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doi:10.2204/iodp.proc.347.108.2015 BiostratigraphyDiatomsQualitative analysis of diatom community composition was carried out on one sample from Site M0064 (Table T2). Sample 347-M0064A-1H-1, 0 cm, contains a typical Baltic Sea assemblage (Andrén et al., 2000; Snoeijs et al., 1993–1998). This assemblage contains both diatoms and chrysophycean cysts. All other samples from Hole M0064A and all samples from Holes M0064B and M0064C, including core tops, were barren of siliceous microfossils. Reworked Cretaceous foraminifers and coccolithophorids were found in Section 347-M0064C-3H-2, 0 cm. Foraminifers and ostracodsA total of 29 samples (21 taken offshore from core catchers and 8 from regular sections during the Onshore Science party [OSP]) from Site M0064 were prepared for foraminiferal and ostracod analysis. Foraminifers do not occur in the sediments sampled at this site. The lack of foraminifers suggests that low oxygen and/or salinity may have prevented the occurrence of foraminifers in the basin. Almost no microfossils >63 µm were present, even in the upper dark brown sediment (Unit I, Core 1, Section 1 in each hole), potentially suggesting low-oxygen conditions, a theory supported by the laminated nature of sediments in this interval (see “Lithostratigraphy”). However, a few testate amoebae occurred in Sample 347-M0064D-1H-1, 15–17 cm. Only one juvenile ostracod valve of Paracyprideis sp. was found at this site at 0.16 mbsf in Hole M0064D; the sediments were otherwise barren with respect to ostracods. Palynological resultsSite M0064 is situated in the central part of the southern Baltic Sea. The vegetation of the borderlands in that region belongs to the cool temperate forest zone with mixed coniferous and deciduous trees. However, the boreal-forest vegetation zone is very close to the site. The palynological analyses for this site were carried out on Hole M0064A. A total of 12 samples from Hole M0064A were analyzed (see PalyM0064.xls in PALYNOLOGY in “Supplementary material”). However, the palynomorphs in all samples appeared to have been degraded/oxygenated to a high degree, and no sample contained enough palynomorphs in situ to yield statistically relevant data. Only five samples contained in situ pollen preserved well enough to identify nonsaccate pollen. The pollen concentration per cubic centimeter varied from 0 to ~1000 grains, which is a factor 500 to 1000 lower than the concentration encountered in samples with good preservation at other sites. Two samples from the depth interval of ~6.5–8.5 mbsf contain a few Pinus (pine), Picea (spruce), Betula (birch), Juniperus (juniper), and Quercus (oak) pollen grains. The sample at ~6.5 mbsf furthermore contains several steppe element pollen grains (Artemisia/Chenopodiacea). This assemblage may imply a late glacial/early Holocene age, but as stated above, the statistical relevance of the data is too low for a reliable age estimate. Samples deeper than ~15 mbsf contain high amounts of degraded material, and there were often more reworked than in situ pollen. In Sample 347-M0064A-12H-CC, the number of reworked dinoflagellate cysts surpassed that of reworked pollen grains. Some of these cysts could be identified to the genus level and thus allowed age estimation for the reworked material. The genera comprise Apectodinium, Wetzeliella, and Charlesdowniea (Fig. F4). The reworked material thus is of Paleogene origin (Powell, 1992; K. Dybkjær, pers. comm., 2014). Reworked pollen includes Picea and Pinus as well as Carya pollen grains. |
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