Ash layers in deep-sea sediments as tracers of arc volcanic activity: Japan and Central America as case studies

Abstract Arc volcanic activity on opposite sides of the Pacific Ocean (Japan and Central America) has been investigated by examining the number of volcanic ash layers recorded in Neogene and Quaternary deep-sea sediments. The data suggest that ash layers counted in deep-sea sediments may provide a reliable record of arc volcanism. The study is based on a quantitative analysis of arc volcanic activity using cores collected on DSDP (Deep-Sea Drilling Project) and ODP (Ocean Drilling Program) legs. Five distinct parameters which might affect ash distribution in marine sediments were reviewed: nature of the eruption, wind influence, settling conditions, diagenesis, and plate motion. Of these five, past atmospheric circulation was the most significant. The main constraint on the analysis is that temporal scattering of ash is not directly related to wind pattern variations. Results of this analysis are correlated with dating of terrestrial volcanic sequences. Although marine tephra records for individual regions reveal minor differences in the episodes of volcanic activity, a general correlation exists between activity of arc volcanism in Japan and in Central America. Two important pulses of arc volcanism occurred during Middle Miocene times (18–13 Ma) and Plio-Quaternary times (5–0 Ma). These episodes of intense volcanism are separated by a well recorded quiescent period during Late Miocene times. These correlating episodes of the volcanic record indicate a direct link between arc volcanism and the global tectonic evolution of the Pacific ocean margins.     

Diagenetic trends of a tertiary low-rank coal series

The Mahakam delta (Kalimantan, Indonesia) coals represent all the evolution stages between freshly-deposited plant/peat material, lignites and bituminous coals. The geochemical techniques used to study this coal series included elemental analysis, extraction of humic compounds, infrared spectroscopy and ¹³C nuclear magnetic resonance of the total coal.The main mechanisms of early maturation in this series are loss of oxygenated compounds, aromatisation and condensation of the organic matter. These changes, which have already been suggested for other coal series and partially reported for sedimentary organic matter, were confirmed and described in more detail for the Mahakam coal series.     

Long lasting interactions between tectonic loading, unroofing, post-rift thermal subsidence and sedimentary transfers along the western margin of the Gulf of Mexico: Some insights from integrated quantitative studies

After Jurassic rifting, numerous carbonate platforms (i.e., the Orizaba, Cordoba and Golden Lane-Tuxpan platforms) developed during the Lower and Middle Cretaceous episode of thermal subsidence along the western passive margin of the Gulf of Mexico, with intervening basinal domains (i.e., the Tampico-Misantla, Zongolica, Veracruz and Deep Gulf of Mexico - DGM - basins).During the Late Cretaceous-Paleocene, the east-verging Sierra Madre Oriental thrust belt developed, resulting in tectonic uplift and unroofing of the allochthonous units (i.e. tectonic units made up of former Orizaba and Cordoba platforms and Zongolica Basin series). This new topography provided also an important source of clastics to feed the adjacent foredeep, where coeval tectonic loading accounted for the bending of the foreland lithosphere. However, shallow water facies or even emersion persisted until the Eocene in the forebulge area (at the present location of the Golden Lane), preventing locally the clastics to reach the DGM. This topographic barrier was ultimately bypassed by the clastics only during the Oligocene and Neogene, once (1) the prograding clastic wedge had exceeded accommodation, and (2) the long lasting thermal subsidence of the passive margin could overpass the effect of the bending and force the former bulge to sink.Numerous paleo-thermo-meters (Tmax, Ro), paleo-thermo-barometers (fluid inclusions), PVT and coupled forward kinematic and thermal modeling have been used to calibrate and date the progressive unroofing of the thrust belt. Coupled tectonic and sedimentologic modeling was applied in the foreland to predict the distribution of sand versus shale ratios in the Oligocene to Plio-Quaternary clastic sedimentary wedge of the passive margin, where gravitational gliding of post-Eocene series occurred during the Neogene along major listric faults.Mantle dynamics are advocated as the main process accounting for post-orogenic uplift and regional tilting of the basement, which initiated a massive transfer of sediments from the Cordillera towards the Gulf of Mexico, from Oligocene onward, resulting in a destabilization and gravitational collapse of the western slope of the Gulf of Mexico in Neogene times.     

