Paleoenvironmental reconstruction of Jurassic dinosaur habitats of the Vega Formation, Asturias, Spain
Paleoenvironmental reconstruction of Jurassic dinosaur habitats of the Vega Formation, Asturias, Spain
Geological Society of America Bulletin (November 2011) 124 (3-4): 596-610
- actinides
- aluminum
- Archosauria
- Asturias Spain
- biogenic structures
- C-13/C-12
- carbon
- carbon dioxide
- cerium
- chemical composition
- chemical ratios
- Chordata
- concretions
- depositional environment
- Diapsida
- dinosaurs
- Europe
- fluvial environment
- habitat
- Iberian Peninsula
- ichnofossils
- isotope ratios
- isotopes
- Jurassic
- lanthanum
- lithostratigraphy
- lutetium
- major elements
- Mesozoic
- metals
- Morrison Formation
- neodymium
- O-18/O-16
- oxygen
- paleoatmosphere
- paleoclimatology
- paleoecology
- paleoenvironment
- paleosols
- pedogenesis
- provenance
- rare earths
- Reptilia
- rhizoliths
- samarium
- secondary structures
- sedimentary rocks
- sedimentary structures
- semi-arid environment
- Southern Europe
- Spain
- stable isotopes
- terrestrial environment
- Tetrapoda
- Th/U
- thorium
- titanium
- trace elements
- tracks
- United States
- Upper Jurassic
- uranium
- Vertebrata
- weathering
- whole rock
- ytterbium
- Ti/Al
- subhumid environment
- La/Ce
- Vega Formation
- Yb/Lu
- Playa de Vega
- Gijon-Villaviciosa Basin
Jurassic-aged strata of Asturias, Spain, contain trace fossils including sauropod, theropod, and ornithopod dinosaur footprints, but their paleoenvironmental context has been relatively unstudied. A coastally exposed continuous section at Playa de Vega shows a clear transition from the marine Middle Jurassic Rodiles Formation to the terrestrial Upper Jurassic Vega Formation. Within the >100 m of Vega Formation stratigraphy that was logged there, four distinct types of paleosols were identified: (1) Entisols, (2) Inceptisols, (3) Vertisols, and (4) composite or cumulative paleosols. The paleosol types and their features indicate a floodplain depositional setting with short stature, shrubby vegetation. Theropod and ornithopod tracks have been identified at the base of the section, indicating that a dinosaurian fauna was present at Playa de Vega during the Jurassic. Results from well-characterized climofunctions based on modern soils and paleosol B horizon chemical composition of the Inceptisols and Vertisols yield mean annual precipitation estimates of 400-980 mm yr (super -1) and mean annual temperature estimates of 8-15 degrees C. The presence of Vertisols, with both evidence for shrink-and-swell behavior and dispersed pedogenic carbonate, is consistent with a strongly seasonal precipitation regime. The delta (super 13) C analyses of pedogenic carbonates yield values that range from -7.09 per mil to -8.88 per mil (relative to Vienna Peedee belemnite [VPDB]) and indicate carbon dioxide levels about six times pre-industrial levels, consistent with previous results. The Asturian vertebrate track assemblage is remarkably similar to that of the Morrison Formation (western United States), but it has greater overall richness. The pattern is reversed for body fossils. The reconstructed paleoenvironmental and paleoclimatic conditions indicate similar depositional settings in both places, but with a cooler, wetter, more seasonal environment in Asturias. The greater seasonality indicated by the Vega Formation relative to the Morrison Formation may explain the observed differences in richness.