Consulta: creatorFacets:"Wefer, Gerold"
Registros recuperados: 3
Data/hora: 02/06/2024 06:28:48

Reconstructing marine productivity of the Cariaco Basin during marine isotope stages 3 and 4 using organic-walled dinoflagellate cysts
Provedor de dados: 5
Autores: Gonzalez, Catalina; Dupont, Lydie M.; Mertens, Kenneth; Wefer, Gerold.
An organic-walled dinoflagellate cyst analysis was carried out on sediment core MD03-2622, retrieved from the Cariaco Basin. The core comprises the 73-30 ka interval. Down core changes in cyst abundance, accumulation rate, and composition of cyst assemblages were used to identify climatic and oceanographic changes at orbital and millennial time scales in this near-equatorial seasonal upwelling area. Throughout the sequence, dinoflagellate cyst assemblages were dominated by heterotrophic dinocysts (mainly Brigantedinium spp.), with the exception of four autotrophic-dominated (mainly Spiniferites ramosus) intervals around 58, 53, 46, and 37 ka. At orbital time scales, changes in the dinoflagellate productivity seem to follow low-latitude insolation, with the...
Tipo: Text
Ano: 2008
URL: https://archimer.ifremer.fr/doc/00237/34805/33327.pdf

Abrupt changes of temperature and water chemistry in the late Pleistocene and early Holocene Black Sea
Provedor de dados: 5
Autores: Bahr, Andre; Lamy, Frank; Arz, Helge W.; Major, Candace; Kwiecien, Olga; Wefer, Gerold.
[1] New Mg/Ca, Sr/Ca, and published stable oxygen isotope and Sr-87/(86) Sr data obtained on ostracods from gravity cores located on the northwestern Black Sea slope were used to infer changes in the Black Sea hydrology and water chemistry for the period between 30 to 8 ka B. P. ( calibrated radiocarbon years). The period prior to 16.5 ka B. P. was characterized by stable conditions in all records until a distinct drop in delta O-18 values combined with a sharp increase in Sr-87/(86) Sr occurred between 16.5 and 14.8 ka B. P. This event is attributed to an increased runoff from the northern drainage area of the Black Sea between Heinrich Event 1 and the onset of the Bolling warm period. While the Mg/Ca and Sr/Ca records remained rather unaffected by this...
Tipo: Text
Palavras-chave: Black Sea; Ostracods; Trace elements.
Ano: 2008
URL: https://archimer.ifremer.fr/doc/00209/31989/30432.pdf

Abrupt shifts of the Sahara-Sahel boundary during Heinrich Stadials
Provedor de dados: 5
Autores: Collins, James A.; Govin, A.; Mulitza, Stefan; Heslop, David; Zabel, M.; Hartmann, J.; Rohl, U.; Wefer, Gerold.
Relict dune fields that are found at 14° N in the modern-day African Sahel are testament to equatorward expansions of the Sahara desert during the late Pleistocene. However, difficulties of dating dune formation mean that abrupt millennial-scale climate events are not always resolved in these records. High-resolution marine core studies have identified Heinrich Stadials as the dustiest periods of the last glacial, although no studies have mapped the spatio-temporal evolution of dust export from West Africa. We use the major-element composition of four marine sediment cores to reconstruct the spatial extent of Saharan-dust versus river-sediment input to the continental margin from West Africa over the last 60 ka. This allows us to map the position of the...
Tipo: Text
Ano: 2013
URL: http://archimer.ifremer.fr/doc/00182/29279/27696.pdf