Coulees volcaniques dans le paleozoique superieur des zones internes helleniques (Grece continentale) — environnement sedimentaire et caracterisation petrographique

Volcanic flows of Late Paleozoic age in the Pelagonian zone belonging to the internal Hellenic zones, have been studied, for the first time, from petrographical and geochemical viewpoints.

Relevant petrographical data and the geochemical analysis lead us to consider that:

1. (a) the basic lavas can be linked to tholeitic basalts.

2. (b) the acid lavas are associated to metarhyolites.

3. (c) the two magmatic flows do not originate from the same parental magma.

The geochemical results obtained, compared to those from other deposits of nearly the same age outcropping around the Mediterranean, indicate that the latest Hercynian volcanism has been affected by intra-plate distension phenomena preceding the great Lower Mesozoic break-up which caused the formation of the Tethys Ocean.

It is remarkable that in the Mesogean Basin the sedimentary environment is nearly similar to that described in this paper. The volcanic flows end up in a sialic sedimentary basin containing coarse detritic formations that resulted from erosion of the Variscan chain along the southern margin of the European continent.

Abstract

Dans la zone pélagonienne appartenant aux zones internes helléniques, des coulées volcaniques d'âge paléozoïque supérieur sont étudiées, pour la première fois, pétrographiquement et géochimiquement. Les différents agencements pétrographiques et les analyses géochimiques nous apprennent que:

1. (a) les laves basiques peuvent être rattachées á la famille des basaltes tholéitiques.

2. (b) les laves acides s'apparentent aux métarhyolites.

La quantification des différents éléments analyses nous amène á considérer que les deux lignées magmatiques ne sont pas issues d'un même magma parental.

La comparaison des résultats géochimiques avec d'autres gisements, sensiblement contemporains affleurant autour de la Méditerranée actuelle, nous indique que le volcanisme fini-hercynien est assujetti á des phénomènes de distension intraplaques, préparatoires á la grande fracturation mésozoïque inférieure ayant donné naissance á l'océan téthysien.

Ce qui est remarquable dans le bassin mésogéen, c'est que l'environnement sédimentaire est toujours, á peu près, comparable á celui que nous décrivons ici. En effet, les coulées volcaniques s'épanchent dans un bassin sédimentaire á fond sialique au sein de formations détritiques grossières nées de la destruction de la chaîne varisque sur la bordure méridionale du continent europeen.     

The Multiscale TROPIcal CatchmentS critical zone observatory M-TROPICS dataset I: The Nyong River Basin,Cameroon

Simultaneously acquiring time series of climate, hydrology and hydrochemical data over decades on river systems is pivotal to understand the complex interactions involving rock, soil water, air and biota in the Critical Zone, to build integrated modelling and to propose predictive scenarios. Among the Critical Zone Observatories (CZOs) implemented in the past 25 years, only a few are located in the humid Tropics despite the importance of these regions in terms of population density, fast-changing land use, biodiversity hotspots, biomass stock on continents, size of river systems, etc. Since 1994, weathering and erosion processes and fluxes have been investigated at both local (experimental watershed) and regional scales in the Nyong River Basin (Cameroon) which belongs to the Critical Zone Observatories network named Multiscale TROPIcal CatchmentS (M-TROPICS). The data shared by M-TROPICS in Cameroon are: (1) rainfall; (2) air temperature, air relative humidity, wind speed and direction, and global radiation; (3) stream and river water level; (4) pH, electrical conductivity, water temperature and suspended particulate matter (SPM) concentration; (5) major ion, alkalinity and dissolved organic carbon (DOC) concentrations. The dataset already contributed to describe the water partitioning in these tropical humid watersheds, to better understand the factors controlling chemical weathering and physical erosion in tropical ecosystems, particularly the role of organic matter. The dataset also contributed to calculate elemental weathering fluxes and saprolite production rate and to propose denudation rates on tropical cratonic landscapes. Hydrological modelling allowed quantification of the geographical water sources contributing to streamflow. DOC data were used to determine greenhouse-gas emissions and carbon budgets from African inland waters. However, long-term solute concentrations at the outlet of a small tributary of the Nyong River exhibit non-stationary behaviour over the last 26 years. The processes governing those fluctuations are not yet fully understood and might be related to changes in the hydrological regime, land-cover and land-use. The latter highlights the need for longer time-series and continued support for CZOs particularly in the humid tropics.     

