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Datasets with PANGAEA technical keyword @acex302pc
Mostrando recursos 1 - 20 de 62
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Consolidation tests, elastic properties and grain size mesurements at the consolidations samples from different Holes of IODP Expedition 302 - O'Regan, Matthew; Moran, K; Baxter, CDP; Cartwright, J; Vogt, Christoph; Kölling, Martin
The Integrated OceanDrilling Program's Expedition 302, the Arctic Coring Expedition (ACEX), recovered the first Cenozoic sedimentary sequence from the central Arctic Ocean. ACEX provided ground truth for basin scale geophysical interpretations and for guiding future exploration targets in this largely unexplored ocean basin. Here, we present results from a series of consolidation tests used to characterize sediment compressibility and permeability and integrate these with high-resolution measurements of bulk density, porosity and shear strength to investigate the stress history and the nature of prominent lithostratigraphic and seismostratigraphic boundaries in the ACEX record. Despite moderate sedimentation rates (10-30m Myr**-1) and high permeability...
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Abundances and ebridian skeleton contents from IODP Exp302 - Onodera, Jonaotaro; Takahashi, Kozo
Abundant and diversified ebridians recovered during IODP Expedition 302 (ACEX) have been identified and counted in order to establish their taxonomy and to decipher the biostratigraphic potential of ebridians in the central Arctic Ocean. In the ACEX samples these fossils are preserved in Lithologic Units 1/6 and 2, which consist mainly of dark silty clay and biosiliceous ooze, respectively. Thirty taxa have been distinguished, three of which are described as new species (Ammmodochium lomonosovense, Pseudammodochium karyon, and pseudammodochium psichion). The most dominant ebridian species is Pseudammodochium dictyoides throughout the biosiliceous section. The second dominant species varies alternately throughout the section....
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Abundances and contents of major silicoflagellates from IODP Holes of Exp302 - Onodera, Jonaotaro; Takahashi, Kozo
The silicoflagellate taxa obtained in IODP Expedition 302 (ACEX) were identified and counted in order to establish the silicoflagellate biostratigraphy in the central Arctic Ocean. These microfossils in the ACEX samples were preserved in the Lithology Units 1/6 and 2, which are dark silty clay and biosiliceous ooze, respectively. The silicoflagellate skeletons in the ACEX samples are assigned to 56 taxa. Seven taxa were described as new species, which were abundant in Lithology Unit 2. Comparison with several study cases outside the Eocene Arctic Ocean suggested that the silicoflagellate assemblages in ACEX were unique in Lithology Unit 2. The dominance...
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(Table 2) Geochemical analysis from IODP Exp302 - Ogawa, Yusuke; Takahashi, Kozo; Yamanaka, Toshiro
Geochemical analyses of biogenic opal, total organic carbon (TOC), total sulfur (TS), and stable sulfur isotopic composition were conducted on the middle Eocene section of the ACEX cores obtained by IODP Expedition 302. The analyzed %TS contents were high in all the examined intervals, indicating sufficient sea water was present in the deep layer of the paleo Arctic basin in contrast with the low salinity surface waters determined by freshwater siliceous microfossils. From the high %TS in Lithological Unit 1/6, the extent of sea water supply from outside of the Arctic basin appeared to have increased after 45 Ma. The...
12.
Major and trace element concentrations of sediments from the IODP Exp302 sites - Martinez, Nahysa C; Murray, Richard W; Dickens, Gerald Roy; Kölling, Martin
We analyzed a suite of sediment samples recovered in the central Arctic Ocean for major, trace, and rare earth elements in order to assess changes in terrigenous source material throughout the Cenozoic. The terrigenous component consists of two end-members. Input from a shale-like composition dominates bulk sediments, especially those deposited during the Paleocene and since the Miocene, and may represent sediment supply from the eastern Laptev Sea. Therefore, even though the environment and transport mechanisms may have varied from ice free to ice dominated, sequences of the early Paleogene and later Neogene appear to have been influenced by a single...
15.
Nd-Sr isotopes in fossil fish debris from IODP Exp302 - Gleason, James D; Thomas, Deborah J; Moore, Theodore C; Blum, Joel D; Owen, Robert M; Haley, Brian A
Strontium and neodymium radiogenic isotope ratios in early to middle Eocene fossil fish debris (ichthyoliths) from Lomonosov Ridge (Integrated Ocean Drilling Program Expedition 302) help constrain water mass compositions in the Eocene Arctic Ocean between 55 and 45 Ma. The inferred paleodepositional setting was a shallow, offshore marine to marginal marine environment with limited connections to surrounding ocean basins. The new data demonstrate that sources of Nd and Sr in fish debris were distinct from each other, consistent with a salinity-stratified water column above Lomonosov Ridge in the Eocene. The 87Sr/86Sr values of ichthyoliths (0.7079 - 0.7087) are more radiogenic...
17.
Freshwater fern Azolla in and around Arctic and Nordic seas - Barke, Judith; van der Burgh, Johan; van Konijnenburg-van Cittert, Johanna H A; Collinson, Margaret E; Pearce, Martin A; Bujak, Jonathan; Heilmann-Clausen, Claus; Speelman, Eveline N; van Kempen, Monique M L; Reichart, Gerd-Jan; Lotter, André F; Brinkhuis, Henk
For a short time interval (c. 1.2 Myr) during the early middle Eocene (~49 Myr), the central Arctic Ocean was episodically densely covered by the freshwater fern Azolla, implying sustained freshening of surface waters. Coeval Azolla fossils in neighboring Nordic seas were thought to have been sourced from the Arctic. The recognition of a different Azolla species in the North Sea raised doubts about this hypothesis. Here we show that no less than five Azolla species had coeval blooms and spread in the Arctic and NW European regions. A likely trigger for these unexpected Azolla blooms is high precipitation prevailing...
20.
Geochemistry and mineralogy of Eocene-Oligocene sediments of IODP Hole 302-M0002A - März, Christian; Vogt, Christoph; Schnetger, Bernhard; Brumsack, Hans-Jürgen
In 2004, Integrated Ocean Drilling Program Expedition 302 (Arctic Coring Expedition, ACEX) to the Lomonosov Ridge drilled the first Central Arctic Ocean sediment record reaching the uppermost Cretaceous (~430 m composite depth). While the Neogene part of the record is characterized by grayish-yellowish siliciclastic material, the Paleogene part is dominated by biosiliceous black shale-type sediments. The lithological transition between Paleogene and Neogene deposits was initially interpreted as a single sedimentological unconformity (hiatus) of ~26 Ma duration, separating Eocene from Miocene strata. More recently, however, continuous sedimentation on Lomonosov Ridge throughout the Cenozoic was proclaimed, questioning the existence of a hiatus....
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