On the sensitized photo-oxidation of alkylbenzenes in seawater

Several homologous monoalkylated benzenes were photo-oxidized as surface films on and dissolved in pure water and purified natural seawater by solar and equivalent artificial UV irradiation in the presence of anthraquinone as photo-sensitizer. The main reaction products were the 1-phenylalkanones, the corresponding secondary alcohols, benzaldehyde and, when the side chain contained four or more carbon atoms, the products of what appears to be a Norrish type II photo-degradation. The detection among the reaction products of an aldehyde with one carbon atom less than the olefin produced by the Norrish type II photo-degradation suggests a photolytic decomposition of 1-alkenes, resulting in the formation of highly reactive compounds capable of abiotic reactions in the electronic ground state with a variety of organic compounds occurring in seawater.     

Climatological characteristics of the tropics in China： climate classification schemes between German scientists and Huang Bingwei

Reviewing some important German scientists who have developed climatic regionalization schemes either on a global or Chinese scale, their various definitions of the tropical climate characteristics in China are discussed and compared with Huang Bingwei‘s climate classification scheme and the identification of the tropical climate therein. It can be seen that, due to different methodological approaches of the climatic regionalization schemes, the definitions of the tropics vary and hence also their spatial distribution in China. However, it is found that the tropical climate type occupies only a peripheral part of southern China, though it firmly represents a distinctive type of climate that is subsequently associated with a great economic importance for China. As such, the tropical climate type was mostly identified with its agro-climatological significance, that is by giving favourable growing conditions all-year round for perennial crops with a great heat demand. Tropical climate is, hence, conventionally regarded to be governed by all-year round summer conditions “where winter never comes“.     

Reconstructed streamflow for Citarum River, Java, Indonesia: linkages to tropical climate dynamics

The Citarum river basin of western Java, Indonesia, which supplies water to 10 million residents in Jakarta, has become increasingly vulnerable to anthropogenic change. Citarum??s streamflow record, only ~45?years in length (1963-present), is too short for understanding the full range of hydrometeorological variability in this important region. Here we present a tree-ring based reconstruction of September?CNovember Citarum streamflow (AD 1759?C2006), one of the first such records available for monsoon Asia. Close coupling is observed between decreased tree growth and low streamflow levels, which in turn are associated with drought caused by ENSO warm events in the tropical Pacific and Indian Ocean positive dipole-type variability. Over the full length of record, reconstructed variance was at its weakest during the interval from ~1905?C1960, overlapping with a period of unusually-low variability (1920?C1960) in the ENSO-Indian Ocean dipole systems. In subsequent decades, increased variance in both the streamflow anomalies and a coral-based SST reconstruction of the Indian Ocean Dipole Mode signal the potential for intensified drought activity and related consequences for water supply and crop productivity in western Java, where much of the country??s rice is grown.     

Die Paleozän-Eozän-Transgression in Südlibyen

Zusammenfassung An der Peripherie der Serir Tibesti (Südlibyen und nördlicher Grenzbereich der Rebublik Tschad) wurden 10 lithostratigraphische Profile aufgenommen und miteinander korreliert, um das Vorgreifen der Paleozän-Eozän-Transgression auf den afrikanischen Kontinent zu verfolgen. Es zeigt sich, daß der Höhepunkt der in der Oberkreide begonnenen Transgression während der Ablagerung der oberpaleozänen Operculinoides-Schichten und des untereozänen Kheir Mergels erreicht war. Ein direkter Zusammenhang zwischen dem Sedimentationsraum nördlich des Tibesti und dem Niger-Becken mittels der Hoggar-Tibesti-Pforte (Furon 1951, p. 71) wird abgelehnt, da die größte Verbreitung des mer saharienne südlich des Hoggar-Tibesti in der Oberkreide und nicht im Paleozän stattfand.