GGR Critical Review of Analytical Developments in 2006–2007

In 2005 the Geostandards and Geoanalytical Research editorial team, in the true spirit of scientific endeavour, embarked on an experiment of our own. We decided to trial a new kind of review, somewhat different from those more typically observed in journals, and one that would provide readers with a summary of analytical developments across a broad range of topics appropriate to the Earth sciences. The first contribution of this kind appeared in 2005, and reported on developments in 2003 (Hergt et al. 2005). The second, this time a biennial review, was published in 2006 and reported on highlights of the 2004 and 2005 literature (Hergt et al. 2006). Based on reprint requests, positive remarks at conferences and strong citations we consider the experiment a resounding success and proudly present here the third in this series. This comprises six individual review sections that cover the main analytical technologies and topical application fields in geoanalysis and geochemistry, including geological and environmental reference materials, ICP‐thermal and secondary ionisation‐mass spectrometry, as well as neutron activation analysis, X‐ray fluorescence and atomic absorption spectrometry.     

'Just‐in‐time’ in Australia: a review

Just‐in‐time (JIT) became a widely used phrase in the 1980s but the ideas underlying it have received little attention from Australian geographers. It is often perceived as simply a system of increasing the efficiency of factories whereas, in reality, it involves changes to systems of firms across a broad range of sectors. This paper explains the meaning of JIT, reviews the literature on this topic in Australia, and suggests that it may return some cohesion to the study of ‘economic geography’ and provide a catalyst for resolving the growing tensions between time and place.     

Variability in luminescent lamination and initial 230Th/232Th activity ratios in a late Holocene stalagmite from northern Norway

Luminescent lamination in a stalagmite from northern Norway is used to construct a ～2780-year long, floating record of annual growth rate. Thermal ionisation mass-spectrometric (TIMS) U–Th ages (n = 12) were determined along the growth axis and three subsample locations and ages (corrected and uncorrected for initial ²³⁰Th/²³²Th activity) were selected as anchor points for the floating chronology. On the basis of these anchor points, termination of growth occurred between AD 1729 and AD 1826. The annual banding records are used to evaluate the initial ²³⁰Th/²³²Th activity ratio adopted for correction of the U–Th ages. To achieve a reasonable fit between U–Th ages and estimates predicted by the anchored annual band age models, mean initial ²³⁰Th/²³²Th activity ratios of between 0.44 and 1.47 must be invoked. However, there remains a reasonable degree of scatter about the expected linear relationship between annual bands and U–Th chronology for individual subsamples indicating that the use of a single correction factor for Holocene stalagmites should be applied with caution.Stalagmite growth rate fluctuates on annual to centennial scale. The growth termination of the stalagmite presented here could have been a result of environmental change associated with the Little Ice Age, or, possibly local percolation pathway changes after an M_s ～ 6 earthquake in the region in AD 1819. Stable-isotope data from the same axis of growth show a pattern similar to the large-scale growth rate variations, and these combined proxy records are interpreted as showing gradual cooling and/or shortening of the vegetation growth season for the last 3000 years.     

Investigating the last deglaciation of the Scandinavian Ice Sheet in southwest Sweden with 10Be exposure dating

In this study we have obtained 17 cosmogenic exposure ages from three well‐developed moraine systems – Halland Coastal Moraines (HCM), Göteborg Moraine (GM) and Levene Moraine (LM) – which were formed during the last deglaciation in southwest Sweden by the Scandinavian Ice Sheet (SIS). The inferred ages of the inner HCM, GM and LM are 16.7 ± 1.6, 16.1 ± 1.4 and 13.6 ± 1.4 ka, respectively, which is slightly older than previous estimates of the deglaciation based on the minimum limiting radiocarbon ages and pollen stratigraphy. During this short interval from 16.7 ± 1.6 to 13.6 ± 1.4 ka a large part (100–125 km) of the marine‐based sector of the SIS in southwest Sweden was deglaciated, giving an average ice margin retreat between 20 to 50 m a^?1. The inception of the deglaciation pre‐dated the Bølling/Allerød warming, the rapid sea level rise at 14.6 cal. ka BP and the first inflow of warm Atlantic waters into Skagerrak. We suggest that ice retreat in southwest Sweden is mainly a dynamical response governed by the disintegration of the Norwegian Channel Ice Stream and not primarily driven by climatic changes. Copyright © 2011 John Wiley & Sons, Ltd.     

