New Pliocene and Pleistocene acritarchs from the North Atlantic, Arctic Ocean and Bering Sea

Acritarchs have received limited attention in palynological studies of the Cenozoic, although they have much potential both for refining Neogene and Quaternary stratigraphy, especially in mid- and high northern latitudes, and developing palaeoceanographical reconstructions. Here we formally describe and document the stratigraphical and palaeotemperature ranges (from foraminiferal Mg/Ca) of four new acritarch species: Cymatiosphaera? aegirii sp. nov., Cymatiosphaera? fensomei sp. nov., Cymatiosphaera? icenorum sp. nov. and Lavradosphaera canalis sp. nov. In reviewing the stratigraphical distributions of all species of the genus Lavradosphaera De Schepper & Head, 2008, we demonstrate their correlation potential between the North Atlantic and Bering Sea in the Pliocene. Additionally, Lavradosphaera lucifer De Schepper & Head, 2008 and Lavradosphaera canalis sp. nov., while not themselves overlapping stratigraphically, have morphological intermediates that do partially overlap and may represent an evolutionary trend consequent upon climate cooling in the Late Pliocene. Finally, we show that the highest abundances of the acritarchs presented here were living in the eastern North Atlantic, in surface-water temperatures not very different from today.

Relative abundance and ranges of selected diatoms from Pliocene-Pleistocene sections of ODP Leg 177, Atlantic sector of the Southern Ocean

During Ocean Drilling Program (ODP) Leg 177, seven sites were drilled aligned on a transect across the Antarctic Circumpolar Current in the Atlantic sector of the Southern Ocean. The primary scientific objective of Leg 177 was the study of the Cenozoic paleoceanographic and paleoclimatic history of the southern high latitudes and its relationship with the Antarctic cryosphere development. Of special emphasis was the recovery of Pliocene-Pleistocene sections, allowing paleoceanographic studies at millennial or higher time resolution, and the establishment of refined biostratigraphic zonations tied to the geomagnetic polarity record and stable isotope records. At most sites, multiple holes were drilled to ensure complete recovery of the section. A description of the recovered sections and the construction of a multihole splice for the establishment of a continuous composite is presented in the Leg 177 Initial Reports volume for each of the sites (Gersonde, Hodell, Blum, et al., 1999). Here we present the relative abundance pattern and the stratigraphic ranges of diatom taxa encountered from shore-based light microscope studies completed on the Pliocene-Pleistocene sequences from six of the drilled sites (Sites 1089-1094). No shore-based diatom studies have been conducted on the Pliocene-Pleistocene sediments obtained at Site 1088, located on the northern crest of the Agulhas Ridge, because of the scattered occurrence and poor preservation of diatoms in these sections (Shipboard Scientific Party, 1999b). The data included in our report present the baseline of a diatom biostratigraphic study of Zielinski and Gersonde (2002), which (1) includes a refinement of the southern high-latitude Pliocene-Pleistocene diatom zonation, in particular for the middle and late Pleistocene, and (2) presents a biostratigraphic framework for the establishment of age models of the recovered sediment sections. Zielinski and Gersonde (2002) correlated the diatom ranges with the geomagnetic polarity record established shipboard (Sites 1090 and 1092) (Shipboard Scientific Party, 1999c, 1999d) and on shore (Sites 1089, 1091, 1093, and 1094) by Channell and Stoner (2002). The Pliocene-Pleistocene diatom zonation proposed by Zielinski and Gersonde (2002) relies on a diatom zonation from Gersonde and Bárcena (1998) for the northern belt of the Southern Ocean. Because of latitudinal differentiation of sea-surface temperature, nutrients, and salinity between Antarctic and Subantarctic/subtropical water masses, the Pliocene-Pleistocene stratigraphic marker diatoms are not uniformly distributed in the Southern Ocean (Fenner, 1991; Gersonde and Bárcena, 1998). As a consequence, Zielinski and Gersonde (2002) propose two diatom zonations for application in the Antarctic Zone south of the Polar Front (Southern Zonation, Sites 1094 and 1093) and the area encompassing the Polar Front Zone (PFZ) and the Subantarctic Zone (Northern Zonation, Sites 1089-1092). This accounts especially for the Pleistocene zonation where Hemidiscus karstenii, whose first abundant occurrence datum and last occurrence datum defines the subzonation of the northern Thalassiosira lentiginosa Zone, occurs only sporadically in the cold-water realm south of the PFZ and thus is not applicable in sections from this area. However, newly established marker species assigned to the genus Rouxia (Rouxia leventerae and Rouxia constricta) are more related to cold-water environments and allow a refinement of the Pleistocene stratigraphic zonation for the southern cold areas. A study relying on quantitative counts of both Rouxia species confirms the utility of these stratigraphic markers for the identification of sequences attributed to marine isotope Stages 6 and 8 in the southern Southern Ocean (Zielinski et al., 2002).

