Submarine landform assemblages and sedimentary processes related to glacier surging in Kongsfjorden, Svalbard

High-resolution swath-bathymetry data from inner Kongsfjorden, Svalbard, reveal characteristic landform assemblages formed during and after surges of tidewater glaciers, and provide new insights into the dynamics of surging glaciers. Glacier front oscillations and overriding related to surge activity lead to the formation of overridden moraines, glacial lineations of two types, terminal moraines, associated debris lobes and De Geer moraines. In contrast to submarine landform assemblages from other Svalbard fjords, the occurrence of two kinds of glacial lineations and the presence of De Geer moraines suggest variability in the landforms produced by surge-type tidewater glaciers. All the landforms in inner Kongsfjorden were deposited during the last c. 150 years. Lithological and acoustic data from the innermost fjord reveal that suspension settling from meltwater plumes as well as ice rafting are dominant sedimentary processes in the fjord, leading to the deposition of stratified glacimarine muds with variable numbers of clasts. Reworking of sediments by glacier surging results in the deposition of sediment lobes containing massive glacimarine muds. Two sediment cores reveal minimum sediment accumulation rates related to the Kongsvegen surge from 1948; these were 30 cm a-1 approximately 2.5 km beyond the glacier front shortly after surge termination, and rapidly dropped to an average rate of 1.8 cm a-1 in ∼ 1950, during glacier retreat

Stratified glacimarine basin-fills in West Greenland fjords

Acoustically stratified sediments that infill glacially eroded bedrock basins are common in fjords (Seramur et al. 1997; Gilbert et al. 1998; Hogan et al. 2012; Dowdeswell & Vasquez, 2013). Internally, such stratified sediments are often characterised by relatively smooth reflections that parallel the seafloor. Sills between basins usually comprise bedrock, sometimes covered by a thin veneer of glacimarine sediment and/or till. Fjords in West Greenland, including Rink Fjord and the Vaigat, contain bedrock basins infilled by acoustically stratified sediment (Fig. 1). The basin fills are a product of rain-out from turbid meltwater plumes, probably supplemented by iceberg-rafting and downslope resedimentation.This is the author accepted manuscript. The final version is available from Geological Society of London via https://doi.org/10.1144/M46.8

Heterodinuclear titanium/zinc catalysis: synthesis, characterization and activity for CO2/epoxide copolymerization and cyclic ester polymerization

The preparation of heterodinuclear complexes, especially those comprising early-late transition metals coordinated by a simple or symmetrical ancillary ligand, represents a fundamental challenge and an opportunity to prepare catalysts benefitting from synergic properties. Here, two new mixed titanium(IV)-zinc(II) complexes, [LTi(OiPr)2ZnEt] and[LTi(OiPr)2ZnPh], both coordinated by a diphenolate tetra(amine) macrocyclic ligand (L), are prepared. The synthesis benefits from the discovery that reaction of the ligand with a single equivalent of titanium tetrakis(iso-propoxide) allows the efficient formation of a mono-Ti(IV) complex, [LTi(OiPr)2]. All new complexes are characterized by a combination of single crystal X-ray diffraction, multinuclear NMR spectroscopy and mass spectrometry techniques. The two heterobimetallic complexes, [LTi(OiPr)2ZnEt] and [LTi(OiPr)2ZnPh], feature trianionic coordination by the macrocyclic ligand and bridging alkoxide groups coordinate to both the different metal centres. The heterodinuclear catalysts are compared to the mono-titanium analogue, [LTi(OiPr)2], in various polymerization reactions. In the alternating copolymerizations of carbon dioxide and cyclohexene oxide, the mono-titanium complex is totally inactive whilst the heterodinuclear complexes show moderate activity (TOF = 3 h-1); it should be noted the activity is measured using just 1 bar pressure of carbon dioxide. In the ring opening polymerization of lactide and ε-caprolactone, the mono-Ti(IV) complex is totally inactive whilst the heterodinuclear complexes show moderate-high activities, qualified by comparison to other known titanium polymerization catalysts (L-lactide, kobs = 11 x 10-4 s-1 at 70 °C, 1 M in [lactide]) and ε-caprolactone (kobs = 5 x 10-4 s-1 at 70 °C, 0.9 M in [ε-caprolactone])

Submarine Landforms and Glacimarine Sedimentary Processes in Lomfjorden, East Spitsbergen

Understanding the role of fjords in modulating the long-term interaction between ice sheets and glaciers with the surrounding ocean requires the investigation of glacigenic landform and sediment archives. In Svalbard, there is a wealth of data from fjords in west Spitsbergen that constrains the glacial history of this sector of the Svalbard-Barents Sea Ice Sheet (SBIS) since the Last Glacial Maximum (LGM), and the nature and timing of subsequent ice retreat. In contrast, however, very little is known about the glacial history of fjords in east Spitsbergen. This paper combines multibeam swath-bathymetry, sub-bottom profiles, lithological data and radiocarbon dates from Lomfjorden, Svalbard, to provide the first insights into the dynamics of tidewater glaciers and associated glacimarine sedimentary processes in a northeast Spitsbergen fjord. At the LGM, a fast-flowing ice stream drained the SBIS through Lomfjorden, serving as a tributary to a south-north flowing ice stream in Hinlopenstretet. Ice advance is recorded by streamlined bedrock, glacial lineations and drumlins. A radiocarbon date of ∼9.7 ka BP from the outer fjord provides a minimum date for retreat of this ice stream, and suggests that Lomfjorden was ice-free earlier than fjords in west Spitsbergen. Ice retreat occurred in a slow and step-wise manner, indicated by the presence of recessional moraines and De Geer moraines. By 4.5 ka BP the local tidewater glaciers had probably retreated inland of their present positions. The limited extent of glacigenic landform assemblages in front of these glaciers implies that any Holocene re-advances were probably restricted. The principal sedimentary processes during deglaciation were suspension settling from meltwater, causing deposition of weakly stratified, bioturbated mud in ice-distal settings at rates of 0.02–0.08 cm a−1, and gravitational mass flows forming sandy turbidites in ice-proximal areas. Iceberg ploughmarks and ice-rafted debris provide evidence for the presence of large icebergs during deglaciation. Our data suggest an early and extensive deglaciation in east Spitsbergen fjords and show that previous reconstructions of the extent of the SBIS need to be revised as new data emerges from east Spitsbergen. The data confirm that tidewater glaciers from different regions of Spitsbergen behaved differently since the LGM, and that variations in landform-sediment assemblages occur even within geographically adjacent fjords

Gegenwart und Zukunft des GIS-Einsatzes im Umweltbereich Dokumentation

Available from TIB Hannover: F02B832+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman