Cover Image

HARDBACK
$38.00



View/Hide Left Panel

Late Cenozoic Climate History of the Ross Embayment from the AND-1B Drill Hole: Culmination of Three Decades of Antarctic Margin Drilling

Cooper, A. K., P. J. Barrett, H. Stagg, B. Storey, E. Stump, W. Wise, and the 10th ISAES editorial team, eds. (2008). Antarctica: A Keystone in a Changing World. Proceedings of the 10th International Symposium on Antarctic Earth Sciences. Washington, DC: The National Academies Press.

T. R. Naish,1,2 R. D. Powell,3 P. J. Barrett,1 R. H. Levy,4 S. Henrys,1 G. S. Wilson,5 L. A. Krissek,6 F. Niessen,7 M. Pompilio,8 J. Ross,9 R. Scherer,3 F. Talarico,10 A. Pyne,1 and the ANDRILL-MIS Science team11

ABSTRACT

Because of the paucity of exposed rock, the direct physical record of Antarctic Cenozoic glacial history has become known only recently and then largely from offshore shelf basins through seismic surveys and drilling. The number of holes on the continental shelf has been small and largely confined to three areas (McMurdo Sound, Prydz Bay, and Antarctic Peninsula), but even in McMurdo Sound, where Oligocene and early Miocene strata are well cored, the late Cenozoic is poorly known and dated. The latest Antarctic geological drilling program, ANDRILL, successfully cored a 1285-m-long record of climate history spanning the last 13 m.y. from subsea-floor sediment beneath the McMurdo Ice Shelf (MIS), using drilling systems specially developed for operating through ice shelves. The cores provide the most complete Antarctic record to date of ice-sheet and climate fluctuations for this period of Earth’s history. The >60 cycles of advance and retreat of the grounded ice margin preserved in the AND-1B record the evolution of the Antarctic ice sheet since a profound global cooling step in deep-sea oxygen isotope records ~14 m.y.a. A feature of particular interest is a ~90-m-thick interval of diatomite deposited during the warm Pliocene and representing an extended period (~200,000 years) of locally open water, high phytoplankton productivity, and retreat of the glaciers on land.

HISTORICAL OVERVIEW

The remarkable late Cenozoic record of glacial history in the Ross Embayment recovered in late 2006 by the ANDRILL-MIS Project is the culmination of work begun over three decades ago to document and understand the more recent glacial history of Antarctica by drilling close to the margin. Ironically, although the last 3 million years of Earth’s climate is often said to be the best studied interval of the Cenozoic, the contribution of Antarctic ice volume changes is the most poorly understood. Until this most recent hole was drilled, the middle Cenozoic record was better known from several holes in both the McMurdo region and Prydz Bay (Table 1). This is in general because the older strata were exposed closer to the coast through basin uplift, where younger strata had been removed by Neogene erosion, but also because in offshore basins glacial debris from the last glacial advance

1

Antarctic Research Centre, Victoria University of Wellington, Wellington, New Zealand (t.naish@gns.cri.nz, peter.barrett@vuw.ac.nz, alex.pyne@vuw.ac.nz).

2

Geological and Nuclear Sciences, Lower Hutt, New Zealand (t.naish@gns.cri.nz, s.henrys@gns.cri.nz).

3

Department of Geology and Environmental Geosciences, Northern Illinois University, DeKalb, IL, USA (ross@geol.niu.edu).

4

ANDRILL Science Management Office, University of Nebraska-Lincoln, 126 Bessey Hall, Lincoln, NE 68588-0341, USA (rlevy2@unl.edu).

5

Department of Geology, University of Otago, PO Box 56, Dunedin, New Zealand (gary.wilson@otago.ac.nz).

6

Department of Geosciences, The Ohio State University, Columbus, OH, USA (krissek@mps.ohio-state.edu).

7

Department of Marine Geophysics, Alfred Wegener Institute, Postfach 12 01 61, Columbusstrasse, D-27515, Bremerhaven, Germany (fniessen@awi-bremerhaven.de).

8

Istituto Nazionale di Geofisica e Vulcanologia, Via della Faggiola, 32,

9

I-56126 Pisa, Italy (pompilio@pi.ingv.it).

New Mexico Geochronology Research Laboratory, Socorro, NM 87801, USA (jirhiker@nmt.edu).

10

Università di Siena, Dipartimento di Scienze delle Terra, Via Laterina 8, I-53100 Siena, Italy (talarico@unisi.it).

11

See http://www.andrill.org/support/references/appendixc.html.



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 71
Cooper, A. K., P. J. Barrett, H. Stagg, B. Storey, E. Stump, W. Wise, and the 10th ISAES editorial team, eds. (2008). Antarctica: A Keystone in a Changing World. Proceedings of the 10th International Symposium on Antarctic Earth Sciences. Washington, DC: The National Academies Press. Late Cenozoic Climate History of the Ross Embayment from the AND-1B Drill Hole: Culmination of Three Decades of Antarctic Margin Drilling T. R. Naish,1,2 R. D. Powell,3 P. J. Barrett,1 R. H. Levy,4 S. Henrys,1 G. S. Wilson,5 L. A. Krissek,6 F. Niessen,7 M. Pompilio,8 J. Ross,9 R. Scherer,3 F. Talarico,10 A. Pyne,1 and the ANDRILL-MIS Science team11 ABSTRACT Cenozoic is poorly known and dated. The latest Antarctic geological drilling program, ANDRILL, successfully cored Because of the paucity of exposed rock, the direct physical a 1285-m-long record of climate history spanning the last 13 record of Antarctic Cenozoic glacial history has become m.y. from subsea-floor sediment beneath the McMurdo Ice known only recently and then largely from offshore shelf Shelf (MIS), using drilling systems specially developed for basins through seismic surveys and drilling. The number operating through ice shelves. The cores provide the most of holes on the continental shelf has been small and largely complete Antarctic record to date of ice-sheet and climate confined to three areas (McMurdo Sound, Prydz Bay, and fluctuations for this period of Earth’s history. The >60 cycles Antarctic Peninsula), but even in McMurdo Sound, where of advance and retreat of the grounded ice margin preserved Oligocene and early Miocene strata are well cored, the late in the AND-1B record the evolution of the Antarctic ice sheet since a profound global cooling step in deep-sea oxygen isotope records ~14 m.y.a. A feature of particular interest is a ~90-m-thick interval of diatomite deposited during the warm Pliocene and representing an extended period (~200,000 1 Antarctic Research Centre, Victoria University of Wellington, Wel- years) of locally open water, high phytoplankton productiv- lington, New Zealand (t.naish@gns.cri.nz, peter.barrett@vuw.ac.nz, alex. ity, and retreat of the glaciers on land. pyne@vuw.ac.nz). 2 Geological and Nuclear Sciences, Lower Hutt, New Zealand (t.naish@ gns.cri.nz, s.henrys@gns.cri.nz). HISTORICAL OVERVIEW 3 Department of Geology and Environmental Geosciences, Northern Illinois University, DeKalb, IL, USA (ross@geol.niu.edu). The remarkable late Cenozoic record of glacial history in the 4 ANDRILL Science Management Office, University of Nebraska- Ross Embayment recovered in late 2006 by the ANDRILL- Lincoln, 126 Bessey Hall, Lincoln, NE 68588-0341, USA (rlevy2@unl. MIS Project is the culmination of work begun over three edu). decades ago to document and understand the more recent 5 Department of Geology, University of Otago, PO Box 56, Dunedin, New Zealand (gary.wilson@otago.ac.nz). glacial history of Antarctica by drilling close to the margin. 6 Department of Geosciences, The Ohio State University, Columbus, OH, Ironically, although the last 3 million years of Earth’s climate USA (krissek@mps.ohio-state.edu). is often said to be the best studied interval of the Cenozoic, 7 Department of Marine Geophysics, Alfred Wegener Institute, Postfach the contribution of Antarctic ice volume changes is the most 12 01 61, Columbusstrasse, D-27515, Bremerhaven, Germany (fniessen@ poorly understood. Until this most recent hole was drilled, awi-bremerhaven.de). 8 Istituto Nazionale di Geofisica e Vulcanologia, Via della Faggiola, 32, the middle Cenozoic record was better known from several 9 I-56126 Pisa, Italy (pompilio@pi.ingv.it). holes in both the McMurdo region and Prydz Bay (Table New Mexico Geochronology Research Laboratory, Socorro, NM 87801, 1). This is in general because the older strata were exposed USA (jirhiker@nmt.edu). closer to the coast through basin uplift, where younger strata 10 Università di Siena, Dipartimento di Scienze delle Terra,Via Laterina had been removed by Neogene erosion, but also because in 8, I-53100 Siena, Italy (talarico@unisi.it). 11 See http://www.andrill.org/support/references/appendixc.html. offshore basins glacial debris from the last glacial advance 71

