Fig. 3: Plan and stratigraphic sections of the Calio excavation.

Layer 1 is a dark brown topsoil with a sandy clay texture (maximum thickness of >40 cm in B1U3). Layer 2 is a grey conglomerate rock composed of tightly cemented sand and gravel containing various rock types, along with stone artefacts and extinct fossil fauna. This conglomerate layer covers almost the entire surface of the excavation units, except for squares B1U5 and B1U6. Layers 3a and 3b share similarities in both colour and texture, consisting of brown, dark brown and yellowish-brown sandy gravel layers with tabular cross-bedding, but moderately cemented. Layer 4 is similar to layer 2, a conglomerate sediment, but it is only found in a few excavation units, particularly squares B1U6 and B1U2. This layer has a thickness of only about 5–10 cm and appears discontinuous, reappearing in other units, giving it an intercalated appearance. Layer 5a is dark brown with a sandy gravel texture. At the base of this layer, layer 5b consists of yellowish-brown sandy intercalations, contrasting in colour with the overlying layer but sharing the same sandy gravel texture. Layer 5c has a thickness of only 2–12 cm. At the base of layer 5b there is a layer resembling the conglomerate with similar characteristics, but it was not further excavated due to its extreme hardness. The deepest stone artefact (artefact 6; A6) was excavated from layer 3b at a depth of 56 cm in square B1U2. F1, the Celebochoerus maxilla dated using US–ESR.