Re: The Lands of Kansas


"Aidan Karley" <doIlookDAFTenoughTOpost@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
wrote in message
news:VA.00000c3f.0979f4f7@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
In article <3rOHf.552365$084.444602@attbi_s22>, George wrote:
Correct me if I am wrong, but isn't Iceland about 65 million years old,
and
if so, then Europe and N. America would have necessarily split before
then.
In fact, as I understand it, the north Atlantic first opened up about
200
mya.

The rifting of the NW Europe part of the Atlantic was about 56-54
Myr.
An incomplete triple junction developed under the "Forties" area of the
North
Sea, coupled with extension and thermal effects in the Witch Ground,
Central
and Viking Grabens. Separation failed on this front and moved west to
produce
a line of volcanic centres from Lundy to Ulster, Mull, Ardnamurchan,
Small
Isles, Skye, Darwin and Anton Doorin seamounts (which either have surface
exposure or are BIG seismic features) and separation moved further west
to the
incomplete ruptures along the Porcupine and Rockall troughs (beta factor
in
excess of 5) and the final rupture along the present-day western
seaboard. The
air-fall tuffs, lavas, etc from that are major seismic and lithological
markers throughout the North Sea, and also causes of severe wellbore
instability in some areas and hole angles.
These hiccoughs and starts of the spreading are taken by some to
indicate a slow start to the Icelandic plume, which eventually settled
into a
position to form the Faroes Islands (which only agreed a median line and
economic zone with the UK a few years ago, resulting in rapidly
increasing
seismic shooting and drilling in the Faroes Trough). That would imply
that
Iceland as a whole can't be much older than 40 million years. (NB it
would be
possible to get older stuff coming up from depth in Iceland, of course.
But
not large quantities.)

Thinking back on it, I believe the central North Atlantic opened up
between North America and NW Africa some significant time earlier than
the
northern North Atlantic, but I don't have the details to hand. The South
Atlantic though ... hmmm, some people think the Falklands (sorry,
Malvinas)
Islands did a ~135degree rotation at around 195 to 165 million yearsm
which
would imply that opening had happened then. But I think the drilled
(North
Malvinas) basins have showed themselves to be somewhat younger than that.
Which is not inconsistent with that date for opening starting there.

--
Aidan Karley FGS
Aberdeen, Scotland,
Location: 57°10'11" N, 02°08'43" W (sub-tropical Aberdeen), 0.021233

Obviously, you have more experience with the northernmost portion of the
Atlantic than I do, so I will defer to you on this issue. I'm more
familiar with the Mid-Atlantic opening (at the latitude at which we find,
say, the state of Virginia), which I understand was triassic, in age.

George


.

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