OCR for page 71
72 ANTARCTICA: A KEYSTONE IN A CHANGING WORLD TABLE 1 Antarctic Coastal and Continental Shelf Rock-Drilling Sites, 1973 to 2006 Ross Sea Hays, Frakes et al., 1975 DSDP 28 1973 270 77°26'S 178°30'W -634 m 423 m 62% gneiss - E Paleozoic 271 77°26'S 178°30'W -562 m 233 m 7% diamict clasts - E Pliocene 272 77°26'S 178°30'W -629 m 439 m 37% diamict - E Miocene 273 77°26'S 178°30'W -491 m 333 m 25% diamict - E Miocene McMurdo Sound area - onshore Kyle, 1981 DVDP 1973 1 77°50'S 166°40'E 67 m 201 m 98% basalt - L Quat 1973 2 77°51'S 166°40'E 47 m 179 m 96% basalt - L Quat 1973 3 77°51'S 166°40'E 48 m 381 m 90% basalt - L Quat Powell, 1981 1974 10 77°35'S 163°31'E 3m 182 m 83% diamict - L Miocene 1974 11 77°35'S 163°25'E 80.2 m 328 m 94% diamict - L Miocene 1974 12 77°38'S 162°51'E 75.1 m 185 m 98% migmatite - E Paleozoic McMurdo Sound area - offshore DVDP 15 1975 15 77°26'S 164°23'E -122 m 62 m 52% Barrett and Treves, 1981 black sand - E Pleist MSSTS 1979 1 77°34'S 163°23'E -195 m 230 m 62% Barrett, 1986 mudstone - L Oligocene CIROS 1986 1 77°05'S 164°30'E -197 m 702 m 98% Barrett, 1989 boulder congl - L Eocene CIROS 1984 2 77°41'S 163°32'E -211 m 168 m 67% Barrett and Hambrey, 1992 gneiss - E Paleozoic CRP 1997 1 77°00'S 163°45'E -154 m 148 m 86% CRST, 1998 diamict - E Miocene 1998 2 77°00'S 163°43'E -178 m 624 m 95% CRST, 1999 mudstone - Oligocene 1999 3 77°00'S 163°43'E -295 m 939 m 97% CRST, 2000 sandstone - Devonian ANDRILL 2006 1 77°55'S 167°01'E -840 m 1285 m 98% Naish et al., 2006 basalt - E Miocene Prydz Bay Barron, Larsen et ODP 119 1988 739 67°17'S 75°05'E -412 m 487 m 34% diamict - L Eo-E Oligocene al., 1988 1988 740 68°41'S 76°43'E -808 m 226 m 32% red beds - ?Triassic 1988 741 68°23'S 76°23'E -551 m 128 m 26% sandst, siltst -?E Cretaceous 1988 742 67°33S 75°24'E -416 m 316 m 53% mudst, diamict - ?Eo-Olig 1988 743 66°55'S 74°42'E -989 m 97 m 22% diamict - Pleistocene O'Brien, Cooper, Richter et ODP 188 2000 1166 67°42'S 74°47'E -475 m 381 m 19% claystone - L Cretaceous al., 2001 Antarctic Peninsula Barker, Camerlenghi, Acton et ODP 178 1998 1097 66°24'S 70°45'W -563 m 437 m 14% diamict - E Pliocene al., 1999 1998 1098 64°52'S 64°12'W -1010 m 47 m 99% mud - Holocene 1998 1099 64°57'S 64°19'W -1400 m 108 m 102% mud - Holocene 1998 1100 66°53'S 65°42'W -459 m 111 m 5% diamict - Pleistocene 1998 1102 66°48'S 65°51'W -431 m 15 m 6% diamict - Pleistocene? 1998 1103 64°00'S 65°28'W -494 m 363 m 12% diamict - L Miocene SHALDRIL 2005 1 62°17'S 58°45'W -488 m 108 m 87% http://shaldril.rice.edu/ mud - L Pleistocene Anderson et al., 2007 SHALDRIL 2006 3 63°51'S 54°39'W -340 m 20 m 32% mudst - L Eo/E Oligocene 2006 5 63°15'S 52°22'W -506 m 23 m 40% muddy sand - mid Miocene 2006 6 63°20'S 52°22'W -532 m 21 m n/a muddy sand - E Pliocene 2006 12 63°16'S 52°50'W -442 m 4m 64% mudst - Oligocene

OCR for page 71
73 NAISH ET AL. prevented penetration and recovery of the older record from much more frequent cycles of climate, ice volume, and sea gravity coring (Anderson, 1999). Plainly deep-drilling tech- level in the late Quaternary (Hays et al., 1976) in response nology was required from an appropriate location. Here we to variations in Earth’s orbital parameters calculated by summarize the history and rationale behind this successful Milankovitch. How far back in time these should be evident outcome. was not clear, but there seemed no reason why they should By the early 1970s the International Geophysical Year not have influenced the Antarctic ice sheet from the time of (1956-1958) had already resulted in a vast increase in knowl- its inception. edge of rock types, ages, and history of the continent itself While deep ocean sediments were useful for their (Bushnell and Craddock, 1970), but the history of its ice continuous record of past ocean chemistry, providing an sheet was still a mystery. This changed in early 1973 with the ice volume-temperature signal, they could not provide voyages of the Glomar Challenger to the South Indian Ocean information on the extent of ice or regional climate in the and Ross Sea (Leg 28) (Hayes et al., 1975) and the Tasman high latitudes. This could only come out of sediment cores Sea and Southwest Pacific Ocean (Leg 29) (Kennett et al., from the Antarctic margin, where the direct influence of ice 1974). The first of these cruises showed that the Antarctic advance and retreat (and perhaps also sea-level fall and rise) ice sheet, which had previously been seen as a Quaternary could be obtained. feature, had been in existence since at least the Oligocene. In the early 1970s two drilling platforms were available. The second yielded the first oxygen isotope measurements The Glomar Challenger operated by the Deep Sea Drilling on deep-sea calcareous microfossils, providing the first Project and a land-based system put together for the Dry evidence of dramatic ocean cooling and global ice volume Valley Drilling Project, an initiative of the United States, increase at the Eocene-Oligocene boundary (Shackleton and Japan, and New Zealand to explore the late Cenozoic history Kennett, 1974). of the McMurdo Dry Valleys (Smith, 1981). Over the next The 1970s was also a period in which detailed paleonto- three decades both of these platforms (and their successors) logical and chronological studies of cores from continuously ran in parallel (Table 1, Figure 1) with varying degrees of deposited deep-sea sediments displaced the long-held view success. of four major Quaternary glaciations (Flint, 1971), showing FIGURE 1 Locations of geological drill sites on land and on the Antarctic continen- tal shelf. Details and references are given in Table 1. McMurdo Sound drill sites are shown in Figure 2A.

