Le 24 avril 2008, par Jeff,
Well, for my first serious attempt, I was lucky enough to identify a nice photo of a segment of the Kunlun fault, on Peter Luffi’s web site. Now it’s my turn to propose an image ; this being my first attempt, I do not have a good feeling for what constitutes a good or bad challenge, but since I quite like this (geological) feature, let’s have a go :
For my first challenge, I’ll be conservative and have Schott’s law in effet ; after all, I feel compelled to be newbie-friendly.
44.9 E - 24.5 S Superb giga-pressure-shadows developed around the Neoproterozoic Saririaky anorthosite body acting as a rigid inclusion in the Ampanihy ductile shear zone that developed at the eastern margin of the Graphite Sequence of SW Madagascar. At a larger scale it’s even more spectacular : this anorthosite body appears to be pulled apart from the similar Ankafotia body located 40-50 km to NNE.
(Jeff announced WoGE #121 on my site at 14:36 GMT, 04/24/08 ; this answer was posted at 3:15 GMT, 04/25/08)
Lost Geologist : Sorry I thought my CMS did include the data automagically.
Peter : Well done, did you know the image/region beforehand ? Or how did you find it ? anyway, back to you...
Oh how bad I found it within 5 minutes but was too lazy to watch the clock to post in time. :-D
Well done Peter !
I didn’t know the region beforehand, I actually haven’t seen before such a nice regional-scale pressure shadow. But I was almost sure from the very beginning that I have to look for well exposed ductile shear zones in low-topography Precambrian high-grade terrains. Given the shear zone’s orientation and the scale of view, it was pretty easy to exclude most options...
BTW, WoGE #122 is posted.
Absolument. Comment croyez vous que je l’ai découverte ?
(sauf que la these de Manu Martelat, c’est 98. La structure en question a du etre decrite dans son papier a CRAS : MARTELAT J.E., VIDAL G., LARDEAUX J.M., NICOLLET C., et RAKOTONDRAZAFY R. (1995) - Images spatiales et tectonique profonde des continents : l’exemple du Sud-Ouest de Madagascar. C. R. Acad. Sci., Paris, 321, 325-332. Je ne peux pas verifier pour le moment, je n’ai pas acces au Web of Science d’ici).
Les adresses correctes sont de la forme http://jfmoyen.free.fr/spip.php ?articleXXX
Les adresses correctes sont de la forme