Neogene changes in Southern Ocean sedimentation based on mass accumulation rates at four continental margins

Handwerger, D.; Jarrard, Richard D.

doi:10.1029/2002pa000850

Cited by 13 publications

(10 citation statements)

References 59 publications

(92 reference statements)

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“…Considering the substantial increase in sedimentation documented in 2010 and 2011 in these cores, the benthic foraminiferal density alone did not account for compaction or dilution [ 9 ]. To account for compaction and dilution, a benthic foraminiferal accumulation rate (BFAR) approach was taken to determine changes from the down-core section to the upper section of each record [ 39 , 40 ]. BFAR were reported as the number of foraminifera per unit area over time (fcm −2 yr −1 ).…”

Section: Methodsmentioning

confidence: 99%

A Decline in Benthic Foraminifera following the Deepwater Horizon Event in the Northeastern Gulf of Mexico

et al. 2015

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Sediment cores were collected from three sites (1000–1200 m water depth) in the northeastern Gulf of Mexico from December 2010 to June 2011 to assess changes in benthic foraminiferal density related to the Deepwater Horizon (DWH) event (April-July 2010, 1500 m water depth). Short-lived radioisotope geochronologies (210Pb, 234Th), organic geochemical assessments, and redox metal concentrations were determined to relate changes in sediment accumulation rate, contamination, and redox conditions with benthic foraminiferal density. Cores collected in December 2010 indicated a decline in density (80–93%). This decline was characterized by a decrease in benthic foraminiferal density and benthic foraminiferal accumulation rate (BFAR) in the surface 10 mm relative to the down-core mean in all benthic foraminifera, including the dominant genera (Bulimina spp., Uvigerina spp., and Cibicidoides spp.). Cores collected in February 2011 documented a site-specific response. There was evidence of a recovery in the benthic foraminiferal density and BFAR at the site closest to the wellhead (45 NM, NE). However, the site farther afield (60 NM, NE) recorded a continued decline in benthic foraminiferal density and BFAR down to near-zero values. This decline in benthic foraminiferal density occurred simultaneously with abrupt increases in sedimentary accumulation rates, polycyclic aromatic hydrocarbon (PAH) concentrations, and changes in redox conditions. Persistent reducing conditions (as many as 10 months after the event) in the surface of these core records were a possible cause of the decline. Another possible cause was the increase (2–3 times background) in PAH’s, which are known to cause benthic foraminifera mortality and inhibit reproduction. Records of benthic foraminiferal density coupled with short-lived radionuclide geochronology and organic geochemistry were effective in quantifying the benthic response and will continue to be a valuable tool in determining the long-term effects of the DWH event on a larger spatial scale.

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Section: Methodsmentioning

confidence: 99%

A Decline in Benthic Foraminifera following the Deepwater Horizon Event in the Northeastern Gulf of Mexico

et al. 2015

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“…The dating of Site 1165 is based on a combination of diatom and radiolarian biostratigraphies [ Bohaty and Whitehead , 2001; Whalen and Lazarus , 2001; Florindo et al , 2003b] and magnetostratigraphy [ Florindo et al , 2003b]. The base of the hole is dated at about ∼21 Ma, and there is a long‐term trend of decreasing sedimentation rates from the bottom to the top of the hole [ Handwerger and Jarrard , 2003]. The quality of preservation of diatoms and radiolarians decreases below 608 mbsf, and no diatoms are found below 754 mbsf, making dating difficult in this lower part of the hole.…”

Section: Datingmentioning

confidence: 99%

“…No IRD older than 10 Ma was found at Site 751, approximately 400 km north of Site 744 [ Breza , 1992]. In general, IRD appears earlier at sites which are closer to the continent, reflecting the location of iceberg melting, probably because sea surface temperatures fell and the polar front moved northward through time [ Handwerger and Jarrard , 2003].…”

Section: Introductionmentioning

confidence: 99%

“…20, PA2017, doi:10.1029/2004PA001067, 2005 Copyright 2005 by the American Geophysical Union. 0883-8305/05/2004PA001067 Prydz Bay trough-mouth fan has been prograding, indicating grounded ice at the shelf break, at least since the late Miocene, and prograded most rapidly in the Pliocene to early Pleistocene [Harris et al, 1999;Handwerger and Jarrard, 2003], and drilling and downhole logging into the fan at ODP Site 1167 indicates that there were several advances and retreats of ice from the shelf break during the late Pliocene to early Pleistocene [Passchier et al, 2003].…”

