Large scale geological maps of Spain

[Peregrinopaul]

I have come across this site which gives you immediate access to all the large scale (1:50000) geological survey maps of Spain, the standard maps published by national geological surveys all over the world. There are over 1100 separate sheets!

MapasIGME - Portal de cartografía del IGME: MAGNA 50 - Mapa Geológico de España a escala 1:50.000 (2ª Serie)

El Mapa Geológico Nacional (MAGNA), realizado entre 1972 y 2003 por el Instituto Geológico y Minero de España se distribuye en hojas 1:50.000 (1:25.000 en los casos particulares de Canarias, Ibiza-Formentera, Menorca, Ceuta y Melilla). En el Mapa Geológico se representa la naturaleza de los...

info.igme.es

When you open the portal, scrolling down one screen gives you an interactive key map, and scrolling further gives you a complete list.

When you select a map, several versions are offered. I recommend the one called “Maps editado escaniado” - scanned.

The map comes up in great detail, and is much bigger than your screen, so you navigate around. My mouse, on Mac, offers me a “+”cursor, which is not useful because it seems to zoom in to a ridiculous extent, and the result is not helpful.
Here's an example I just looked at, inspired by VN's photos of tha Vasco on another thread.



Navigating to the right hand side reveals a regional key map, with towns and cities marked, so you can more easily see where you are. At the bottom are the very revealing geological sections.

Be warned. These are addictive!

 

[Peregrinopaul]

This is interesting. Roncesvalles, a detail from the Valcarlos sheet. It only shows data for Spain.

The walk over the top of the Route Napoleon - at least in Spain - traverses a thick succession of chaotically folded and faulted Ordovician quartzite and schists - blue grey on the map: approx 450my old. These would have been sedimentary sandstones and shales severely metamorphosed by heat and pressure caused by the collision of the Iberian peninsula with France.

The drastic downhill slope into Roncesvalles results from the presence of a massive thrust fault running roughly E-W, bringing the Ordovician, (and a thin wedge of Devonian) into direct contact with the much more recent (60my) and softer sediments of the Palaeocene, (Tertiary, shown orange). Just before Roncesvalles you step across a 400my time-slip.
Shown here on the section.

 

[Icacos]

On the Francés, there was one rock formation that particularly caught my interest - an outcropping of rock that first appeared in the far distance at around one o’clock. It seemed to remain there for several days but very slowly it drew nearer until we eventually passed it close by at three o’clock, as I recall. Can anyone tell me where that would be?

And, of course, there were those rocky cliffs - again on the Francés - into which were carved those fascinating homes. A quick look on Google is not helping me with their location, but I think they were in the vicinity of Atapuerca.

 

[keith duke scott]

I have come across this site which gives you immediate access to all the large scale (1:50000) geological survey maps of Spain, the standard maps published by national geological surveys all over the world. There are over 1100 separate sheets!

MapasIGME - Portal de cartografía del IGME: MAGNA 50 - Mapa Geológico de España a escala 1:50.000 (2ª Serie)

El Mapa Geológico Nacional (MAGNA), realizado entre 1972 y 2003 por el Instituto Geológico y Minero de España se distribuye en hojas 1:50.000 (1:25.000 en los casos particulares de Canarias, Ibiza-Formentera, Menorca, Ceuta y Melilla). En el Mapa Geológico se representa la naturaleza de los...

info.igme.es

When you open the portal, scrolling down one screen gives you an interactive key map, and scrolling further gives you a complete list.

When you select a map, several versions are offered. I recommend the one called “Maps editado escaniado” - scanned.
View attachment 101243
The map comes up in great detail, and is much bigger than your screen, so you navigate around. My mouse, on Mac, offers me a “+”cursor, which is not useful because it seems to zoom in to a ridiculous extent, and the result is not helpful.
Here's an example I just looked at, inspired by VN's photos of tha Vasco on another thread.
View attachment 101244


Navigating to the right hand side reveals a regional key map, with towns and cities marked, so you can more easily see where you are. At the bottom are the very revealing geological sections.
View attachment 101245 View attachment 101246
Be warned. These are addictive!

I love maps. This looks super cool. My son and I plan on doing the camino next year from le puy in france. Then we want to get a tattoo of the route map. Thanks for the cool suggestion.

 

[VNwalking]

Paul, I'm sitting here with my jaw hanging open.
Wow, thank you.
Bookmarked.
This is the ultimate rabbit hole. More to the point it means we can carry these as we go, which adds another dimension to appreciation of where we are day by day. At a walking pace there is time to appreciate the complexity.

Just before Roncesvalles you step across a 400my time-slip.

Oooooooooooo. "Chicken skin," as we say where I grew up.
I'm sure most caminos are full of such POIs, and mostly we have no idea.
Ha! Not any more.

 

[keith duke scott]

Paul, I'm sitting here with my jaw hanging open.
Wow, thank you.
Bookmarked.
This is the ultimate rabbit hole. More to the point it means we can carry these as we go, which adds another dimension to appreciation of where we are day by day. At a walking pace there is time to appreciate the complexity.

Oooooooooooo. "Chicken skin," as we say where I grew up.
I'm sure most caminos are full of such POIs, and mostly we have no idea.
Ha! Not any more.

It must be crispy chicken skin

 

[Meg Worland]

On the Francés, there was one rock formation that particularly caught my interest - an outcropping of rock that first appeared in the far distance at around one o’clock. It seemed to remain there for several days but very slowly it drew nearer until we eventually passed it close by at three o’clock, as I recall. Can anyone tell me where that would be?

And, of course, there were those rocky cliffs - again on the Francés - into which were carved those fascinating homes. A quick look on Google is not helping me with their location, but I think they were in the vicinity of Atapuerca.

Not sure of the first rocky outcrop you mentioned but think the homes carved into cliffs were in Tosantos.

 

[Peregrinopaul]

Sometimes the maps look like art.
This is the region around Castrojeritz. The horizontal layers of the recent Miocene limestones and sandstones, (yellow, blue), are cut through by erosion so that the sedimentary boundaries follow the contours. It looks exactly like a topographic map as result. I say "recent" in geological terms: about 12Ma.
And in section:

 

[Kathor1]

@Peregrinopaul, I‘d be interested to hear what you can see around the area of Triacastela in comparison to Galicia in general. This aspect of geology was mentioned in a recent online course about the Camino de Santiago in which I participated.

 

[Peregrinopaul]

@Peregrinopaul, I‘d be interested to hear what you can see around the area of Triacastela in comparison to Galicia in general. This aspect of geology was mentioned in a recent online course about the Camino de Santiago in which I participated.

Can you give me a clue as to the kind of thing I'm looking for?

 

[Kathor1]

Can you give me a clue as to the kind of thing I'm looking for?

Limestone around Triacastela versus granite in most of Galicia. Is that correct?

 

[basquelady]

On the Francés, there was one rock formation that particularly caught my interest - an outcropping of rock that first appeared in the far distance at around one o’clock. It seemed to remain there for several days but very slowly it drew nearer until we eventually passed it close by at three o’clock, as I recall. Can anyone tell me where that would be?

And, of course, there were those rocky cliffs - again on the Francés - into which were carved those fascinating homes. A quick look on Google is not helping me with their location, but I think they were in the vicinity of Atapuerca.

"And, of course, there were those rocky cliffs - again on the Francés - into which were carved those fascinating homes. A quick look on Google is not helping me with their location, but I think they were in the vicinity of Atapuerca"
Nájera perhaps?

 

[VNwalking]

Be warned. These are addictive!

Paul, you need to put this warning in bold font at the top of your post.
(He's not kidding, folks. They are. I just learned that the KT boundary runs almost directly underneath Santo Domingo de Silos, just a little to the West, and that the Lana between there and Covarrubias either crosses it or just skirts it to the North. It's not clear...very off topic but It is my pet peeve that every time I want to look art something on a topo map it happens to be where four maps meet. )

 

[Peregrinopaul]

Limestone around Triacastela versus granite in most of Galicia. Is that correct?

The simple answer is yes and no!
I'm going to have to be careful when I elaborate, because the geology of much of Galicia is a total nightmare, and I'm not going to pretend that I understand more than the superficial basics, which are:
The Galician edge of Iberia was on the leading edge of the collision between Gondwana (primordial Africa, S America, Australia, Antarctica and bits of southern and central Europe) and Laurasia (N America, N Europe and Asia). This formed the supercontinent Pangea about 300Ma ago.

