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 Conclusions...................................................................................................................36 2.1.8 Acknowledgements.......................................................................................................37 2.1.9 References.....................................................................................................................37 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 References.....................................................................................................................80 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