Late Miocene to early Pliocene climate variability off NW Africa (ODP Site 659)
Colin, C.; Siani, G.; Liu, Z.; Blamart, D.; Skonieczny, C.; Zhao, Y.; Bory, A.; Frank, N.; Duchamp-Alphonse, S.; Thil, F.; Richter, T.; Kissel, C.; Gargani, J. (2014). Late Miocene to early Pliocene climate variability off NW Africa (ODP Site 659). Palaeogeogr. Palaeoclimatol. Palaeoecol. 401: 81-95. dx.doi.org/10.1016/j.palaeo.2014.02.015 In: Palaeogeography, Palaeoclimatology, Palaeoecology. Elsevier: Amsterdam; Tokyo; Oxford; New York. ISSN 0031-0182; e-ISSN 1872-616X, more |  |
| Author keywords | African monsoon; ITCZ; Dust input; Messinian Salinity Crisis; Cape Verdeplateau |
| Authors | | Top | - Colin, C.
- Siani, G.
- Liu, Z.
- Blamart, D.
- Skonieczny, C.
| - Zhao, Y.
- Bory, A.
- Frank, N.
- Duchamp-Alphonse, S.
| - Thil, F.
- Richter, T., more
- Kissel, C.
- Gargani, J.
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| Abstract | A high resolution delta O-18 record obtained on benthic foraminifera (Cibicides wuellerstorfi) combined with clay mineralogy, major element concentrations and Sr-Nd isotopes have been investigated for the ODP Site 659 located off North Africa in order to reconstruct African monsoon intensity between 6.2 and 4.9 Myr. Mineralogical and geochemical results indicate that sedimentation on the Cape Verde plateau results from a mixture of sediments deriving from the neighbouring Saharan arid region and the wet African equatorial zone (Sahelian Band), characterised by a low and a high state of weathering, respectively. Past variations in terrigenous inputs from these areas allow us to track past extension and displacement of the West African Monsoon-ITCZ system. Maximal summer insolation induced a northward migration of the inter-tropical convergence zone (ITCZ), wetter conditions in the Sahel, and a diminishing of wind erosion over the South Sahara and Sahel. In addition, there was an increase in river input to the Cape Verde plateau of sediments derived from southern sedimentary sources, which are characterised by high kaolinite contents and CIA values and low K/Al and Ti/AI ratios. On the other hand, minimal summer insolation induced a southward movement of the ITCZ, drier climate in the Sahel and stronger easterly winds resulting in an increase in dust transport from the Sahara to the Cape Verde Plateau. Dust particles are characterised by high illite and smectite content and by a low chemical state of weathering (low CIA values and high K/AI and Ti/AI ratios). Finally, our results provide new clues regarding the re-flooding of the Mediterranean Sea at the end of the MSC (5.33 Myr). This event was associated with enhanced aridity in the Sahara, implying a reorganisation of the atmospheric circulation and a southward migration of the ITCZ. |
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