The Upper Rhône Delta Sedimentary Record in the Arles-Piton Core: Analysis of Delta-Plain Subenvironments, Avulsion Frequency, Aggradation Rate and Origin of Sediment Yield

Results from analyses of the Arles‐Piton sediment core, retrieved from the apex of the Rhône Delta, highlight processes of Holocene deltaic construction controlled mainly by hydrosedimentary variability and channel avulsions. The alluvial suite was investigated for grain size, sedimentary structures, CaCO₃, organic matter, heavy minerals and chrono‐stratigraphy (¹⁴C and archaeological/historical dates). The study shows the succession of six facies associations: a distributary channel (before 6157‐5843 BC), a swamp (5719‐5530/4796‐4463 BC), a distal flood plain (5719‐5530/4796‐4463 BC), a distributary channel (4796‐4463/2900‐2503 BC), a proximal flood plain (2900‐2503 BC/AD 270‐290), and a crevasse splay (after AD 270‐290). Substantial changes in hydrodynamics are strongly linked to three channel avulsions (before 6157‐5843 BC, after 4796‐4463 BC and after 2900‐2503 BC). A correlation with the whole channel avulsion history of the Rhône Delta allowed us to propose an average rhythm of channel avulsion of c. 1450 years. From 5719‐5530 BC to AD 270‐290, the flood plain aggraded at the average rate of 2.5 mm/a. The aggradation rates were higher both in the proximal and distal flood plains, where sedimentation process is continuous. They were lower both in the active distributary channels, because of frequent truncation of the alluvial suite, and the abandoned channels where detritic inputs are minimum. The sediment supply arriving to the upper Rhône Delta was derived mainly from proximal source areas (Massif Central, Southern Alps) during the last 8000 years, except during the hydrological changes of Roman antiquity during which detritic inputs were derived firstly from the Northern Alps and Southern Alps, and secondly from the Massif Central.     

High‐resolution record of environmental changes and tephrochronological markers of the Last Glacial–Holocene transition at Lake Lautrey (Jura,France)

This paper presents the results of a multiproxy investigation including volume magnetic susceptibility (κ), mineral and pollen analyses of Late Glacial sediments from Lake Lautrey (Jura, France). Small‐scale lithological variations have been identified with high stratigraphic resolution in order to establish lithostratigraphic correlations between cores. κ measurements, combined with mineralogical analyses, provide information on past sedimentary processes. This combined approach reflects major changes in terrestrial habitats and soil processes which may relate to the climatic events characterising the Late Glacial climatic warming and cooling phases. During warm intervals, the record indicates increased lake productivity via carbonate precipitation and decreased input of detrital material. In contrast, cooler intervals show reduced lake productivity, catchment area instability and increased detrital inputs. Several short interruptions in reforestation and in soil stabilisation can be identified and linked with abrupt colder events occurring through the Bølling. A general trend of warming is recorded from the coldest part of the Younger Dryas. Three tephra layers were also detected. The mineral composition analyses show that the upper tephra layer corresponds to the Laacher See eruption (Eifel, Germany) while the lower ones may relate to the volcanic activity of the Chaîne des Puys (Massif Central, France) around 13 000 cal. yr BP. These two events, recognised for the first time outside the Massif Central region, may provide additional chronostratigraphic markers for the Late Glacial sedimentary records of the Jura mountains and northern Alps. Copyright © 2004 John Wiley & Sons, Ltd.     

Possible non-thermal effects in stellar nuclear reactions

The slowing down of charged ions in dense plasma is examined. It is found that under conditions prevailing in late phases of evolution, the nuclei can react while slowing down.The consequence of such an additional nuclear reaction on the product of the nuclear burning is discussed briefly.Partly supported by the United States-Israel Binational Science Foundation Grant 45, and National Research Council of Canada, grant A-514.     

