Re: NASA Worldwind, & Large scale features in Africa

Once again, my enquiries dangle unresponded for days. What ever happened
to all the denizens here? Used to be I'd ask a dumb question here
and get ten eloquent and enlightening replies. Has everyone moved
to a new home somewhere? ...

on 15 May 2005 07:41:49 GMT, pete <vincent@xxxxxxxxxxxxxxx> sez:
` on Sat, 14 May 2005 11:00:29 +0100, Aidan Karley
` <doIlookDAFTenoughTOpost@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> sez:

` ` In article <d63srr$ocu$3@xxxxxxxxxxxxxxxxxxxxxx>, Pete wrote:
` ` > Anyway, the region is pretty
` ` > much directly south of Sicily, and about 1.5x as far south of
` ` > the coast as sicily is above it. You should have no trouble
` ` > discerning the concentrically circular shape, it is quite striking.
` ` > The central basin is a vast dune field, with huge dunes easily
` ` > discernable in the image.
` ` >
` ` Hmm, yes, the structure is very prominent. On Google's imagery,
` ` there is a central area of irregular dune feeding into a northern field
` ` of seif dunes. Scale of many kilometers, peak-peak.
` ` My political maps have it in Lybia, with the SW border of Lybia
` ` taking a distinct bow to encompass the SW sector of the rim.
` ` Ink-on-paper maps name it as the Idhan Murzuq, centred at about 24N
` ` 13E, and surrounded by the towns of Ghat, Awbari, Murzuq, Al Qatrun,
` ` and Madama (in Niger). It lays between the Hoggar and Tibesti ranges,
` ` which my memory tells me are hotspot scars (my memory is fallible).
` ` Using Cornell's Digital Earth (http://atlas.geo.cornell.edu) to
` ` zoom in and look at the geology of the area I see that the structure
` ` has a concentric age distribution with old (Ordovician, occasionally
` ` pre-Cambrian) at the margins and recent (Quaternary) in the centre.
` ` It looks to me like a normal (if large) synclinal basin. In
` ` scale it's comparable with the Paris Basin. Nothing terribly remarkable
` ` there.

` Umm, as an utter non-geologist, but simply a fan*, I can
` recognize that the proper term for this sort of thing would be
` a basin, but short of a glacier to sit on it and push the middle
` down, I'm not clear on what should cause it, particularly such
` a large one. "Synclinal" is just descriptive isn't it, or does
` it enfold an implied mechanism?

` *(how is that possible? why not, people are fans of lots of things; I live
` in BC, where geology is everywhere, and on the coast I see the boundary
` between the cordilleran basolith and the vancouver island sediments, where
` for instance a granite headland can be seen on a gulf island beach pushed
` up against a black marble formation, peppered with quarter-sized white
` ammonites, in layers which have been compressed in a series of loops like
` ribbons in a fancy gift bow. Stunning.)


` ` I'm trying to remember the addresses for some sites giving quick
` ` overviews of the resource potential of different countries, because
` ` something of this scale would certainly be considered a likely target
` ` for oil exploration (kitchen area in the centre, centrifugal migration;
` ` stratigraphy exposed around the margins, plenty of potential for
` ` faulted traps). On the other hand, since I've 3 friends working in
` ` Lybia at the moment, maybe I'll just ask them when they get back. They
` ` might be mud men, but they do have some idea about geography.
` `
` ` --
` ` Aidan Karley, FGS
` ` Aberdeen, Scotland,
` ` Location: 57?10'11" N, 02?08'43" W (sub-tropical Aberdeen), 0.021233


` --
` ==========================================================================
` vincent@triumf[munge].ca Pete Vincent
` Disclaimer: all I know I learned from reading Usenet.

--
==========================================================================
vincent@triumf[munge].ca Pete Vincent
Disclaimer: all I know I learned from reading Usenet.
.

Relevant Pages

  • Re: NASA Worldwind, & Large scale features in Africa
    ... `> much directly south of Sicily, and about 1.5x as far south of ... ` there is a central area of irregular dune feeding into a northern field ... Scale of many kilometers, peak-peak. ... ` scale it's comparable with the Paris Basin. ...
    (sci.geo.geology)
  • Re: NASA Worldwind, & Large scale features in Africa
    ... > much directly south of Sicily, and about 1.5x as far south of ... there is a central area of irregular dune feeding into a northern field ... Scale of many kilometers, peak-peak. ... My political maps have it in Lybia, with the SW border of Lybia ...
    (sci.geo.geology)