Segalen L., Renard M., Lee Thorp J.A., Emmanuel L., Le Callonnec L., de Rafelis M., Senut B., Pickford M., Mélice Jean-Luc. (2006). Neogene climate change and emergence of C-4 grasses in the Namib, southwestern Africa, as reflected in ratite C-13 and O-18. Earth and Planetary Science Letters, 244 (3-4), p. 725-734. ISSN 0012-821X.
Titre du document
Neogene climate change and emergence of C-4 grasses in the Namib, southwestern Africa, as reflected in ratite C-13 and O-18
Année de publication
2006
Auteurs
Segalen L., Renard M., Lee Thorp J.A., Emmanuel L., Le Callonnec L., de Rafelis M., Senut B., Pickford M., Mélice Jean-Luc
Source
Earth and Planetary Science Letters, 2006,
244 (3-4), p. 725-734 ISSN 0012-821X
Stable light isotopes in ratite eggshells have been shown to be reliable indicators of shifts in climate and environmental conditions in the past. Here, we show that delta(18)O and delta(13)C values in fossil and modern ratite eggshells collected in the aeolianite deposits of the southern and central Namib Desert track regional distinctions and global climate shifts throughout the Neogene. 6180 values, although variable, are consistently higher in the central compared to the southern Namib throughout the record. delta(18)O trends during the Miocene differ for the two regions, but track each other post-Miocene. Throughout the Miocene, delta(13)C values for ratite eggshells from both the central and Southern Namib regions are indistinguishable showing that the flora remained C-3 throughout. The overall negative (-3 parts per thousand) shift in mean values for Miocene biostratigraphic zones is consistent with the response of C-3 photosynthesis to pCO(2) shifts from 180 to 320ppmv as estimated from marine alkenone studies and/or evolution of the delta(13)C of the atmospheric CO2. Evidence for C-4 plants occurs post-Miocene, with the development of the southern, winter rainfall and central/northern, summer rainfall zonation apparent today. These data provide independent corroboration that the expansion Of C-4-dominated ecosystems after similar to 7 Ma cannot be attributed to a reduction Of pCO(2) below a 500 ppmv threshold, as earlier proposed. Proliferation of C-4 plants in the Namib after similar to 5 Ma and, elsewhere, may be related rather to energy budgets and rainfall seasonality shifts resulting from large-scale atmospheric and oceanic circulation reorganisation. (c) 2005 Elsevier B.V. All rights reserved.
Plan de classement
Sciences du milieu [021]
;
Géologie et formations superficielles [064]
Description Géographique
NAMIBIE
Localisation
Fonds IRD [F B010035647]
Identifiant IRD
fdi:010035647
