Browsing by Author "Strömberg, B"

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    Deglaciation of Fennoscandia
    (Elsevier, 2016-09-01) Stroeven, AP; Hättestrand, C; Kleman, J; Heyman, J; Fabel, D; Fredin, O; Goodfellow, BW; Harbor, JM; Jansen, JD; Olsen, L; Caffee, MW; Fink, D; Lundqvist, J; Rosqvist, GC; Strömberg, B; Jansson, KN
    To provide a new reconstruction of the deglaciation of the Fennoscandian Ice Sheet, in the form of calendar-year time-slices, which are particularly useful for ice sheet modelling, we have compiled and synthesized published geomorphological data for eskers, ice-marginal formations, lineations, marginal meltwater channels, striae, ice-dammed lakes, and geochronological data from radiocarbon, varve, optically-stimulated luminescence, and cosmogenic nuclide dating. This is summarized as a deglaciation map of the Fennoscandian Ice Sheet with isochrons marking every 1000 years between 22 and 13 cal kyr BP and every hundred years between 11.6 and final ice decay after 9.7 cal kyr BP. Deglaciation patterns vary across the Fennoscandian Ice Sheet domain, reflecting differences in climatic and geomorphic settings as well as ice sheet basal thermal conditions and terrestrial versus marine margins. For example, the ice sheet margin in the high-precipitation coastal setting of the western sector responded sensitively to climatic variations leaving a detailed record of prominent moraines and other ice-marginal deposits in many fjords and coastal valleys. Retreat rates across the southern sector differed between slow retreat of the terrestrial margin in western and southern Sweden and rapid retreat of the calving ice margin in the Baltic Basin. Our reconstruction is consistent with much of the published research. However, the synthesis of a large amount of existing and new data support refined reconstructions in some areas. For example, the LGM extent of the ice sheet in northwestern Russia was located far east and it occurred at a later time than the rest of the ice sheet, at around 17–15 cal kyr BP. We also propose a slightly different chronology of moraine formation over southern Sweden based on improved correlations of moraine segments using new LiDAR data and tying the timing of moraine formation to Greenland ice core cold stages. Retreat rates vary by as much as an order of magnitude in different sectors of the ice sheet, with the lowest rates on the high-elevation and maritime Norwegian margin. Retreat rates compared to the climatic information provided by the Greenland ice core record show a general correspondence between retreat rate and climatic forcing, although a close match between retreat rate and climate is unlikely because of other controls, such as topography and marine versus terrestrial margins. Overall, the time slice reconstructions of Fennoscandian Ice Sheet deglaciation from 22 to 9.7 cal kyr BP provide an important dataset for understanding the contexts that underpin spatial and temporal patterns in retreat of the Fennoscandian Ice Sheet, and are an important resource for testing and refining ice sheet models. © 2015 The Authors. Under a Creative Commons license.
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    Mass balance assessment of initial weathering processes derived from oxygen cionsumption rares in waste sulfide ore
    (United States Department of The Interior Bureau of Mines, 1994-04-24) Strömberg, B; Banwart, SA; Bennett, JW; Ritchie, AIM
    A stoichiometric model for initial weathering processes in fresh waste rock has been developed for Aitik ore. Based on element mass balances, solubility equilibrium, mineralogy of unreacted waste rock, and literature data, we identified the dominant geochemical processes and determined geochemical reaction rates for weathering of pyrite, chalcopyrite, calcite, plagioclase and biotite using fluxes derived from large experimental columns filled with waste rock. The oxidation rate of reduced Fe and S was based on Oz-consumption rates that were previously determined in the columns. In the fresh waste rock, acidity production from pyrite weathering and rapid consumption of acidity by calcite dissolution dominate the proton balance. At an acidity production rate of 7.8 meq. kg-I year! of waste rock and a calcite alkalinity reservoir of 0-60 meq. kg-I, we expect the waste rock leachate to remain near-neutral pH for 0-8 years. When calcite is consumed and pH drops, dissolution of previously precipitated copper on the the order of 0-1.8 mmole copper kg-I of waste rock may temporarily increase the pollution load at the site.