Chenaillet geotraverse - an ancient continent-ocean transition

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Part of The Shear Zone Channel. Join Rob on a field walk across a classic section in the French Alps, above the ski-resort of Montgenevre. The section, a geo-trail in the Geoparc des Alpes Cottiennes, is justly famous for revealing in outcrop examples of oceanic detachment faults, once sea-floor exposed mantle, stunning pillow basalts.... and much more besides! If this pricks your curiosity, why not also watch the videos on this channel on "Interpreting a rifted continental margin" and "Hyperextension ".
#Alps #geopark #tectonic. #montgenevre

Опубликовано:

8 авг 2023

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Комментарии : 14

@hongyuanZhang-pr6wt 3 месяца назад

It is a great journey with beautiful ophiolite and useful profile explanation.

@adamc1966 4 месяца назад

Perfect weather for the hike.

@robbutler2095 4 месяца назад

Another great day in the Alps...

@SaeedAhmed-sb4qb 11 месяцев назад

Dear Rob, thank you for sharing of knowledge with us. Only on request to improve volume of videos.

@stuart.swales 11 месяцев назад

Thanks for that excursion, Rob. Brings back great memories of really fab geology! Was up Chenaillet with an OUGS group in June 2014. Back then it was before the lifts reopened, so a good day's walk up from Montgenevre, traversing over to Sestriere. Patches of snow still about, enough to kick steps. Still boggled at that detachment though. And those pillows...

@robbutler2095 11 месяцев назад

Very little snow these days! Glad you enjoyed the trip down memory lane....

@user-ij3qo6xl9s 10 месяцев назад

It is a great journey and talk on the complex relics of the initial Jurassic Atlantic. The profile clearly shows complete ophiolite assemblages as well as both ductile and brittle extensional shearing phenomena related to rift. You said this is a continental margin oceanic crust. Can I say only the series of serpentinised mantle- radiolarian chert represent the rifting process; while the limestone and flysch represent later contractional process?

@robbutler2095 10 месяцев назад

Not really. turbidites and limestone (or any sedimentary rock) can be deposited in any basin setting tectonically - plenty of "flysch" (=turbidites) in submarine basins of any tectonic style. It's a hang-over from old Alpine literature that flysch is necessarily a "syn-orogenic" rather than "syn-rift" deposit. It's associations and context that matter.

@lundysden6781 11 месяцев назад

Is there any heavy metal deposits near the detachment zone? Gold maybe? Very complex and interesting. Nice work. We have something similar here in the NE United States but its across about 60 miles to see it all.

@robbutler2095 11 месяцев назад

Interesting thought. I'm not aware of any (significant) gold mineralisation along these serpentinites.... talc etc elsewhere.

@ThomasEckhardt 5 месяцев назад

Great video, love the pillow lava piles! Were the holes drilled for paleo magnetic measurements?

@robbutler2095 5 месяцев назад

Good question. I think some were drilled to sample for petrology/geochemistry ... but the clusters in the pillows likely are palaeomag... Not clear which scientific publications came from this (unethical) sampling...

@NatureGirl 11 месяцев назад

Love your vids! Mylonites are the result of ductile deformation in shear zones, but you say they are deep water rocks. Does that mean Shear Zones occur in deep oceanic areas?

@robbutler2095 11 месяцев назад

Sorry for not making that clear! The mylonites of the Jurassic limestones (Gondran) formed during Alpine orogenesis (probably c 30-35 million years ago) - so as the distal margin was being telescoped .... they were deposited under deep water.... In contrast - the sheared gabbros etc (and mantle detachment zone) formed as the continental margin rifted apart (in Jurassic times - say c170 million years ago). Thanks for the question!