GGR Biennial Critical Review: Analytical Developments Since 2010

Advances in the chemical and isotopic characterisation of geological and environmental materials can often be ascribed to technological improvements in analytical hardware. Equally, the creation of novel methods of data acquisition and interpretation, including access to better reference materials, can also be crucial components enabling important breakthroughs. This biennial review highlights key advances in either instrumentation or data acquisition and treatment, which have appeared since January 2010. This review is based on the assessments by scientists prominent in each of the given analytical fields; it is not intended as an exhaustive summary, but rather provides insight from experts of the most significant advances and trends in their given field of expertise. In contrast to earlier reviews, this presentation has been formulated into a unified work, providing a single source covering a broad spectrum of geoanalytical techniques. Additionally, some themes that were not previously emphasised, in particular thermal ionisation mass spectrometry, accelerator‐based methods and vibrational spectroscopy, are also presented in detail.     

10Be exposure age constraints on the Late Weichselian ice‐sheet geometry and dynamics in inter‐ice‐stream areas,western Svalbard

The Late Weichselian ice sheet of western Svalbard was characterized by ice streams and inter‐ice‐stream areas. To reconstruct its geometry and dynamics we investigated the glacial geology of two areas on the island of Prins Karls Forland and the Mitrahalvøya peninsula. Cosmogenic ¹⁰Be surface exposure dating of glacial erratics and bedrock was used to constrain past ice thickness, providing minimum estimates in both areas. Contrary to previous studies, we found that Prins Karls Forland experienced a westward ice flux from Spitsbergen. Ice thickness reached >470 m a.s.l., and warm‐based conditions occurred periodically. Local deglaciation took place between 16 and 13 ka. At Mitrahalvøya, glacier ice draining the Krossfjorden basin reached >300 m a.s.l., and local deglaciation occurred at c. 13 ka. We propose the following succession of events for the last deglaciation. After the maximum glacier extent, ice streams in the cross‐shelf troughs and fjords retreated, tributary ice streams formed in Forlandsundet and Krossfjorden, and, finally, local ice caps were isolated over both Prins Karls Forland and Mitrahalvøya and their adjacent shelves.     

GGR Critical Review of Analytical Developments in 2008–2009: An Introduction

This collection of articles represents the fourth in a series of reviews in which authors have aimed at capturing the key advances in a range of analytical fields ( Hergt et al. 2005, 2006, 2008 ). The publication period under review is 2008–2009 and the intention here is to provide readers with a summary of the most influential developments published during this period, across a broad range of topics appropriate to the Earth and environmental sciences. Most authors comment on the ways in which the emphases of research in their specific fields of examination have changed over time. All note an increase in rigour and focus on data quality. Whether advances have taken place in instrumentation, sample manipulation or data deconvolution, there are a large number of dedicated scientists out there contributing to the high quality of geochemical data employed in geological and environmental research.     

Vertical Hydraulic Gradient Estimation in Clay Till,Using MiHPT Advanced Direct-Push Technology

The vertical transport of contaminants from source areas is employed in many risk assessment models and screening tools in order to estimate the contaminant mass discharge (CMD) into underlying aquifers. The key parameters for estimating CMD are the contaminant source area and concentration, and the vertical water flux, the latter of which depends on the vertical hydraulic conductivity and the vertical hydraulic gradient in the subsurface. This study focuses on advancing the use of the combined membrane interface probe hydraulic profiling tool (MiHPT) to investigate the vertical hydraulic gradient across a clay till overlying a sandy aquifer at a contaminated site in Denmark. Only the HPT is necessary for the estimate of vertical hydraulic gradient. The hydraulic head, clay till thickness, and resulting vertical hydraulic gradients found using the MiHPT compared well with observations from nearby nested wells. The parameter with the largest discrepancy was the thickness of the clay till. The advantage of the MiHPT is its relatively quick depth discrete access to information regarding subsurface permeability, vertical hydraulic gradients and contaminant distribution across a site. In this case study, performance of additional dissipationtests during the HPT log to acquire determination of the vertical hydraulic gradient increased the cost by 3% compared to standard HPT logs.