Re: NASA Worldwind, & Large scale features in Africa

In article <d7r4a2$5sj$1@xxxxxxxxxxxxxxxxxxxxxx>, Pete wrote:
> What causal process is implied in the term "synclinal basin"?
> Is it just a coincidental function of mountain building surrounding
> the area, or is the basin the driver and the surrounding ridges its
> result?
>
It's very variable. "Synclinal basin" is a descriptive term with
no implication of a theory of origin. Like describing something as
sweet piece of pie - it could be sweet because of the nature of it's
ingredients, it could be sweet because the cook decided to sprinkle
sugar on it after making it, or it could be sweet because the baker's
delivery cart parked under a tree full of aphids excreting honeydew.
Recalling the maps I drew up a couple of weeks ago (BTW, have
you tinkered with Cornell's Atlas? it's a useful piece of kit ; java
only, so should work with any system.), the northern arc of hills
stretches from the Tibesti in the East to the vicinity of the a'Hoggar
in the west;
http://www.ingentaconnect.com/content/geol/jgs/2000/00000157/00000005/a
rt00001 talks about a NW-SE lineament which would form the NE margin of
this structure, and of late Proterozoic origin. IF that is supported
then it would suggest that this margin at least has been somewhat
active for an extended period (covering the age of the sediments seen
in the middle of the basin), which would suggest uplift on this margin
and possibly passive accumulation in a subsiding basin in the centre.
But against this is the (disputed) interpretation of the a'Hoggar as
being the head of a mantle plume which has caused a local (1000km
diameter) bulge, with this basin being just one facet on it's flank.
Sorry, but between the tectonic history of the Western Siberian
Basin, the North Sea and Western European marginal islands, the Arabian
Platform, the Kura foredeep, the Malagasy- African Trough and next
month, the Niger delta, I don't have time, energy or inclination to
learn about the tectonic history of the Western Sahara too. Should I
get a job that takes me to Lybia ('xopowo') or Algeria (ughh!), well
I'll dig something out of the library for the plane(s) down there. But
not until. I've got a lamp to install in the bedroom and a lawn to cut.

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

.

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