Contemporary terminal-moraine ridge formation at a temperate glacier: Styggedalsbreen, Jotunheimen, southern Norway

Terminal-moraine ridges up to 6 m high have been forming at the snout of Styggedalsbreen for two decades. Based on intermittent observations during this period, combined with a detailed study of ridge morphology, sedimentary structures and composition during the 1993 field season, a model of terminal-moraine formation that involves the interaction of glacial and glacio-fluvial processes at a seasonally oscillating ice margin is presented. In winter, subglacial debris is frozen-on to the glacier sole; in summer, ice-marginal and supraglacial streams deposit sediments on the wasting ice tongue. The ice tongue overrides an embryonic moraine ridge during a late-winter advance and a double layer of sediment (diamicton overlain by sorted sands and gravels) is added to the moraine ridge during the subsequent ablation season. Particular ridges grow incrementally over many years and exert positive feedback by enhancing snout up-arching during the winter advance and constraining the course of summer meltwater streams close to the ice margin. The double-layer annual-meltout model is related to moraine formation by the stacking of subglacial frozen-on sediment slabs (Krüger 1993). Moraine ridges of this type have a complex origin. are not push moraines, and may be characteristic of dynamic high-latitude and high-altitude temperate glaciers.     

The Late Devensian Lateglacial palaeoenvironmental record from Whitrig Bog, SE Scotland. 1. Lithostratigraphy, geochemistry and palaeobotany

This is the first of a series of articles presenting the results of a multi-proxy investigation aimed at reconstructing changes in the ecosystem and climate of Whitrig Bog, SE Scotland, during the last glacial-inter-glacial transition (Devensian Lateglacial, c . 14–10 ka BP). We present here the results from sediment lithology, chemistry, pollen, and plant macrofossil analyses. These data are used to infer the nature of the local catchment soils and both local and regional terrestrial vegetation. The interstadial period ( c . 13–11 ka BP) is characterized by a successional sequence developing from a landscape with bare, poorly developed minerogenic soils supporting a sparse herbaceous flora into open birch woodland with juniper scrub and stable organic soils. At c . 11 ka BP the Younger Dryas climatic cooling event caused an abrupt reversion to an open herbaceous arctic/alpine flora (e.g. macrofossil evidence of Silene furcata and Oxyria digyna ) and high levels of minerogenic erosion into the basin, indicating environmental response to a cold Arctic climate. In addition to this Younger Dryas climatic reversal, two lesser reversion episodes occurred earlier during the interstadial. The more pronounced of the two, late in the intersladial, is characterized by high levels of erosion and a change from birch/juniper woodland to an open herbaceous flora. The older oscillation occurs approximately mid-way through the interstadial sequence and is marked by similar pollen changes, albeit shorter lived and more subtle.     

Presolar silicon carbide from the Indarch (EH4) meteorite: Comparison with silicon carbide populations from other meteorite classes

Abstract— Presolar SiC from the Indarch (EH4) meteorite was studied by scanning electron microscopy (SEM), by ion probe analysis for C and Si isotopic compositions, and by static source mass spectrometry for noble gas and C isotopic compositions. The data obtained are compared to SiC data from other meteorites, especially from Murchison (CM2), for which there is the most information available. The isotopic compositions of the major elements in SiC from Indarch and Murchison are similar. Stepped combustion data suggest a mean δ¹³C for SiC from both meteorites of ～+1430%o. Silicon isotopes in Indarch and Murchison SiC also compare well. In some other important respects, however, SiC in the two meteorites are different. Morphologically, SiC from Indarch appears finer grained than SiC from Murchison and is entirely composed of submicron grains. The finer-grained nature of Indarch SiC is confirmed by its noble gas characteristics. The mean Ne-E/Xe-S ratio for bulk Indarch SiC is significantly lower than the same ratio in Murchison (625 ± 47 vs. ～3500) but is similar to that of the finest grain-size fractions (<1 μm) in Murchison. A comparison of noble gas data from SiC from several different meteorites suggests that it might be Murchison SiC, rather than Indarch SiC, that is unusual. The grain-size disparities in SiC between meteorites are difficult to explain by residue processing differences or differing parent body processing. Instead, we speculate that a grain-size sorting mechanism for SiC may have operated in the solar nebula.     