We know with certainty what happened when Pangea broke up - we're livingwith the result - but working out the paleogeographic arrangements when Pangea formed is is different ball game.
Certainly, the parts of Iberia directly involved in the crunch are a mess. Much of western Galicia has bedrock which we can call granite which originated in the collision zone.

East of the "suture", still in Galicia, the huge sedimentary sequences which had been deposited from the late Precambrian to the Silurian, once horizontal, were drastically contorted into concertina folds, and were changed by heat and pressure from shales, mudstones and sandstones into metamorphic rocks like slate and schist. On the map above they are shown in cream and grey. These are the rocks you walk over from Ponferrada to more or less Sarria. There are some beds of pure limestone.
On the geological map they are impressive to look at. This map has O Cebreiro at centre. (Triacastela is just off the left side.)
This is a real doozy, because it illustrates exactly what you see when strata are turned vertical, or almost. We all know what the topography is like but the dense contours have almost no influence on the pattern.
Section

As @t2andreo would say, hope this helps.

 

[VNwalking]

. These are the rocks you walk over from Ponferrada to more or less Sarria.

So please, Paul...another geographically related query but a completely different tangent. (From someone who just likes rocks but only has a sketchy autodidact's knowledge of them (except for volcanology and a little paleontology, which I've actually studied).

How did gold-bearing rocks end up in there? Las Medulas, for example. The shift is dramatic, walking down from there to Puente de Domingo Flores, onto all that shale. Plugs from plate-edge volcanics? Here's the map in question:

http://info.igme.es/cartografiadigital/datos/magna50/jpgs/d1_G50/Editado_MAGNA50_191.jpg

 

[Peregrinopaul]

...How did gold-bearing rocks end up in there? Las Medulas, for example.

I hadn’t looked at this area, nor have I visited it, much to my regret. It’s another of those bucket-list locations that seem to be disappearing into the unforeseeable future. (I suppose at least Zumaia and Las Medulas could be achieved in one go, age and covid willing).
Your question has caused me to burn the midnight oil, as our time zones are not compatible. That’s OK. As you’re aware, I’m a sucker for this stuff and I thought I might drop in on the zoom meeting while I was at it as I’m up so late, but I misinterpreted the time differential and discovered just now that I’m 24 hours out of kilter.

I’ve been googling, which is rarely helpful, as relevant sites are usually complex academic papers that are not conducive to late night comprehension, maybe comprehension at any time, if indeed you can access them without paying a fee. (There’s an in-joke there - my surname is Fee, and throughout my life people have thought they were being very original when they’d come up with “I’ll do it for a small fee” - which I am). But I digress.

You might assume you’ve asked a straight-forward question. I thought so too. But getting into anything geological west of Astorga is scary stuff.
One unique problem: you might reasonably expect that when you want an answer to a question like this, just have a look at the geological map - as we both have. I’ve noticed that most of these maps were first published in the early 1970’s. If you consider the time involved in on-the-ground field work, you can assume that the data probably originates in the ’60s. That means that interpretations made by the survey geologists on the ground probably pre-date plate tectonics. Since that revolution, an enormous amount of research has been directed to unravelling the complexities of Spanish geology, which cannot possibly be understood otherwise.

So, here’s my superficial take on an obviously engrossing matter.
As I’ve outlined above, the area represents a zone drastically affected by the collision of Gondwana and Laurasia. Hence the early Paleozoic sediments have been contorted, faulted and metamorphosed in what is usually called the Variscan orogeny. This means that 300Ma ago there would have existed a colossal mountain range, rivalling the present day Alps. That mountain range geographically disappeared over the millions of years since due to erosion, and would have been reduced to a peneplain - basically a flat surface. Enter the collision of Iberia with western Europe in the Alpine orogeny, maybe 50Ma ago - very recently - resulting in the Pyrenees and the mountains of Galicia, Leon and Asturias. It seems, as I understand it, that the region of the old Variscan- (Pangean) - mountain range was uplifted and dramatically thrust faulted yet again, initiating in the development of not only mountains, but basins too. Enter another period of intense erosion, which continues to this day, but in its early stages resulted in the deposition of the Tertiary sediments in the “hollows” - if I can put it that way. These sediments, in the Las Medullas area were river flood deposits, (conglomerates, gravels and sands), which drained the mountain areas.The gold, I think, must have originated in nearby igneous plutonic intrusions, dating back to the earlier chaos when Pangea formed - these outcrop both north of Ponferrada, and also much more to the the SW. The gold would have been concentrated by natural gravitational processes - much like the California environment(?).
This map may interest you.

 

[VNwalking]

You might assume you’ve asked a straight-forward question

Haha, no actually. I has a look at that map and knew it was going to be super comolicated - and that I was way out of my depth.

I'm sorry to have sent you on a prolinged late night journey into this rabbit hole— but you're right, it's completely engrossing! I had assumed given the ages of the various sediments the story would be something akin to what you described, the double whammy of old rocks colliding into each other then getting reworked. I didn't think, though, of sedimentary deposition of that gold from somewhere else, assuming it had to be primary.

Plate tectonics fascinates me, because it's a slow-motion version of the same kind of thing you see on the skin of an active lava lake — with plates of hardened crust separating and colliding and spinning and getting subducted under each other in an endless dance.

 

[Peregrinopaul]

Plate tectonics fascinates me, because it's a slow-motion version of the same kind of thing you see on the skin of an active lava lake — with plates of hardened crust separating and colliding and spinning and getting subducted under each other in an endless dance.

I like the analogy. I'm still browsing, by the way.

 

[VNwalking]

Gracias.
Me too. LOL. I'm rationing myself to lookng at one map every 2 days.

 

[Peregrinopaul]

Gracias.
Me too. LOL. I'm rationing myself to lookng at one map every 2 days.

That’s impressive!

 

[Peregrinopaul]

Which reminds me of an anecdote which VN will appreciate. A decade ago, well more, I took my year 10 students on a camp to Broome, a well known international tourist destination in the NW of W Australia. We were walking over the Mesozoic rocks exposed near the lighthouse and “happened” to come across a dinosaur footprint. (I’d done my homework). “That’s impressive!”, says I.
The next day I had booked a camel ride along the famed Cable Beach. As we ambled along on a dozen docile beasts we passed by a young lady sunbathing in the altogether. A voice from a camel behind me sang out, “Hey Mr Fee, that’s impressive!”

 

[VNwalking]

That’s impressive

Not really. It takes 2 days to begin to get a handle on what the map says.

 

[Former member 2537]

The URL ends in "?language=es". If you change that to "=en" you'll get the site in English. I don't see a language choice dropdown.

Rabbit hole indeed!

 

[Peregrinopaul]

The URL ends in "?language=es". If you change that to "=en" you'll get the site in English. I don't see a language choice dropdown.

Rabbit hole indeed!

My reaction to this message was going to be a huge "thank you" until I discovered that the "en" doesn't extend to the map keys - obviously in retrospect since they are scans.
I have been spending an aggravating amount of time trying - sometimes unsuccesfully - to tranlate the totally unfamiliar Spanish nomenclature for rock types. For the benefit of my fellow rabbit-holers (and one in particular) I did find this very useful glossary of terms, but be warned again, it will demonstrate what we are up against!

https://pubs.usgs.gov/of/1991/0579/report.pdf

 

[Peregrinopaul]

Anyway, my obsession continues.
On my 3rd VdlP, I took a short cut by the main road to Tabara, instead of branching off at Granja, further north.
I was subjected to a boring, but flat ride in dangerously heavy traffic, (trucks short-cutting the corner between 2 autovias). The only distinctive feature was a low ridge, a couple of km away on my left which shadowed me the whole way. It wasn’t particularly interesting and I have no photo, but here’s a screenshot from Google maps


Well, I downloaded the map, the geological map, and here’s the relevant portion.

Wow! The low ridge was concealing a series of similar ridges composed of the green stuff, paralleling the road.
The green formations are old, Ordovician in fact, dating back about 480Ma. The road itself is traversing a minor tongue of the Meseta, (yellow stuff), covered here and there by VERY recent alluvial deposits. (The red streaks on the ridges are alluvial fans).