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10 lithostratigraphic sections were surveyed along the periphery of the Serir Tibesti (southern Libya and northern border area of Republic Chad). Their correlation resulted in analysing the Paleocene-Eocene transgression on the African continent. It was found out that this transgression starting with the Upper Cretaceous reached its climax during sedimentation of the upper Paleocene Operculinoides-Schichten and lower Eocene Kheir Marl. A direct connection between the sedimentation area north of the Tibesti mountains and the Niger basin via the Hoggar-Tibesti-Straits (Furon 1951, p. 71) is not encountered as the climax of the extension of the mer saharienne south of Hoggar-Tibesti coincides with the Upper Cretaceous and not with the Paleocene.

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Résumé A la périphérie du Sérir Tibesti (Libye méridionale et zone frontière septentrionale de la République du Tchad) 10 coupes lithostratigraphiques ont été établies. Une corrélation effectuée entre eux démontre le caractère progressif de la transgression du Paléocène-Eocène vers le continent africain. Cette transgression dont le début a été daté au Crétacé supérieur a atteint son extension la plus large au temps de la sédimentation des séries à Operculinoides (Paléocène supérieur) et des marnes Kheir (Eocène inférieur). L'idée d'une connexion directe entre l'aréal de sédimentation au nord du Tibesti et celui du bassin de Niger par moyen du détroit Hoggar-Tibesti (Furon 1951, p. 71) n'a pas pu être acceptée étant donné que l'extension la plus large de la «mer saharienne» au sud du Hoggar-Tibesti s'est passée au Crétacé supérieur et non pas au Paléocène.

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- , 10 ( ). , , Kheir. , Hogger-Tibesti (Turon 1951, p. 71) , . . mer saharienne Hogger-Tibesti , .

     

Evidence of quaternary transtensional tectonics in the Nekor basin (NE Morocco)

The geodynamic processes in the western Mediterranean are driven by both deep (mantle) processes such as slab‐rollback or delamination, oblique plate convergence and inherited structures. The present‐day deformation of the Alboran Sea and in particular the Nekor basin area is linked to these coeval effects. The seismically active Nekor basin is an extensional basin formed in a convergent setting at the eastern part of the Rif Chain whose boundaries extend both onshore and offshore Morocco. We propose a new structural model of the Nekor basin based on high‐resolution offshore data compiled from recent seismic reflection profiles, swath bathymetry acquisitions and industrial seismic reflection profiles. The new data set shows that the northern limit of the basin is oriented N49° with right‐stepping faults from the Bousekkour–Aghbal fault to the sinistral Bokkoya fault zone. This pattern indicates the presence of an inherited left‐lateral basement fault parallel to the major inherited Nekor fault. This fault has been interpreted as a Quaternary active left‐lateral transfer fault localized on weak structural discontinuities inherited from the orogenic period. Onshore and offshore active faults enclose a rhombohedral tectonic Nekor Basin. Normal faults oriented N155° offset the most recent Quaternary deposits in the Nekor basin, and indicate the transtensional behaviour of this basin. The geometry of these faults suggests a likely rollover structure and the presence at depth of a crustal detachment. Inactive Plio‐Quaternary normal faults to the east of the Ras Tarf promontory and geometries of depocentres seem to indicate the migration of deformation from east to west. The local orientations of horizontal stress directions deduced from normal fault orientations are compatible with the extrusion of the Rifian units and coherent with the westward rollback of the Tethyan slab and the localization of the present‐day slab detachment or delamination.     

Early Holocene environmental history of sunken landscapes: pollen, plant macrofossil and geochemical analyses from the Borkum Riffgrund, southern North Sea

A vibrocore from the sea floor of the southern North Sea provides a ~1,500-year record of early Holocene vegetation history and mire development in a landscape now 33 m below sea-level. Pollen, plant macrofossil and geochemical analyses of an AMS ¹⁴C dated sand–peat–marine mud sequence document the paludification on Pleistocene sands ~10,700 cal BP, the subsequent development of eutraphentic carr vegetation and the gradual inundation by the transgressing sea ~9,350 cal BP. Pinus–Corylus woodland prevailed on terrestrial grounds after hazel had immigrated ~10,700 cal BP. Salix dominated the carr vegetation throughout 1,300 years of peat formation, because Alnus did not spread in the Borkum Riffgrund area until 9,300 BP. Brackish reed vegetation with Phragmites established after inundation and siliciclastic marine sediments were being deposited. This article also examines the detection and suitability of key horizons indicative of marine influence. XRF-Scanning provides the most detailed results in the briefest possible time to pinpoint spectra best suitable for AMS ¹⁴C dating of classical key horizons such as start of peat formation and transgressive contact. The combined application of botanical and geochemical methods allows determining new key horizons indicative of marine influence, namely the earliest marine inundation and the onset of sea-level influence on coastal ground water level.     

