Waxing (and Waning) lyrical on hiatuses: Eocene ‐ Quaternary Indian Ocean hiatuses as proxy indicators of water mass production

Ramsay, A. T. S.; Sykes, T. J. S.; Kidd, Robert B.

doi:10.1029/94pa01397

Cited by 40 publications

(7 citation statements)

References 59 publications

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“…Such modifications can have either a climatic or a tectonic origin (Rebesco et al, ). It was suggested that late Neogene fluctuations of AABW intensity were driven by glacial alternating with interglacial periods in Antarctic (Pekar & DeConto, ; Ramsay et al, ). We hypothesize that the alternating reflection amplitudes of the drifts and the temporary reduction of flow speeds causing the formation of sediment waves in depths similar to modern AABW may reflect oscillations of Neogene Antarctic glaciation.…”

Section: Discussionmentioning

confidence: 99%

Neogene Modifications of Circulation in the Northeastern African‐Southern Ocean Gateway

Fischer

Uenzelmann-Neben

2018

Geochem Geophys Geosyst

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In the African‐Southern Ocean gateway, several water masses originating in the Atlantic, Indian, and Southern oceans meet and mix. As a consequence, the gateway is crucial for the maintenance of the global thermohaline circulation. Newly acquired multichannel seismic reflection data collected across the southern Mozambique Ridge are used to reconstruct the impact of paleoceanographic modifications on the Neogene and Quaternary circulation in the northeastern African‐Southern Ocean gateway. The data show the occurrence of mid‐Miocene (~15 Ma) to early Pliocene (~5 Ma) contourite drifts and erosional features interpreted as evidence for the onset of current‐controlled sedimentation in the late Neogene resulting from mid‐Miocene cooling and closure of the Indonesian gateway. The Quaternary is characterized by a relocation of Antarctic Bottom Water inflow and the inception of two branches of the North Atlantic Deep Water circulation subsequent to the final closure of the Central American Seaway and the Northern Hemisphere Glaciation. Therefore, the two events triggered the onset of unhindered deep and bottom water circulation from the Atlantic into the Indian Ocean, whereas the Antarctic Intermediate Water circulation decreased due to the final closure of the Indonesian gateway. Our results show that tectonic and climatic events, which themselves may be linked, continuously modified the Cenozoic paleoceanic circulation in the African‐Southern Ocean gateway, and indicate that ocean gateways governing the global water mass exchange act as an excellent location to reconstruct such modifications based on the interpretation of contourite drifts and erosional features.

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Section: Discussionmentioning

confidence: 99%

Neogene Modifications of Circulation in the Northeastern African‐Southern Ocean Gateway

Fischer

Uenzelmann-Neben

2018

Geochem Geophys Geosyst

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“…Neodymium signatures representing proto‐CDW have also been reconstructed for the late Eocene using fossil fish teeth from the Southern Kerguelen Plateau (ODP Site 738) (Scher et al, ). Proto‐AABW is thought to have existed by the early Eocene, based on the distribution of hiatuses in the Indian Ocean (Ramsay et al, ) and unradiogenic Nd compositions reconstructed at Kerguelen Plateau and the Indian Ocean basin ( ε Nd = −9.3 ± 1.5; Huck et al, ).…”

Section: Regional Setting and Hydrographymentioning

confidence: 99%

No Change in Southern Ocean Circulation in the Indian Ocean From the Eocene Through Late Oligocene