Just to clarify this age business, which I know only too well is not easy to get your head around, I might plagiarise an inspired idea of David Attenborough.
If we assume that the Palaeozoic Era, of which the Ordovician is a part, began 24 hours ago, (instead of 550 Ma) then these Ordovician rocks were laid down about 21 hrs ago. The dinosaurs went extinct 2 hrs 50 mins ago, the sedimentary cover of the Meseta - think Castrojeriz - dates back 52 mins and Homo sapiens appeared on the African scene less than 30 secs ago. (Calling Palaeozoic rocks old, is relative, of course. I only have to go inland from my home a few hundred km and I’m driving over bedrock seven times older than that).

But I digress - again. What is really interesting is the geological section. As at O Cebreiro, we see the ancient Palaeozoic deep-sea sediments, once horizontal, caught up in the collision of Gondwana and Laurasia, 15 hrs ago.

It boggles my imagination how immense the resulting mountains must have been, now reduced to mere topographic ripples. This ancient eroded landscape must continue under the more familiar rock strata of the Meseta, reappearing briefly much further east in the Zaragoza region. There, we are relatively far from the collision zone, the Palaeozoic rocks are only buckled, and are not cooked into schists and the like by their proximity to the heat and pressure of the action.
This is a section from the Zaragoza region.

You can clearly see the Tertiary Meseta sediments (west) "lapping" onto the ancient eroded Palaeozoic landscape, in what is called an unconformity. The unconformity meanders across the modern landscape with little connection to the contours.

Back in Teriary (52 mins!) times this Palaeozoic landscape was probably almost (?) completely buried. A considerable thickness of the yellow strata has obviously eroded away.The yellow Meseta strata in the section were laid down in an epicontinental shallow sea, not unlike the present day North Sea which only exists because of the inundation which occurred after the last ice age. Oh dear. Am I rambling?

I’m sobered by the notion that it has taken a pandemic to motivate me to delve into the geological structure of Spain, having ridden over it, in almost blissful ignorance, for the past decade. I remember once consulting the Wikipedia article, but giving up in bafflement. Maps speak to me.

 

[VNwalking]

and here’s the relevant portion.

This is the coolest thing in a while. And it goes to show how as they age, formations that have amazing stories can be hiding in plain sight as something that isn't

particularly interesting

Oh dear. Am I rambling?

Yes, but please continue.

If I can peel you away from the ancient rocks of Plata, here's an area that's South of the Viejo, north of the Via de Bayona, a reasonably easy detour from the former. These salt diatremes sit in a complex little nest of formations. Not so old but still. . .

And I have a stupid question, but you say you have the key sussed. What's the spiral symbol just west of the diatreme at Salinas de Bureba, right of center in the screenshot?

 

[Peregrinopaul]

And I have a stupid question,

Hi VN. There’s going to be a break in transmission now as I drove down here to Perth yesterday for a surgery appointment. Nothing drastic, but hospital tomorrow. I’ll have a look at this when I get home and to my computer. An iPhone is not conducive!

 

[VNwalking]

May it be easy! Please take your time...

 

[ChristianSdeM]

This is the coolest thing in a while. And it goes to show how as they age, formations that have amazing stories can be hiding in plain sight as something that isn't




Yes, but please continue.

If I can peel you away from the ancient rocks of Plata, here's an area that's South of the Viejo, north of the Via de Bayona, a reasonably easy detour from the former. These salt diatremes sit in a complex little nest of formations. Not so old but still. . .

And I have a stupid question, but you say you have the key sussed. What's the spiral symbol just west of the diatreme at Salinas de Bureba, right of center in the screenshot?
View attachment 102066

It indicates the presence of fossils.

Fantastic maps!

 

[VNwalking]

indicates the presence of fossils.

Thank you, @ChristianSdeM .
(Hmmm. This is especially dangerous information, potentially leading to a complete cessation of forward progress.)

 

[Icacos]

Unfortunately, I don’t think I have the wherewith at the moment to disseminate these maps. If it weren’t for Covid I’m sure I could get my geologist son to sit down and explain a few things to me. But thank you @Peregrinopaul for all this information; it’s certainly lurking in my brain waiting for further attention.

 

[Peregrinopaul]

These salt diatremes sit in a complex little nest of formations. Not so old but still. . .