The future of containerization: perspectives from maritime and inland freight distribution

As containerization enters its peak growth years, its potential future developments over maritime and inland freight transport systems are being questioned. A series of issues can either further accelerate the adoption of containerization worldwide or, alternatively, could impose an upper limit to the extraordinary contribution that containers have implied for logistics systems and global commodity chains. These mainly include macro-economic, technical/operational and governance factors. Future containerization will be largely determined by interactions within and between four domains ranging from a functional to a spatial perspective. The logistical domain involves the functional organization of transport chains and their integration in supply chains. The transport domain involves the operation of transport services and intermodal operations. The infrastructural domain involves the provision and management of basic infrastructure for both links and nodes in the transport system. The locational domain relates to the geographical location of nodes and sites in the economic space and forms a basic element for their intrinsic accessibility in terms of centrality or intermediacy. It is underlined that the future of containerization will dominantly be shaped by inland transport systems.     

Integrated scenarios of acidification and climate change in Asia and Europe

Two integrated assessment models, one for climate change on a global scale (IMAGE 2) and another for the regional analysis of the impacts of acidifying deposition (RAINS), have been linked to assess the impacts of reducing sulphur emission on ecosystems in Asia and Europe. While such reductions have the beneficial effect of reducing the deposition of acidifying compounds and thus the exceedance of critical loads of ecosystems, they also reduce the global level of sulphate aerosols and thus enhance the impact of increased emissions of greenhouse gases, and consequently increase the risk of potential vegetation changes. The calculations indicate that about 70% of the ecosystems in Asia would be affected by either acid deposition or climate change in the year 2100 (up from 20% in 1990) for both sulphur emission scenarios (controlled and uncontrolled), whereas in Europe the impacted area would remain at a level of about 50%, with a dip early next century. More generally, the effects of reducing sulphur emissions and thus enhancing climate change would about balance for the Asian region, whereas for Europe the desirable impact of sulphur emission reductions would greatly outweigh its undesirable effects.     

The Lac Cornu retrograded eclogites (Aiguilles Rouges massif,Western Alps,France): evidence of crustal origin and metasomatic alteration

Metabasic rocks interbedded in amphibolite facies supracrustal gneisses outcrop around Lac Carnu in the Aiguilles Rouges massif (Western Alps). The cores of the thickest boudinaged lenses are made up of eclogitic amphibolites grading outwards into amphibolites. The common assemblage is unzoned garnet + symplectitic clinopyroxebe + hornblende + plagioclase. In a slightly amphibolitized sample, minimum P and T conditions of equilibrium between garnet and omphacite inclusions are 780°C and 11 Kb. A polymetamorphic pre-Alpine evolution of the massif is thus demonstrated. Eclogitic amphibolites show variations in major element composition similar to the Skaergaard evolution in the Al₂O₃ ? FeO + Fe₂O₃ ? MgO triangle. Variation diagrams in which Zr is taken as differentiation index also indicate magmatic trends for Mn, Ti, P, Ni, Co, Y, V and Cr, Ca, K, Na, Sr, Rb and Si were mobile during the evolution of the rocks. The igneous trend can be described by a quantitative model of fractional crystallization in which a noritic assemblage separated in the initial stage. This provides evidence of crustal P, T conditions of differentiation for the original materoal and in situ evolution for the eclogites. A second group of amphibolites shows banded structure and transitional terms with the surrounding gneisses. A volcano-sedimentary origin is suggested though the process cannot be modelled. The rocks may result from complex interactions of magnetic, metasomatic and sedimentary processes. It is concluded that Lac Cornu metabasites were originally continental tholeiites, though several geochemical criteria tend to indicate an oceanic origin. This casts some doubt on the validity of these criteria, when applied to metamorphic rocks.     

Variation in chlorophylla concentrations and Margalef’s index of pigment diversity in two solar salt ponds,Aveiro, Portugal

Variations of chlorophylla and Margalef's pigment diversity index were studied in two solar salt ponds at Aveiro (Esmolas and Tanoeiras). Portugal. In the Esmolas ponds, mean chlorophyll a values varied between 2.49 and 13.33 mg m⁻³ in the non-growing season, and between 5.43 and 40.55 mg m⁻³ in the growing season. In the Tanoeiras ponds, mean chlorophylla values were between 8.12 and 14.85 mg m⁻³ in the non-growing season, and 8.65 and 21.19 mg m⁻³ in the growing season. Fluctuations of Margalef's pigment diversity index were more irregular.