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Pre- and post-depositional alteration of botanical macro-remains: A case study from Olduvai Gorge, Tanzania

Bamford, Marion K.
Quaternary international 2012 v.275 pp. 97-103
Hominidae, Liliopsida, Magnoliopsida, bark, case studies, cracking, culms, death, fauna, flora, fossils, pith, ridging, shrublands, vascular bundles, weathering, wetlands, wind, woodlands, Tanzania
Fossil macroplants from Beds I and II, Olduvai Gorge (around 1.9–1.7 Ma), have been used to reconstruct the past vegetation associated with the early hominids and fauna. A taphonomic study of these remains together with modern analogous wetlands, bushlands, open woodlands and the plant taxa have been used to improve interpretation and reconstruction of the fossil flora. Weathering or degradation can occur at two different stages of the taphonomic cycle. Firstly, between death and burial: monocots and dicots show different weathering signatures. Aerial weathering of monocot culms results in removal of the epidermal layers exposing the pith and vascular bundles, whereas sub-aqueous weathering of the culms also shows collapse and ridging of the epidermal layers. Aerial weathering of dicot stems results in loss of bark and radial cracking. Secondly, between preservation and recovery: the exterior of the fossil is either worn smooth by wind or water after long exposure or can become more eroded as in the case of less durable, smaller fragments. Fracturing of culms and stems may also occur but results in clear breaks that can be matched to the part and counterpart. Recognition of the weathering signatures aids in interpreting the depositional and post-depositional conditions. The abundance and distribution of plant macrofossils at Olduvai Gorge is affected by living plant abundance and depositional setting within the Fault Compartments.