Isabel Hernando-Alonso, a researcher at the Centro Nacional de Investigación sobre la Evolución Humana (CENIEH), has led a study, published in the journal Quaternary Geochronology, reporting the first application of the Electron Spin Resonance (ESR) dating technique to the fluvial sediments inside Cueva de Silo (Atapuerca, Burgos). The results suggest a minimum age of 900,000 years for the deposits found at the lower levels, although more ancient dates were also found, which are possibly the result of filtration from higher caves.

The work centered on two different areas of this cave: Sala del Caos and Galería de las Arenas. The deposits preserved in these cavities are fluvial sediments brought by floods of the Arlanzón River that entered the caves.

“It is important to know the chronology of these events because they are responsible for forming the system of cavities at the Sierra de Atapuerca, and they could be the key to more detailed correlations for the formation of the karst and of other sites such as Gran Dolina or Sima del Elefante”, comments Hernando-Alonso.

The Atapuerca karst

During the Pleistocene, there were climatic variations which facilitated a progressive fall in the water level in the rivers that formed "steps" in the valleys known as fluvial terraces. This successive entrenchment in the fluvial network is also responsible for the formation of the different horizontal conduits that comprise the karst at Atapuerca.

“Dating the sediments allows us to correlate the formation of the different karst levels with the fluvial terraces of the Arlanzón River, so that we can understand much better the overall geological context of the Arlanzón basin”, she adds.

This work is part of the doctoral thesis that Hernando-Alonso is undertaking at the CENIEH, as part of the UBU-CENIEH program, funded by an FPI predoctoral researcher contract (PRE2019-090919), for the Atapuerca research project (PGC2018-093925-B-C31).