A palaeomagnetic experiment on crustal uplift in West Greenland

In the Nordre Strømfjord shear zone of central West Greenland it is believed that the gneisses exposed at the coast reached a maximum depth of burial about 10 km deeper than those now adjacent to the inland ice. This theory was tested palaeomagnetically. Further sampling up the mountain K?llingeh?tten was carried out to ascertain changes of direction of magnetization with height.The magnetic susceptibility ellipsoids were determined for each specimen and were used to correct their directions of magnetization for the effects of anisotropy. Complicated but compact polar wander paths were derived for both the fjord and mountain traverses. The path for the fjord is consistent with the geological model but does not support it. This inconclusive result may be the consequence of a low rate of polar wander. The mean palaeomagnetic poles are 27.7°N, 276.6° E (dp = 13.8°,dm = 17.3°) for Nordre Strømfjord and 25.3°N, 300.4°E (dp = 11.5°,dm = 14.1°) for K?llingeh?tten.     

A method for estimating sediment budgets of washover deposits using digital terrain models

Washover fans are located on small barriers in fetch-limited micro-tidal coastal environments in Denmark. These washover fans are formed during high-energy storm events and we present a method to quantify their volumes and to estimate sediment exchanges between washover fans and their adjacent morphologies. We use high resolution digital terrain models (DTMs) based on light detection and ranging (LiDAR) data. We have delineated landforms using known methods of scale analysis and geomorphometric classification. We quantified volumes of the delineated landforms and estimated the related sediment budgets. These computed volumes were compared using different pre-depositional surfaces. Finally, we assessed the sediment exchange and associated sources of sediments of the washover fans. We applied a scale analysis to determine suitable DTM resolution and focal statistics window size as input to a geomorphometric classification analysis. Landform areas and landforms were delineated using morphometric threshold values, and volumes and sediment budgets of the delineated landforms were computed using different assumptions to define the pre-depositional surface. Resulting washover fan volumes were validated against digital elevation model (DEM) of difference (DoD) derived volumes. Sediment budgets were derived from representative volumes of the washover fans and adjacent berms. We show that quantification of washover features derived from DTMs, using geomorphometric analysis is feasible and that the presented approach provides estimates of washover deposit volumes with an accuracy between 1% and 28% compared to control volumes. © 2021 John Wiley & Sons, Ltd.     

Stratigraphical distribution of platinum-group minerals in the Eastern Layered Series, Rum, Scotland

Abundant and diverse platinum-group minerals (PGM) occur throughout the Tertiary layered intrusion on Rum, Scotland. In this paper we document the distribution of PGM within the Eastern Layered Series (ELS) on Rum, which comprises 16 alternating units of olivine-dominant feldspathic peridotite grading to plagioclase-dominant allivalite. The PGM occur in six main chrome-spinel layers in the Eastern Layered Series and are clearly associated with minor concentrations of interstitial sulphides. Common PGM phases include: Pd–Cu alloys, Pt–Fe alloys, native Pt, laurite, moncheite, sperrylite, isomertiete, cooperite and braggite along with a large number of other less common arsenide, bismuthotelluride and sulphide phases. Analyses of the discrete chromitite layers yield up to ΣPGE + Au 2618 ppb. Although present throughout the 750-m-thick ELS, there are clear stratigraphical changes in the PGM assemblage. The presence of PGM in the ELS on Rum are interpreted as being caused by mantle melting associated with the proto-Icelandic `hot spot', followed by localised concentration because of the combined effects of magma mixing, sulphide-silicate liquid immiscibility and fractional crystallisation. Most of the PGM are magmatic in origin but some grains show evidence of hydrothermal alteration. Received: 27 November 1999 / Accepted: 27 April 2000     

Modelling the ocean response to secular surface temperature transitions

The ocean response to surface temperature transients is simulated with the use of the Hamburg large-scale geostrophic (LSG) ocean general circulation model (OGCM). The transition, from the present to a climate corresponding to a doubling of the atmospheric CO₂ content, is compared with the reversed transition. For the Atlantic, the time scale for the deep ocean to adjust to the temperature changes was similar for both transitions. In the Pacific, the time scale is shorter for the present to warm transition than for the reverse case, a result of increased production of Antarctic bottom water (AABW) during the warm climate. While the transition from cold to warm climate shows no secular variability, the reversed transition generates considerable variability on time scales of 300–400 years. For the warm climate, oscillations with periods of 45 years are found in the Southern Ocean. Results of principal oscillation pattern (POP) analysis indicate that these oscillations are due to interaction between convection in the Southern Ocean and advected salinity anomalies in the Antarctic Circumpolar Current (ACC) and the Southern Pacific Ocean. Received: 19 September 1995 / Accepted: 15 March 1996     

On fast pulsations in flare continua

Pulsations with periods down to 0.05 s have been observed in continuum emission following flares. In pulsating events several frequencies may be excited, simultaneously or in time succession. Pulsations occur both in classical type IV events and in short-lasting continuum events. The power spectrum shows no large variation during one or two hours. Some implications of fast pulsations for the generation mechanism are discussed.Proceedings of the Workshop on Radio Continua during Solar Flares, held at Duino (Trieste), Italy, 27–31 May, 1985.