The response of Antarctic ice volume, global sea-level and southwest Pacific Ocean circulation to

272 Pages·2014·12.97 MB·English

by  Molly Patterson

The response of Antarctic ice volume, global sea-level and southwest Pacific Ocean
circulation to orbital variations during the Pliocene to Early Pleistocene

by
Molly O’Rourke Patterson

A thesis
Submitted to Victoria University of Wellington
In fulfilment of the requirements for the degree of
Doctor of Philosophy
In Geology

Victoria University of Wellington
2014

ABSTRACT
This thesis investigates orbitally-paced variations in the extent of East Antarctic Ice Sheet
(EAIS), and the “downstream” influence of these ice sheet variations on ocean circulation
and sea level variability during the Pliocene and Early Pleistocene - a time period
characterised by a major global cooling step that culminated in the development of a bipolar
glaciated world. Three unique records are examined from (1) the Antarctic margin, (2) the
southwest Pacific Ocean, and (3) shallow-marine sedimentary strata exposed in Wangnaui
Basin, New Zealand.

The Integrated Ocean Drilling Program (IODP) Site U1361 recovered a continuous
sedimentary Early Pliocene to Early Pleistocene (4.3 to 2.0 Ma) record from the lowermost
continental rise on the Wilkes Land margin offshore of the EAIS. A facies model and
stratigraphic framework were developed that allowed for the identification of glacial
advances (massive and laminated mudstones) and retreats (diatom-rich mudstones) across
the continental shelf, with evidence for prolonged retreats spanning several glacial to
interglacial cycles throughout the Pliocene. These cycles are followed by an extensive Early
Pleistocene interval (~2.6 Ma) of diatom-rich mudstone with evidence for reworking by
bottom currents, interpreted to be the consequence of downslope density currents associated
with increased sea ice production after 2.6 Ma. Frequency analysis on Iceberg Rafted Debris
(IBRD) from Site U1361 reveals that under an Early Pliocene warm climate state (4.3 to 3.3
Ma), that ice discharge off the EAIS occurred in response to climate change paced by the 40-
kyr cycles of obliquity. Whereas, the colder climate state of Late Pliocene to Early
Pleistocene (3.3 to 2.0 Ma) resulted in a transferral of orbital variance to 20-kyr-duration,
precession-dominated variability in IBRD preceding the development of a more stable
marine-based margin of the EAIS at ~2.6 Ma, which is hypothesized to reflect the declining
influence of oceanic forcing as the high-latitude Southern Ocean cooled thereby increasing
the seasonal duration and extent of sea-ice. The precession-paced influence on IBRD and ice
volume variability of the EAIS was strongly modulated by 100-kyr-eccentricity, which is
expressed lithologically in cycles of two alternating lithofacies 1) diatom-rich mudstones and
2) massive and laminted mudstones in the Site U1361 record.

A compilation of benthic stable isotope records from Ocean Drilling Program (ODP) Site
1123 in the southwest Pacific Ocean was also developed. The δ18O record identified a 40-kyr
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obliquity pacing, consistent with other benthic δ18O records globally for this time period, thus
allowing for an orbitally-tuned timescale to be developed for this site. Long-term trends in
both the δ18O and δ13C records at ODP Site 1123 coincide with major developments of the
Antarctic Ice Sheet and Northern Hemisphere glaciation at 3.33 Ma and ~2.6 Ma
respectively. A gradual reduction in the deep water δ13C gradient between the southwest
Pacific (ODP Site 1123) and equatorial Pacific (ODP Site 849) between 3.33 and 2.6 Ma
coincides with expansion of the Antarctic Ice Sheet, enhanced Antarctic Bottom Water
(AABW) production, invigorated atmospheric zonal circulation in the southern hemisphere
mid-latitudes, and increased meridional sea surface temperature (SST) gradients in the
Pacific Ocean.

