Browsing by Author "Hättestrand, C"

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    Characteristic cosmogenic nuclide concentrations in relict surfaces of formerly glaciated regions
    (Wiley, 2006-08-21) Stroeven, AP; Harbor, J; Fabel, D; Kleman, J; Hättestrand, C; Elmore, D; Fink, D
    This chapter contains sections titled: Significance of relict surfaces Characteristic cosmogenic nuclide concentrations in relict surfaces Conclusions © 2006 by Blackwell Science Ltd
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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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    Slow, patchy landscape evolution in northern Sweden despite repeated ice sheet glaciation
    (Geological Society of America, 2006-01-01) Stroeven, AP; Harbor, J; Fabel, D; Kleman, J; Hättestrand, C; Elmore, D; Fink, D; Fredin, O
    The conventional assumption that erosion by ice sheets is pervasive and effective in landscape evolution is tested in northern Sweden using geomorphic mapping and cosmogenic nuclide analyses of formerly glaciated surfaces. The following evidence indicates that recent glaciations in this region have produced only slow and patchy landscape evolution: (1) Geomorphic mapping shows that at least 20% of the repeatedly glaciated study region in the northern Swedish mountains has landforms that are relict, i.e., clearly nonglacial in origin. (2) The contrast between cosmogenic apparent exposure ages from relict landforms in the northern Swedish mountains and from overlying glacial erratics and juxtaposed glacially eroded bedrock surfaces, which are consistent with last deglaciation, implies that the relict landforms have been preserved through multiple glacial cycles. (3) Apparent 10Be and 26Al exposure ages for tor summit bedrock surfaces in the northern Swedish lowlands reveal that these relict landforms have survived at least eleven exposure and ten burial events with little or no erosion over the past ∼1 m.y. (4) The northern Swedish lowland and mountains are primarily covered by glacial landforms. However geomorphic mapping suggests that even these landforms may have undergone limited erosion during the last glacial cycle. Cosmogenic 10Be and 36Cl data from what appear to be heavily scoured areas in one glacial corridor indicate erosion of only ∼2 ± 0.4 m of bedrock during the last glaciation. These results suggest that in some areas the overall modification produced by ice sheets may be more restricted than previously thought, or it has occurred preferentially during earlier Quaternary glacial periods. © 2020 GeoScienceWorld