Late Holocene Climatic Change: The little ice age and El Nino from planktonic foraminifera in sediments off walvis bay, South West Africa

The variation in abundance of the species G. bulloides and G. pachyderma with depth in a core of diatomaceous sediment off Walvis Bay, South West Africa, seems to correlate with the Little Ice Age that occurred during the late Holocene. Although similar research, using species and oxygen isotope variations has been completed in similar sediment off northern Venezuela and in the Santa Barbara Basin (Kipp and Towner 1975, Dunbar 1983), these are the first downcore foraminiferal species records of the South West African deposit. The abundances of some of the minor species, most notably G. ruber, show very distinctive peaks at apparently random intervals. It is thought that these sudden and short-lived increases could be linked to major El-Nino-type events. In order to measure accurately all the down-core foraminiferal changes, we had to develop a chemical solution which dissolves diatoms and organic material without damaging the foraminiferal skeletons. It consists of K2CO3, CaCl2, NaOH and H202 in particular concentrations. By using this technique, it is possible to prevent biassing of the foraminiferal signal during extraction of foraminifera from diatomaceous mud