Late Pleistocene (MIS 3–4) climate inferred from micromammal communities and δO of rodents from Les Pradelles,France

The middle Paleolithic stratigraphic sequence of Les Pradelles (Charente, France) spans from the end of Marine Isotope Stage (MIS) 4 until the middle of MIS 3. Micromammal remains are present in all the stratigraphic levels, offering a rare opportunity to address the questions of both environmental and climatic fluctuations throughout this period. Climate modes were studied through the taphonomy, biodiversity and oxygen isotope compositions of phosphate (δ¹⁸O_p) from 66 samples of rodent tooth enamel. The δ¹⁸O_p values from the lower sedimentary levels provide summer mean air temperatures of 19 ± 2°C (level 2/1) and of 16 ± 2°C (levels 2A, 2B and 4A). Within the middle of sequence (level 4B), a paleobiodiversity change can be identified with an increase of Dicrostonyx torquatus, which is associated with the largest amplitude in δ¹⁸O_p values and the highest maximal δ¹⁸O_p values. At the top of the sequence (level 5-2), a biodiversity change is observed with the increase of Microtus arvalis, but without any change in δ¹⁸O_p values. The association of cold rodent species with unexpected high and large amplitudes in the δ¹⁸O_p values of their teeth, possibly indicative of aridity, suggests their deposition during a Heinrich event.     

The effects of surface weathering on the geochemical analysis of archaeological lithic samples using non‐destructive polarized energy dispersive XRF

The purpose of this paper is to show the effects of lithic artifact surface weathering on whole rock non‐destructive polarized energy dispersive X‐ray fluorescence (P‐ED‐XRF) major and trace element determinations. Chemical results for a weathered and subsequently mechanically ground subset of New Hampshire Ossipee archaeological flakes, cataloged as hornfels, show that both groups of elements are variably affected by weathering. A graphic approach is developed and proposed to highlight the role and importance of immobile elements. A case is made and an analytical method is proposed for the routine use of P‐ED‐XRF spectrometers to determine the chemical makeup of lithic artifacts and therefore provide a data set compatible with existing geochemical databases and literature. The use of specific variation diagrams is adopted to portray the weathering trend. Internationally approved geochemical rock type diagrams are used to correct the rock type previously assigned to Ossipee artifacts and in turn narrow down potential quarry sources. © 2011 Wiley Periodicals, Inc.     

Example of Neogene tectonic indentation in the Eastern Betic Cordilleras: the Arc of Aguilas (Southeastern Spain)

Abstract

Neogene deformations have deeply disturbed the initial architecture of the pile of nappes within the Eastern Betic zone. The Arc of Aguilas, displaying a southeast-facing concavity, is a spectacular example of such a post-nappe structuration. Miocene deposits involved in the torsion of the Arc provide a chronology of the deformation. The Arc of Aguilas is one element within a system of rigid-plastic indentation including the following units, from the inner (SE) to the outer (NW) zones : — A rigid block, little deformed, located in the present day abyssal plain, play the part of the indenter.

— A structural pad corresponding to the Aguilas Arc itself. It was severely folded during Miocene times.

— A large peripheral zone mainly subjected to faulting during the Neogene (essentially strike-slip faults). These faults control the evolution of different types of sedimentary basins during the Late Neogene (Tortonian to Pliocene).

Two large shear zones: N020 sinistral (Palomares and Terreros faults), N100 dextral (Las Moreras faults) guided the deformation of the Aguilas Arc within a compressive stressfield of which major tensor axis oscillated between NW-SE and N-S.     

Influence of plankton concentration on gametogenesis and spawning of the black lip pearl oyster Pinctada margaritifera in Ahe atoll lagoon (Tuamotu archipelago, French polynesia)

Pearl culture industry represents one of the dominant business sector of French Polynesia. However, it still entirely relies on unpredictable spat collection success. Our aim was to assess the influence of natural plankton concentration fluctuations on maturation and spawning of the black lip pearl oyster Pinctada margaritifera, during a 4months survey conducted in Ahe atoll lagoon. Plankton concentration was assessed by chlorophyll a extraction and by microscope counts while gonadic index, gonado-visceral dry weights and histology were used to measure pearl oysters reproduction activity. We found that (i) plankton concentration fluctuations were mainly related to wind regime, (ii) gametogenesis rate was mainly related to plankton concentration, (iii) spawning occurred when maximal gonad storage was reached, (iv) plankton concentration was the main spawning synchronizing factor. These results contribute explaining P. margaritifera spat collection variability in French Polynesian atoll lagoon.     

