The middle to late Miocene climatic development of Southwest Africa derived from the sedimentological record of ODP Site 1085A

Roters, Bastian; Henrich, Rüdiger

doi:10.1007/s00531-008-0398-9

Cited by 17 publications

(8 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the eastern Pacific, nearly 50% of the diatom assemblages were replaced by cold‐water species during a major middle Miocene cooling from 14.9 to 12.4 Ma, reflecting increased upwelling and cooling of surface waters [ Barron and Baldauf , 1990]. Increased Antarctic glaciations promoting intermediate and bottom water formation [ Diekmann et al , 2003] and intensification of the Hadley circulation [ Flohn , 1978], combined with an intensified Southern Hemisphere southeast wind system [ Roters and Henrich , 2010], are inferred causes. Both mechanisms intensified upwelling at the west coasts of the Southern Hemisphere continents.…”

Section: Discussionmentioning

confidence: 99%

Miocene to Pliocene development of surface and subsurface temperatures in the Benguela Current system

et al. 2011

View full text Add to dashboard Cite

The initiation of the Benguela upwelling has been dated to the late Miocene, but estimates of its sea surface temperature evolution are not available. This study presents data from Ocean Drilling Program (ODP) Site 1085 recovered from the southern Cape Basin. Samples of the middle Miocene to Pliocene were analyzed for alkenone‐based (U37K′, SSTUK) and glycerol dialkyl glycerol tetraether (GDGT) based (TEX86, TempTEX) water temperature proxies. In concordance with global cooling during the Miocene, SSTUK and TempTEX exhibit a decline of about 8°C and 16°C, respectively. The temperature trends suggest an inflow of cold Antarctic waters triggered by Antarctic ice sheet expansion and intensification of Southern Hemisphere southeasterly winds. A temperature offset between both proxies developed with the onset of upwelling, which can be explained by differences in habitat: alkenone‐producing phytoplankton live in the euphotic zone and record sea surface temperatures, while GDGT‐producing Thaumarchaeota are displaced to colder subsurface waters in upwelling‐influenced areas and record subsurface water temperatures. We suggest that variations in subsurface water temperatures were driven by advection of cold Antarctic waters and thermocline adjustments that were due to changes in North Atlantic deep water formation. A decline in surface temperatures, an increased offset between temperature proxies, and an increase in primary productivity suggest the establishment of the Benguela upwelling at 10 Ma. During the Messinian Salinity Crisis, between 7 and 5 Ma, surface and subsurface temperature estimates became similar, likely because of a strong reduction in Atlantic overturning circulation, while high total organic carbon contents suggest a “biogenic bloom.” In the Pliocene the offset between the temperature estimates and the cooling trend was reestablished.

show abstract

Section: Discussionmentioning

confidence: 99%

Miocene to Pliocene development of surface and subsurface temperatures in the Benguela Current system

et al. 2011

View full text Add to dashboard Cite

show abstract

“…The time interval of 11.8–11.4 Ma ago has been delineated as the Antarctic glaciation period Mi5 [ Miller et al , 1991; Westerhold et al , 2005]. The enhanced cooling during this time could have led to an increase in wind strength [ Roters and Henrich , 2010] and, subsequently, to an upwelling pulse. After 11.4 Ma, productivity tends to decrease, as reflected by a decrease in dinoflagellate cyst accumulation rates.…”

Section: Discussionmentioning

confidence: 99%

“…Our suggestion of enhanced input of terrigenous material at 11.3 and 11.2 Ma is supported by the study of Kastanja et al [2006], who found high values of terrigenous input at about 11.3 Ma. There is strong evidence that the Namib Desert was not fully developed and that most terrestrial material was transported into the research area via the Orange River [ Diekmann et al , 2003; Partridge , 1993; Roters and Henrich , 2010; Siesser , 1980]. The increase in nutrient availability in the upper water might therefore be the result of enhanced fluvial input during that time.…”

Section: Discussionmentioning

confidence: 99%

The Benguela upwelling related to the Miocene cooling events and the development of the Antarctic Circumpolar Current: Evidence from calcareous dinoflagellate cysts

