Oops...cold fusion....
Well I guess that you've just provided Shell management with full
justification as to why their reserves projections might be so way out.
If there is indeed this range of interpretational uncertainty possible
in the basic geological model with "well calibrated seismic
interpretation" in an important oil province ...then......?
A point well worth making, however, is that the two models imply very
different scenarios in terms of volume balance and evolution of
salt/sediment budgets. With the interpretations and the data constraints
available these two models are testable.
Its not my field, but I would further guess that one might expect a
chemical signature of an impact event that could be picked up in the
sedimentary record... ?
But maybe the real challenge is now to convince the readers of Nature
that geoscience interpretation can in reality go a bit beyond
necromancy. Coming up with agreed set of "tests" that can narrow this
interpretational divergence would be a start.
If not, I look forward to watching the geo-diplomatic game unfold.
Alan
-----Original Message-----
From: Tectonics & structural geology discussion list
[mailto:[log in to unmask]] On Behalf Of John Underhill
Sent: 22 March 2004 11:09
To: [log in to unmask]
Subject: DEFORMATION ASSOCIATED WITH SALT WITHDRAWAL BASINS
Hello,
As some of you may already have seen, well-calibrated seismic
interpretation in the Southern North Sea has led me to conclude that the
genesis of the "Silverpit crater" may not have been the result of a
meteor strike after all. Instead, these data demonstrate that the
unusual feature formed as a result of the (slightly more mundane)
process of (Upper Permian, Zechstein Group) evaporite withdrawal.
If you are interested, the article itself was published in Nature last
week under its Brief Communication section. The full citation for the
article is: Underhill, J.R. 2004. An alternative origin for the
"Silverpit crater". Nature (18 March 2004); doi:10.1038/nature02476.
The article and all-important figure can be found through the Nature WWW
site or, if that proves difficult (I think a subscription may be
needed), details are available on the following Geol.Soc of London www
site:
http://www.geolsoc.org.uk/template.cfm?name=Silverpit2
where a pdf of the relevant figure can also be viewed and downloaded.
(I would have attached a pdf here but unfortunately its size exceeds
that permitted by the site).
I am now trying to catalogue deformation in similar settings and am
aware of the work of Mike Branney on caldera collapse following volcanic
eruption, ice-melt collapse pits and ice cauldrons resulting from
subglacial heating. I am also aware of Steve Maione and Malcolm Jenyon's
studies on ring faults associated with salt withdrawal and deformation
above salt pillows respectively.
However, I am sure there are more analogues out there and would be
grateful for any pointers that members of the discussion group can give
please.
In particular, I am interested in learning of examples where fault
patterns affect one stratigraphic level and not others. (In the
Silverpit example, only the Top Chalk Group appears to have been
affected by annular sytle of brittle faulting).
Thanks for any help and references that members can give to me on the
above.
I would, of course, be equally happy to continue the debate regarding
the origin of the "Silverpit Crater", if this is of interest.
Best Wishes
John
Professor John Underhill
Chair of Stratigraphy & Fellow of the Royal Society of Edinburgh (FRSE)
Work Address & Contact Details:
Grant Institute of Earth Science,
School of Geosciences,
The University of Edinburgh,
The King's Buildings,
West Mains Road,
Edinburgh,
EH9 3JW,
Scotland, U.K.
Telephone: 0131-650-8518 (direct line)
Telephone: 0131-650-1000 (switchboard)
Fax Number: 0131-668-3184
Telex: 727442 (UNIVED G)
e-mail address: [log in to unmask]
Home page: http://www.geos.ed.ac.uk/contacts/homes/jru/
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