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  • 1
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    Early and middle Miocene Antarctic glacial history from the sedimentary facies distribution in the AND-2A drill hole, Ross Sea, Antarctica (2011)
    Geological Society of America (GSA)
    Details
    Publication Date: 2011-11-01
    Description: In 2007, the Antarctic Geological Drilling Program (ANDRILL) drilled 1138.54 m of strata [~]10 km off the East Antarctic coast, including an expanded early to middle Miocene succession not previously recovered from the Antarctic continental shelf. Here, we present a facies model, distribution, and paleoclimatic interpretation for the AND-2A drill hole, which enable us, for the first time, to reconstruct periods of early and middle Miocene glacial advance and retreat and paleoenvironmental changes at an ice-proximal site. Three types of facies associations can be recognized that imply significantly different paleoclimatic interpretations. (1) A diamictite-dominated facies association represents glacially dominated depositional environments, including subglacial environments, with only brief intervals where ice-free coasts existed, and periods when the ice sheet was periodically larger than the modern ice sheet. (2) A stratified diamictite and mudstone facies association includes facies characteristic of open-marine to iceberg-influenced depositional environments and is more consistent with a very dynamic ice sheet, with a grounding line south of the modern position. (3) A mudstone-dominated facies association generally lacks diamictites and was produced in a glacially influenced hemipelagic depositional environment. Based on the distribution of these facies associations, we can conclude that the Antarctic ice sheets were dynamic, with grounding lines south of the modern location at ca. 20.1-19.6 Ma and ca. 19.3-18.7 Ma and during the Miocene climatic optimum, ca. 17.6-15.4 Ma, with ice-sheet and sea-ice minima at ca. 16.5-16.3 Ma and ca. 15.7-15.6Ma. While glacial minima at ca. 20.1-19.6 Ma and ca. 19.3-18.7 Ma were characterized by temperate margins, an increased abundance of gravelly facies and diatomaceous siltstone and a lack of meltwater plume deposits suggest a cooler and drier climate with polythermal conditions for the Miocene climatic optimum (ca. 17.6-15.4Ma). Several periods of major ice growth with a grounding line traversing the drill site are recognized between ca. 20.2 and 17.6 Ma, and after ca. 15.4 Ma, with evidence of cold polar glaciers with ice shelves. The AND-2A core provides proximal evidence that during the middle Miocene climate transition, an ice sheet larger than the modern ice sheet was already present by ca. 14.7 Ma, [~]1 m.y. earlier than generally inferred from deep-sea oxygen isotope records. These findings highlight the importance of high-latitude ice-proximal records for the interpretation of far-field proxies across major climate transitions.
    Print ISSN: 0016-7606
    Electronic ISSN: 1943-2674
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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  • 2
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    Orbitally paced shifts in the particle size of Antarctic continental shelf sediments in response to ice dynamics during the Miocene climatic optimum (2013)
    Geological Society of America (GSA)
    In: Geosphere
    Details
    Publication Date: 2013-01-29
    Description: The AND-2A drill hole (ANDRILL [Antarctic Geological Drilling Program] Southern McMurdo Sound Project), ~10 km from the East Antarctica coastline, records nearly 6 m.y. of sedimentation across the Miocene climatic optimum at a high-latitude site. Sedimentological studies of bedforms and particle size distributions indicate that the paleoenvironment was strongly affected by waves and currents, consistent with deposition in a glacially influenced neritic environment. We document abrupt shifts in mud percent within glacial-interglacial cycles ca. 17.8 Ma and between ca. 16.7 and 15.7 Ma that we attribute to the hydrodynamic effects of wave stirring tied to episodes of ice growth and decay. Although wave climate and geodynamic forcing of the paleobathymetry simultaneously affect wave stirring on a high-latitude shelf, both are ultimately controlled by the size of the ice sheet. The mud percent record displays cyclicity at short-eccentricity time scales (94–99 k.y.) and, unexpectedly, ice retreat phases interpreted from the particle size record coincide with eccentricity minima. We attribute the eccentricity-paced ice retreat phases during the late Early Miocene polythermal glacial conditions and the cool orbital parameters to marine ice sheet instability in response to changes in ocean circulation and heat transport. The particle size record of the AND-2A core provides unique near-field evidence for orbitally paced changes in high-latitude climate and ice volume during the Miocene climatic optimum and important insights into the mechanisms of ice sheet growth and decay in a period of global warmth.
