New Papers on Triassic - Jurassic Extinctions and Boundary

Paul bristolia at yahoo.com
Tue Jan 23 13:11:52 EST 2007

The latest issue, vol. 244, no. 1-4 (February 9,
2007), of Palaeogeography, Palaeoclimatology,
Palaeoecology is devoted to “Triassic-Jurassic
Boundary events: problems, progress, possibilities”.
It contains a number of papers, which discuss the
various theories about what created the Triassic
- Jurassic extinctions. The table of contents can be
found at:

http://www.sciencedirect.com/science/journal/00310182

They include:

Hesselbo, S. P., McRoberts, C. A., and Palfy, J., 2007,
Triassic–Jurassic boundary events: Problems, progress,
possibilities. Palaeogeography, Palaeoclimatology,
Palaeoecology. vol. 244, no. 1-4 , pp. 1-10.

In the above paper, they stated:

"The debate about extraterrestrial versus volcanic drivers
for environmental change has not yet been concluded, and
it is noteworthy that all of the candidate indicators of
extraterrestrial impact - reports of PGE's and soft sediment
deformation - occur shortly prior to CAMP volcanic activity.
Pure coincidence aside, this observation keeps alive the idea
that there is an 'impact signal'-LIP connection, even if the
mechanisms remain highly controversial; for example,
impact decompression melting, as recently articulated by
Elkins-Tanton and Hager (2005), or lithospheric gas
explosion (Phipps Morgan et al., 2005)."

Another paper is:

Michalíka, J., Lintnerovab, O., Gadzickic, A., and Sotakd,
J., 2007, Record of environmental changes in the Triassic-
Jurassic boundary interval in the Zliechov Basin, Western
Carpathians. Palaeogeography, Palaeoclimatology,
Palaeoecology. vol. 244, no. 1-4 pp. 71-88.

This paper states:

“The negative delta 13C excursion is correlated with a
positive delta 18O peak and the beds containing the
excursion are overlain by a thin layer with unusual
lithological and mineral composition. This layer is
composed of small calcitized microspheres showing
complex alteration during diagenesis. The origin of this
layer, traceable over tens of kilometres, is problematic
(impact ejecta, volcanic glass, or altered aragonitic
particles).”

Yours,

Paul H.