Heinrich

Zonneveld

Bickert³

et al. 2011

Paleoceanography

View full text Add to dashboard Cite

Sediment samples from ODP Site 1085 were investigated in order to obtain more information on the initiation and development of the Benguela upwelling system during the middle and upper Miocene. In particular, our intent was to establish the causes of the upwelling as well as the response of the upwelling regime to the development of the Antarctic Circumpolar Current. Based on changes in the calcareous dinoflagellate cyst association, we found an initial increase of the dinoflagellate cyst productivity, probably related to the initiation of upwelling about 11.8 Ma ago. Two distinct increases in cyst productivity in conjunction with temperature decreases of the upper water masses reflect upwelling pulses off Namibia and occur at the end of the Miocene cooling events Mi5 (about 11.5 Ma) and Mi6 (about 10.5 Ma). Both cooling events are associated with an ice volume increase in Antarctica and are thought to have led to an increase in southeasterly winds, possibly causing these two upwelling pulses. We demonstrate a decrease in dinoflagellate cyst productivity and enhanced terrigenous input via the Orange River after the Mi5 event. At about 11.1 Ma, the dinoflagellate cyst productivity increases again. The polar cyst species Caracomia arctica occurs here for the first time. This implies an influence of subantarctic mode water and therefore a change in the quality of the upwelling water which allowed the Benguela upwelling to develop into modern conditions. From about 10.4 Ma, C. arctica forms a permanent part of the association, pointing to an establishment of the upwelling regime.

show abstract

“…In southern Africa, progressive aridification of the climate began in the mid-Miocene (10-15 Ma), associated with the establishment of the Benguela upwelling system (Zachos et al, 2001;Cowling et al, 2009;Dupont et al, 2011). Approximately 10 Ma, the seasonal summer-dry climatic regime found in the present day in the CFR was established (Krammer et al, 2006;Roters & Henrich, 2010). The progressive aridification and the opening of new niches in the CFR in the last 10 million years (Myr) have been hypothesized to have triggered rapid speciation in several CFR clades (Verboom et al, 2009).…”

Section: Geomorphic and Climatic Historymentioning

confidence: 99%

Contrasting evolutionary hypotheses between two mediterranean‐climate floristic hotspots: the Cape of southern Africa and the Mediterranean Basin

Valente

Vargas

2013

Journal of Biogeography

View full text Add to dashboard Cite

Aim The Cape of southern Africa and the Mediterranean Basin, two of the world's five mediterranean-climate biodiversity hotspots, are exceptionally species-rich and constitute a well-described example of ecological convergence. However, the area-adjusted plant species diversity of the Cape is on average more than double that of the Mediterranean Basin. Here, we investigate the causes of this diversity asymmetry by drawing on phylogenetic information from a variety of plant groups and focusing on three competing hypotheses: diversity disparities arising from differential clade ages, diversification rates or diversity limits.Location Cape of southern Africa and the Mediterranean Basin.Methods We reviewed a variety of studies in order to contrast the geography, geomorphic history, biogeographical connectivity and ecological context in the two hotspots. We also tested the relationship between clade age and species richness in both regions based on phylogenetic information from 39 clades.Results Clades are on average older in the Cape than in the Mediterranean Basin. Clade age is a strong predictor of species diversity in the Cape, suggesting that diversity-dependent regulatory mechanisms may be weak. In contrast, we failed to find a relationship between age and diversity in the Mediterranean Basin, indicating that a diversity limit may have been achieved in multiple clades. Main conclusionsThe Cape has a higher species density than the Mediterranean Basin owing to a combination of older clade ages, high rates of diversification in certain lineages and an exceptionally high upper limit to diversity. High richness in the Cape is linked to long-term lineage persistence in a heterogeneous but stable evolutionary context. In contrast, the climatically unstable Mediterranean Basin has offered fewer opportunities for diversity accumulation in the long term (owing to high extinction rates), but appears to be a hotspot of recent rapid speciation.

show abstract

The middle to late Miocene climatic development of Southwest Africa derived from the sedimentological record of ODP Site 1085A

Cited by 17 publications

References 38 publications

Miocene to Pliocene development of surface and subsurface temperatures in the Benguela Current system

Miocene to Pliocene development of surface and subsurface temperatures in the Benguela Current system

The Benguela upwelling related to the Miocene cooling events and the development of the Antarctic Circumpolar Current: Evidence from calcareous dinoflagellate cysts

Contrasting evolutionary hypotheses between two mediterranean‐climate floristic hotspots: the Cape of southern Africa and the Mediterranean Basin

Contact Info

Product

Resources

About