The Jurassic (dinosaur) coast of Asturias: Part 1

The Jurassic Coast in northern Spain is located in Asturias between the autonomous communities of Galicia (to the west) and Cantabria (to the east). The Jurassic Period is the middle part of the Mesozoic Era, extending from ~200–145 million years ago. So we are going back in time more than 35 million years from the time period recorded in sediments of the Basque Geopark (previous two posts). Unlike the Geopark sequence that is more or less continuous through 60 m.y., these sedimentary rocks are discontinuous.

What to see and where to see it

This geology map of the eastern part of Asturias shows the Jurassic rocks in light blue. The Museo del Jurásico de Asturias (MUJA—located near Colunga on the map) has an excellent web site with instructions about where to go and what to see: The field guide referenced below also has useful information. We visited the following sites (from east to west): Ribadesella, Tereñes (between Ribadesella and Vega), Vega Beach (P Vega), Griega Beach (near Colunga), and Tazones.
Here is a view of Jurassic sedimentary rocks at Tereñes, between Ribadesella and Vega Beach (see map). There are not continuous cliff exposures like in the Basque Geopark, but this made some of the coastal locations easier to access. Like the Geopark, views are best during low tides. I choose a three-day period 2.5 weeks before our Geopark visit, another period of the month with a large tidal range. The photo demonstrates why this part of Spain is referred to as “Green Spain”.
This stratigraphic column shows the geologic units (formations—Fm.) that are visible along the Jurassic Coast. It is from the field guide referenced below. The column shows the types of sediments, the environments within which they were deposited, and the types of fossils that have been found. The most popular fossils are, of course, the dinosaur fossils that are primarily trace fossils—imprints of their footprints. In this post, we’ll look at the older (marine) part—Gijón and Rodiles Formations—and the transition to primarily non-marine environments (Vega Formation). In my next post, we’ll look at the upper non-marine and very shallow marine part where most of the dinosaur footprints are found—Tereñes and Lastres Formations.

Where was Spain during the Jurassic Period?

This map shows the configuration of the continents during the Early Jurassic around 191–183 million years ago. This was the time when the continents were beginning to break apart, and the North Atlantic Ocean was beginning to open, following the collision that brought all of the continents together (Pangea) around 200 million years ago. Spain was then close to North America, as shown by the orange dot. The large ocean between Africa and Eurasia is the Tethys Ocean that closed as the Atlantic opened.

The marine Gijon and Rodiles Formations

We viewed the Gijón Formation at Vega Beach. It consists of limestones (left photo) that accumulated along a flat coastline that was oriented NW-SE. The water was up to 50 m (164 ft) deep and filled with a wide variety of organisms, including oysters that made reefs (upper-right photo). Organisms such as worms made tracks and trails in the sediment (lower-right photo). Bones of sea reptiles such as icthyosaurs and plesiosaurs have been recovered.

The museum (MUJA) has an image to show what the environment looked like at this time. The ocean was warm and shallow water inlets were salty because of the desert-latitude (around 30°) location. Lagunas salinas=salty lagoons. Costa baja e irregular=flat and irregular coast. Bancos submarinos=underwater barrier bars. Mar abierto y somero=open and shallow sea.
We viewed the Rodiles Formation at Vega Beach, where it overlies the Gijón Formation, and at Ribadesella. These rhythmic layers of limestone (light colored) and marl (dark colored—means limey mud) are typical of the Rodiles Formation.

Transition to a terrestrial environment

Take a look at the photo above of the cliff face at Vega Beach with Rodiles Formation layers. Maybe you can see some reddish layers at the distant end of this sequence. These layers mark the start of the Vega Formation that was deposited in rivers (also see stratigraphic column above). The Vega Formation marks a time when tectonic activity caused the land to be uplifted and the sea to withdraw. Uplifted older rocks were eroded and the eroded sediments flowed northeastward toward the sea. Because of the tectonic uplift, there is a significant time gap between the deposits of the Rodiles and Vega Formations.

The Vega Formation starts the part of the Jurassic Coast layers with extensive dinosaur footprints. My next post will illustrate why the Jurassic Coast is also called the Dinosaur Coast. Stay tuned!

The photo to the left is the footprint of a three-toed dinosaur, maybe an ornithopod.


García-Ramos et al., Austurian Jurassic Coast Field Trip Guide, 2008: International conference in Oviedo, Spain.

Posted in


  1. Lynn on October 12, 2023 at 1:19 am

    Hard to now imagine Spain was so close to North America!

    How many times have I seen white-ish squiggly lines in rocks (traveling through French and Spanish wine regions most recently). Perhaps they were root casts… can they be found in formations other than Vega?

    • Landscapes Revealed on October 12, 2023 at 9:07 am

      Sure, root casts can be found in any sediments formed in terrestrial environments. If the sediments are deposited in the ocean, though, the squiggly white lines would be animal borrows. Whether by plants or animals, we call it bioturbation! In either case, the layers get churned up by biological activity and sediments generally have a mottled coloration.

Subscribe to Blog

Enter your email address to subscribe to this blog and receive notifications of new posts by email.