Sedimentary environment of the Nottinghambukta delta, SW Spitsbergen

Abstract: The Nottinghambukta delta is a very young landform (< 50 years old). It was cre− ated by the capture (possibly due to a rapid neotectonic event) of the proglacial stream sys− tem of Kvisla River to the South by the Bratteggelva catchment. The delta plain shows a lobate, but asymmetric form. The northern part remains in a state of equilibrium between large scale glaciofluvial deposition and the erosional energy of tides, whereas, in the south− ern, rapid progradation predominates. During high tides, almost the whole delta plain (ex− cept northern part of the proximal zone) is submerged and delta distributary channels be− come tidal channels. In the proximal parts of the distributary channels, the lithofacies vary from massive sandy gravel and planar cross−beds in gravel or sandy gravel to horizontally stratified sandy gravel. In the distal zone, only ripple cross−lamination in sandy gravel, sand or silty sand is present. Interchannel areas are generally finer−grained and are represented by sandy gravel assemblages which change to ripple cross−lamination in sand (silty sand) and laminated silt (sandy silt). The gravel deposits are quite immature and consist of lithoclasts exclusively. The grain−size distribution of sand is extremely polymodal, probably as a result of slight reworking of moraine material, with mixing of material from different fluvial envi− ronments, common changes in velocity of feeder streams and addition of eolian sediment