Chenaillet geotraverse - an ancient continent-ocean transition

[@hongyuanZhang-pr6wt]

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

[@stuart.swales]

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]

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

[@adamc1966]

Perfect weather for the hike.

[@robbutler2095]

Another great day in the Alps...

[@SaeedAhmed-sb4qb]

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

[@maxontani7986]

Even if my english is very poor, it has been a great pleasure to follow your walk between these beatiful rock formations. Thank you for sharing your knowledge.

[@robbutler2095]

glad you're enjoying the films

[@张宏远-z8t]

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]

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]

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]

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

[@muzikhed]

Spectacular tour alright and what an ending with that pillow- lava cliff. You fortunately had very nice weather trekking about in shorts, I wonder how many kilometres you hiked about making this video ?

[@robbutler2095]

All shot in one go - over a few hours... sun always shines in the Alps....

[@geolyn]

An excellent video well photographed for those who cannot make the journey themselves. How do you manage to get such good weather? 😄

[@MikeGreenwood51]

Try going in Summer. Or if you like to see a few meters of snow -go in winter. December shoter days and likely snowing (Real snowing like a meter or two. June long days, High sun, snow melting. July take a parasol and sun glasses.

[@ThomasEckhardt]

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

[@robbutler2095]

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]

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]

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!