OCR for page 71
74 ANTARCTICA: A KEYSTONE IN A CHANGING WORLD The ship-based system had the advantage that it could 1. Provide new knowledge on the late Neogene behav- be deployed at a number of places around the Antarctic ior and variability of the Ross Ice Shelf and Ross Ice Sheet margin, but was limited by ice conditions and poor recovery and the West Antarctic ice sheet, and their influence on global of glacimarine sediments from near-shore shelf basins. Nev- climate, sea-level, and ocean circulation. ertheless, the cores taken have provided useful constraints on 2. Provide new knowledge on the Neogene tectonic the Cenozoic history of the Antarctic ice margin and climate evolution of the West Antarctic Rift System, Transantarctic from the Ross Sea, Prydz Bay, and Antarctic Peninsula sec- Mountains, and associated volcanism. tors (Table 1). The land-based system, once adapted for sea ice, had the advantage that it could yield long and continuous A key outcome of the project will be to provide age core with near-complete recovery. However, it was rather control for, and determine the environmental significance of, cumbersome and required an ice platform that was firmly seismic reflectors that have been mapped regionally within tied to land. Although the system has been improved through the Victoria Land Basin (Fielding et al., 2007; Henrys et the MSSTS-1, CIROS, and Cape Roberts Projects (Table al., 2007) in order to assess the regional impact of global 1), continuing to exploit the fast-ice rim around McMurdo climatic and local tectonic events. A second key outcome of Sound as a drilling platform, attractive drilling targets the project will be to use paleoclimatic proxies and boundary beneath fast sea ice elsewhere on the Antarctic margin have conditions to help constrain numerical climate and dynami- yet to be identified. cal ice-sheet models. This paper presents an overview of the The results from both ship-based and sea-ice-based MIS Project, and the details are reported in the Initial Results drilling have provided a framework for the Cenozoic history volume (Naish et al., 2007). of the Antarctic ice sheet (Kennett and Warnke, 1992, 1993; Barrett, 1999), but more detail has become known for Oli- TECTONIC AND STRATIGRAPHIC SETTING gocene and early Miocene times, especially from the 1500 m of strata cored off Cape Roberts (Naish et al., 2001; Barrett, Ross Island lies at the southern end of the Victoria Land 2007), than in subsequent times. The first results of the shift Basin (VLB), a ~350-km-long, half-graben hinged on its from sea-ice- to shelf-ice-based drilling reported below add western side at the TAM front (Figure 2). Major rifting a great deal to the late Cenozoic story. in the VLB has occurred since the latest Eocene, perhaps having been initiated in the Cretaceous (Cooper and Davey, 1985; Brancolini et al., 1995), and has accommodated up THE ANDRILL MCMURDO ICE-SHELF PROJECT to 10 km of sediment. A new rift history, based on the CRP The aim of the MIS Project was to obtain a continuous sedi- drill cores linked to a new regional seismic stratigraphic ment core through approximately 1200 m of Neogene (~0-10 framework (Fielding et al., 2007; Henrys et al., 2007), Ma) glacimarine and volcanic sediment that had accumulated indicates that crustal stretching during the Oligocene syn- in the Windless Bight region of the MIS (Figure 2A). The rift phase produced rapid subsidence, followed by ther- present-day MIS forms the northwest part of Ross Ice Shelf mally controlled slower subsidence in the early Miocene. where it has been pinned by Ross Island for the last ~10 ka Renewed rifting within the center of the VLB beginning in (McKay et al., 2007), and is nourished by ice sourced locally the late Miocene has continued through to present day. This and from the East Antarctic ice sheet (EAIS) outlet glaciers forms the Terror Rift (Cooper et al., 1987) and is associated in the southern Transantarctic Mountains (TAM). The drill with alkalic igneous intrusions and extrusive volcanism site was situated above a flexural moat basin formed in (e.g., Beaufort Island and Ross Island). Quaternary loading response to Quaternary volcanic loading of the crust by Ross of the crust by the Ross Island volcanoes has added signifi- Island, superimposed on regional subsidence associated with cantly to subsidence near Ross Island, and the development Neogene extension of the Terror Rift (Horgan et al., 2005; of an enclosing moat (Stern et al., 1991). The Terror Rift has Naish et al., 2006) (Figure 2B). accommodated up to 3 km of Neogene sediment beneath Between October 29 and December 26, 2006, a single Windless Bight. Here the load-induced subsidence caused 1284.87-m-deep drill core (AND-1B) was recovered from by Ross Island has contributed significantly to the genera- the bathymetric and depocentral axis of the moat in 943 m tion of accommodation space, especially during the last 2 of water from an ice-shelf platform. The drilling technology m.y. (Horgan et al., 2005). employed a sea-riser system in a similar fashion to the Cape Neogene strata have now been extensively mapped in Roberts Project (CRP), but utilized a combination of soft southern McMurdo Sound from the Drygalski Ice Tongue sediment coring in upper soft sediments and continuous wire south to Ross Island. These Neogene strata show a thicken- line diamond-bit coring. Innovative new technology, in the ing and eastward-dipping succession extending under Ross form of a hot-water drill and over-reamer, was used to make Island in the vicinity of the MIS Project drill site. Analysis an access hole through 85 m of ice and to keep the riser free of these strata, which have now been sampled by MIS project during drilling operations. drilling, will contribute significantly to the young tectonic The MIS project has two key scientific objectives: history of the West Antarctic Rift System.

OCR for page 71
75 NAISH ET AL. FIGURE 2 (A) Location of key geographi- cal, geological, and tectonic features in southern McMurdo Sound. Volcanic centers of the Erebus Volcanic Province include Mt. Erebus (E), Mt. Terror (T), Mt. Bird (B), White Island (W), Black Island (B), Mt. Discovery (D), Mt. Morning (M), and Minna Bluff (MB). Boundary faults of the southern extension of Terror Rift are also shown. Location of ANDRILL Program drill sites and previous programs (DVDP, CIROS, MSST) are shown. (B) Schematic structural-stratigraphic cross-section across the VLB (located in [A] as “A-A”) shows the stratigraphic context of the MIS and SMS drill sites with respect to previous drilling in Southern McMurdo Sound. The cross-section is compiled from interpreted seismic reflection data, previous drill core data from MSSTS-1 and CIROS-1 (Barrett, 1986, 1989), and models for the evolution of the VLB. CHRONOSTRATIGRAPHY OF “AND-1B” representing more than half of the last 7 Ma. Thus the AND- 1B record provides several highly resolved “windows” into A preliminary age model for the upper 700 m of drill core the development of the Antarctic ice sheets during the late constructed from diatom biostratigraphy (Scherer et al., Cenozoic. Strata below ~620 mbsf are late Miocene in age 2007) and radiometric ages on volcanic material (Ross et (5-13 m.y.). At the time of writing, the chronostratigraphic al., 2007) allows a unique correlation of ~70 percent of the data available for this interval include three radiometric ages magnetic polarity stratigraphy with the Geomagnetic Polar- on volcanic clasts from near 1280 mbsf constraining the age ity Time Scale (Wilson et al., 2007). The age model provides for the base of the AND-1B drill core to <13.5 m.y. Work several well-constrained intervals displaying relatively continues to improve the age control on the lower part of the rapid (<1m/k.y.) and continuous accumulation of sediment cored interval. punctuated by several 0.5 m.y. to 1.0 m.y. stratal hiatuses