(I'm back...none the worse for wear, but poorer.)
I've never really associated salt with Spain, so looking into this was a revelation. The evaporites from the Triassic seas are very significant, though usually deeply buried. They date back to the time of the break-up of Pangea. I found this cool graphic, showing the area of evaporites, salt and gypsum, reconstructed to that time. The modern geography is just discernible in dotted outline
.
Also, here's a diamond drill-core into the zone. The halite is so pure it looks like ice!

I hope you won't mind me being picky, but the evaporite intrusions punching through to the surface at Salinillas are diapirs, not diatremes. The latter is a term used for igneous volcanic intrusions.

 

[Peregrinopaul]

Afterthought: apparently the salt layers played a significant role in "lubricating" the complex folding of the Pyrennees.

 

[Peregrinopaul]

Sexy geology.

 

[VNwalking]

I hope you won't mind me being picky, but the evaporite intrusions punching through to the surface at Salinillas are diapirs, not diatremes.

Paul. Please do not apologize. Thank you for the correction! (My only formal training in geology has been patchy - paleontology as my career demanded, and volcanology out of that and fascination both.
Diapirs it is.
I first got interested doing a virtual Viejo last year, learning of a salt mine at Poza de la Sal just a little south of the camino that created a huge amount of wealth since Roman times:

El esplendor de la villa de Poza de la Sal se debe a sus salinas, ya explotadas desde antes de la época romana y cuyo valor estratégico justificaba la fortificación de la villa para su defensa en la Edad Media. Estas salinas junto con las de Añana en Álava, eran las principales del norte de la península ibérica.

La sal era, hasta hace pocas décadas, un material precioso, usado como conservante alimentario, pero, hasta la explotación minera de los yacimientos subterráneos, su producción estaba limitada a las salinas costeras y de manantiales de interior, por lo que su posesión era muy codiciada. A tal punto llegaba su importancia que se utilizaba como forma de pago ya desde época romana, siendo este el origen del término salario.

And then the very beginning of the Via de las Asturias there is a salt mine that is even older.

Salt Valley of Añana · Real Kalea, 32, 01426 Gesaltza Añana, Araba, Spain

★★★★★ · Tourist attraction

www.google.com.mm

In both cases the diapirs were sources of income and trade goods going way back.

 

[VNwalking]

The halite is so pure it looks like ice!

Beautiful. Pure salt!

Edit: I was completely unaware of the big picture. This is a much bigger rabbit hole than I imagined!
Your post got me digging a little deeper, and while most of this is way over my head it is totally engrossing; the area we are talking about is a smidgen of this:


From:
Saura, E., L. Ardèvol i Oró, A. Teixell, and J. Vergés (2016), Rising and falling diapirs, shifting depocenters, and flap overturning in the Cretaceous Sopeira and Sant Gervàs subbasins (Ribagorça Basin, southern Pyrenees), AGU Tectonics, 35, 638–662.

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agupubs.onlinelibrary.wiley.com

 

[Peregrinopaul]

Beautiful. Pure salt!

Edit: I was completely unaware of the big picture. This is a much bigger rabbit hole than I imagined!.

You and me both!

That section is certainly revealing; a mountain range slurped on salt. And all those red lines are thrust fault slides. The Mesozoic is even thrust over the tertiary flysch beds of the Ebro basin - the same flysch that you marvelled at in Zumaia. I looked further west and that doesn’t happen - the flysch laps up onto the Mesozoic. The brown palaeozoic forming the axis of the range is really messed up, having been subjected to mountain building twice.

The Camino Aragones runs along a similar section from the Somport.

Forgive me if I digress once again apropos of nothing. Your comment about going down the rabbit hole again. I read recently that Charles Dodgson, aka Lewis Carroll, lived in a house near Ripon in Yorkshire, (co-incidentally close to where my brother lives). The area is plagued by sink holes, which have from time to time swallowed houses and which apparently were the inspiration for Alice’s excursion underground. Would you believe that the area is underlain by evaporites laid down in the Zechstein Sea which once flooded an area from the North Sea right into northern Europe as far as Poland - not quite contemporaneous with the evaporites under the Pyrenees, but close. Subterranean ground water creates voids resulting in the subsidence. So your comment is curiously apt…curiouser and curiouser.

 

[Peregrinopaul]