• Aridity in Equatorial Africa During the Last 225,000 Years: A Record of Opal Phytoliths/ Freshwater Diatoms from the Zaire (Congo) Deep-Sea Fan (Northeast Angola Basin)

      Jansen, J. F.; Alderliesten, C.; Houston, C. M.; De Jong, A. F. M.; van der Borg, Klaas; Van Iperen, J. M. (Department of Geosciences, The University of Arizona, 1989-01-01)
      Maps of accumulation rates of freshwater diatoms and opal phytoliths in the surface sediments of the Zaire fan show that both types of microfossils were supplied to the ocean floor by the Zaire River, and that opal phytoliths also have a southern source, probably the region of the Namibian desert. The PhFD ratio, of opal phytoliths to freshwater diatoms, can be regarded as an aridity index for equatorial Africa, and probably for large parts of the central and southern Atlantic. In two cores, the record of the PhFD ratio indicates humidity ca 225-190 ka BP, aridity 190-135 ka BP with maxima ca 170 and 140 ka BP and a humid excursion 150 ka BP, an increase in humidity 115 ka BP, a less humid period 90-30 ka BP, more humidity ca 30-17 ka BP with possibly more arid intervals ca 22.5 and 20 ka BP. In general, glacial (sub) stages were more arid and interglacial (sub) stages more humid. For the last 20 ka, the PhFD ratio corresponds closely with the known climatic events in tropical Africa.
    • Dating of the Upper Pleistocene Lithic Industry of Sardinia

      Hofmeijer, G. Klein; Alderliesten, C.; van der Borg, Klaas; Houston, C. M.; De Jong, A. F. M.; Martini, F.; Sauges, M.; Sondaar, P. Y.; De Visser, J. A. (Department of Geosciences, The University of Arizona, 1989-01-01)
      During an excavation of 1986 and 1987, a joint team from Utrecht, Siena and the Soprintendenza di Sassari a Nuoro, found a pre-Neolithic lithic industry in Corbeddu Cave, Oliena, Sardinia, which was dated to 8000-17,000 BP. The artifact typology is different from that of the mainland of the same period. The lithic and bone artifacts suggest an endemic isolated economy of the Upper Pleistocene in Sardinia.
    • The Timing of the Post-Glacial Marine Invasion of Kau Bay, Halmahara, Indonesia

      Barmawidjaja, D. M.; De Jong, A. F. M.; van der Borg, Klaas; Van der Kaars, W. A.; Van der Linden, W. J. M.; Zachariasse, W. J. (Department of Geosciences, The University of Arizona, 1989-01-01)
      Kau Bay, Halmahera, Indonesia is a small marine basin that is separated from the adjacent SW Pacific Ocean by a shallow sill, 40m deep. Radiocarbon dating on piston cores in combination with a study on microfossils demonstrate that Kau Bay was a freshwater lake in Weichselian times. At 10,000 BP, the Bay became reconnected with the open ocean. If sill depth did not change in the intervening years, sea level at 10,000 BP stood 40m below the present level.