Formation of low-pressure reaction textures during near-isothermal exhumation of hot orogenic crust (Bohemian Massif,Austria)

Two types of aluminous paragneiss from the Loosdorf complex (Bohemian Massif, NE Austria) contain coarse-grained granulite assemblages and retrograde reaction textures that are investigated to constrain the post-peak history of the Gföhl unit in the southern Bohemian Massif. Both types have a peak assemblage garnet–biotite–sillimanite–plagioclase–K-feldspar–quartz–granitic melt ± kyanite ± ilmenite ± rutile, recording peak metamorphic conditions of $$0.9–1.1 GPa and $$780–820°C estimated by isochemical phase equilibrium modelling. The first sample type (Ysper paragneiss) developed (i) cordierite coronae around garnet and (ii) cordierite–spinel and cordierite–quartz reaction textures at former garnet–sillimanite interfaces. Calculated chemical potential relationships indicate that the textures formed in the course of a post-peak near-isothermal decompression path reaching $$0.4 GPa. Texture formation follows a two-step process. Initially, cordierite coronae grow between garnet and sillimanite. As these coronae thicken, they facilitate the development of local compositional domains, leading to the formation of cordierite–spinel and cordierite–quartz symplectites. The second sample type (Pielach paragneiss) exhibits only discontinuous cordierite coronae around garnet porphyroblasts but lacks symplectites. The formation of cordierite there also indicates near-isothermal decompression to 0.4–0.5 GPa and 750–800°C. This relatively hot decompression path is explained by the contemporaneous exhumation of a large HP–UHT granulite body now underlying the Loosdorf complex. The timing of regional metamorphism in the granulites and the southern Bohemian Massif in general is well constrained and has its peak at $$340 Ma. Monazite from Loosdorf paragneiss samples yield a slightly younger age of $$335 Ma. Although the ages overlap within error, they are interpreted to reflect near-isothermal decompression and exhumation resulting in the formation of the observed reaction textures.     

Tectonic controls on Cenozoic foreland basin development in the north‐eastern Andes,Colombia

In order to evaluate the relationship between thrust loading and sedimentary facies evolution, we analyse the progradation of fluvial coarse‐grained deposits in the retroarc foreland basin system of the northern Andes of Colombia. We compare the observed sedimentary facies distribution with the calculated one‐dimensional (1D) Eocene to Quaternary sediment‐accumulation rates in the Medina wedge‐top basin and with a three‐dimensional (3D) sedimentary budget based on the interpretation of ～1800 km of industry‐style seismic reflection profiles and borehole data. Age constraints are derived from a new chronostratigraphic framework based on extensive fossil palynological assemblages. The sedimentological data from the Medina Basin reveal rapid accumulation of fluvial and lacustrine sediments at rates of up to ～500 m my^?1 during the Miocene. Provenance data based on gravel petrography and paleocurrents reveal that these Miocene fluvial systems were sourced from Upper Cretaceous and Paleocene sedimentary units exposed to the west in the Eastern Cordillera. Peak sediment‐accumulation rates in the upper Carbonera Formation and the Guayabo Group occur during episodes of coarse‐grained facies progradation in the early and late Miocene proximal foredeep. We interpret this positive correlation between sediment accumulation and gravel deposition as the direct consequence of thrust activity along the Servitá–Lengupá faults. This contrasts with one class of models relating gravel progradation in more distal portions of foreland basin systems to episodes of tectonic quiescence.