    Electronic ISSN: 1553-040X
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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  • 3
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    Orbital forcing of the East Antarctic ice sheet during the Pliocene and Early Pleistocene (2014)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2014-10-31
    Description: Nature Geoscience 7, 841 (2014). doi:10.1038/ngeo2273 Authors: M. O. Patterson, R. McKay, T. Naish, C. Escutia, F. J. Jimenez-Espejo, M. E. Raymo, S. R. Meyers, L. Tauxe, H. Brinkhuis, A. Klaus, A. Fehr, J. A. P. Bendle, P. K. Bijl, S. M. Bohaty, S. A. Carr, R. B. Dunbar, J. A. Flores, J. J. Gonzalez, T. G. Hayden, M. Iwai, K. Katsuki, G. S. Kong, M. Nakai, M. P. Olney, S. Passchier, S. F. Pekar, J. Pross, C. R. Riesselman, U. Röhl, T. Sakai, P. K. Shrivastava, C. E. Stickley, S. Sugasaki, S. Tuo, T. van de Flierdt, K. Welsh, T. Williams & M. Yamane
    Print ISSN: 1752-0894
    Electronic ISSN: 1752-0908
    Topics: Geosciences
    Published by Nature Publishing Group (NPG)
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  • 4
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    An Antarctic stratigraphic record of stepwise ice growth through the Eocene-Oligocene transition (2017)
    Geological Society of America (GSA)
    Details
    Publication Date: 2017-03-01
    Description: Earth’s current icehouse phase began ~34 m.y. ago with the onset of major Antarctic glaciation at the Eocene-Oligocene transition. Changes in ocean circulation and a decline in atmospheric greenhouse gas levels were associated with stepwise cooling and ice growth at southern high latitudes. The Antarctic cryosphere plays a critical role in the ocean-atmosphere system, but its early evolution is still poorly known. With a near-field record from Prydz Bay, Antarctica, we demonstrate that Antarctic ice growth was stepwise and had an earlier onset than previously suggested. Prydz Bay lies downstream of a major East Antarctic Ice Sheet drainage system, and its sedimentary records uniquely constrain the timing of ice-sheet advance onto the continental shelf. We investigated a detrital record extracted from three Ocean Drilling Program drill holes within a new depositional and chronological framework spanning the late Eocene to early Oligocene (ca. 36–33 Ma). The chemical index of alteration (CIA) and the S index, calculated from the major-element geochemistry of bulk samples, yielded estimates of chemical weathering intensities and mean annual temperature on the East Antarctic continent. We document evidence for late Eocene mountain glaciation along with transient warm events at 35.8–34.8 Ma. From 34.4 Ma, associated with the Eocene-Oligocene transition precurso r 18 O excursion, glaciers advanced into Prydz Bay, coincident with a decline in chemical weathering and temperature. We conclude that Antarctic continental ice growth commenced with the Eocene-Oligocene transition "precursor" glaciation, during a time of Subantarctic surface ocean cooling and a decline in atmospheric p CO 2 . These results call for dynamic high-latitude feedbacks that are currently poorly represented in Earth system models and emphasize the need for additional near-field glacio-sedimentological, high-latitude sea-surface temperature and p CO 2 records across the Eocene-Oligocene transition.
    Print ISSN: 0016-7606
    Electronic ISSN: 1943-2674
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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  • 5
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    A sedimentological record of early Miocene ice advance and retreat, AND-2A drill hole, McMurdo Sound, Antarctica (2019)
    Details
    Publication Date: 2021-05-11
    Description: The lowest 501 m (similar to 1139-638 m) of the AND-2A core from southern Mc-Murdo Sound is the most detailed and complete record of early Miocene sediments in Antarctica and indicates substantial variability in Antarctic ice sheet activity during early Miocene time. There are two main pulses of diamictite accumulation recorded in the core, and three significant intervals with almost no coarse clasts. Each diamictite package comprises several sequences consistent with ice advance-retreat episodes. The oldest phase of diamictite deposition, Composite Sequence 1 (CS1), has evidence for grounded ice at the drill site and has been dated around 20.2-20.1 Ma. It likely coincides with cooling associated with isotope event Mi1aa. This is overlain by a diamictite-free, sandstone-dominated interval, CS2 that includes three coarsening-upward deltaic cycles, is inferred to mark substantial warming, and has an inferred age range between 20.1 and 20.05 Ma. Above this is an interval with variable amounts of diamictite (CS3), with indicators of ice grounding, that is inferred to record ice advance relative to CS2, and is overlain by an similar to 100-m-thick mud-rich interval (CS4) with no sedimentological evidence for direct glacial influence at the drill site (ca. 19.4-18.7 Ma). A third overlying diamictite-rich interval (CS5) overlies an unconformity spanning 18.7-17.8 Ma (coinciding with isotope event Mi1b), and records a return to more ice-influenced conditions at the drill site in late early Miocene time. The overall picture for the early Miocene (spanning the period 20.2-17.35 Ma) is one of ice advance alternating with periods of ice retreat and hence significant global climate fluctuations after the permanent establishment of the Antarctic ice sheet at the Eocene/Oligocene boundary, and preceding the relative warmth of the middle Miocene climatic optimum (ca. 17.5-14.5 Ma). Sedimentary cyclicity in CS1 and CS2 is consistent with similar to 21 k.y. precession but in CS3 the frequency is closer to 100 k.y. (consistent with eccentricity), with a possible change to 20 k.y. precession in CS4. CS5 cyclicity is consistent with obliquity forcing. Provenance data are consistent with local Trans antarctic Mountains glacial activity under precessional control in CS1 and more southerly ice-cap build up under 100 k.y. eccentricity and obliquity control during CS3 and CS5, respectively.
