scholarly journals Late Eocene–early Miocene evolution of the southern Australian subtropical front: a marine palynological approach

2021 ◽  
Vol 40 (2) ◽  
pp. 175-193
Author(s):  
Frida S. Hoem ◽  
Isabel Sauermilch ◽  
Suning Hou ◽  
Henk Brinkhuis ◽  
Francesca Sangiorgi ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Late Eocene ◽  
Early Miocene ◽  
Ocean Drilling Program ◽  
Subtropical Front ◽  
Leeuwin Current ◽  
Ocean Drilling ◽  
Early Oligocene ◽  
Integrated Ocean Drilling Program ◽  
Oceanographic Conditions

Abstract. Improvements in our capability to reconstruct ancient surface-ocean conditions based on organic-walled dinoflagellate cyst (dinocyst) assemblages from the Southern Ocean provide an opportunity to better establish past position, strength and oceanography of the subtropical front (STF). Here, we aim to reconstruct the late Eocene to early Miocene (37–20 Ma) depositional and palaeoceanographic history of the STF in the context of the evolving Tasmanian Gateway as well as the potential influence of Antarctic circumpolar flow and intense waxing and waning of ice. We approach this by combining information from seismic lines (revisiting existing data and generating new marine palynological data from Ocean Drilling Program (ODP) Hole 1168A) in the western Tasmanian continental slope. We apply improved taxonomic insights and palaeoecological models to reconstruct the sea surface palaeoenvironmental evolution. Late Eocene–early Oligocene (37–30.5 Ma) assemblages show a progressive transition from dominant terrestrial palynomorphs and inner-neritic dinocyst taxa as well as cysts produced by heterotrophic dinoflagellates to predominantly outer-neritic/oceanic autotrophic taxa. This transition reflects the progressive deepening of the western Tasmanian continental margin, an interpretation supported by our new seismic investigations. The dominance of autotrophic species like Spiniferites spp. and Operculodinium spp. reflects relatively oligotrophic conditions, like those of regions north of the modern-day STF. The increased abundance in the earliest Miocene of Nematosphaeropsis labyrinthus, typical for modern subantarctic zone (frontal) conditions, indicates a cooling and/or closer proximity of the STF to the site . The absence of major shifts in dinocyst assemblages contrasts with other records in the region and suggests that small changes in surface oceanographic conditions occurred during the Oligocene. Despite the relatively southerly (63–55∘ S) location of Site 1168, the rather stable oceanographic conditions reflect the continued influence of the proto-Leeuwin Current along the southern Australian coast as Australia continued to drift northward. The relatively “warm” dinocyst assemblages at ODP Site 1168, compared with the cold assemblages at Antarctic Integrated Ocean Drilling Program (IODP) Site U1356, testify to the establishment of a pronounced latitudinal temperature gradient in the Oligocene Southern Ocean.

scholarly journals IODP Expedition 318: From Greenhouse to Icehouse at the Wilkes Land Antarctic Margin

2011 ◽  
Vol 12 ◽  
pp. 15-23 ◽  
Author(s):  
C. Escutia ◽  
H. Brinkhuis ◽  
A. Klaus ◽  
Keyword(s):  
Middle Eocene ◽  
Second Phase ◽  
Last Deglaciation ◽  
Ocean Drilling Program ◽  
Ocean Drilling ◽  
Integrated Ocean Drilling Program ◽  
Tectonic History ◽  
Wilkes Land ◽  
History Of

