136 resultados para 1210


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A relatively complete lower Paleocene to lower Oligocene sequence was recovered from the Southern High of Shatsky Rise at Sites 1209, 1210, and 1211. The sequence consists of nannofossil ooze and clay-rich nannofossil ooze. Samples from these sites have been the target of intensive calcareous nannofossil biostratigraphic investigations. Calcareous nannofossils are moderately preserved in most of the recovered sequence, which extends from nannofossil Zones CP1 to CP16. Most traditional zonal markers are present; however, the rarity and poor preservation of key species in the uppermost Paleocene and lower Eocene inhibits zonal subdivision of part of this sequence.

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A pulse of intense carbonate dissolution occurred during the early late Paleocene at 58.4 Ma. A prominent 5 to 25 cm-thick dark brown clay-rich calcareous nannofossil ooze was found on Shatsky Rise at Sites 1209, 1210, 1211, and 1212 during Ocean Drilling Program Leg 198. The layer corresponds to the lower part of planktonic foraminiferal Zone P4 and coincides with the evolutionary first occurrence of the nannolith Heliolithus kleinpellii, an important component of late Paleocene assemblages and a marker for the base of Zone CP5. The clay-rich layer contains common crystals of phillipsite, fish teeth, and phosphatic micronodules and corresponds to a prominent peak in magnetic susceptibility that probably reflects these high amounts of detrital and authigenic materials. Detailed quantitative analysis of planktonic foraminiferal assemblages across the clay-rich nannofossil ooze layer shows that fundamental changes in faunal composition occurred before, during, and after deposition of the clay-rich ooze. Planktonic foraminifers in the clay-rich layer are characterized by a low-diversity, largely dissolved assemblage dominated by representatives of the genus Igorina (mainly Igorina tadjikistanensis and Igorina pusilla). Conversely, Igorina albeari, morozovellids, acarininids, globanomalinids, subbotinids, and chiloguembelinids are common below the clay-rich layer, almost disappear within it, and reappear in low abundances above the clay-rich layer. These changes in faunal compositions are likely a response to a change in carbonate saturation that caused increased dissolution on the seafloor owing to the shoaling of the lysocline and the carbonate compensation depth.

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A diverse assemblage of marine palynomorphs was recovered from the Oligocene - Miocene section of CRP-2/2A. Most of the assemblage is composed of previously unrecognised species. Three distinct groups of marine palynomorph were recognised: (1) prasinophytes, mainly Cymatiosphaera, (2) acritarchs, mainly Leiosphaeridia and Sigmopollis although Leiofusa is an important component of the bottom half of the hole, and (3) dinoflagellate cysts. About 27 species of in situ dinoflagellate cysts were recorded, of which seven apparently undescribed species of Lejeunecysta form a prominent component. Reworked specimens of several species of the Paleogene Transantarctic Flora occur in CRP-2/2A sediments. Several abundance peaks of reworked taxa from the Transantarctic Flora are recorded. Three marine palynomorph zones were recognised (MP3, MP2, MP1), considered to be early Oligocene, late Oligocene, and late Oligocene/early Miocene in age respectively. Samples from the Quaternary and Pliocene part of CRP-2/2A were also examined. These proved either barren or yielded very sparse low diversity floras.

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The Tara Oceans Expedition (2009-2013) was a global survey of ocean ecosystems aboard the Sailing Vessel Tara. It carried out extensive measurements of evironmental conditions and collected plankton (viruses, bacteria, protists and metazoans) for later analysis using modern sequencing and state-of-the-art imaging technologies. Tara Oceans Data are particularly suited to study the genetic, morphological and functional diversity of plankton. The present data set includes properties of seawater, particulate matter and dissolved matter that were measured from discrete water samples collected with Niskin bottles during the 2009-2013 Tara Oceans expedition. Properties include pigment concentrations from HPLC analysis (10 depths per vertical profile, 25 pigments per depth), the carbonate system (Surface and 400m; pH (total scale), CO2, pCO2, fCO2, HCO3, CO3, Total alkalinity, Total carbon, OmegaAragonite, OmegaCalcite, and dosage Flags), nutrients (10 depths per vertical profile; NO2, PO4, N02/NO3, SI, quality Flags), DOC, CDOM, and dissolved oxygen isotopes. The Service National d'Analyse des Paramètres Océaniques du CO2, at the Université Pierre et Marie Curie, determined CT and AT potentiometrically. More than 200 vertical profiles of these properties were made across the world ocean. DOC, CDOM and dissolved oxygen isotopes are available only for the Arctic Ocean and Arctic Seas (2013).

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The greater part of this Monograph is devoted to detailed descriptions of 1426 samples of deposits from the floor of the Atlantic Ocean stored in the Challenger Office, Edinburgh, which had been collected during thirty-five cruising expeditions between 1857 and 1911. The remaining part discusses the results of the work. The work of examining and describing in detail this abundant mass of material was in progress when the late Sir JOHN MURRAY met his death in March 1914. By that time about three-fourths of the descriptive work had been completed under his supervision. Sir John's trustees arranged for the completion of the descriptive work by Mr Chumley, and this was done in the Challenger Office during the two succeeding years. Later, after he had removed to Glasgow, Mr Chumley prepared the notes discussing the results. The trustees have pleasure in recording, on the suggestion of Mr Chumley, the courtesy of Dr G. W. Lee of the Geological Survey of Scotland, for help in determining many of the rarer mineral particles contained in the deposits.

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We present new isotopic and micropaleontological data from a depth transect on Shatsky Rise that record the response of the tropical Pacific to global biotic and oceanographic shifts during the mid-Maastrichtian. Results reveal a coupling between the upper ocean, characterized by a weak thermocline and low to intermediate productivity, and intermediate waters. During the earliest Maastrichtian, oxygen and neodymium isotope data suggest a significant contribution of relatively warm intermediate water from the North Pacific. Isotopic shifts through the early Maastrichtian suggest that this warmer water mass was gradually replaced by cooler waters originating in the Southern Ocean. Although the cooler water mass remained dominant through the remainder of the Maastrichtian, it was displaced intermittently at shallow intermediate depths by North Pacific intermediate water. The globally recognized "mid-Maastrichtian event" ~69 Ma, manifested by the brief appearance of abundant inoceramid bivalves over shallow portions of Shatsky Rise, is characterized by an abrupt increase (~2°-3°C) in sea surface temperatures, a greater flux of organic matter out of the surface ocean, and warmer (~4°C) intermediate waters. Results implicate simultaneous changes in surface waters and the sources/distribution patterns of intermediate water masses as an underlying cause for widespread biotic and oceanographic changes during mid-Maastrichtian time.