Late Miocene-Pliocene glacial cyclicity in a deep-sea sediment drift on the Antarctic Peninsula continental margin [Elektronische Ressource] : sedimentary and diagenetic processes / vorgelegt von Daniel A. Hepp

Daniel A. Hepp

Informations

• Publié par: universitat_bremen
• Publié le: 01 janvier 2007
• Nombre de lectures: 14
• Langue: English
• Poids de l'ouvrage: 10 Mo

Extrait

Late Miocene-Pliocene glacial cyclicity in a deep-sea
sediment drift on the Antarctic Peninsula continental
margin: Sedimentary and diagenetic processes



Dissertation
zur Erlangung des
Doktorgrades in den Naturwissenschaften
am Fachbereich Geowissenschaften
der Universität Bremen






vorgelegt von
M. A. Daniel A. Hepp









Bremen, Mai 2007




















Tag des Kolloquiums:
22. Juli 2007


Gutachter:
Prof. Dr. T. Mörz
Prof. Dr. R. Stein


Prüfer:
Prof. Dr. R. Henrich
Prof. Dr. H.-J. Kuss
Table of Content
Abstract (Zusammenfassung) .............................................................................................................. 1
1 Introduction................................................................................................................................. 5
1.1 The role of southern high latitude processes in the global climate regime ............................5
1.1.1 West and East Antarctic Ice Sheet dynamic ...................................................................5
1.1.2 Thermohaline circulation and the Southern Ocean.........................................................6
1.1.3 Why is the late Miocene/early Pliocene warming episode from special interest? ..........8
1.2 The Pacific continental margin of the West Antarctic Peninsula.........................................10
1.2.1 Geological and oceanographic background ..................................................................10
1.2.2 Why is Drift 7 (ODP Site 1095) the place to go for?....................................................12
1.2.3 The link between ice sheet dynamics, sedimentary processes and drift build up .........14
1.3 Publications ..........................................................................................................................15
1.4 References ............................................................................................................................15
2 Manuscripts ............................................................................................................................... 19
2.1 Manuscript 1: Pliocene glacial cyclicity in a deep-sea sediment drift on the Pacific Margin
of the Antarctic Peninsula (ODP Leg 178, Site 1095) .........................................................19
2.1.1 Abstract.........................................................................................................................19
2.1.2 Introduction...................................................................................................................20
2.1.3 Regional setting ............................................................................................................20
2.1.4 Methods ........................................................................................................................25
2.1.5 Results...27
2.1.6 Discussion.....................................................................................................................29
2.1.7 Conclusions36
2.1.8 Acknowledgements.......................................................................................................37
2.1.9 References37
2.2 Manuscript 2: A late Miocene-early Pliocene Antarctic deepwater record of cyclic iron
reduction events....................................................................................................................41
2.2.1 Abstract.........................................................................................................................41
2.2.2 Introduction...................................................................................................................41
2.2.3 Regional setting ............................................................................................................43
2.2.4 Methods ........................................................................................................................44
2.2.5 Results...47
2.2.6 Discussion.....................................................................................................................49
2.2.7 Conclusion ....................................................................................................................55 2.2.8 Acknowledgement ........................................................................................................56
2.2.9 Reference list ................................................................................................................56
2.3 Manuscript 3: An approach to quantify the Pliocene ice sheet dynamics via slope failure
frequencies recorded in Antarctic Peninsula rise sediments.................................................61
2.3.1 Abstract.........................................................................................................................61
2.3.2 Introduction...................................................................................................................61
2.3.3 Methods ........................................................................................................................64
2.3.4 Results...74
2.3.5 Discussion.....................................................................................................................76
2.3.6 Conclusion ....................................................................................................................79
2.3.7 Acknowledgement ........................................................................................................80
2.3.8 References80
3 Selected Abstracts ..................................................................................................................... 85
3.1 Reconstruction of Antarctic ice-sheet history from drift sediments.....................................85
3.2 Comparison of glacial-interglacial turbidite deposits in West Antarctic Peninsula deep-sea
drifts......................................................................................................................................86
3.3 Pliocene glacial cyclicity and diagenetic effects in a deep-sea sediment drift on the Pacific
margin of the Antarctic Peninsula (ODP Leg 178, Site 1095) .............................................87
3.4 Cyclic diagenetic alterations in drift sediments (Antarctic Peninsula pacific margin) ........88
4 Conclusion ................................................................................................................................. 89
5 Acknowledgement (Danksagung) ............................................................................................ 91
[ Abstract (Zusammenfassung) ] 1
Abstract (Zusammenfassung)
The presented sedimentological, geochemical and paleoceanographical work is intended to
improve the understanding of the regional influence of West Antarctic Ice Sheet dynamics and
changes in oceanographic conditions on (1) sedimentary processes and (2) the preservation of proxies
in the sedimentary record. A crucial feature for interpreting ice sheet dynamics is the understanding of
the glacial driven sedimentary transport system across the shelf to the slope and subsequently to the
deep-sea sediment bodies. Giant deep-sea sediment drifts are widespread features along the Pacific
Continental Margin of the West Antarctic Peninsula, representing the most proximal continuous
sedimentary recorders for West Antarctic ice events and glacial-interglacial cyclicity. Sediment
physical and geochemical records, and X-ray images derived from ODP Site 1095 (Drift 7, ODP Leg
178) were used to identify pattern in glacial-interglacial cyclicity and associated sedimentary and
diagenetic processes during late Miocene and Pliocene. Two boundary types dividing half-cycles have
been recognized: (1) interglacial-to-glacial transitions are characterized by a sharp boundary and
abrupt change in lithology, (2) glacial-to-interglacial transitions are diffuse and can be described as a
gradual change from a full glacial to a full interglacial stage. The transitions are characterized by a
gradual decline of sediment physical and geochemical values with a marked reduction in
sedimentation rates. A prominent feature of the glacial-to-interglacial transition is the loss of the
magnetic susceptibility signal. This loss is related to a massive ice sheet collapse at the end of
deglaciation phases. Ice sheet collapse and meltwater formation increase the stratification of the water
column and weaken the bottom water formation and convection, but foster short lived diatom blooms
resulting in high fluxes of organic matter to the seafloor. The high organic fluxes result in temporary
suboxic to anoxic near surface sediment conditions causing pronounced diagenetic alteration and
demagnetization of magnetic iron. At long time-scales the intensity and loss of magnetic susceptibility
in sixty-four zones of sediment cores from ODP Site 1095 reflect global long-term trends as well as
the local variability of primary export production. In this context, warm Pliocene climate conditions
for West Antarctic Peninsula region