OCR for page 71
76 ANTARCTICA: A KEYSTONE IN A CHANGING WORLD RELATIONSHIP TO REGIONAL SEISMIC 1. Rg (Surface C, bilious green reflector): This STRATIGRAPHY regionally extensive discontinuity is correlated with top of a ~60-m-thick interval late Miocene volcanic sandstone (LSU Prior to drilling the MIS target, five distinctive reflectors 7) and the base of a 150-m-thick, high-velocity (3000 ms–1) marking regional stratal discontinuities had been mapped interval of diamictite cycles (LSU 6.4). 40Ar/39Ar dates on through a grid of seismic data in the vicinity of the drill ashes beneath Rg indicate that this discontinuity is <13.8 site (HPP and MIS lines) (Naish et al., 2006) (Figure 2), Ma. and linked to marine seismic reflection data and reflector 2. Rh (Surface B, dark green): This regionally nomenclature in McMurdo Sound (Fielding et al., 2007). We extensive discontinuity is correlated with the base of a have used whole-core velocity measurements and VSP first ~180-m-thick interval of late Miocene-early Pliocene, pyrite- arrival travel-time picks (see Hansaraj et al., 2007; Naish et cemented, high-velocity volcanic sandstone and mudstone al., 2007) to derive a time-depth conversion curve to convert (LSU 5). Regionally the green reflector correlates with the the seismic reflection section to depth. We have summarized base of volcanic bodies in the VLB north of Ross Island. It in Figure 3 and below our correlation of the regional seismic is also correlated with the base of White Island volcano (Fig- stratigraphy with the AND-1B drill core. ure 2) dated at ~7.6 Ma (Alan Cooper, University of Otago, unpublished data). FIGURE 3 Integrated plot correlating seismic reflectors with the lithologic log. We have used the whole-core velocity (c) to derive a time-depth conversion curve (b) together with VSP arrival times to map the seismic reflection profile from MIS-1 (a) to drill hole depth and correlate with core lithologies and lithostratigraphic units (e). Seismic stratigraphic units identified are from the MIS Science Logistics and Implementation Plan (SLIP) (Naish et al., 2006) and have been mapped regionally (Fielding et al., 2007).

OCR for page 71
77 NAISH ET AL. 3. Ri (Surface A2, b-clino, red reflector): This regionally extensive reflector marks the base of a ~100-m- thick seismically opaque interval that separates high-ampli- tude reflections of the underlying unit. It corresponds with the base of prograding clinoforms north of Ross Island, and locally marks the base of flexure associated with Ross Island volcanic loading (Horgan et al., 2005). In AND-1B, Surface A2 correlates with the boundary between the ~90-m- thick, low-density, low-velocity (1700 ms–1), early Pliocene diatomite interval (LSU 4.1), and the higher-velocity (<2500 ms–1) diamictites of LSU 4.2 beneath. Diatom assemblages indicate the age of this surface lies between 5.0 Ma and 4.0 Ma. Regionally this reflector has been traced into western VLB, where it is correlated biostratigraphically in MSSTS-1 to core at about 20 mbsf that yields a Pliocene age of 4.6-4.0 Ma based on diatom microfossils (Naish et al., 2006). 4. Rj (Surface A1, turquoise reflector): This region- ally extensive reflector marks the base of a ~150-m-thick unit of strongly alternating high- and low-amplitude reflections. These dramatic cycles in density and velocity reflect regular alternations between diatomite and diamictite in late Plio- cene (LSU 3). The turquoise reflector separates strata above that are younger than ~3.0 Ma and below greater than ~3.5 Ma. STRATIGRAPHIC ARCHITECTURE The 1285-m-long AND-1B drill core provides the first high- resolution, late Neogene record from the Antarctic margin (Figure 4) as well as the first long geological record from under a major ice shelf. Details of the lithostratigraphic sub- division, facies analysis, and sequence stratigraphy are pre- sented in an Initial Results volume (Krissek et al., 2007). Glacial-Interglacial Cyclostratigraphy At the time of writing, 60 unconformity-bounded glacima- rine sedimentary cycles, of probable Milankovitch duration have been identified, representing repeated advances and retreats of an ice sheet across the drill site during the late Neogene. Bounding unconformities, glacial surfaces of ero- sion (GSEs), are typically sharp and planar and mark disloca- tions between enclosing facies. Facies immediately beneath display a range of intraformational deformation features, including physical mixing of lithologies, clastic intrusions, faulting, and soft-sediment deformation. Facies above these surfaces are typically diamictites and conglomerates, and are interpreted as subglacial tillites or near grounding-line FIGURE 4 Lithostratigraphy, chronostratigraphy, and sequence stratigraphy of the AND-1B drillcore. Cyclic variations in litholo- gies reflect periodic fluctuations of the ice margin in western Ross Embayment during the last 13 Ma. Sources: * = After Ross et al. (2007); ^ = After Wilson et al. (2007).

OCR for page 71
78 ANTARCTICA: A KEYSTONE IN A CHANGING WORLD glacimarine deposits. In many cycles the facies succession itoid and metamorphic rocks from the Byrd Glacier region reflects retreat of the grounding line through ice shelf into imply the long-term existence of a grounded Ross Ice Sheet open-ocean environments at the interglacial minimum, fol- with short ice-shelf phases, and ice streaming from the south- lowed by ice readvance characterized by progressively more ern Transantarctic Mountains. Once a magnetostratigraphy glacially influenced facies in the upper parts, culminating in is developed for this section of the core together with new 40 Ar/39Ar ages, further sedimentological and petrographic a GSE at the glacial maximum. work should provide an important history of Antarctic ice sheet behavior during the “big” late Miocene, Mi-glaciations Major Chronostratigraphic Intervals and of Miller et al. (1991). Their Cyclic Character Here we summarize the sedimentary succession cored in Late Miocene, Diamictite/Mudstone-Sandstone Sedimentary AND-1B by subdividing it into nine chronostratigraphic Cycles of LSU 6.1-6.3 (1069.2-759.32 mbsf) intervals largely on the basis of characteristic facies cycles, with their glacial and climatic implications (Figure 4). The This section is characterized by cycles of subglacial and latter are addressed in more detail by Powell et al. (2007). grounding-line diamictites that pass upward into a gla- Three of the intervals lack cyclicity: interval 1 (a volcanic cimarine retreat succession of redeposited conglomerate, sandstone), interval 4 (largely volcanic ash), and interval 6 sandstone and mudstone. These units are overlain by a (the ~90-m-thick diatomite). more distal hemipelagic terrigenous mudstone with out- size clasts and lonestones. The retreat facies succession is 1. Late Miocene volcanic sandstone (1275.24-1220.15 then followed by a proglacial advance facies assemblage in mbsf), LSU 7. which clast abundance increases together with the occur- 2. Late Miocene diamictite-dominated sedimentary rence of submarine outwash facies, which is truncated by cycles (1220.15-1069.2 mbsf), LSU 6.4. a glacial surface of erosion. In contrast with the underly- 3. Late Miocene, diamictite/mudstone and sandstone ing diamictite-dominated interval, over 60 percent of this sedimentary cycles (1069.2-759.32 mbsf), LSU 6.1-6.3. unit comprises strata representing periods of both ice-shelf 4. Late Miocene-early Pliocene? lapilli tuff, lava flow, cover and open ocean, though still with significant ice raft- and volcanic sandstone and mudstone (759.32-586.45 mbsf), ing, over the drill site. These observations imply a warmer LSU 5. climate for this whole period, and the association increased 5. Early Pliocene diamictite/diatomite sedimentary subglacial meltwater. cycles (586.45-459.24 mbsf), LSU 4.2-4.4. 6. Early Pliocene diatomite (459.24-382.98mbsf), Late Miocene-early Pliocene Volcanic Sandstone and LSU 4.1. Mudstone of LSU 5 (759.32-586.45mbsf) 7. Late Pliocene diamictite and diatomite sedimentary cycles (459.25-146.79 mbsf), LSU 3. This interval is dominated by subaqueously redeposited 8. Late Pliocene-early Pleistocene diamictite/volcanic volcanic sediments, many with near-primary volcanic char- mudstone and sandstone cycles (146.79-82.72 mbsf), LSU 2. acteristics. The volcaniclastic sediments are organized into 9. Middle-late Pleistocene, diamictite-dominated sedi- sediment gravity flow deposits (mostly proximal turbidites), mentary cycles (82.72-0mbsf), LSU 1. indicating a nearby active volcanic center delivering primary volcanic material into a deep basin (several hundred meters water depth). A series of fining upward, altered and degraded Late-Miocene Diamictite-Dominated Cycles of LSU 6.4 pumice lapilli tuffs occur at 623, 603, and 590 mbsf, and a (1220.15-1069.2 mbsf) pure fine volcanic glass sand occurs at 577 mbsf. All of these This interval is dominated by thick massive diamictite with have been targeted for argon geochronology. A plagioclase thin stratified mudstone interbeds, representing alterna- Hawaiite lava with chilled margins and “baked sediments” tions between basal glacial and glacimarine deposition. under its lower contact interrupts the volcanic sediment The diamictites, which form over 90 percent of the interval, gravity flows at 646.49-649.30 mbsf, and has been dated by 40Ar/39Ar at 6.38 Ma. The source of this lava and the contain medium- to high-grade metamorphic basement clasts known from the Byrd Glacier region (Talarico et al., 2007). redeposited volcanic units is thought to be nearby because At this stage we have been conservative in our recognition of the freshness of the glass and angular nature of clasts in of grounding-line features in the core that might be used to the breccias. The unit is virtually devoid of out-size clasts identify boundaries of the sedimentary cycles. More detailed or other features indicative of iceberg rafting or grounding- study is likely to find features such as sets of alternating line proximity, suggesting that much of the 120-m-thick sharp-based massive and stratified diamictites, representing interval was deposited rapidly in open water. At this stage we subglacial and pro-grounding-line environments. The domi- consider this volcanic interval to represent a single eruptive nance of subglacial deposition and the occurrence of gran- sequence with very high rates of accumulation.

