Holocene colluvial (debris‐flow and water‐flow) processes in eastern Norway: stratigraphy,chronology and palaeoenvironmental implications

Very little is known about the temporal pattern and the palaeoenvironmental implications of Holocene colluvial processes (debris‐flow and water‐flow processes) in eastern Norway. In this study, well‐dated sedimentary successions from 19 deep excavations are used to reconstruct Holocene colluvial activity in upper Gudbrandsdalen, eastern Norway. Following deglaciation, debris‐flow and water‐flow events have been common in upper Gudbrandsdalen throughout the Holocene, with 62% of the recognised debris‐flow and water‐flow units deposited prior to 5000 cal. yr BP. Relatively high colluvial activity is recorded at ca. 8600–7400, 2400–1900 and 800–400 cal. yr BP, with a conspicuous peak at ca. 8500–8100. Periods of relatively low colluvial activity are recorded at ca. 7100–6500, 5900–5300 and 3500–2500 cal. yr BP. Two different weather situations, unusually heavy rains and warm periods during the snowmelt season, are responsible for triggering colluvial processes in this area. These different weather situations may in turn be related to different climatic conditions. Copyright © 2007 John Wiley & Sons, Ltd.     

Facies architecture and sedimentology of a meandering fluvial system: a Palaeogene example from the Weisselster Basin, Germany

The Schleenhain open pit coal mine, located 30 km south of Leipzig, Germany, exposes Upper Eocene and Oligocene non-marine strata representing fluvial deposition in the centre of the Weisselster Basin. Active mining and successive cuts provided the rare opportunity to obtain a three-dimensional perspective of laterally extensive surface outcrops. These were used to construct a detailed fence diagram, which provided the basis for recognition of key architectural elements in the weakly consolidated meandering stream deposits. In addition to the eight basic architectural elements of Miall (1985 ), the element SL (shallow lake deposits) was newly defined and the element CH (channel) was subdivided into CHg (palaeo-river system) and CHk (small channel). The profiles contain parts of two fining-upward cycles, which are separated by an unconformity spanning the Early Oligocene. Deposits of the first cycle begin with transverse sand bars (downstream accretion deposits-DA) and point bars (lateral accretion deposits-LA). The upper part of the cycle is represented by overbank fines (OF) and the element SL, which consists of laterally discontinuous lenses of dark, plant-bearing, kaolinite-rich clays, that were deposited in shallow lakes adjacent to the active channel. Coal seams interlayered with palaeosols are the main constituents of element OF. Sheetlike bodies of medium to fine gravels (gravel bars and bedforms-GB) on an erosive coal surface mark the beginning of the second cycle. Dissolution of underlying Permian salts and sulphates prior to, during, and after the deposition of the Palaeogene strata caused the development of two synclines within the outcrop. Coal seams and clay horizons which thicken and dip towards the centre of the synclines, provide evidence for their chronological development.     

Transfer of results from reed research into practice as illustrated by reed protection measures in Berlin

There is great interest in solving the question of how far the successful establishment of common reed for shore restoration is influenced by genetically determined characteristics of different reed clones. For this purpose, ten reed clones were planted at six artificial sand banks in 1995, according to a special planting design. The growth and expansion performance of the clones was compared.The reed plants grew without significant stress in the first vegetation period, resulting in newly established reed stands in a very good condition at the end of the season. Despite the same site conditions at the experimental plots, the planted clones differed significantly in their morphology and stand structure. By comparison, reed plants of the same clone exhibited strong similarity on all experimental plots. These results appear to justify the assertion that, at least during the initial phase of establishing a reed stand, the development of stand structure is determined more by genetically controlled programmes than by site conditions. Only long-term investigations will be able to clarify to what extent stable stand structures are formed by genetically controlled programmes after polycormons reach maturity.     

A modelling study of the effects of land management and climatic variations on groundwater inflow to Lake St Lucia, South Africa

Over the past few years groundwater has been recognized as an important contributor of freshwater to Lake St Lucia, South Africa during periods of prolonged drought. This has led to a management strategy aiming at increasing the groundwater recharge and minimizing groundwater use through active manipulation of the vegetation. For the Eastern Shores on the edge of Lake St Lucia, the replacement of vast areas of pine (Pinus elliottii) plantations with grassland over the past decade, combined with a strict burning regime, has led to a general rise of the water table, which has increased the groundwater seepage to Lake St Lucia. A numerical groundwater model has been applied to assess the effects of local management strategies on the mass balance of a shallow aquifer and these are compared to the effects of predicted climate and sea-level change for this area. The simulations indicate that local management actions that are being applied to the Eastern Shores have positive effects on the groundwater flux into Lake St Lucia and that they outweigh potential negative effects of future climate and sea-level change predicted for this area.     

Kinematics and geochronology of Early Cretaceous thrusting in the northwestern paleozoic of Graz (Eastern Alps)

Abstract

The multiply deformed Upper Austro-Alpine nappe pile of the Graz area is built up of low-grade metamorphosed Paleozoic rocks which are discordantly overlain by sediments of Santonian (Late Cretaceous) age (“Gosau” formation). Slices of Permo-Mesozoic rocks are absent. Analyses of structures, microfabrics, strain and shear directions were used to decipher the kinematic history; geochronological investigations to date the age of thrusting. K/Ar and Rb/Sr ages of synkinematically grown mica suggest an eo-Alpine (Early Cretaceous) age for the major deformation D1. D1 is characterized by non-coaxial rock flow which caused SW- to W directed nappe imbrication. Incremental strain measurements indicate the progressive superposition of D2 over Dl. In the higher nappe (Rannach Nappe) nappe imbrication continued during D2 changing the direction of nappe transport from SW to NW. Enhanced flattening strain in the deeper nappe (Schöckel Nappe) led to recumbent folds in all scales during D2. This study emphasized two interpretations : (1) The Alpine deformation in the Upper Austro-Alpine nappe pile of the Paleozoic of Graz started in the Earliest Cretaceous (about 125 Ma.). (2) The emplacement of nappes followed a curved translation path in the studied area.     

Stellar kinematics and populations of early-type galaxies with the SAURON and OASIS integral-field spectrographs

We summarise the results and achievements of integral-field spectroscopy of early-type galaxies, observed as part of a survey using both the SAURON and OASIS spectrographs. From the perspective of integral-field spectroscopy, these otherwise smooth and featureless objects show a wealth of structure, both in their stellar kinematics and populations. We focus on the stellar content, and examine properties on both kiloparsec scales with SAURON, and scales of 100’s of parsecs with OASIS. These complementary studies reveal two types of kinematically distinct components (KDCs), differing primarily in their intrinsic sizes. In previous studies, KDCs and their host galaxies have generally been found to be unremarkable in other aspects. We show that large KDCs, typical of the well-studied cases, indeed show little or no age differences with their host galaxy. The KDCs detected with the higher spatial-resolution of OASIS are intrinsically smaller and include, in contrast, a significant fraction of young stars. We speculate on the relationship between KDCs and their host galaxies, and the implications for young populations in early-type galaxies.     

Tidal dissipation from free drift sea ice in the Barents Sea assessed using GNSS beacon observations

Ocean Dynamics - One of the major challenges facing global hydrodynamic tidal models is the modelling of the interaction between sea ice and tides in high-latitude waters. Recent studies have shown...     

Primordial magnetic field,inflation and cosmic strings

The possibility of a primordial magnetic field is discussed. The formation of closed, superconducting cosmic strings before the end of inflation is pointed out as a mechanism able to preserve a magnetic field inside the loops which could provide seeds for galactic magnetic fields.