The Jurassic (dinosaur) coast of Asturias: Part 2

For three amazing days in early September, we went dinosaur hunting along the Jurassic Coast in northern Spain. We were seeking the tracks of dinosaurs that inhabited this coastal region around 155–145 million years ago, and we found a lot!

Some background information

Please see my last post for location of the Jurassic coast in northern Spain, the location of Spain on Earth during the Jurassic Period, and a stratigraphic column of the geologic units we viewed along this part of the coast: Part 1 focused on the sediments deposited in oceanic environments during the Early Jurassic Period. This post focuses on the sediments deposited in terrestrial and coastal environments during the Late Jurassic Period—this is the part with dinosaur footprints.

A fabulous place to visit for more background information is the Museo Jurásico de Asturias (MUJA), whose location is shown on the map below. The museum, built in the shape of a three-toed dinosaur, is filled with superb specimens and explanations of the region. On the right side of the photo is Playa de La Griega (Griega Beach), an easy place to visit (more about this location below). This photo is from the field guide reference listed at the bottom of this post.
We enjoyed a two-night stay in Lastres, a scenic fishing town that has been listed as one of the “most beautiful villages in Spain” (see location on map above). Hotel Eutimio is an excellent family-owned lodge and restaurant. In a village known for fish and seafood, there are many delicious restaurants. Griega Beach is on the other side of the bay in this photo.
Here’s what the Asturian coast looked like during the Late Jurassic Period (diagram from the MUJA). In the Early Jurassic, the coast was flat and the preserved sedimentary rocks were deposited in the ocean (see previous post). At the beginning of the Late Jurassic, tectonic activity created mountains and caused the sea to retreat. This change is marked by the Vega Formation of river sediments (see previous post).

This post focuses on the Tereñes and Lastres Formations where most of the dinosaur footprints are found. Interpretation of diagram (from left to right): Mountainous relief in the southeast of the region; Alluvial plain with meandering rivers (Vega Fm); Fluvially-dominated delta (Lastres Fm); Interior sea (Tereñes Fm); Barrier reef. Fluvial=rivers. Alluvial=sediment carried by water, mostly in rivers.

Tereñes Formation

We observed the Tereñes Formation at Ribadesella, Mirador Tereñes, Griega Beach, and Tazones (see map in previous post).

These tracks at Griega Beach are the biggest footprints known in Spain and among the largest in the
world. They were created by herbivorous sauropods, a group that includes the largest animals that ever lived on land. This type of trace fossil is a mold—the mud “molds” to the shape of the dinosaur’s foot and is preserved when sand fills in the depressions. In these exposures along the beach, the sand has been eroded away, exposing the footprints in the mud.
This is a mural in the MUJA illustrating sauropods in a coastal setting with trees whose foliage they would have eaten.
This photo of Griega Beach shows how the ripples in the photo above probably formed. The tidal range was about 3 meters (9.8 feet) that day. When the tidal level was high, the waves were on this part of the beach and the moving water created ripples that were then exposed when the water receded during low tide (the time of this photo). In the background is the town of Lastres where we stayed. As shown in the mural of sauropods above, the dinosaurs were living in a coastal setting where the water level would have risen and fallen with the tides.

Lastres Formation

The best place for footprint fossils that we visited was Tazones, located west of Lastres (see map in previous post).

Left image: A map of Tazones. We visited Tazones port, where we saw three-toed dinosaurs (photos in Tereñes section above), and the beach northwest of Faro (lighthouse) de Tazones, where we saw the largest number of footprints in the Lastres Formation. Right photo: The beach site near the lighthouse. Here is an unlikely layer balanced on an inserted boulder overlying a mudstone layer with dinosaur footprints (side view).

An amazing “trample zone” with numerous sauropod footprints at Tazones. It’s not too hard to imagine those giant dinosaurs walking around in the mud. After that, sand would have been swept into the area, filling the depressions and preserving the footprints. This exposure is at the coastline where waves are attacking the rocks. The overlying sand layers was removed and, inevitably, the mud layer will eventually be eroded away too. The layers were all tilted during the Alpine-Pyrenean Orogeny about 40 million years ago.

Cultural note about Asturias

In my next post, we’ll go to the Picos de Europa for a 10-day trek.


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

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