    Description: Published
    Description: 1780-1803
    Description: 5A. Paleoclima e ricerche polari
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 6
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    Middle Miocene to Pliocene History of Antarctica and the Southern Ocean (2008)
    Elsevier B.V.
    Details
    Publication Date: 2017-04-04
    Description: This chapter explores the Middle Miocene to Pliocene terrestrial and marine records of Antarctica and the Southern Ocean. The structure of the chapter makes a clear distinction between terrestrial and marine records as well as proximal (on or around Antarctica) and more distal records (Southern Ocean). Particular geographical regions are identified that reflect the areas for which the majority of palaeoenvironmental and palaeoclimatic information exist. Specifically, the chapter addresses the terrestrial sedimentary and fjordal environments of the Transantarctic Mountains and Lambert Glacier region, the terrestrial fossil record of Antarctic climate, terrestrial environments of West Antarctica, and the marine records of the East Antarctic Ice Sheet (EAIS), the West Antarctic Ice Sheet (WAIS) and the Antarctic Peninsula Ice Sheet (APIS), as well as the marine record of the Southern Ocean. Previous and current studies focusing on modelling Middle Miocene to Pliocene climate, environments and ice sheets are discussed.
    Description: Published
    Description: 401-463
    Description: 1.8. Osservazioni di geofisica ambientale
    Description: 3.8. Geofisica per l'ambiente
    Description: reserved
    Keywords: Middle Miocene ; Pliocene ; Antarctica ; Southern Ocean ; 03. Hydrosphere::03.01. General::03.01.06. Paleoceanography and paleoclimatology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: book chapter
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  • 7
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    Orbitally induced oscillations in the East Antarctic ice sheet at the Oligocene/Miocene boundary (2001)
    In:  EPIC3Nature, 413, pp. 719-723
    Details
    Publication Date: 2019-07-16
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 8
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    Sequence stratigraphy of the ANDRILL AND-2A drillcore, Antarctica: A long-term, ice-proximal record of Early to Mid-Miocene climate, sea-level and glacial dynamism (2011)
    Elsevier B.V.
    Details
    Publication Date: 2017-04-04
    Description: Present understanding of Antarctic climate change during the Early to Mid-Miocene, including major cycles of glacial expansion and contraction, relies in large part on stable isotope proxies from deep sea core drilling. Here, we summarize the lithostratigraphy of the ANDRILL Southern McMurdo Sound Project drillcore AND- 2A. This core offers a hitherto unavailable ice-proximal stratigraphic archive from a high-accommodation continental margin setting, and provides clear evidence of repeated fluctuations in climate, ice expansion/ contraction and attendant sea-level change over the period c. 20.2–14.2 Ma, with a more fragmentary record of Late Miocene and Pliocene time. The core is divided into seventy-four high-frequency (fourth- or fifthorder) glacimarine sequences recording repeated advances and retreats of glaciers into and out of the Victoria Land Basin. The section can be resolved into thirteen longer-term, composite (third-order) sequences, which comprise packages of higher frequency sequences that show a consistent stratigraphic stacking pattern (Stratigraphic Motif). The distribution of the six recognized motifs indicates intervals of less and more iceproximal, and temperate to subpolar/polar climate, through the Miocene period. The core demonstrates a dynamic climate regime throughout the Early to Mid-Miocene that may be correlated to some previouslyrecognized events such as the Mid-Miocene Climatic Optimum, and provides a detailed reference point from which to evaluate stable isotope proxy records from the deep-sea.
    Description: Published
    Description: 337-351
    Description: 1.8. Osservazioni di geofisica ambientale
    Description: 2.2. Laboratorio di paleomagnetismo
    Description: JCR Journal
    Description: restricted
    Keywords: Miocene ; Antarctica ; Sequence stratigraphy ; Cyclicity ; Mid-Miocene Climatic Optimum ; ANDRILL SMS project ; 04. Solid Earth::04.05. Geomagnetism::04.05.06. Paleomagnetism ; 04. Solid Earth::04.05. Geomagnetism::04.05.07. Rock magnetism ; 04. Solid Earth::04.05. Geomagnetism::04.05.09. Environmental magnetism
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 9
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    Soft-sediment deformation features in core from CRP-2/2A, Victoria Land Basin, Antarctica (2000)
    PANGAEA
    In:  EPIC3Terra Antartica, Bremerhaven, PANGAEA, 7(3), pp. 401-412
    Details
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: PANGAEA Documentation , notRev
    Format: application/pdf
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  • 10
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    Origin of breccias in the CRP-1 core (1998)
    PANGAEA
    In:  EPIC3Terra Antartica, Bremerhaven, PANGAEA, 5(3), pp. 401-409
    Details
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: PANGAEA Documentation , notRev
    Format: application/pdf
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