Early Pliocene Temperature Changes in the Antarctic Seas

Ciesielski, Paul F; Weaver, Fred M.

doi:10.1130/0091-7613(1974)2<511:eptcit>2.0.co;2

Cited by 113 publications

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“…The vertical water mass structure of the Vema Channel during this interval was probably similar to the present, with both AABW and NADW present in the western South Atlantic. A major cooling trend was initiated in the southern oceans at 4.3 Ma (Ciesielski and Weaver, 1974). Evidence for this cooling trend includes a northward displacement of siliceous sediments off East Antarctica at 3.86 Ma (Weaver, 1973), possible expansion of the west Antarctic ice sheet to its present dimensions as early as 3.95 to 3.90 Ma (Ciesielski and Weaver, 1974), and major glaciation in Argentine Patagonia at 3.59 Ma (Mercer, 1976).…”

Section: Discussionmentioning

confidence: 99%

Climatically Induced Changes in Vertical Water Mass Structure of the Vema Channel during the Pliocene: Evidence from Deep Sea Drilling Project Holes 516A, 517, and 518

Hodell¹,

Kennett²,

Leonard³

1983

Initial Reports of the Deep Sea Drilling Project

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Pliocene changes in the vertical water mass structure of the western South Atlantic are inferred from changes in benthic foraminiferal assemblages and stable isotopes from DSDP Holes 516A, 517, and 518. Factor analysis of 34 samples from Site 518 reveals three distinct benthic foraminiferal assemblages that have been associated with specific subsurface water masses in the modern ocean. These include a Nuttalides umbonifera assemblage (Factor 1) associated with Antarctic Bottom Water (AABW), a Globocassidulina subglobosa-Uvigerina peregrina assemblage (Factor 2) associated with Circumpolar Deep Water (CPDW), and an Oridorsalis umbonatus-Epistominella exigua assemblage associated with North Atlantic Deep Water (NADW). Bathymetric gradients in Δ 13 C between Holes 516A (1313 m), 517 (2963 m), and 518 (3944 m) are calculated whenever possible to monitor the degree of similarity and/or difference in the apparent oxygen utilization (AOU) of water masses located at these depths during the Pliocene. Changes in bathymetric Δ 13 C gradients coupled with benthic foraminiferal assemblages record fundamental changes in the vertical water mass structure of the Vema Channel during the Pliocene from 4.1 to 2.7 Ma.At Site 518, the interval from 4.1 to 3.6 Ma is dominated by the N. umbonifera (Factor 1) and O. umbonatus-E. exigua (Factor 3) assemblages. The Δ 13 C gradient between Holes 518 (3944 m) and 516A (1313 m) undergoes rapid oscillations during this interval though no permanent increase in the gradient is observed. However, δ13 C values at Site 518 are clearly lighter during this interval. These conditions may be related to increased bottom water activity associated with the re-establishment of the West Antarctic Ice Sheet in the late Gilbert Chron (-4.2 to 3.6 Ma) (Osborn et al., 1982).The interval from 3.6 to 3.2 Ma is marked by a dominance of the G. subglobosa-U. peregrina (Factor 2) assemblage and lack of a strong Δ 13 C gradient between Holes 518 (3944 m) and 516A (1313 m). We suggest that shallow circumpolar waters expanded to depths of a least 3944 m (Site 518) during this time.The most profound faunal and isotopic change occurs at 3.2 Ma, and is marked by dominance of the N. umbonifera (Factor 1) and O. umbonatus-E. exigua (Factor 3) assemblages, a l.l‰ enrichment in δ 18 θ, and a large negative increase in the Δ 13 C gradient between Holes 518 and 516A. These changes at Site 518 record the vertical displacement of circumpolar waters by AABW and NADW. This change in vertical water mass structure at 3.2 Ma was probably related to a global cooling event and/or final closure of the Central American seaway. A comparison of the present-day δ 13 C structure of the Vema Channel with a reconstruction between 3.2 and 2.7 Ma indicates that circulation patterns during this late Pliocene interval were similar to those of the modern western South Atlantic.

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Section: Discussionmentioning

confidence: 99%

Climatically Induced Changes in Vertical Water Mass Structure of the Vema Channel during the Pliocene: Evidence from Deep Sea Drilling Project Holes 516A, 517, and 518

Hodell¹,

Kennett²,

Leonard³

1983

Initial Reports of the Deep Sea Drilling Project

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“…In the Southern Ocean a warm early Pliocene gave way to late Piacenzian cooling that is signalled by a range of sea ice proxies, and by the retreat of certain organisms to lower latitudes (e.g. Ciesielski and Weaver 1974;Berkman et al, 2004;Whitehead et al, 2005).…”

