Blombos Cave - Excavation History and Stratigraphy

Excavation History and Stratigraphy

Blombos Cave is some 100 metres (330 ft) from the coast and 35 metres (115 ft) above sea level. The cave is a wave-cut bench in Mio/Pliocene Wankoe Formation aeolian deposits. Interior cave deposits, including those in recesses, cover more than 80 square metres (860 sq ft). About 20 square metres (220 sq ft) of the MSA has been excavated to a depth of about 2 metres (6.6 ft) below the original surface. The depositional history of the MSA levels is complex. Probably just prior to the accumulation of the M3 phase, large calcrete roof blocks up to 3 metres (9.8 ft) thick were dislodged creating a variable and uneven floor surface. Further rockfall onto the MSA deposits occurred after the M3 phase occupation at circa 130-140 ka.

Subsequent human occupation left debris scattered over and around these blocks up to a height of more than 2 metres (6.6 ft). Compaction has caused deposits to drape over and around large spalls with some examples of near vertical layering. Near the rear and side cave wall, MSA deposits have in some instances shrunk, leaving a gap that later filled with LSA deposits. In places large rocks have shifted or broken, causing shearing of deposits and infills. Despite these anomalies, most MSA deposits are in situ and undisturbed. By identifying and excluding material from contaminated areas, archaeologists are confident of the integrity of more than 95 per cent of recovered MSA material.