Environmental comparisons of the Awash Valley, Turkana Basin and lower Omo Valley from upper Miocene to Holocene as assessed from stable carbon and oxygen isotopes of mammalian enamel

• Published in: Palaeogeography, palaeoclimatology, palaeoecology Vol. 562; p. 110099
• Main Authors: Paquette, Jesseca, Drapeau, Michelle S.M.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15-01-2021
• Subjects: Aridity index; Diet; Ecosystem; Herbivores; Mixed feeders; Water deficit; Aridity index; Herbivores; Diet; Mixed feeders; Ecosystem; Water deficit
• ISSN: 0031-0182; 1872-616X
• DOI: 10.1016/j.palaeo.2020.110099

The Awash Valley, Turkana Basin and lower Omo Valley of East Africa are three regions that have been particularly important for documenting the environment from the late Miocene to the Holocene, but these basins have never been compared throughout that large temporal sequence. In this context, we compare changes in the diet of herbivores with mixed diets (hippopotamids, elephantids, suids and bovids), the total large-vertebrate diet in the ecosystem, as well as water deficit from these three basins between 7.4 Ma and 10 ka to determine how they were different. Our sample consists of a compilation of more than 3000 published mammalian stable isotopic values. Our results show that the Awash valley becomes more arid through time, corresponding broadly with an increase in C4 plants, but that relationship is not clear in the other two basins. The Awash and Turkana are broadly similar in overall aridity while the lower Omo Valley is clearly more mesic between 4 and 2.5 Ma. However, the Turkana and Omo are similar in ecosystem values, while it is the Awash that presents a landscape with more C4 plants. When comparing the diets, the three basins are similar, with an increase in C4 plants after ~4 Ma (after 3.0–3.4 Ma in the lower OmoValley), with all taxa converging by 1.9–2.4 Ma on a similar diet with mostly C4 plants. Elephants vary little throughout the sequence when compared to the other taxa. Our data suggest that, except for elephantids, all taxa studied track the expansion of C4 plants in East Africa and that this expansion may be, in part, related to a general increase in aridity.
•Diets of bovids, suids and hippos, but not elephants, track the C4-plant expansion.•At ~4 Ma, C3-plant increases in the diet of all taxa in the Awash and Turkana basins.•Only bovids' diet suggests more C3 plants in the Omo Valley throughout the Pliocene.•Landscape structure was similar in the Omo and Turkana, but the Omo was more mesic.•Aridity increases in the Awash, suggesting it contributed to C4-plant expansion.