Finally, a shallow-marine, continental margin stratigraphic section from the Turakina River
Valley in the Wanganui Basin, New Zealand, was used to record local sea-level changes,
dominated by orbitally-driven, global glacio-eustasy, during the mid-Pliocene interval (3.2 to
3.0 Ma). This interval was selected as it precedes the build-up of significant Northern
Hemisphere Ice Sheet, thus allowing for an independent assessment of the orbtial-scale
variability of Antarctic Ice Sheet volume. Grain size based proxy of percent mud was
employed to reconstruct paleobathymetric changes, which displayed 100-kyr cycles
consistent with ~20 m variations in local water depths during the mid-Pliocene. Combined
with IBRD record from Site U1361, this reconstruction suggests that the marine margins of
East Antarctica varied at orbital timescale, and provided a significant contribution to global
eustatic sea-level variations during the mid Pliocene (consistent with global mean sea-level
estimates of up to ~+20 m above present from related studies).

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ACKNOWLEDGEMENTS
First and foremost, I would like to thank Rob McKay and Tim Naish for supervising this
project. You two have been nothing but supportive, encouraging and entertaining throughout
this process. Rob, you really know how to bring the rigor (fist pump).

Thanks to all the staff and students in the Antarctic Research Centre. In particularly, Gavin
Dunbar for his helpful insight towards lab and field work that aided in the development of
data sets presented in Chapters 4 and 5 of this thesis. I would also like to thank Lionel Carter
for his useful conversations and insight. Thanks to Lana Cohen for her field assistance.

I am also thankful to the scientist I have interacted with during aspects of work presented in
this thesis as well as towards my professional development over these past few years; Amy
Leventer (Colgate University), Scott Ishman (Southern Illinois University of Carbondale),
Gillian Turner (VUW), Helen Bosotock (NIWA) and Mark Fenwick (NIWA). A special
thanks to Carlota Escutia (Universidad de Granada) for her assistance towards interpretation
of the sediment model presented in Chapter 2, Steven Meyers (University of Wisconsin) for
his enthusiasm and advanced statistical analysis towards data sets discussed in this thesis,
Maureen Raymo (Lamont-Doherty Earth Observatory, Columbia University) for challenging
me intellectually, and Gary Wilson (University of Otago) for the use of the age model
presented in Chapter 4.

This thesis presents large data sets which have only been made possible through a
combination of lab assistance and support from Jennifer Staffenberg, Jane Chewings and
Ashley Pocock. I am especially grateful to Rob Dunbar, Dave Mucciarone and their students
for their hospitality as well as assistance during my visit to Stanford University. Furthermore,
I would like to thank shipboard scientist of Ocean Drilling Program Leg 181 and the
Integrated Ocean Drilling Program Expedition 318 for their successful recovery and data sets
from the marine sediment records presented in this thesis.

Thanks to all my family and friends for their constant support and encouragement throughout
the years. I have particularly appreciated the photos of “the little ones” and packages of wine.
Finally, I want to give a special thanks to Cal. The most SUPPORTIVE and PATIENT special
man-friend any special woman-friend could ever ask for.

Financial support for this thesis comes from the Victoria PhD Scholarship and Marsden
Funds.

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TABLE OF CONTENTS

ABSTRACT
ACKNOWLEDGEMENTS
TABLE OF CONTENTS
LIST OF FIGURES
LIST OF TABLES
REFERENCES
ABBREVIATION INDEX
APPENDIX A
APPENDIX B
APPENDIX C

INTRODUCTION (Page 1)

CHAPTER 1: ORBITAL CLIMATE FORCING AND THE PLIOCENE-EARLY
PLEISTOCENE (Page 8)
1.1 Orbitally driven climate forcing (Page 8)
1.1.1 Introduction (Page 8)
1.1.2 Identifying the 100,000 year ice age cycles since the Mid-Pleistocene
Transition (MPT) (~800,000 years ago) (Page 13)
1.1.3 The Pliocene and Early Pleistocene 40,000 year debate (Page 16)
1.2 The onset of Late Pliocene global cooling and Northern Hemisphere glaciations (Page
19)
1.2.1 Small scale Northern Hemisphere glaciations prior to the Early Pliocene (Page
19)
1.2.2 Amplified warming in the Northern high latitudes during the Pliocene (Page
20)
1.2.3 North Atlantic Ocean circulation (Page 22)
1.2.4 The equatorial Pacific warm pool and proposed mechanisms (Page 24)
1.2.5 East Antarctica and the Southern Ocean during the warm Pliocene (5.332 to
3.330 myr) (Page 28)
1.2.6 West Antarctic and Ross Sea variability during the Pliocene (Page 32)
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1.2.7 Expansion of the Antarctic ice sheet and Northern Hemisphere ice sheets
during the Late Pliocene-Early Pleistocene cooling (~3.330 to ~2.000 Ma)
(Page 34)