Integrated Ocean Drilling Program (IODP) Expedition 318, Wilkes Land Glacial History, drilled a transect of sites across the Wilkes Land margin of Antarctica to provide a long-term record of the sedimentary archives of Cenozoic Antarctic glaciation and its intimate relationships with global climatic and oceanographic change. The Wilkes Land drilling program was undertaken to constrain the age, nature, and paleoenvironment of the previously only seismically inferred glacial sequences. The expedition (January–March 2010) recovered ~2000 meters of high-quality middle Eocene–Holocene sediments from water depths between 400 m and 4000 m at four sites on the Wilkes Land rise (U1355, U1356, U1359, and U1361) and three sites on the Wilkes Land shelf (U1357, U1358, and U1360). <br><br> These records span ~53 million years of Antarctic history, and the various seismic units (WL-S4–WL-S9) have been successfully dated. The cores reveal the history of the Wilkes Land Antarctic margin from an ice-free “greenhouse” Antarctica, to the first cooling, to the onset and erosional consequences of the first glaciation and the subsequent dynamics of the waxing and waning ice sheets, all the way to thick, unprecedented "tree ring style" records with seasonal resolution of the last deglaciation that began ~10,000 y ago. The cores also reveal details of the tectonic history of the Australo-Antarctic Gulf from 53 Ma, portraying the onset of the second phase of rifting between Australia and Antarctica, to ever-subsiding margins and deepening, to the present continental and ever-widening ocean/continent configuration. <br><br> doi:<a href="http://dx.doi.org/10.2204/iodp.sd.12.02.2011" target="_blank">10.2204/iodp.sd.12.02.2011</a>

scholarly journals IODP Expedition 335: Deep Sampling in ODP Hole 1256D

2012 ◽  
Vol 13 ◽  
pp. 28-34 ◽  
Author(s):  
D. A. H. Teagle ◽  
B. Ildefonse ◽  
P. Blum ◽  
Keyword(s):  
Theoretical Models ◽  
Spreading Rate ◽  
Ocean Crust ◽  
Ocean Drilling Program ◽  
Drill Cuttings ◽  
Ocean Drilling ◽  
Ocean Ridges ◽  
Integrated Ocean Drilling Program ◽  
Geological Conditions ◽  
Ocean Lithosphere

Observations of the gabbroic layers of untectonized ocean crust are essential to test theoretical models of the accretion of new crust at mid-ocean ridges. Integrated Ocean Drilling Program (IODP) Expedition 335 ("Superfast Spreading Rate Crust 4") returned to Ocean Drilling Program (ODP) Hole 1256D with the intention of deepening this reference penetration of intact ocean crust a significant distance (~350 m) into cumulate gabbros. Three earlier cruises to Hole 1256D (ODP 206, IODP 309/312) have drilled through the sediments, lavas, and dikes and 100 m into a complex dike-gabbro transition zone. <br><br> Operations on IODP Expedition 335 proved challenging throughout, with almost three weeks spent re-opening and securing unstable sections of the hole. When coring commenced, the comprehensive destruction of the coring bit required further remedial operations to remove junk and huge volumes of accumulated drill cuttings. Hole-cleaning operations using junk baskets were successful, and they recovered large irregular samples that document a hitherto unseen sequence of evolving geological conditions and the intimate coupling between temporally and spatially intercalated intrusive, hydrothermal, contact-metamorphic, partial melting, and retrogressive processes. <br><br> Hole 1256D is now clean of junk, and it has been thoroughly cleared of the drill cuttings that hampered operations during this and previous expeditions. At the end of Expedition 335, we briefly resumed coring before undertaking cementing operations to secure problematic intervals. To ensure the greatest scientific return from the huge efforts to stabilize this primary ocean lithosphere reference site, it would be prudent to resume the deepening of Hole 1256D in the nearest possible future while it is open to full depth. <br><br> doi:<a href="http://dx.doi.org/10.2204/iodp.sd.13.04.2011" target="_blank">10.2204/iodp.sd.13.04.2011</a>

Late Neogene–Quaternary Planktic Foraminiferal Biostratigraphy and Biochronology from ODP Site 807A, Ontong Java Plateau, Western Equatorial Pacific

2020 ◽  
Vol 50 (2) ◽  
pp. 111-127
Author(s):  
Tushar Kaushik ◽  
Ashutosh Kumar Singh ◽  
Devesh Kumar Sinha
Keyword(s):  
Equatorial Pacific ◽  
Ocean Drilling Program ◽  
Ontong Java Plateau ◽  
Faunal Turnover ◽  
Ocean Drilling ◽  
Late Neogene ◽  
Western Equatorial Pacific ◽  
Globorotalia Truncatulinoides ◽  
Oceanographic Conditions ◽  
Foraminiferal Biostratigraphy

