Re: NASA Worldwind, & Large scale features in Africa

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.
.

Relevant Pages

  • Re: NASA Worldwind, & Large scale features in Africa
    ... ` ` 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)