The Kapthurin formation is a basalt

Basalt

Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...

 outcrop in Kenya

Kenya

Kenya , officially known as the Republic of Kenya, is a country in East Africa that lies on the equator, with the Indian Ocean to its south-east...

 near Lake Bogoria

Lake Bogoria

Lake Bogoria is a saline, alkaline lake that lies in a volcanic region in a half-graben basin south of Lake Baringo, Kenya, a little north of the equator. Lake Bogoria, like Lake Nakuru, Lake Elmenteita, and Lake Magadi further south in the Rift Valley, and Lake Logipi to the north, is home at...

 and Lake Baringo

Lake Baringo

Lake Baringo is, after Lake Turkana, the most northern of the Great Rift Valley lakes of Kenya, with a surface area of about and an elevation of about . The lake is fed by several rivers, El Molo, Perkerra and Ol Arabel, and has no obvious outlet; the waters are assumed to seep through lake...

.

Part of the East African Rift System, it is also an important archaeological site

Archaeological site

An archaeological site is a place in which evidence of past activity is preserved , and which has been, or may be, investigated using the discipline of archaeology and represents a part of the archaeological record.Beyond this, the definition and geographical extent of a 'site' can vary widely,...

 in the study of early humans who occupied the area and left Acheulean

Acheulean

Acheulean is the name given to an archaeological industry of stone tool manufacture associated with early humans during the Lower Palaeolithic era across Africa and much of West Asia, South Asia and Europe. Acheulean tools are typically found with Homo erectus remains...

 stone tools and animal bones behind.

Argon argon dating of volcanic ash overlying ochre

Ochre

Ochre is the term for both a golden-yellow or light yellow brown color and for a form of earth pigment which produces the color. The pigment can also be used to create a reddish tint known as "red ochre". The more rarely used terms "purple ochre" and "brown ochre" also exist for variant hues...

fragments found there has dated what may represent some of the earliest human aesthetic sensibility to 285,000 years ago. The ochre fragments must have been brought to the site by human agency and may have been used as body adornment.

Source

Tryon, CA and McBrearty, S, 2002, "Tephrostatigraphy and the Acheulean to Middle Stone Age transition in the Kapthurin Formation, Kenya", Journal of Human Evolution 42, 211-35, qtd in Scarre, C (ed.) (2005). The Human Past, London: Thames and Hudson. ISBN 0-500-28531-4.