Pollen analysis and age model of sediment core GIK-15856-2

Pollen and spores from a deep-sea core located west of the Niger Delta record an uninterrupted area of lowland rain forest in West Africa from Guinea to Cameroon during the last Interglacial and the early Holocene. During other periods of the last 150 ka, a savanna corridor between the western - Guinean - and the eastern - Congolian - part of the African lowland rain forest existed. This so-called Dahomey Gap had its largest extension during Glacial Stages 6, 4, 3, and 2. Reduced surface salinity in the eastern Gulf of Guinea as recorded by dinoflagellate cysts indicates sufficient precipitation for extensive forest growth during Stages 5 and 1. The large modern extension of dry forest and savanna in West Africa cannot be solely explained by climatic factors. Mangrove expansion in and west of the Niger Delta was largest during the phases of sea-level rise of Stages 5 and 1. During Stages 6, 4, 3, and 2, shelf areas were exposed and the area of the mangrove swamps was minimal.

Early Cretaceous palynomorphes from ODP Hole 113-692B

Detailed descriptions of in situ ?Valanginian to Albian Antarctic palynofloras are presented from Weddell Sea claystones with high percentages of organic matter ("black shales") and intercalated volcanic ash layers. The claystones were recovered from two sites (ODP Leg 113, Sites 692 and 693) on the continental margin of Dronning Maud Land. Palynological investigations of these Cretaceous sediments revealed a ?Valanginian-Hauterivian age for the Site 692 sediments and an Aptian-Albian age for Site 693. This paper is focused on the palynomorphs of Site 692. Miospores, dinoflagellate cysts, and acritarchs are listed and compared with early Cretaceous microfloras from the Antarctic Peninsula, Australia, and South America. The dinocyst assemblage of Site 692 seems to be very similar in composition to an assemblage from the South Shetlands (?Valanginian-Hauterivian-Barremian). It also agrees well with associations described from early Early Cretaceous sequences from the Perth Basin, southwestern Australia. According to the Australian miospore zonation schemes, the sporomorph flora from Site 692 belongs to the South Australian Foraminisporis wonthaggiensis Zone (early Valanginian to Hauterivian) or the lower part of the dinocyst Muderongia Superzone (Valanginian to Hauterivian).

210Pb dates, radiocarbon ages and sedimentation and accumulation rates of sediment cores JM99-1198 and MD99-2297

The magnitude of Late Holocene climatic variations are less significant than those that took place during ice ages and deglaciations. However, detailed knowledge about this period is vital in order to understand and model future climate scenarios both as a result of natural climate variation and the effects of global warming. Oceanic heat flux is important for the sensitive climate regime of northern Europe. Our aim is to connect hydrographical changes, reflected by the dinoflagellates cyst (dinocysts) assemblages in the sediments in the Malangen fjord, to local and regional climatic phases. Previous studies have shown that dinocyst assemblages are influenced by temperature, salinity, and the availability of nutrients (e.g. de Vernal et al. 2005, doi:10.1016/j.quascirev.2004.06.014; de Vernal et al. 2001, doi:10.1002/jqs.659; Grosfjeld et al. this volume; Rochon et al. 2008, doi:10.1016/j.marmicro.2008.04.001; Solignac et al. this volume). Dinoflagellates are mostly unicellular organisms that make up one of the main groups of phytoplankton. They are able to regulate their depth within the photic zone and to concentrate along oceanic fronts, which provide nutrient-enriched waters. The dinoflagellate cysts are the hypnozygotes of dinoflagellates naturally produced during the life cycle. Their wall is composed of a highly resistant organic material, which has a high potential to fossilize. Because dinocysts species are linked to particular abiotic and biotic parameters, the dinocyst assemblages provide information about past surface water conditions. Since each fjord has its own hydrographic setting, it is necessary to establish a firm link between the dinocyst composition of the sediment surface samples and the surface water conditions. Indeed the modern dinocyst distribution in subarctic fjords is little known. Thus, in addition to detailing dinocyst results from two shallow cores, several sediment surface samples located along a transect running from the head to the mouth of the fjord, and extending onto the shelf, are also presented.

Neogene palaeoceanographic and palaeoclimatic events inferred from palynological data: Cape Basin off South Africa, ODP Leg 175

Sites 1085, 1086 and 1087 were drilled off South Africa during Ocean Drilling Program (ODP) Leg 175 to investigate the Benguela Current System. While previous studies have focused on reconstructing the Neogene palaeoceanographic and palaeoclimatic history of these sites, palynology has been largely ignored, except for the Late Pliocene and Quaternary. This study presents palynological data from the upper Middle Miocene to lower Upper Pliocene sediments in Holes 1085A, 1086A and 1087C that provide complementary information about the history of the area. Abundant and diverse marine palynomorphs (mainly dinoflagellate cysts), rare spores and pollen, and dispersed organic matter have been recovered. Multivariate statistical analysis of dispersed organic matter identified three palynofacies assemblages (A, B, C) in the most continuous hole (1085A), and they were defined primarily by amorphous organic matter (AOM), and to a lesser extent black debris, structured phytoclasts, degraded phytoclasts, and marine palynomorphs. Ecostratigraphic interpretation based on dinoflagellate cyst, spore-pollen and palynofacies data allowed us to identify several palaeoceanographic and palaeoclimatic signals. First, the late Middle Miocene was subtropical, and sediments contained the highest percentages of land-derived organic matter, even though they are rich in AOM (palynofacies assemblage A). Second, the Late Miocene was cool-temperate and characterized by periods of intensified upwelling, increase in productivity, abundant and diverse oceanic dinoflagellate cysts, and the highest percentages of AOM (palynofacies assemblage C). Third, the Early to early Late Pliocene was warm-temperate with some dry intervals (increase in grass pollen) and intensified upwelling. Fourth, the Neogene "carbonate crash" identified in other southern oceans was recognized in two palynofacies A samples in Hole 1085A that are nearly barren of dinoflagellate cysts: one Middle Miocene sample (590 mbsf, 13.62 Ma) and one Upper Miocene sample (355 mbsf, 6.5 Ma). Finally, the extremely low percentages of pollen suggest sparse vegetation on the adjacent landmass, and Namib desert conditions were already in existence during the late Middle Miocene.