[meteorite-list] Geological Society of America's Geology Highlights

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:25:43 2004
Message-ID: <200305231648.JAA24326_at_zagami.jpl.nasa.gov>

http://www.eurekalert.org/pub_releases/2003-05/gsoa-jga052203.php

Public release date: 22-May-2003
Contact: Ann Cairns
acairns_at_geosociety.org
303-357-1056
Geological Society of America

June GEOLOGY and GSA TODAY media highlights

Boulder, Colo.--The Geological Society of America's June issue of GEOLOGY
contains many potentially newsworthy items.

Highlights are provided below. Please discuss articles of interest with
the authors before publishing stories on their work,
and please make reference to GEOLOGY in stories published. Contact Ann
Cairns at acairns_at_geosociety.org for copies of
articles and for additional information or other assistance.

GEOLOGY

[snip]

Uniquely extensive seismite from the latest Triassic of the United Kingdom:
Evidence for bolide impact?

Michael J. Simms, Department of Geology, Ulster Museum, National Museums and
Galleries of Northern Ireland, Botanic Gardens, Belfast BY9 5AB, Northern Ireland.
Pages 557-560.

At sites across >250,000 km2 of the UK a one- to four-meter-thick sequence of
thin sandstone and mudstone beds, about 200 million year old, show extraordinary
convolutions. This deformation has been interpreted as the result of seismic
shaking of soft sediments soon after deposition, while rippled sands immediately
above this "seismite" are interpreted as deposits from a tsunami triggered by
the same seismic event. The geographic extent of this seismite is unique in
the geological history of the UK and suggests an earthquake of a magnitude too
great to be attributable to fault or volcanic activity. It is suggested
that this seismic event may instead have been caused by the impact, to the west
of Ireland, of a meteorite several kilometers across. Further confirmatory
evidence has yet to be found, although similar "megaseismites" may prove
useful in the search for ancient impact sites.

[snip]

Acid-neutralizing scenario after the Cretaceous-Tertiary impact event.
Teruyuki Maruoka and Christian Koeberl, Department of Geological Sciences,
University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria. Pages 489-492.

Acid rain has been proposed to account for some observations at the
Cretaceous-Tertiary (K-T) boundary. The acid rain would be predicted to have
more seriously affected freshwater environments than marine environments, as
is observed today in highly polluted areas; however, only a minor extinction
of freshwater species at the K-T boundary is evident. The extinction
selectivity implies that either the acid rain was not severe enough to damage
freshwater environments, or that an acid-neutralization mechanism existed only
right after the K-T impact event.

Maruoka and Koeberl propose a mechanism to neutralize the acid using larnite
(Ca2SiO4), produced as a result of the specific lithology at the Chicxulub
impact site. The acid-neutralizing capacity of the larnite grains is high
enough to consume acid produced after the K-T event within several hours to a
level at which freshwater life would not be affected. This scenario
can explain some of the extinction selectivity at the K-T boundary.
Received on Fri 23 May 2003 12:48:02 PM PDT