Dating technique used at sima del elefante
At the beginning of the 20th Century, the construction of a trench which cut into the southwest border of the Sierra de Atapuerca, for the passing of a narrow mining railway, brought to light the presence of numerous karst chambers, many of them filled to the roof.Subsequent excavations and research have centered on three sites: Gran Dolina, Galería and Sima del Elefante.
The basal part (levels TD1 and TD2) contains sterile sediments deriving from the inside of the cave, and apparently the cave was not open to the exterior at this time.The limestone dissolved and ever larger underground caves were formed as the level of the valley descended.Over a million years ago, some of the caves were open to the outside and dry.The galleries in these subterranean cavities are distributed in three clearly differentiated levels, marking the successive drops in the water table of the Arlanzón River, which gradually left the upper conduits inactive.Subsequent collapses and erosive processes caused the collapse of the roofs of these conduits and facilitated access to the interior of the caves by animals and humans since Lower Pleistocene times, at least one million years ago.The occupation and subsequent filling of the cave entrances has preserved traces of the past.
The cave sites in the Sierra de Atapuerca contain one of the richest archeological and paleontological records documenting the course of human evolution in Europe during the Lower and Middle Pleistocene.
Beginning in levels TD3-TD4 (some 900,000 years old) the opening of the cave mouth allowed outside sediments and materials to fill the cave, and this process of infilling continued through to level TD 11 (around 100,000 years ago).
Level TD6 stands out as having yielded 84 human remains, in a test pit of some six square meters, representing a new species of human, ' Homo antecessor', together with faunal remains, pollen and stone tools.
The natural beauty of the galleries is due in no small part to the large number of spectacular stalagmites and stalactites present in the interior of the cave system.
Unfortunately, the presence and activity of humans in the cave during more than 500 years has caused irreversible damage to this once pristine beauty.
By extension, the term karst has been adopted internationally to denote any region with similar characteristics.