OCR for page 71
79 NAISH ET AL. Early Pliocene Diamictite and Diatomite Sedimentary Cycles tite (glacial and glacimarine) to diatomite (open ocean) are of LSU 4.2-4.4 (586.45-459.24 mbsf) dramatic, in many cases occurring in less than a meter of core. Powell et al. (2007) discuss these abrupt facies transi- These cycles can be summarized as comprising, in ascending tions in terms of rapid retreat of an ice sheet or collapse of an stratigraphic order: (1) a sharp-based massive diamictite with ice shelf. Our preliminary age model suggests that the cycles variable amounts of volcanic glass (subglacial to grounding in this interval may have formed in response to orbital forc- zone) passing up into (2) stratified diamictite, sandstone, ing of the ice sheet. This interval will be the focus of further and mudstone with dispersed clasts (grounding-line to dis- work as we evaluate its significance in terms of the global tal glacimarine) followed by (3) stratified diatomite (open climatic deterioration coincident with the development of ocean), which in turn commonly passes up into glacimarine large ice sheets on the northern hemisphere continents (e.g., mudstone and sandstone with dispersed clasts (perhaps an Shackleton et al., 1984; Maslin et al., 1999). indication of an approaching grounding line). The interval that includes the lower part of the diamictite and the under- Late Pliocene-Early Pleistocene Diamictite/Volcanic lying glacimarine lithologies is often physically intermixed Mudstone-Sandstone Cycles of LSU2 (146.79-82.72 mbsf) and displays deformation associated with glacial overriding and shearing but, interestingly, appears to represent little This interval displays lithologic alternations between ice- significant erosion by the advance. These cycles show a dra- proximal facies and open-water volcaniclastic facies. A matic change from hemipelagic open-water sedimentation GSE at 150.90 mbsf is correlated with the Rk-pink reflector to open-water biogenic sediments (diatomite) at interglacial and spans as much as 0.7 m.y. between 2.4 Ma and 1.7 Ma. ice minima. Above this the interval from 146.79 mbsf to 134.48 mbsf represents another glacial-interglacial cycle; that above the Early Pliocene Diatomite of LSU 4.1 (459.24-382.98 mbsf) diamictite is almost entirely made up of redeposited volcanic (basaltic) sandstone. The sandstone is organized into a series This interval is almost solely diatomite, indicating an of normally graded turbidites. The interval from 134.48 mbsf extended period of high-productivity open water over the to 120 mbsf is characterized by an open-water assemblage site. It is of early Pliocene age (~4.2 Ma) and is likely to span of interstratified mudstone and volcanic sandstone that lies a period of about 4.2-4.0 m.y., involving a number of glacial- stratigraphically above weakly stratified diamictite alternat- interglacial cycles. The onset of an inferred warmer period is ing with sparsely fossiliferous claystone and mudstone, captured in the 10 m transition beginning at 460 mbsf from a more typical of grounding line and iceberg zone systems. A clast-rich to clast-poor muddy diamictite through terrigenous muddy-sandy volcanic breccia with near-primary volcanic mud to diatomite, with a decline in mud component, out- material at 117 mbsf has yielded a preliminary 40Ar/39Ar age size clasts, and frequency of cm- to dm-thick gravity flow of ~1.6 Ma on basaltic volcanic glass. deposits. Further research is planned in order to quantify A dramatic change upward into massive diamictite the contemporaneous climate and will involve examination from 109.7 mbsf to 97.2 mbsf indicates the return of the ice of the terrestrial microfossils and estimation of sea-surface sheet to the proximity of the drill site. Our preliminary age temperatures from geochemical and biological proxies. This model suggests that up to ~0.4 m.y., between 1.5 Ma and diatomite appears to coincide with the widely recognized 1.1 Ma is missing between GSE at 109.7 mbsf and at least early Pliocene global warming and accompanying higher sea 2 GSEs in the overlying interval of amalgamated diamictite levels (Dowsett et al., 1999; Ravelo et al., 2004), for which above. From 97.2 mbsf to 92.5 mbsf diamictite and volcanic there is evidence elsewhere on the Antarctic margin (e.g., sandstone passes downward into interstratified bioturbated Whitehead et al., 2005). However, well-dated deposits and volcanic sandstone and mudstone. The interval from 92.5 geomorphological evidence from the adjacent McMurdo Dry mbsf to 86.6 mbsf contains the youngest biosiliceous-bearing Valleys indicate a polar climate persisted there throughout sediments in the AND-1B core. The presence of numerous this period (Marchant et al., 1996). volcaniclastic units and biosiliceous sediments in this interval indicate an extended period of open-water conditions with no Middle to Late Pliocene Diamictite and Diatomite sea ice beyond the calving line. An immediately overlying, Sedimentary Cycles of LSU 3 (382.98-146.79 mbsf) fining upward lapilli tuff between 85.86 mbsf and 85.27 mbsf has yielded a high-precision 40Ar/39Ar age on sanidine phe- Within this interval the core is strongly cyclic in nature, and nocrysts of 1.01 Ma within a short normal polarity interval is characterized by 12 glacial-interglacial cycles that is typi- interpreted as the Jaramillo Subchron. Thus the underlying cally composed of a sharp-based lower interval of diamictite biosiliceous interglacial sediments are tentatively correlated in the upper few meters that passes upward into a ~5- to with warming during the “super-interglacial” associated with 10-m-thick unit of biosiliceous ooze or biosiliceous-bearing Marine Isotope Stage 31. This interval will be the focus of mudstone (diatomite). The lower part of diamictites and the a future concentrated effort to better characterize the impact upper few meters of diatomites are sheared and deformed, of this warm period on ice-sheet behavior. presumably from grounded ice. The transitions from diamic-

