Recent discoveries of dinosaur fossils in Riodeva led us to carry out a systematic study of the geology of
the area. The calcareous-siliciclastic facies rich in fossil bones are attributed to the Villar del Arzobispo
Formation (Tithonian-Berriasian). These transitional facies have been divided into three different units; A)
Marine-influenced siliceous-calcareous deposits, spanning 50 m., conformable over the underlying
calcareous Jurassic marine unit, B) A 170 m detritical alluvial unit, including more than 35 recorded
dinosaur sites (Royo-Torres y Cobos, 2004), and C) A 15-0 m detritical-calcareous unit unconformable
below the erosive overlying formation (Arenas y Arcillas del Collado Formation). We also suggest a
chronological explanation for taxonomical divergences between dinosaur sites previously attributed to
Arenas y Arcillas del Collado formation