Glacifluvial Sediments Research Articles

A 230 ka record of glacial and interglacial events from Aurora Cave, Fiordland, New Zealand

Abstract Caves overrun by glaciers are known to accumulate dateable evidence of past glacial and interglacial events. Results are reported from an investigation of Aurora Cave on the slopes above Lake Te Anau in Fiordland. The cave commenced to form before c. 230 ka B.P. Sequences of glacifluvial sediments interbedded with speleothems are evidence of the number and timing of glacial advances and the status of intervals between them. Twenty‐six uranium series dates on speleothems underpin a chronology of seven glacial advances in the last 230 ka, with the peak of the late Otira glaciation, Aurora 3 advance, at c. 19 ka B.P. With five advances in the Otiran, the last glaciation is more complex than previously recognised. Comparison of the record with that recorded offshore from DSDP Site 594 reveals little matching, but the correspondence of the Aurora sequence with that interpreted from other onshore deposits is more convincing. Glacial deposits on slopes above the cave for a further 660 m may be evidence of the “missing” glacial events of the mid—early Pleistocene.

Wirkungen des pleistozänen kaltzeitlichen Klimas, insbesondere des Bodenfrostes, in den Sedimenten des östlichen Ostfalen (Raum Hannover - Wolfsburg - Helmstedt -Bad Harzburg - Salzgitter-Bad - Hannover) - Teil 1

Abstract. In this first part of the publication - a second part especially about ice-wedges and aeolian processes will follow in the next year - the abundant form inventory of diversified periglacial solifluction layers, of horizons of gelifraction, of congelifractates, of frost kettles "Frostkessel", geologic "Stiche", of the "Hakenschlagen", of glacigen structures of icefoldings and of cryoturbation structures in eastern Lower Saxony (eastern part of Ostfalen) is photographed, described, explained and dated. Most parts of the forms can be found in probably Saalian (Drenthe) glacifluvial and morainic sediments. In the southern part of the loess border which divides the researched region in a northern and a southern part, the Saalian sediments are covered by loessic sediments of high Weichselian age. The loessic deposits are used for the datation of the older diversified solifluction layers as well as for the many cryoturbation phenomena. Mostly the formation of the latter sediments has just begun in the second part of the Saalian time. Recrding to the depth where the cryoturbation phenomenareach down, the mollisol in top of the permafrost had had an extensure of 1,0 to 1,5 m during the Upper Saalian and the whole Weichselian period.

Flux of debris transported by ice at three Alaskan tidewater glaciers

AbstractThe stability of a tidewater terminus is controlled by glacial dynamics, calving processes and sedimentary processes at the grounding line. An investigation of grounding-line sediment dynamics and morainal-bank sediment budgets in Glacier Bay, Alaska, U.S.A., has yielded data that enable us to determine the debris fluxes of Grand pacific, Margerie and Muir Glaciers. Debris flux ranges from 105to 106m3a−1, one to two orders of magnitude lower than the glacifluvial sediment fluxes (106−107m3a−1). Combined, these fluxes represent the highest yields known for glacierized basins. Large debris fluxes reflect the combined effects of rapid glacier flow, driven by the maritime climate of southeast Alaska, and highly erodible bedrock. Englacial-debris distribution is affected by valley width and relief, both of which control the availability of sediment. The number of tributaries controls the distribution and volume of debris in englacial and supraglacial moraines. At the terminus, iceberg-rafting removes up to two orders of magnitude more sediment from the ice-proximal environment than is deposited by melt-out or is dumped during calving events. Rough estimates of the sediment flux by deforming beds suggests that soft-bed deformation may deliver up to an order of magnitude more sediment to the terminus than is released from within the glacier ice.

Flux of debris transported by ice at three Alaskan tidewater glaciers

AbstractThe stability of a tidewater terminus is controlled by glacial dynamics, calving processes and sedimentary processes at the grounding line. An investigation of grounding-line sediment dynamics and morainal-bank sediment budgets in Glacier Bay, Alaska, U.S.A., has yielded data that enable us to determine the debris fluxes of Grand pacific, Margerie and Muir Glaciers. Debris flux ranges from 105 to 106 m3 a−1, one to two orders of magnitude lower than the glacifluvial sediment fluxes (106−107 m3 a−1). Combined, these fluxes represent the highest yields known for glacierized basins. Large debris fluxes reflect the combined effects of rapid glacier flow, driven by the maritime climate of southeast Alaska, and highly erodible bedrock. Englacial-debris distribution is affected by valley width and relief, both of which control the availability of sediment. The number of tributaries controls the distribution and volume of debris in englacial and supraglacial moraines. At the terminus, iceberg-rafting removes up to two orders of magnitude more sediment from the ice-proximal environment than is deposited by melt-out or is dumped during calving events. Rough estimates of the sediment flux by deforming beds suggests that soft-bed deformation may deliver up to an order of magnitude more sediment to the terminus than is released from within the glacier ice.

Late Weichselian glacial stratigraphy in the Brorfelde area, Denmark, based on statistical analysis of different till parameters

Abstract Thick glacifluvial sediments in the Brorfelde area, northwestern Sjaelland, are covered by a visually uniform till material. The till stratigraphic studies using i.a. till fabrics and fold analyses reveal evidence of two ‘Young Baltic’ ice advances correlated with the ‘Belt Sea’ advance and the readvance of the ‘Belt Sea’ ice. At the Brorfelde hills these two ice advances came from the S to ESE and the SW respectively. Statistical analyses of stone countings, grain-size distributions, CaCO3 analyses and till fabrics enable a separation of the seemingly uniform till material into three till units. Two of the units were most probably deposited during the ‘Belt Sea’ advance. The youngest till, deposited during the readvance of the ‘Belt Sea’ ice, is characterized by a high content of Palaeozoic limestone. The deposition of till material during the ice advance from the S to ESE is greater than indicated by the till fabrics. Prior to the statistical treatment of the lithostratigraphical data it was thought to be impossible to separate the till material into different units, corresponding to the two ice advances.