OCR for page 71
80 ANTARCTICA: A KEYSTONE IN A CHANGING WORLD Middle-Late Pleistocene, Diamictite-Dominated Sedimentary imply changes in ice-sheet volume that must have contrib- Cycles of LSU 1 (82-0 mbsf) uted significantly to eustasy (e.g., 10-20 m). Cold early Miocene and Pleistocene till-dominated Between 83 mbsf and 27 mbsf there are at least 8 cycles of intervals with clasts originating in the TAM to the south diamictite and thinner bioturbated and stratified intervals imply that grounded ice from the big outlet glaciers to the of mudstone, volcanic sandstone, and muddy conglomer- south was reaching McMurdo Sound during these times. ate. Like the late Miocene diamictite-dominated cycles, the Today Byrd Glacier-sourced ice in the shelf flows east of high proportion of subglacial and grounding-line proximal Ross Island. Glaciological reconstructions (e.g., Denton and deposits, together with the occurrence of granitoid and meta- Hughes, 2000) require significant ice volume from WAIS to morphic rocks known from the Byrd Glacier region (Talarico direct the flow lines of the southern outlet glaciers into the et al., 2007), implies existence of a grounded Ross Ice Sheet McMurdo region during glacial periods, and also to main- in the middle and late Pleistocene. The implied presence of tain an ice shelf during ensuing interglacial retreats. Thus, a grounded ice sheet for much of this time is intriguing as it we view the sedimentary cycles representing primarily the also corresponds with a period of Earth history dominated expansion and contraction of WAIS in concert with fluctua- by 80-120 ka fluctuations in large Northern Hemisphere ice tions in the flow of TAM outlet glaciers. The TAM outlet sheets. Further work will focus on (1) how this ice sheet glaciers alone do not provide enough ice volume to maintain responded to the late Pleistocene interglacials, which in Ant- an ice sheet or ice shelf in the Ross Embayment. arctic ice-core records indicated polar temperatures warmer Work is planned in the near future to further understand than today (EPICA Community, 2004; Jouzel et al., 2007), and constrain ice-sheet dynamics, especially during periods and (2) the role of orbital forcing on Antarctic ice sheets of hypothesized global warmth that will provide useful ana- (e.g., Huybers and Wunsch, 2005; Raymo et al., 2006) in logues for constraining the behavior of Antarctic ice sheets regulating Pleistocene climate. in the context of future climate change. To achieve this we will integrate our core data—such as clast provenance, bio- IMPLICATIONS FOR ANTARCTIC GLACIAL AND logical and geochemical proxies—with the new generation CLIMATE HISTORY of ice-sheet and climate models. The AND-1B core has the potential to contribute significant SUMMARY new knowledge about the dynamics of the West Antarctic ice sheet (WAIS) and Ross Ice Shelf and Ice Sheet system, Repetitive vertical successions of facies imply at least 60 as well as contributing to understanding the behavior of fluctuations of probable Milankovitch duration between the EAIS outlet glaciers during the late Cenozoic. New subglacial, ice-proximal, and ice-distal open marine envi- chronological data will allow certain intervals of the core to ronments. These have been grouped into three main facies be correlated with other proxy climate records (e.g., ice and associations that correspond to glacial-interglacial variability marine isotope records) and hence the sensitivity of the ice during climatically distinct periods of the late Neogene: sheet to a range of past global climate changes to be evalu- ated. The significant results thus far are that the Ross Ice 1. Cold polar climate with MIS site dominated by Sheet, fed by WAIS and EAIS outlet glaciers, has undergone grounded ice but some retreat to ice-shelf conditions (late significant cyclic variations in extent and timing during the Miocene, ~13-10 Ma and Pleistocene, ~1-0 Ma). late Neogene. A relatively colder and more stable ice sheet 2. Warmer climate with MIS site dominated by dominated the Ross Embayment in the early late Miocene ice-shelf and open-water conditions (hemipelagites), with between 13 Ma and 10 Ma, becoming more dynamic in the occasional periods of grounded ice (early-late Miocene, ~9-6 latest Miocene (9-7 Ma) with subglacial water discharge, Ma). still with periodic grounded ice in the Ross Embayment. 3. Warmer climate with extended periods of open- These conditions were followed by a period around 4 Ma ocean conditions (pelagic diatomites) with periods of sub-ice when the Ross Embayment was relatively ice-free, with shelf and grounded ice deposition (Pliocene, ~5-2 Ma). highly productive, warmer oceanic conditions, followed by a return to cycles of advance and retreat of grounded ice. From The ~90-m-thick early Pliocene (~4.2 Ma) interval of middle Pleistocene to Recent the ice sheet is characterized diatomite shows no apparent glacial cyclicity and represents by a change back to more stable, colder conditions. Our pre- an extended period of ice-free conditions indicative of a liminary analysis of the more than 25 Pliocene sedimentary reduced WAIS. Late Pliocene (~2.6-2.2 Ma) glacial-inter- cycles indicates significant glacial-interglacial variability, glacial cycles characterized by abrupt alternations between with regular oscillations between subglacial/ice proximal subglacial/ice-proximal facies and open marine diatomites and open-ocean ice distal environments, including extended imply significant WAIS volume fluctuations around the time periods of interglacial warmth when the ice was not calving of the early Northern Hemisphere glaciations. A ~4-m-thick into the ocean. Our environmental reconstructions to date interval of diatomaceous mudstone in the middle Pleistocene

