siltstone. A concentration of 3.1 pmol/g at 20 centimeters above KTB is found in the same siltstone layer. Other samples showing detectable concentrations are at 45 centimeters above (1.3 pmol/g, S1W), 30 centimeters above (0.4 pmol/g), 8 centimeters above (0.3 pmol/g), 4 centimeters above (1.0 pmol/g), and 20 centimeters below the KTB (0.6 pmol/g).

Known biogenic (mainly protein) amino acids are detected in all samples at higher concentrations than α
-aminoisobutyric acid in most cases. No other exclusively meteoritic (and/or biologically rare) amino acid could be detected. Isovaline (common in meteorites, rare terrestrial occurrence), however, may be present but detection was extremely difficult as it was eluted with the same retention time as valine (a common protein amino acid).

These results suggest that possibly extraterrestrial amino acids delivered by meteoritic impacts may have persisted in terrestrial as well as marine sediments. They confirm earlier work suggesting that the bolide impacting the earth 65 million years ago was similar in composition to an aqueous altered carbonaceous chondrite. They are consistent with the hypothesis that large asteroid or comet impacts have significantly affected biological evolution.

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The Following is a link to the entire document. However, there are some minor formatting errors.

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