Physiological adaptations in Coleoptera on Spitsbergen

Metabolic rates and Q₁₀ values were determined for three species of Spitsbergen Coleoptera, Amara quenseli, Simplocaria metallica and Rhynchaenus flagellum . The beetles had metabolic rates which were elevated compared to values of Coleoptera from other regions. This is interpreted as an adaptation to the prevailing low temperatures and short activity period on Spitsbergen.
A. quenseli had rates of water loss comparable to values of beetles in temperate and tropical xeric habitats, indicating that the habitat of the beetles on Spitsbergen at least occasionally is xeric.
Determination of cold-hardiness parameters such as supercooling point and haemolymph melting point of A. quenseli beetles revealed that the beetles had values corresponding to those of active insects in the temperate and tropical region. They had no thermal hysteresis factors. Thus, during summer they show no physiological adaptations to cold.     

Mid-Jurassic through mid-Cretaceous extension in the Central Graben of the North Sea - part 2: estimates from faulting observed on a seismic reflection line

Abstract We present an interpretation of the structure and faulting of an industry multichannel line across the Central North Sea Graben. We observe substantial faulting between the mid-Jurassic and mid-Cretaceous and on the base Zechstein (salt) reflector. To estimate the extension from these faults we consider movement along both planar and curved faults. We demonstrate that summing the heave (the horizontal displacement) overestimates the time measure of elongation for planar, ‘domino-type’, faulting. However, for high-angle normal faults and up to 70% extension (β= 1.7) the heave only overestimates the extension by 13%. In the absence of other information, summing the heave provides a useful estimate of extension in the case of domino-type faulting. For curved ‘listric’ faults the heave is only a true measure of the elongation if the antithetic faulting which removes the voids is vertical. Antithetic movement along inclined shear planes implies significantly more extension. We used the two models; of faulting to introduce progressively greater amounts of internal deformation in the crustal rocks and sediments to attempt to reconcile the estimate of extension necessary to give the observed subsidence and that given by analysing the faults visible on the seismic line. Estimates of extension obtained by allowing antithetic faulting along inclined shear planes are consistent with the range of estimates necessary to account for the post-mid-Jurassic subsidence. The estimates for the prior mid-Jurassic faulting are still substantially less than those necessary to explain the subsidence. However, this is not of major concern as there are many reasons as to why analysis of the faulting should underestimate the pre mid-Jurassic extension. Our interpretation of the seismic line implies curved faults bottoming in the lithologically weak Zechstein salt. These faults are decoupled from the region below and, hence, do not reflect the geometry of the faulting in the basement.     

Ecophysiological studies on arthropods from Spitsbergen

The cold-hardiness, high temperature tolerance and metabolic activity of summer specimens of staphylinid beetles ( Atheta graminicola ), collembolans ( Onichiurus groenlandicus ), spiders ( Erigone arctica ), and prostigmatid mites ( Molgus littoralis ) from Spitsbergen were investigated. The animals displayed cold-hardiness and haemolymph melting points within the normal ranges for summer insects from temperate regions, but were less tolerant to high temperatures. Haemolymph from spiders and from one species of collembolans ( Isotoma sp.) was found to contain thermal hysteresis factors. The beetles, collembolans, and mites were found to have oxygen consumption rates above the values of their relatives in other climatic zones, whereas the spiders had values within the range of temperate arachnoids. The study supports the view that polar arthropods have activation energy values lower than those of temperate animals.     

The status of the 'Little Ice Age' in southern Norway: relative-age dating of Neoglacial moraines with Schmidt hammer and lichenometry

A Schmidt hammer was used in conjunction with lichenometry to examine the relative age of the outermost Neoglacial moraines in front of glaciers in the Jotunheimen mountains of southern Norway. Particular attention was directed at (1) the magnitude of the 'Little Ice Age' glacier expansion episode relative to any others of Neoglacial age, and (2) the potential and limitations of the Schmidt hammer in the context of Holocene glacial chronologies. Schmidt hammer R-values were measured at 34 glaciers and the sizes of the lichen Rhizocarpon geographicum agg. at 80 glaciers. Unusually low R-values and large lichens suggest the occurrence of pre- 'Little lee Age' Neoglacial moraines at only a small minority (< 10 %) of the sampled glaciers. The traditional model of relatively large southern Norwegian glaciers during the 'Little Ice Age' is substantiated and it is tentatively suggested that differences in climate or glacier type may account for a regional difference in the status of the 'Little Ice Age' between northern and southern Scandinavia. The incorporation of weathered boulders into 'Little Ice Age' moraines by glacier push mechanisms, and the altitudinally-related variation in boulder surface textures, are identified as major sources of potential error in the use of the Schmidt hammer R-values for relative-age determination of Neoglacial surfaces.