The Stratigraphy of Neogene Silicoflagellates from the Norwegian Sea, ODP Leg 104

Ciesielski, Paul F; Hasson, Phyllis F.; Turner, J.W.

doi:10.2973/odp.proc.sr.104.164.1989

Cited by 7 publications

(2 citation statements)

References 13 publications

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“…A general continued cooling trend eventually reaches the threshold of freezing, setting in motion the powerful positive albedo feedback from snow and ice. Already thirty years ago, Opdyke et al (1966) suggested that "southern-hemisphere glaciation was initiated about 2.5 million years ago", that is, they noticed a strong increase in ice-rafted debris in their piston cores, shortly after 3 Ma (for details, see Barker, Kennett, et al 1990;Bleil and Thiede 1990;Ciesielski, Kristoffersen, et al 1991 ). Thus, we should expect oscillations when the treshold of freezing is just exceeded, as observed.…”

Section: The Third Great Cooling Step: the Northern Hemisphere Entersmentioning

confidence: 99%

Expeditions into the Past: Paleoceanographic Studies in the South Atlantic

1996

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The South Atlantic is tightly coupled to the North Atlantic climate amplifying system. At present, enormous amounts of heat are delivered across the equator to the north, with surface and subsurface waters. The return flow occurs at depth, within the coldwater sphere. During the last glacial the Atlantic Heat Conveyor was much less efficient, that is, the North Atlantic heat piracy is a positive feedback on climate change. This positive feedback is an important ingredient in the orbitally driven climate cycles. The current (that is, late Quaternary) conditions in the South Atlantic are the result of a long evolution of climate and geographic boundary conditions, which started with the opening of the basin at the end of the Jurassic and in the early Cretaceous, by continental breakup and seafloor spreading. Todays margins contain the ancient deposits of a narrow trough with restricted access, including evaporites. Warm-ocean sediments accumulated during the Cretaceous, including organic-rich deposits indicative of poorly oxygenated deep waters. Sinking of the sea floor from cooling of the lithosphere, and ridges produced as hot spot tracks (from Tristan da Cunha on the Mid-Atlantic Ridge) determined the main features of the bathym~try. The leitmotifs of Cenozoic evolution are general cooling (from mountain building and associated regression, and from reduction of atmospheric CO 2 ), the closure of the world-encircling tropical Tethys Ocean and opening of passages in the south, linking ocean basins through a circumpolar Cold Ring. Overall regression and associated polar deepwater production forced new patterns of biogenous deposition which resulted in a large-scale global drop of the Carbonate Compensation Depth (CCD) about 40 million years ago. At th~ same time, the isotopic ratio in the element strontium in seawater (as captured by calcareous fossils) started a long trend toward more radiogenic values, indicating increased supply of continental material. The major reorganization in deepsea sediments (the Auversian Facies Shift) in the late Eocene is also expressed as the onset of deposition of rather pure pelagic carbonates, with opaline and organic-rich sediments being increasingly restricted to ocean margins. Continued cooling eventually led to large-scale deepwater formation in high latitudes, which 'is expressed in the first great cooling step in the deep sea, at the end of the Eocene. The second great cooling step saw the buildup of ice on Antarctica, roughly 15 million years ago, presumably after considerable reduction of atmospheric CO 2 , The third great cooling step consists of ice buildup around the North Atlantic, a step that moved the sY:i,c::m into modem climate dynamics. Concerning the third step, it is commonly surmised that the closing of the Panama Straits was responsible for its timing (about 3 million years ago). We propose (Panama Hypothesis) exactly the reverse: in fact, the emergence ofthe Isthmus greatly favored North Atlantic heat piracy, so that northern glaciations were delayed by severa...

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Section: The Third Great Cooling Step: the Northern Hemisphere Entersmentioning

confidence: 99%

Expeditions into the Past: Paleoceanographic Studies in the South Atlantic

1996

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“…Scientific drilling was conducted adjacent to transform margins during DSDP Leg 36 (Barker, Dalziel et al, 1976) and ODP Leg 114 (Ciesielski, Kristofferson, et al, 1988) in the Falkland area and ODP Leg 122 in the Exmouth Plateau (Haq, von Rad, O'Connell, et al, 1990).…”

Section: Introductionmentioning

confidence: 99%

The Cote d'Ivoire-Ghana Transform Margin Eastern Equatorial Atlantic

Mascle¹,

Lohmann²,

Clift³

1994

ODP Scientific Prospectus

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Expedition 396 methods

Berndt¹,

Zarikian²,

Agarwal³

et al. 2023

Proceedings of the International Ocean Discovery Program

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publications.iodp.org • 3 known because of the deviation of the pipe below the ship, which can vary depending on water currents, tides, and water depth; the hole position is thus known typically within 10 m accuracy.Drilling sites were numbered according to the series that began with the first site drilled by the D/V Glomar Challenger in 1968. Starting with Integrated Ocean Drilling Program Expedition 301, the prefix "U" designates sites occupied by JOIDES Resolution. When drilling multiple holes at a site, hole locations are typically offset from each other by ~20 m. During Expedition 396, we offset holes at an average of 115 m, except for Site U1570, where holes were offset as far as 1772 m. Site U1570 was approved by EPSP as a 2 km long "ribbon" or transect west of Site U1569 with start and end coordinates. This ribbon provided an alternate coring strategy to Site U1569, where deep stratigraphic targets were outcropping at shallower subseafloor depths. A letter suffix distinguishes each hole drilled at the same site. The first hole drilled is assigned the site number modified by the suffix "A," the second hole takes the site number and the suffix "B," and so forth. During Expedition 396, 21 holes were drilled at 10 sites (U1565-U1574; see Figure F4 in the Expedition 396 summary chapter [Planke et al., 2023a]).

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The Stratigraphy of Neogene Silicoflagellates from the Norwegian Sea, ODP Leg 104

Cited by 7 publications

References 13 publications

Expeditions into the Past: Paleoceanographic Studies in the South Atlantic

Expeditions into the Past: Paleoceanographic Studies in the South Atlantic

The Cote d'Ivoire-Ghana Transform Margin Eastern Equatorial Atlantic

Expedition 396 methods

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