Wright

Scher

Seton

et al. 2018

Paleoceanog and Paleoclimatol

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Deciphering the evolution of Southern Ocean circulation during the Eocene and Oligocene has important implications for understanding the development of the Antarctic Circumpolar Current and transition to Earth's “icehouse” climate. To better understand ocean circulation patterns in the Indian Ocean sector of the Southern Ocean, we generated a new fossil fish tooth neodymium isotope record (εNd) from the upper Eocene to upper Oligocene sections (36–23 Ma) of Ocean Drilling Program Sites 744 and 748 (Kerguelen Plateau, Indian Ocean). Reconstructed seawater εNd values from fossil fish teeth are used to trace changes in water masses across ocean basins. The records from Site 748 and Site 744 reveal a gradual shift from εNd values around −6.5 to −7.5 in the late Eocene to εNd values between −7.5 and −8.3 by the late Oligocene, consistent with a Circumpolar Deep Water (CDW) influence at the Kerguelen Plateau throughout the Oligocene. We interpret the shift to less radiogenic values to reflect the increased export of Northern Component Water to the Southern Ocean, likely into the proto‐CDW. However, the records show no major change in water mass composition around the Kerguelen Plateau that would accompany an increase in Pacific throughflow related to the opening of Drake Passage and imply that Pacific throughflow via the Drake Passage occurred by the late Eocene. High‐frequency variability in ɛNd values at Site 744 is interpreted as an imprint of Oligocene glacial activity, with a particularly pronounced excursion at 32.6 Ma roughly coinciding with other glacial weathering indicators around Antarctica.

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“…This detailed analysis of mass wasting in a whole ocean basin shows that hiatuses are common features along margins, but that they do not occur very often at any particular site. This questions the validity of those papers [e.g., Keller and Barron , 1987; Ramsay et al , 1994a, 1994b], which have correlated hiatuses over wide areas assuming that individual hiatuses represent regional oceanographic change. It also makes more complicated the task of determining sequences and sequence boundaries by the use of hiatuses [e.g., Austin et al , 1998].…”

Section: Discussionmentioning

confidence: 99%

“…The study of hiatuses on continental margins has been used to determine paleoceanographic changes such as current strength or changes in corrosiveness of bottom waters [ Ramsay et al , 1994a, 1994b; Spencer‐Cervato , 1998]. In these cases, little emphasis was placed on the products of the erosive event.…”

Section: Introductionmentioning

confidence: 99%

Northwest African Continental Margin: History of sediment accumulation, landslide deposits, and hiatuses as revealed by drilling the Madeira Abyssal Plain

Weaver

2003

Paleoceanography

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ODP drill sites in the Madeira Abyssal Plain reveal sequences of organic‐rich turbidites derived from the northwest African margin, in which each turbidite has a volume of tens to hundreds of cubic kilometers. The frequency of turbidite emplacement has been combined with core and seismic data to show the volume of redeposited sediment. The basin began to fill about 22 Ma with numerous small turbidites, up to 100 per million years, each with volumes of a few cubic kilometers. The total volume of turbidites deposited increased between 16 and 11 Ma, as did their individual volumes, and then declined to 7 Ma. At 7 Ma, there was a dramatic increase in the amount of turbidite input to 768 km3/Myr and a rise in the average volume of each unit to 59 km3. These high values have been maintained to the present day. The variations in the amount of redeposited sediment most likely reflect the rates of sedimentation on the northwest African margin since high sedimentation leads to oversteepening of the slopes and eventual mass wasting. The dramatic changes at about 7 Ma may be due to a large increase in upwelling off northwest Africa caused by circulation changes associated with increased glaciation of the poles. Up to 20% of sediment may be remobilized by landslides, with each event leaving a hiatus. Each of these hiatuses extends over an average area of ∼4800 km2 and represents removal of sediment layers several tens of meters thick and of several hundred thousand years duration.

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Waxing (and Waning) lyrical on hiatuses: Eocene ‐ Quaternary Indian Ocean hiatuses as proxy indicators of water mass production

Cited by 40 publications

References 59 publications

Neogene Modifications of Circulation in the Northeastern African‐Southern Ocean Gateway

Neogene Modifications of Circulation in the Northeastern African‐Southern Ocean Gateway

No Change in Southern Ocean Circulation in the Indian Ocean From the Eocene Through Late Oligocene

Northwest African Continental Margin: History of sediment accumulation, landslide deposits, and hiatuses as revealed by drilling the Madeira Abyssal Plain

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