[1] The formations of the group comprise a sequence of brown limestones in a matrix of black silt, sandstones, claystones and conglomerates deposited under terrestrial conditions, in alluvial fan and fluvial environments.

In geological terms, this area lies within the western Cameros Basin, which is located in the north−westernmost part of the Iberian Range, outcropping in the provinces of Burgos, Soria and La Rioja.

The fluvial system of the Castrillo de la Reina Formation shows a braided channel pattern with well developed and drained floodplains.

The age of the fifth depositional sequence is Late Barremian to Early Aptian as is suggested by charophyte and ostracod biostratigraphy.

In addition, several vertebral centra and femur fragments from a small ornithopod, two spinosaurid theropod vertebrae and a crocodile tooth were recovered from the site.