Sedimentological, physical, bulk geochemical, elemental and rock magnetic properties of the Middle to Late Pleistocene Rodderberg (Eifel/Germany)

The sediment record from Rodderberg potentially provides a climate and environmental record spanning at least the last ca 130 ka. Results from a low resolution pilot study reveal characteristic fluctuations that can be related to global climate variability as reflected in marine isotope stages and document the potential of this site for continuous and high-resolution investigations of the Middle to Late Pleistocene. Here we document the tentative lithology drilled, and show how the elemental composition can be interpreted with regard to lake level fluctuations, related redox conditions, but also to grain-size distribution and changes in lacustrine productivity. Finally, based on major lithological changes, a preliminary depth/age model is suggested that allows reassessing published luminescence ages from the same site.

Mineralogy and nannoplankton distribution in ODP Hole 194-1195A

Significant synchronous shifts in the chemistry, mineralogy, grain sizes and color of the sediments at 6 m below sea floor (mbsf) at ODP Site 1195 on the Marion Plateau (NE Australia) are interpreted to reflect a major regional paleoceanographic change: the initiation of the southern province of the Great Barrier Reef (GBR). The onset of this massive carbonate production centre nearby resulted primarily in increased deposition of carbonate-rich sediments of neritic origin. Both sedimentation rate and terrigenous input record a coincident decline attributed to inshore trapping of materials behind the reefs. Our best estimate places the development of reef framework in the southern part of the GBR between 560 and 670 kyr B.P., based on an age model combining magnetostratigraphic and biostratigraphic data. The proposed estimation agrees with previous studies reporting an age between 500 and 930 kyr B.P., constraining more tightly their results. However, it does not support research placing the birth of the GBR in Marine Isotope Stage (MIS) 11 (~400 kyr), nor the theory of a worldwide modern barrier reef development at that time.

Description and chemical composition of the fossil manganese nodules of the Cambrian manganese deposits of Conception and Trinity bays, Newfoundland

This paper is based upon data collected during the summers of 1912 and 1913. Mr. A. O. Hayes and Prof. van Ingen of Princeton University, while making a study of the general geology, stratigraphy, and palaeontology of the shores of Conception Bay, Newfoundland, came upon the manganiferous rocks of the Lower Cambrian exposed at Manuels, Topsail, Brigus, and other places. The following summer, of 1913, the writer as a member of the Princeton Newfoundland Expedition undertook a more detailed study of these deposits. In this paper therefore there has been an attempt to present as comprehensive a study of the manganese of southeastern Newfoundland. It is primarily chemical in its nature and the analyses herewith presented are from samples taken from the principal manganese-bearing beds.

A refined Pliocene to early Pleistocene chronostratigraphic frame at ODP Hole 653A (West Mediterranean)

Two planktonic foraminiferal oxygen isotope records of ODP Hole 653A (Tyrrhenian Sea) are presented for the time period extending from approximately 0.8 to 3.0 Ma. Six, generally accepted, synchronous bioevents were used to precise the oxygen isotope chronology and to identify the oxygen isotope stages 22 down to 114. Subsequently, this oxygen isotope chronology was used to determine the synchronism or diachronism of various other biostratigraphic events with those recorded in the Singa and Ficarazzi land sections (Italy) and those in other DSDP/ODP sites. New results concern the diachronity of the FOD of the planktonic foraminiferal species N. atlantica, G.truncatulinoides truncatulinoides and G. inflata between ODP Hole 653A and the Italian landsections. Because many species entered the Mediterranean in short term fluxes, strongly related to the southward migration of cool North Atlantic surface waters, their time distribution through the Pliocene-Pleistocene generally corresponds to alternated intervals of presence and absence. This should explain most of the apparently diachronous appearances and disappearances. Alternating presence-absence patterns are of less importance for the various nannofossil events. The LOD of D. surculus occurs during the transition of stage 100 to 101 in both ODP Hole 653A and the Singa section, which is in perfect agreement with the disappearance of this species from the open ocean. The LOD of D. pentaradiatus in the Mediterranean occurs in stages 100-99, which seems to be consistent with the extinction of this species in the southern Hemisphere. G. oceanica, which corresponds to the 4 µm < Gephyrocapsa spp <5.5 µm is recorded in stages 65 to 64 at ODP Hole 653A. The Gephyrocapsa spp. >5.5 µm first occurred in stage 51 at Hole 653A, which fits within the uncertainty interval for this event stretching from stage 51 to 47 in the open ocean and seems therefore a useful tool for conventional biostratigraphy in the Mediterranean.