Section: Introductionmentioning

confidence: 99%

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A high‐resolution record of early Miocene Antarctic glacial history from ODP Site 1165, Prydz Bay

Williams

Handwerger

2005

Paleoceanography

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[1] ODP Site 1165, located 400 km northwest of Prydz Bay, contains a high-resolution early Miocene record of pulses of ice-rafted debris (IRD) originating from the ancestral Lambert Glacier system and the Antarctic coast to the east. The 520 m of early Miocene sediments consist of dark gray claystone with silt laminae (contourites) alternating with decimeter-scale layers of greenish-gray bioturbated claystone that commonly contain ice-rafted debris. Downhole logs also record the alternations between the two facies: the IRD-bearing greenish-grey claystone corresponds to high resistivity and density values because of increased cementation by silica, and corresponds to lower natural gamma radiation values because of diluted clay content. The downhole logs thus allow a continuous and detailed stratigraphic record of the IRD-bearing layers to be obtained. The IRD-bearing layers represent deglaciations and interglacials, when a high flux of icebergs with incorporated material were melting out over the site; the contourite-rich layers represent glacials, when the Polar Current over the site was relatively strong. The sequence is dated by magnetostratigraphy, and the timing of the major IRD pulses is paced by orbital eccentricity, indicating that the volume of the East Antarctic ice sheet also fluctuates on this timescale. After 19.7 Ma, minor precessional and subprecessional IRD layers appear in the record, indicating that the ice sheet becomes more prone to deglaciation through this interval, perhaps associated with the gradual warming trend through the early Miocene.

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“…Because mineralogical heterogeneity is usually the major source of MAR errors, this high‐resolution approach reduces the 95% confidence limits for average chron MAR by >95%. For example, Handwerger and Jarrard [2003] showed that MST‐based carbonate MAR for Site 1124 was much more continuous and precise than that based on discrete carbonate and density analyses. Furthermore, the resulting analysis of brief time periods enables more precise identification of timing of major changes in mass accumulation rates, guiding the choice of intervals for longer‐term averaging.…”

Section: Methodsmentioning

confidence: 99%

Cenozoic mass accumulation rates in the equatorial Pacific based on high‐resolution mineralogy of Ocean Drilling Program Leg 199

Berg

Jarrard

2004

Paleoceanography

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We use continuous mineralogy logs derived from multisensor track physical properties data and reflectance spectroscopy to calculate high‐resolution carbonate, opal, and terrigenous mass accumulation rates (MAR) for the eight sites cored during Ocean Drilling Program Leg 199 in the equatorial Pacific. The largest change in equatorial Pacific sedimentation patterns of the last 55 Myr occurs at the greenhouse/icehouse transition, shortly after the Eocene/Oligocene boundary. Calcite compensation depth deepened dramatically, the equatorial zone of opal accumulation narrowed, and the intertropical convergence zone shifted to the equator. During the Paleogene the opal equatorial accumulation bulge extended to about 12°N, whereas the Neogene bulge extended only to about 7°N. Very low Eocene carbonate MAR was followed by much higher Oligocene and early Miocene MAR, with the carbonate equatorial bulge extending to 4°N. Terrigenous MARs indicate the paleoposition of the intertropical convergence zone and a Pliocene‐Pleistocene increase in Asian dust flux.

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Neogene changes in Southern Ocean sedimentation based on mass accumulation rates at four continental margins

Cited by 13 publications

References 59 publications

A Decline in Benthic Foraminifera following the Deepwater Horizon Event in the Northeastern Gulf of Mexico

A Decline in Benthic Foraminifera following the Deepwater Horizon Event in the Northeastern Gulf of Mexico

A high‐resolution record of early Miocene Antarctic glacial history from ODP Site 1165, Prydz Bay

Cenozoic mass accumulation rates in the equatorial Pacific based on high‐resolution mineralogy of Ocean Drilling Program Leg 199

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