HOLOCENE RELATIVE SEA-LEVEL HISTORY OF FRANZ-JOSEF-LAND, RUSSIA

One of the largest uncertainties in ice-volume changes during the late Quaternary Period is the extent of ice sheets over the Barents and Ka ra seas, Field research on central and eastern Franz Josef Land, Russi a, provide new observations on postglacial emergence and deglaciation that further constrain the magnitude and timing of late Weichselian gl aciations, Radiocarbon dating of driftage from raised-marine sequences place deglacial unloading prior to 9.4 ka. At a number of localities within 1 to 2 km of the present glacier margin, in situ shells from ra ised-marine sediments yield C-14 ages between 9.7 and 8.4 yr B.P., evi dence that outlet glaciers were at or behind present margins by the ea rly Holocene Period. The altitude of the marine limit on Franz Josef L and ranges from 49 to 20 m above sea level (asl) and is low compared t o eastern Svalbard (110 to 60 m asl), The age of the marine limit rang es from greater than or equal to 10.4 ka to ca, 6.0 ka and exhibits gr eater diachrony where emergence is <35 m, A low initial rate of emerge nce reflects glacio-isostatic compensation offset by a eustatic rise i n sea level, and perhaps an additional component from renewed water lo ading of the Barents Sea after deglaciation. The presence of raised be aches at 1 to 4 m asl that are 1 to 2 ka indicates that uplift is inco mplete, Are exponential extrapolation of uplift data for Franz Josef L and and eastern Svalbard yields current maximum uplift estimates of 0. 7 to 1.6 mm/yr, an inferred <5.5 m of uplift remaining, These values a re at least 50% to 80% lower than the inferred uplift residual for a m odeled ice sheet in the Barents and Kara seas, The discrepancy indicat es that further refinement is needed for this ice-sheet model. The com pilation of emergence data from Franz Josef Land, Svalbard, and Novoya Zemyla confine maximum glacio-isostatic compensation to the Barents S ea; comparatively minor ice sheet loads were over Novaga Zemlya and th e southeastern Parents Sea, Emergence isobases since 5 and 9 ka descen d northward across Franz Josef Land, indicating a diminishing glacio-i sostatic response into the Arctic Ocean.