Browsing by Author "Hollis, Christopher J."

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    Eocene (46–44 Ma) Onset of Australia‐Pacific Plate Motion in the Southwest Pacific Inferred From Stratigraphy in New Caledonia and New Zealand
    (Wiley, 2020) Dallanave, Edoardo; Maurizot, Pierre; Agnini, Claudia; Sutherland, Rupert; Hollis, Christopher J.; Collot, Julien; Dickens, Gerald R.; Bachtadse, Valerian; Strogen, Dominic; Morgans, Hugh E.G.
    The Pacific plate circuit went through a complex reorganization during the early to middle Eocene, approximately coinciding with the onset of subduction along the western Pacific margin. However, the timing and dynamics of this change in the southwest Pacific and evolution of subduction beneath the Tonga‐Kermadec Arc are not fully resolved. We present magneto‐biostratigraphic data from an early to middle Eocene sedimentary section exposed in the Koumac‐Gomen area, New Caledonia, which is an emerged portion of the Norfolk Ridge. The 260 m‐thick succession contains a transition from pelagic micrite to terrigenous‐rich calciturbidite that is observed regionally in New Caledonia and which is interpreted to represent a shift from sedimentation on a stable submarine plateau to slope formation developed under a convergent tectonic regime. The stratigraphic contact between pelagic micrite and overlying calciturbidite is not exposed, but our magnetic polarity‐based chronology constrains the age of transition to 46–44 Ma, in agreement with the 45.3 Ma age recently obtained from the Noumea area in southern New Caledonia. We integrate records from New Caledonia with recent magnetostratigraphic data from South Island, New Zealand, where marked variations in terrigenous input occurred during the early and middle Eocene. Synchronous sedimentary changes in the southwest Pacific occurred at the same time as onset of rapid seafloor spreading south of Australia and New Zealand. We infer that the underlying cause of stratigraphic change was inception of slip at a new configuration of the Australia‐Pacific plate boundary, which evolved into the Tonga‐Kermadec subduction system.
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    Large-Amplitude Variations in Carbon Cycling and Terrestrial Weathering during the Latest Paleocene and Earliest Eocene: The Record at Mead Stream, New Zealand
    (University of Chicago Press, 2012) Slotnick, Benjamin S.; Dickens, Gerald R.; Nicolo, Micah J.; Hollis, Christopher J.; Crampton, James S.; Zachos, James C.; Sluijs, Appy
    The late Paleocene to early Eocene was marked by major changes in Earth surface temperature and carbon cycling. This included at least two, and probably more, geologically brief (<200-k.yr.) intervals of extreme warming, the Paleocene-Eocene thermal maximum (PETM) and the Eocene thermal maximum-2 (ETM-2). The long-term rise in warmth and short-term “hyperthermal” events have been linked to massive injections of 13C-depleted carbon into the ocean-atmosphere system and intense global climate change. However, the causes, environmental impact, and relationships remain uncertain because detailed and coupled proxy records do not extend across the entire interval of interest; we are still recognizing the exact character of the hyperthermals and developing models to explain their occurrence. Here we present lithologic and carbon isotope records for a 200-m-thick sequence of latest Paleocene– earliest Eocene upper slope limestone exposed along Mead Stream, New Zealand. New carbon isotope and lithologic analyses combined with previous work on this expanded section shows that the PETM and ETM-2, the suspected H-2, I-1, I-2, and K/X hyperthermals, and several other horizons are marked by pronounced negative carbon isotope excursions and clay-rich horizons. Generally, the late Paleocene–early Eocene lithologic and δ¹³C records at Mead Stream are similar to records recovered from deep-sea sites, with an important exception: lows in δ¹³C and carbonate content consistently span intervals of relatively high sedimentation (terrigenous dilution) rather than intervals of relatively low sedimentation (carbonate dissolution). These findings indicate that, over ~6 m.yr., there was a series of short-termclimate perturbations, each characterized by massive input of carbon and greater continental weathering. The suspected link involves global warming, elevated greenhouse-gas concentrations, and enhanced seasonal precipitation.
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    The DeepMIP contribution to PMIP4: methodologies for selection, compilation and analysis of latest Paleocene and early Eocene climate proxy data, incorporating version 0.1 of the DeepMIP database
    (Copernicus Publications, 2019) Hollis, Christopher J.; Dunkley Jones, Tom; Anagnostou, Eleni; Bijl, Peter K.; Cramwinckel, Margot J.; Cui, Ying; Dickens, Gerald R.; Edgar, Kirsty M.; Eley, Yvette; Evans, David; Foster, Gavin L.; Frieling, Joost; Inglis, Gordon N.; Kennedy, Elizabeth M.; Kozdon, Reinhard; Lauretano, Vittoria; Lear, Caroline H.; Littler, Kate; Lourens, Lucas; Meckler, A. Nele; Naafs, B. David A.; Pälike, Heiko; Pancost, Richard D.; Pearson, Paul N.; Röhl, Ursula; Royer, Dana L.; Salzmann, Ulrich; Schubert, Brian A.; Seebeck, Hannu; Sluijs, Appy; Speijer, Robert P.; Stassen, Peter; Tierney, Jessica; Tripati, Aradhna; Wade, Bridget; Westerhold, Thomas; Witkowski, Caitlyn; Zachos, James C.; Zhang, Yi Ge; Huber, Matthew; Lunt, Daniel J.
    The early Eocene (56 to 48 million years ago) is inferred to have been the most recent time that Earth's atmospheric CO2 concentrations exceeded 1000 ppm. Global mean temperatures were also substantially warmer than those of the present day. As such, the study of early Eocene climate provides insight into how a super-warm Earth system behaves and offers an opportunity to evaluate climate models under conditions of high greenhouse gas forcing. The Deep Time Model Intercomparison Project (DeepMIP) is a systematic model–model and model–data intercomparison of three early Paleogene time slices: latest Paleocene, Paleocene–Eocene thermal maximum (PETM) and early Eocene climatic optimum (EECO). A previous article outlined the model experimental design for climate model simulations. In this article, we outline the methodologies to be used for the compilation and analysis of climate proxy data, primarily proxies for temperature and CO2. This paper establishes the protocols for a concerted and coordinated effort to compile the climate proxy records across a wide geographic range. The resulting climate “atlas” will be used to constrain and evaluate climate models for the three selected time intervals and provide insights into the mechanisms that control these warm climate states. We provide version 0.1 of this database, in anticipation that this will be expanded in subsequent publications.