CHAPTER 2: PLIOCENE-EARLY PLEISTOCENE SEDIMENTATION PROCESSES
AND STRATIGRAPHY FOR IODP SITE U1361 DRILL CORE RECOVERED OFF
THE WILKES LAND MARGIN, EAST ANTARCTICA (Page 40)
2.1 Introduction (Page 40)
2.1.1 Setting and general depositional processes (Page 42)
2.1.2 Adelie Land Bottom Water (ALBW) formation along the Wilkes Land margin,
Antarctica (Page 44)
2.1.3 IODP Site U1361 Chronology (Page 46)
2.1.4 Previous high latitude deep-sea channel levee/ridge depositional models (Page
48)
2.2 Methods (Page 55)
2.2.1 Iceberg Rafted Debris Mass Accumulation Rate calculation (Page 56)
2.2.2 Grain size distribution of the fine grain (<150 µm) material (Page 56)
2.2.3 Productivity indicators (Page 57)
2.2.4 Identification of iceberg rafted debris versus lag deposits (Page 58)
2.2.5 Distribution of laminae (Page 59)
2.3 Results (Page 60)
2.3.1 Lithofacies (Page 61)
2.4 Discussion (Page 63)
2.4.1 Facies interpretation (Page 63)
2.4.2 Identification of glacial to interglacial sedimentation processes (Page 65)
2.4.3 Stratigraphic framework (Page 70)
2.4.4 Diatom-rich/bearing Mudstone during Late Pliocene-Early Pleistocene cooling
(3.3 to 2.0 Ma) (Page 72)
2.5 Conclusion (Page 74)

CHAPTER 3: ORBITAL RESPONSE OF THE EAST ANTARCTIC ICE SHEET
DURING THE PLIOCENE-EARLY PLEISTOCENE: IMPLICATIONS FOR
GLOBAL SEA LEVEL CHANGES (Page 76)
3.1 Introduction (Page 76)
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3.2 Methods (Page 78)
3.2.1 Frequency analysis (Page 78)
3.2.2 Theoretical background to frequency analysis (Page 79)
3.3 Results (Page 80)
3.4 Discussion (Page 84)
3.4.1 Iceberg rafted debris as a proxy (Page 84)
3.4.2 Cyclostratgraphy framework (Page 86)
3.4.3 Implications for an East Antarctic contribution to sea level during the warm
Early Pliocene (Page 89)
3.4.4 Significance of the Site U1361 iceberg rafted derbis orbital signature (Page 89)
3.5 Conclusions (Page 92)

CHAPTER 4: BOTTOM WATER INFLOW INTO THE SOUTHWEST PACIFIC
OCEAN DURING THE PLIOCENE-EARLY PLEISTOCENE (Page 94)
4.1 Introduction (Page 94)
4.1.1 ODP Site 1123 and bottom water inflow into the southwest Pacific Ocean
(Page 95)
4.1.2 Using stable carbon isotopes to identify changes in deepwater circulation
(Page 98)
4.1.3 Southern Ocean ventilation and the G-I cycle (Page 99)
4.1.4 Lithostratigraphy (Page 102)
4.2 Methods (Page 102)
4.2.1 Age model (Page 103)
4.2.2 Stable isotopes (Page 105)
4.2.3 Comparison to pre-existing stable isotope records (Page 107)
4.2.4 Sortable silt analysis (Page 108)
4.2.5 Frequency analysis (Page 109)
4.3 Results (Page 110)
4.3.1 Stable isotopes (Page 112)
4.3.2 Interbasinal stable isotope gradients (Page 118)
4.3.3 Sedimentological parameters (Page 121)
4.4 Discussion (Page 123)
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4.4.1 The deposition of terrigenous material and the vigor of pacific abyssal in-flow
during the warm Early to mid-Pliocene (Page 123)
4.4.2 Pliocene-Early Plesitocene orbital forcing on ice volume and the carbon cycle
(Page 127)
4.4.3 Southern Ocean ventilation during the Late Pliocene cooling and the onset of
the bipolar world (Page 128)
4.5 Summary (Page 134)