OCR for page 71
81 NAISH ET AL. Bushnell, V. C., and C. Craddock, eds. 1970. Antarctic Map Folio Series. also represents similar open-ocean interglacial conditions. New York: American Geographical Society, Map 64-29. The last million years is dominated by deposition from Cape Roberts Science Team (CRST). 1998. Initial Report on CRP-3. Terra grounded ice with periods of sub-ice-shelf sedimentation Antartica 5:1-187. like the present day. Cape Roberts Science Team (CRST). 1999. Studies from the Cape Roberts Project, Ross Sea, Antarctica. Initial Report on CRP-2/2A. Terra Antar- tica 6(with supplement):1-173. ACKNOWLEDGMENTS Cape Roberts Science Team (CRST). 2000. Studies from the Cape Roberts Project, Ross Sea, Antarctica. Initial Report on CRP-3. Terra Antartica The ANDRILL project is a multinational collaboration of the 7(with supplement):1-209. Antarctic Programs of Germany, Italy, New Zealand, and the Cooper, A. K., and F. J. Davey. 1985. Episodic rifting of the Phanerozoic United States. Antarctica New Zealand is the project operator rocks of the Victoria Land basin, western Ross Sea, Antarctica. Science 229:1085-1087. and has developed the drilling system in collaboration with Cooper, A. K., F. J. Davey, and J. C. Behrendt. 1987. Seismic stratigraphy Alex Pyne at Victoria University of Wellington and Webster and structure of the Victoria Land Basin, Western Ross Sea, Antarctica. Drilling and Enterprises Ltd. Antarctica New Zealand sup- In The Antarctic Continental Margin: Geology and Geophysics of the ported the drilling team at Scott Base and Raytheon Polar Western Ross Sea, eds. A. K. Cooper and F. J. Davey. Earth Science Services supported the science team at McMurdo Station and Series 5B:27-77. Houston, TX: Circum-Pacific Council Energy Mineral Resources. the Crary Science and Engineering Laboratory. Scientific Denton, G. H., and T. J. Hughes. 2000. Reconstruction of the Ross ice support was provided by the ANDRILL Science Manage- drainage system, Antarctica, at the last glacial maximum. Geografiska ment Office, University of Nebraska-Lincoln. Scientific Annaler 82:143-166. studies are jointly supported by the U.S. National Science Dowsett, H. J., J. A. Barron, R. Z. Poore, R. S. Thompson, T. M. Cronin, S. Foundation, NZ Foundation for Research, the Italian Antarc- E. Ishman, and D. A. Willard. 1999. Middle Pliocene Paleoenvironmen- tal Reconstruction: PRISM2. U.S. Geological Survey Open File Report tic Research Program, the German Science Foundation, and 99-535, http://pubs.usgs.gov/openfile/of99-535/. the Alfred-Wegener-Institute. EPICA Community Members. 2004. Eight glacial cycles from an Antarctic ice core, Nature 429:623-628. Fielding, C. R., J. Whittaker, S. A. Henrys, T. J. Wilson, and T. R. Naish. REFERENCES 2007. Seismic facies and stratigraphy of the Cenozoic succession in Anderson, J. B. 1999. Antarctic Marine Geology. Cambridge: Cambridge McMurdo Sound, Antarctica: Implications for tectonic, climatic and University Press. glacial history. Palaeogeography, Palaeoclimatology, Palaeoecology. Anderson, J. B., J. Wellner, S. Wise, S. Bohaty, P. Manley, T. Smith, F. In Antarctica: A Keystone in a Changing World—Online Proceedings Weaver, and D. Kulhanek. 2007. Seismic and chronostratigraphic for the Tenth International Symposium on Antarctic Earth Sciences, eds. results from SHALDRIL II, Northwestern Weddell Sea. In Antarctica: Cooper, A. K., C. R. Raymond et al., USGS Open-File Report 2007- A Keystone in a Changing World—Online Proceedings for the Tenth 1047. Short Research Paper 090, doi:10.3133/of2007-1047.srp090. International Symposium on Antarctic Earth Sciences, eds. Cooper, Flint, R. F. 1971. Glacial and Quaternary Geology. New York: Wiley. A. K., C. R. Raymond et al., USGS Open-File Report 2007-1047. Short Hansaraj, D., S. A. Henrys, T. R. Naish, and ANDRILL MIS-Science Team. Research Paper 094, doi:10.3133/of2007-1047.srp094. 2007. McMurdo Ice Shelf seismic reflection data and correlation to the Barker, P. F., A. Camerlenghi, G. D. Acton et al. 1999. Proc. Ocean AND-1B drill hole. In Antarctica: A Keystone in a Changing World Drilling Program, Initial Report 178, http://www-odp.tamu.edu/ —Online Proceedings for the Tenth International Symposium on Ant- publications/178_IR/178TOC.HTM. arctic Earth Sciences, eds. Cooper, A. K., C. R. Raymond et al., USGS Barrett, P. J., ed. 1986. Antarctic Cenozoic history from the MSSTS-1 drill Open-File Report 2007-1047, Extended Abstract 101, http://pubs.usgs. hole, McMurdo Sound, Antarctica. NZ DSIR Bulletin, 237 pp. gov/of/2007/1047/. Barrett, P. J. ed. 1989. Antarctic Cenozoic history from the CIROS-1 drill- Hayes, D. E., L. A. Frakes et al. 1975. Initial Reports of the Deep Sea hole, McMurdo Sound, Antarctica. NZ DSIR Bulletin, 245 pp. Drilling Project, vol. 28. Washington, D.C.: U.S. Government Printing Barrett, P. J. 1999. Antarctic climate history over the last 100 million years. Office. Terra Antartica 3:53-72. Hays, J. D., J. Imbrie, and N. J. Shackleton. 1976. Variations in the earth’s Barrett, P. J. 2007. Cenozoic climate and sea level history from glacimarine orbit: Pacemaker of the ages. Science 194:1121-1132. strata off the Victoria Land coast, Cape Roberts Project, Antarctica. In Henrys, S. A., T. J. Wilson, J. M. Whittaker, C. R. Fielding, J. M. Hall, Glacial Processes and Products, eds. M. J. Hambrey, P. Christoffersen, and T. Naish. 2007. Tectonic history of mid-Miocene to present N. F. Glasser, and B. Hubbart. International Association of Sedimentolo- southern Victoria Land Basin, inferred from seismic stratigraphy in gists Special Publication 39:259-287. McMurdo Sound, Antarctica. In Antarctica: A Keystone in a Changing Barrett, P. J., and M. J. Hambrey. 1992. Plio-Pleistocene sedimentation in World—Online Proceedings for the Tenth International Symposium Ferrar Fiord, Antarctica. Sedimentology 39:109-123. on Antarctic Earth Sciences, eds. Cooper, A. K., C. R. Raymond et Barrett, P. J., and S. B. Treves. 1981. Sedimentology and petrology of al., USGS Open-File Report 2007-10477, Short Research Paper 049, core from DVDP 15, western McMurdo Sound. In Dry Valley Drilling doi:10.3133/of2007-1047.srp049. Project, ed. L. D. McGinnis. Antarctic Research Series 81:281-314. Horgan, H., T. Naish, S. Bannister, N. Balfour, and G. Wilson. 2005. Seismic Washington, D.C.: American Geophysical Union. stratigraphy of the Ross Island flexural moat under the McMurdo-Ross Barron, J., B. Larsen et al. 1989. Proc. Ocean Drilling Program, Initial Ice Shelf, Antarctica, and a prognosis for stratigraphic drilling. Global Report 119. College Station, TX: Ocean Drilling Program. Planetary Change 45:83-97. Brancolini, G., et al. 1995. Descriptive text for the seismic stratigraphic atlas Huybers, P., and C. Wunsch. 2005. Obliquity pacing of the late Pleistocene of the Ross Sea, Antarctica. In Geology and Seismic Stratigraphy of the glacial terminations. Nature 434:491-494. Antarctic Margin, eds. A. K. Cooper, P. F. Barker, and G. Brancolini, Jouzel, J., et al. 2007. Orbital and Millennial Climate variability over the Antarctic Research Series 68:271-286. Washington, D.C.: American past 800,000 years. Science 317:793-796. Geophysical Union.