Section: Marine Pliocenementioning

confidence: 99%

Climate and environment of a Pliocene warm world

Salzmann

Williams

Haywood

et al. 2011

Palaeogeography, Palaeoclimatology, Palaeoecology

163

105

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The Pliocene Epoch, 5.33 -2.58 million years ago (Ma), was a generally warmer and wetter interval with atmospheric CO 2 -concentrations at or slightly above modern levels. This paper provides an overview of Pliocene vegetation, sea surface temperatures and climate modelling outcomes.. Most prominent changes in Pliocene biome distribution compared to today include a northwards shift of temperate and boreal vegetation zones in response to a warmer and wetter climate as well as an expansion of tropical savannas and forests at the expense of deserts. Modelling experiments using the Hadley Centre climate model identified significantly higher Pliocene sea surface temperatures at the high-latitudes with only minor warming predicted in the tropics. Global mean annual surface temperatures (MAT) are estimated to have been 2 to 3ºC higher during the Piacenzian (3.6-2.58 Ma) than today with a reduced equator to pole gradient. The marine realm during the Pliocene was characterised by a reconfiguration of ocean gateways, particularly the narrowing of the Indonesian Seaway and closure of the Central American Isthmus, which produced essentially a modern pattern of ocean circulation. In the Southern Ocean a warm early Pliocene gave way to late Piacenzian cooling. Proxy data indicate a reduced east to west sea surface temperature gradient in the tropical Pacific during the Pliocene warmth. The Pliocene is one of the most intensively studied geological intervals of the pre-Quaternary. No other warm period in the geological past yields such a unique combination of near modern atmospheric CO 2 -concentrations, palaeogeography and palaeobiology. However, this paper also identifies data gaps and shortcomings in the reconstruction of Pliocene environments using proxy data and climate models on which future research should focus.

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“…9, "G") (also see Denton et al, 1971). Kvasov and Verbitzky (1981) mapped several stages in a progressive growth of the ice sheet through the Oligocene-Miocene with a maximum expansion at 5 Ma, before an early Pliocene warming and possible disintegration of the West Antarctic ice sheet as postulated by Ciesielski and Weaver (1974; see also Footnote 2 and Fig. 2).…”

Section: Paleogeographic Reconstructions For the Earlymentioning

confidence: 99%

Paleogene Glacial History of Antarctica in Light of Leg 120 Drilling Results

Wise¹,

Breza²,

Harwood³

et al. 1992

Proceedings of the Ocean Drilling Program

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The Paleogene glacial history of Antarctica has been inferred largely from indirect evidence of glaciation gathered from the oceans beyond that remote, ice-shrouded, and inhospitable continent. This evidence includes the "proxy" stable isotopic record from the world's oceans; the occurrence of ice-rafted debris (IRD) in the Southern Ocean; inflections in sea-level curves; the presence of hiatuses in the deep-sea record; and changes in clay mineral assemblages, in the diversities of microfossil assemblages, and in the steepness of latitudinal biotic gradients. Ocean Drilling Program Leg 120 has added an important dimension to this growing body of evidence through the discovery of lowest Oligocene IRD at Site 748 on the Southern Kerguelen Plateau at a record distance north of the Antarctic continent (58°S latitude) and within a pelagic biosiliceous-carbonate ooze sequence that has yielded a complementary oxygen isotope record of the cryospheric event. We deduce that an ice sheet reached sea level during the earliest Oligocene (35.8-36.0 Ma) and that the effect was immediate and profound. In addition to the IRD, this event was manifested at Site 748 by a dramatic cooling of the surface waters surrounding the continent as indicated by a sharp increase in the percentage of cold-water calcareous nannoplankton, an increase in planktonic foraminiferal δ 18 θ values, and an increase in the percentage of biosiliceous material in the sediment. The temperature of the bottom waters over the plateau also decreased, and the volume of ice on the continent increased.We have reviewed the accumulated evidence from this and other investigations of the past two decades on and around Antarctica, and have concluded that ice sheets were present on the continent during the Oligocene, including the earliest Oligocene. Not necessarily permanent features, they probably went through many advances and contractions and may have disappeared completely at times. The rapid ice advance during the earliest Oligocene reached sea level at several widely scattered localities around the continent, but only for a brief period of time at some of these localities. Differences of opinion among investigators concern primarily the size and persistence of the Oligocene ice sheet(s).Tantalizing evidence of undated till deposits subjacent to well-dated Oligocene glaciomarine sequences along the Antarctic margin and possible occurrences of IRD beyond suggest the presence of glaciers during the late Eocene and possibly even during the early-middle Eocene. Included among the studies in this Scientific Results volume are new age calibrations from Eltanin piston cores taken at relatively low latitudes (38° to 58°S) in the southeast Pacific from which Eocene IRD has been reported. There is little agreement, however, among investigators as to whether an ice sheet was present at any time during the Eocene, particularly during early-middle Eocene times.

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Early Pliocene Temperature Changes in the Antarctic Seas

Cited by 113 publications

References 0 publications

Climatically Induced Changes in Vertical Water Mass Structure of the Vema Channel during the Pliocene: Evidence from Deep Sea Drilling Project Holes 516A, 517, and 518

Climatically Induced Changes in Vertical Water Mass Structure of the Vema Channel during the Pliocene: Evidence from Deep Sea Drilling Project Holes 516A, 517, and 518

Climate and environment of a Pliocene warm world

Paleogene Glacial History of Antarctica in Light of Leg 120 Drilling Results

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