CHAPTER 5: IDENTIFYING ORBITAL PACING OF ANTARCTIC ICE VOLUME
VARIATIONS FROM MID-PLIOCENE SEA LEVEL FLUCTUATIONS RECORDED
IN A FAR-FIELD SHALLOW-MARINE CONTINENTAL MARGIN SEDIMENT
RECORD: THE WANGANUI BASIN, NEW ZEALAND (Page 136)
5.1 Introduction (Page 136)
5.1.1 Geological Setting and Paleogeography (Page 140)
5.1.2 Pliocene-Pleistocene sea level records and cyclostratigraphy from Wanganui
Basin, New Zealand (Page 142)
5.1.3 The Turakina River Section of Wanganui Basin (Page 144)
5.2 Methodology (Page 147)
5.3 Results/Discussion (Page 151)
5.3.1 Lithostratigraphy (Page 151)
5.3.2 Cyclostratigraphy (Page 160)
5.3.3 Implications of the Turakina River Section cyclostratigraphy (Page 162)
5.3.4 Future work (Page 164)

CHAPTER 6: SUMMARY AND CONCLUDING REMARKS (Page 166)
6.1 Reconstructing southern high latitude Earth system responses during the warm Early
Pliocene climate (5.3 to 3.3 Ma) (Page 166)
6.2 Southern high latitude Earth system responses and feedbacks through the global Late
Pliocene cooling event (3.3 to 2.7 Ma) (Page 168)

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LIST OF FIGURES
Figure 1: Mid-Pliocene Sea Surface Temperature and Land Surface Temperature anomalies
(Page 2)
Figure 1.1: Orbital parameters frequency modulations for the last million years (Page 9)
Figure 1.2: Schematic diagram of Earth’s orbital configuration (Page 10)
Figure 1.3: Orbital parameters related to the deep sea benthic δ18O stack recording ice volume
(Page 12)
Figure 1.4: Power spectra analysis highlighting the 100-ky cycle of ice volume (Page 16)
Figure 1.5: Seasonal cycle when Northern Hemisphere winter solstice is at perihelion (Page
18)
Figure 1.6: Northern Hemisphere Ice-Rafted Debris since 50 Ma years ago (Page 20)
Figure 1.7: The Lake El’gygytgyn northern Siberia record (Page 21)
Figure 1.8: Enhanced NADW formation and circulation (Page 23)
Figure 1.9: Proxy records inferring the Pacific warm pool (Page 27)
Figure 1.10: Geological records inferring East Antarctic Ice Sheet and sea ice extent (Page 30)
Figure 1.11: Early Pliocene East Antarctic Ice Sheet records (Page 31)
Figure 1.12: Step wise cooling from the Early Pliocene to Early Pleistocene bi-polar world
(Page 38)
Figure 2.1: Location and bathymetry of the Wilkes Land margin (Page 43)
Figure 2.2: Seismic reflection profile of the Wilkes Land continental margin (Page 44)
Figure 2.3: Adélie Land depression ocean circulation (Page 46)
Figure 2.4: Magnetostratigraphic tie points for U1361 (Page 48)
Figure 2.5: Schematic diagram of turbidite facies (Page 54)
Figure 2.6: IBRD MAR versus lag deposits (Page 59)
Figure 2.7: Ternary diagram displaying textural classification of lithofacies (Page 60)
Figure 2.8: Representative photo of Early Pleistocene Diatom-rich/bearing Mudstone (Page
62)
Figure 2.9: Representative photo of Pliocene lithofacies (Page 62)
Figure 2.10: Cross plot of biogenic opal wt. percent and Ba/Al (Page 63)
Figure 2.11: Schematic diagrams displaying interpreted climate stages influence on
depositional processes at Site U1361 (Page 69)
Figure 2.12: Stratigraphic log with lithology, facies, bioturbation, lithostratigraphy cycles and
grain size data (Page 71)
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