OCR for page 71
82 ANTARCTICA: A KEYSTONE IN A CHANGING WORLD Kennett, J. P., and D. A. Warnke, eds. 1992. The Antarctic Paleoenviron- Powell, R. D., T. R. Naish, L. A. Krissek, G. H. Browne, L. Carter, E. A. ment: A Perspective on Global Change, Part 1. Antarctic Research Cowan, G. B. Dunbar, R. M. McKay, T. I. Wilch, and the ANDRILL-MIS Series, vol. 56. Washington, D.C.: American Geophysical Union. Science team. 2007. Antarctic ice sheet dynamics from evidence in the Kennett, J. P., and D. A. Warnke, eds. 1993. The Antarctic Paleoenviron- ANDRILL-McMurdo Ice Shelf Project drillcore (AND-1B). In Antarc- ment: A Perspective on Global Change, Part 2. Antarctic Research tica: A Keystone in a Changing World—Online Proceedings for the Tenth Series, vol. 60. Washington, D.C.: American Geophysical Union. International Symposium on Antarctic Earth Sciences, eds. Cooper, A. Kennett, J. P., R. E. Houtz et al. 1974. Initial Reports of the Deep Sea K., C. R. Raymond et al., USGS Open-File Report 2007-1047, Extended Drilling Project, vol. 29. Washington, D.C.: U.S. Government Printing Abstract 201, http://pubs.usgs.gov/of/2007/1047/. Office. Ravelo, A. C., D. H. Andreasen, L. Mitchell, A. O. Lyle, and M. W. Wara. Krissek, L. A., G. Browne, L. Carter, E. Cowan, G. Dunbar, R. McKay, 2004. Regional climate shifts caused by gradual global cooling in the T. Naish, R. Powell, J. Reed, T. Wilch, and the ANDRILL-MIS Sci- Pliocene epoch. Nature 429:263-267. ence Team. 2007. Sedimentology and stratigraphy of the ANDRILL Raymo, M. E., L. E. Lisecki, and K. H. Nisancioglu. 2006. Plio-Pleistocene ice volume, Antarctic climate, and the global 18O record. Science McMurdo Ice Shelf (AND-1B) core. In Antarctica: A Keystone in a Changing World—Online Proceedings for the Tenth International Sym- 313:492-495. Ross, J., W. C. McIntosh, and N. W. Dunbar. 2007. Preliminary 40Ar/39Ar posium on Antarctic Earth Sciences, eds. Cooper, A. K., C. R. Raymond et al., USGS Open-File Report 2007-1047, Extended Abstract 148, results from the AND-1B core. In Antarctica: A Keystone in a Chang- http://pubs.usgs.gov/of/2007/1047/. ing World—Online Proceedings for the Tenth International Symposium Kyle, P. R. 1981. Geological history of Hut Point Peninsula as inferred from on Antarctic Earth Sciences, eds. Cooper, A. K., C. R. Raymond et al., DVDP 1, 2 and 3 drill cores and surface mapping. In Dry Valley Drill- USGS Open-File Report 2007-1047, Extended Abstract 093, http://pubs. ing Project, ed. L. D. McGinnis. Antarctic Research Series 81:427-445. usgs.gov/of/2007/1047/. Washington, D.C.: American Geophysical Union. Scherer, R., D. Winter, C. Sjunneskog, and P. Maffioli. 2007. The diatom Marchant, D. R., G. H. Denton, C. C. Swisher, III, and N. Potter, Jr. 1996. record of the ANDRILL-McMurdo Ice Shelf project drillcore. In Late Cenozoic Antarctic paleoclimate reconstructed from volcanic ashes Antarctica: A Keystone in a Changing World—Online Proceedings for in the Dry Valleys region of southern Victoria Land. Geological Society the Tenth International Symposium on Antarctic Earth Sciences, eds. of America Bulletin 108:181-194. Cooper, A. K., C. R. Raymond et al., USGS Open-File Report 2007- Maslin, M. A., Z. Li, M.-F. Loutre, and A. Berger. 1999. The contribution of 1047, Extended Abstract 171, http://pubs.usgs.gov/of/2007/1047/. orbital forcing to the progressive intensification of Northern Hemisphere Shackleton, N. J., and J. P. Kennett. 1974. Paleotemperature history of glaciation. Quaternary Science Reviews 17:411-426. the Cenozoic and the initiation of Antarctic glaciation: Oxygen and McKay, R., Dunbar, G., Naish, T. R., Barrett, P., Carter, L., Harper, M. 2007. Carbon isotope analyses in DSDP Sites 277, 279 and 281. In Initial Retreat of the Ross Ice Shelf since the Last Glacial Maximum derived Reports of the Deep Sea Drilling Project, vol. 29, eds. J. P. Kennett, from sediment cores in deep basins surrounding Ross Island. Paleo- R. E. Houtz et al., pp. 743-756. Washington, D.C.: U.S. Government climatology, Paleogeography, Paleoecology. A Sediment Model and Printing Office. Retreat History for the Ross Ice (Sheet) Shelf in the Western Ross Sea Shackleton, N. J., et al. 1984. Oxygen isotope calibration of the onset of Since the Last Glacial Maximum. In Antarctica: A Keystone in a Chang- ice-rafting and history of glaciation in the North Atlantic region. Nature ing World—Online Proceedings for the Tenth International Symposium 307:620-623. on Antarctic Earth Sciences, eds. Cooper, A. K., C. R. Raymond et al., Smith, P. M. 1981. The role of the Dry Valley Drilling Project in Antarctic USGS Open-File Report 2007-1047, Extended Abstract 159, http://pubs. and international science policy. In Dry Valley Drilling Project, ed. usgs.gov/of/2007/1047/. L. D. McGinnis. Antarctic Research Series 81:1-5. Washington, D.C.: Miller, K. G., J. D. Wright, and R. G. Fairbanks. 1991. Unlocking the ice American Geophysical Union. house: Oligocene-Miocene oxygen isotopes, eustasy, and margin ero- Stern, T. A., F. J. Davey, and G. Delisle. 1991. Lithospheric flexure induced sion. Journal of Geophysical Research 96:6829-6848. by the load of the Ross Archipelago, southern Victoria Land, Antarc- Naish, T. R., et al. 2001. Orbitally induced oscillations in the East Antarctic tica. In Geological Evolution of Antarctica eds. M. R. A. Thomson, ice sheet at the Oligocene/Miocene boundary. Nature 413:719-723. A. Crame, and J. W. Thomson, pp. 323-328. Cambridge: Cambridge Naish, T. R., R. H. Levy, R. D. Powell, and the ANDRILL MIS Science University Press. and Operations Teams. 2006. ANDRILL McMurdo Ice Shelf Scientific Talarico, F., et al. 2007. Clast provenance and variability in MIS (AND-1B) Logistical Implementation Plan. ANDRILL Contribution No. 7. Lin- core and their implications for the paleoclimatic evolution recorded in coln: University of Nebraska-Lincoln. the Windless Bight, southern McMurdo Sound area (Antarctica). In Naish, T. R., R. D. Powell, R. H. Levy, and the ANDRILL-MIS Science Antarctica: A Keystone in a Changing World—Online Proceedings for Team. 2007. Initial science results from AND-B, ANDRILL McMurdo the Tenth International Symposium on Antarctic Earth Sciences, eds. Ice Shelf Project, Antarctica. Terra Antartica 14(2). Cooper, A. K., C. R. Raymond et al., USGS Open-File Report 2007- O’Brien, P. E., A. K. Cooper, C. Richter et al. 2001. Proc. Ocean 1047, Extended Abstract 118, http://pubs.usgs.gov/of/2007/1047/. Drilling Program, Initial Report 188, http://www-odp.tamu.edu/ Whitehead, J. M., S. Wotherspoon, and S. M. Bohaty. 2005. Minimal Ant- publications/188_IR/188ir.htm. arctic sea ice during the Pliocene. Geology 33:137-140. Powell, R. D. 1981. Sedimentation conditions in Taylor Valley inferred from Wilson, G. S., et al. 2007. Preliminary chronostratigraphy for the upper textural analyses of DVDP cores. In Dry Valley Drilling Project, ed. L. 700 m (late Miocene-Pleistocene) of the AND-1B drillcore recovered D. McGinnis. Antarctic Research Series 81:331-350. Washington, D.C.: from beneath the McMurdo Ice Shelf, Antarctica. In Antarctica: A American Geophysical Union. Keystone in a Changing World—Online Proceedings for the Tenth International Symposium on Antarctic Earth Sciences, eds. Cooper, A. K., C. R. Raymond et al., USGS Open-File Report 2007-1047, Extended Abstract 092, http://pubs.usgs.gov/of/2007/1047/.