Sea-floor distribution and Late Quaternary faunal patterns of planktonic and benthic foraminifers in the Angola Basin

• Main Author: Leeuwen, R.J.W. van
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 1989
• Subjects: Earth Sciences; Antarctic; Antarc*
• Online Access: https://dspace.library.uu.nl/handle/1874/205897

The distribution of planktonic and benthic foraminifers was examined in some hundred core-tops from the Angola Basin, mainly from depths below 2000 metres. A number of biofacies have been discriminated in the planktonic faunas on the sea-floor and these show a clear relation with the hydrography of the (near-) surface waters. Species distribution can generally be described satisfactorily in terms of surface-water temperature and fertility. However, if the thermocline reaches into the photic zone, faunas different from those of the surface-mixed layer are found at the top of the thermocline. The faunal differences between the top of the thermocline and the surface-water can not simply be attributed to differences in temperature and fertility. We suppose that some species are specifically linked up with a steep thermal gradient, whereas others can flourish in thermally homogeneous water only. The deep-sea benthic foraminiferal faunas vary primarily with depth. In addition there appear to be differences between the area along the African continent and areas far away from the continent. Faunal contrasts are found also within these areas. The lateral differences must be due to variations in sediment-related parameters and it is suggested that the amount of organic matter at and in the bottom plays a crucial role. Depth-related changes in the faunas are thought to be controlled by vertical gradients in bottom-water temperature and in the amount of organic matter arriving at the bottom. It should be mentioned that our results do not support the widely accepted idea that there is a relation between Nuttallides umboniferus and Antarctic Bottom Water. In a more general sense, we contend that fauna/water-mass relations are actually to be reduced to relations between fauna and bottomwater temperature. Late Quaternary faunal change was studied in five piston-cores from depths between 2000 and 4000 metres in the marginal area of the north-eastern Angola Basin. A climate stratigraphy was established for the last 150,000 years ...