ABSTRACT A biostratigraphic and biochronological study from the late Neogene–Quaternary section of Ocean Drilling Program (ODP) Site 807A, located on the Ontong Java Plateau, western equatorial Pacific, revealed 50 planktic foraminiferal events, enabling the identification of eight late Neogene–Quaternary biozones, from the Globorotalia plesiotumida Interval Zone to the Globorotalia truncatulinoides Interval Zone. A significant faunal turnover (17 events) from late Pliocene identified in cores 7 and 8, between 70 and 55 meters below seafloor (mbsf), and spanning 0.67 million years (Myr). This noteworthy turnover may be the result of a shift in oceanographic conditions pertaining to the closure of the Indo–Pacific Seaway, followed by the Northern Hemisphere Glaciation. This study provides a high resolution biostratigraphic and biochronological framework for ODP Site 807A that will aid in correlation and timing the various paleoceanographic changes over the last 6 million years in the western equatorial Pacific.

High resolution CO2 record of the great Plio-Pleistocene glaciations using boron isotopes

2020 ◽  
Author(s):  
Rachel Brown ◽  
Thomas Chalk ◽  
Paul Wilson ◽  
Eelco Rohling ◽  
Gavin Foster
Keyword(s):  
High Resolution ◽  
Northern Hemisphere ◽  
Large Scale ◽  
Boron Isotope ◽  
Ocean Drilling Program ◽  
Proxy Record ◽  
Ocean Drilling ◽  
Integrated Ocean Drilling Program ◽  
Great Transition ◽  
Adequate Test

&lt;p&gt;The intensification of Northern Hemisphere glaciation (iNHG) at 3.4-2.5 million years ago (Ma) represents the last great transition in Cenozoic climate state with the development of large scale ice sheets in the Northern Hemisphere that waxed and waned with changes in insolation. Declining atmospheric CO&lt;sub&gt;2&lt;/sub&gt; levels are widely suggested to have been the main cause of iNHG but the CO&lt;sub&gt;2&lt;/sub&gt; proxy record is too poorly resolved to provide an adequate test of this hypothesis. The boron isotope-pH proxy, in particular, has shown promise when it comes to accurately estimating past CO&lt;sub&gt;2&lt;/sub&gt; concentrations and is very good at reconstructing relative changes in CO&lt;sub&gt;2&lt;/sub&gt; on orbital timescales. Here we present a new orbitally resolved record of atmospheric CO&lt;sub&gt;2 &lt;/sub&gt;(1 sample per 3 kyr) change from Integrated Ocean Drilling Program Site 999 (12.74&amp;#730;N, -78.74 &amp;#730;E) spanning ~2.6&amp;#8211;2.4&amp;#160;Ma based on the boron isotope (&amp;#948;&lt;sup&gt;11&lt;/sup&gt;B) composition of planktic foraminiferal calcite, &lt;em&gt;Globingerinoides ruber&lt;/em&gt; (senso stricto, white). &amp;#160;We find that &amp;#948;&lt;sup&gt;11&lt;/sup&gt;B values of &lt;em&gt;G. ruber&lt;/em&gt; show clear glacial-interglacial cycles with a magnitude that is similar to those of the Mid-Pleistocene at the same site and elsewhere.&amp;#160; This new high-resolution view of CO&lt;sub&gt;2&lt;/sub&gt; during the first large glacial events of the Pleistocene confirms the importance of CO&lt;sub&gt;2&lt;/sub&gt; in amplifying orbital forcing of climate and offers new insights into the mechanistic drivers of natural CO&lt;sub&gt;2&lt;/sub&gt; change.&amp;#160;&lt;/p&gt;

scholarly journals Fresh-water and salt-water distribution in passive margin sediments: Insights from Integrated Ocean Drilling Program Expedition 313 on the New Jersey Margin

Geosphere ◽  
2013 ◽  
Vol 9 (4) ◽  
pp. 1009-1024 ◽  
Author(s):  
Johanna Lofi ◽  
Jennifer Inwood ◽  
Jean-Noël Proust ◽  
Donald H. Monteverde ◽  
Didier Loggia ◽  
...  
Keyword(s):  
New Jersey ◽  
Fresh Water ◽  
Water Distribution ◽  
Salt Water ◽  
Passive Margin ◽  
Ocean Drilling Program ◽  
Ocean Drilling ◽  
Integrated Ocean Drilling Program
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