Unraveling the patterns of late Holocene debris-flow activity on a cone in the Swiss Alps: Chronology, environment and implications for the future

Debris-flow activity on the forested cone of the Ritigraben torrent (Valais, Swiss Alps) was assessed from growth disturbances in century-old trees, providing an unusually complete record of past events and deposition of material. The study of 2246 tree-ring sequences sampled from 1102 Larix decidua Mill., Picea abies (L.) Karst. and Pinus cembra ssp. sibirica trees allowed reconstruction of 123 events since AD 1566. Geomorphic mapping permitted identification of 769 features related to past debris-flow activity on the intermediate cone. The features inventoried in the study area covering 32 ha included 291 lobes, 465 levées and 13 well-developed debris-flow channels. Based on tree-ring records of disturbed trees growing in or next to the deposits, almost 86% of the lobes identified on the present-day surface could be dated. A majority of the dated material was deposited over the last century. Signs of pre-20th century events are often recognizable in the tree-ring record of survivor trees, but the material that caused the growth anomaly in trees has been completely overridden or eroded by more recent debris-flow activity.Tree-ring records suggest that cool summers with frequent snowfalls at higher elevations regularly prevented the release of debris flows between the 1570s and 1860s; the warming trend combined with greater precipitation totals in summer and autumn between 1864 and 1895 provided conditions that were increasingly favorable for releasing events from the source zone. Enhanced debris-flow activity continued well into the 20th century and reconstructions show a clustering of events in the period 1916–1935 when warm–wet conditions prevailed during summer in the Swiss Alps. In contrast, very low activity is observed for the last 10-yr period (1996–2005) with only one debris-flow event recorded on August 27, 2002. Since sediment availability is not a limiting factor, this temporal absence of debris-flow activity is due to an absence of triggering events, which not only shifted from June and July to August and September over the 20th century, but also seemed to be initiated primarily by persistent precipitation rather than summer thunderstorms. From the reconstructions, based on RCM simulations, there are indications that debris-flow frequencies might continue to decrease in the future, as precipitation events are projected to occur less frequently in summer but become more common in spring or autumn.     

High-pressure yield strength of rocksalt structures using quartz Raman piezometry

The Raman frequencies of quartz are used to evaluate deviatoric stresses in rocksalt-structure media in diamond-anvil cell experiments to pressures up to 20 GPa. The piezospectroscopic effect in quartz is modeled by first-principles calculations. Non-hydrostatic stresses measured in halogen salts give yield strength estimates of 3 GPa in the B1 structure (NaCl), and 4.5 GPa for the B2 structure (KCl and KBr). Raman measurements in MgO show that the yield strength is reached at around 6 ± 1 GPa. Measurements on quartz alone indicate similar yield strength. The estimated yield strength in MgO is thus likely a lower bound, in consistency with former radial X-ray diffraction measurements that gave a yield strength of 8 ± 1 GPa, and lower-pressure large-volume press experiments indicating a yield strength of 6 GPa at 5 GPa. Former values of the yield strength below 2 GPa determined by pressure gradient measurements were underestimated due to unverified assumptions in boundary conditions. The yield strength increases with increasing coordination of ionic solids, likely contributing to increase viscosity at phase transitions near the upper–lower mantle boundary.     

Thermodynamic properties of chlorite CCa-2. Heat capacities, heat contents and entropies

The heat capacities of the international reference clay mineral chlorite CCa-2 from Flagstaff Hill, California, were measured by low temperature adiabatic calorimetry and differential scanning calorimetry, from 5 to 520 K (at 1 bar). The studied chlorite is a Fe-bearing trioctahedral chlorite with an intermediary composition between ideal clinochlore (Si₃Al)(Mg₅Al)O₁₀(OH)₈ and chamosite (Si₃Al)(Fe₅Al)O₁₀(OH)₈. Only few TiO₂ impurities were detected in the natural chlorite sample CCa-2. Its structural formula, obtained after subtracting the remaining TiO₂ impurities, is (Si_2.633Al_1.367)(Al_1.116Mg_2.952Mn_0.012Ca_0.011)O₁₀(OH)₈. From the heat capacity results, the entropy, standard entropy of formation and heat content of the chlorite were deduced. At 298.15 K, the heat capacity of the chlorite is 547.02 (±0.27) J mol⁻¹ K⁻¹ and the molar entropy is 469.4 (±2.9) J mol⁻¹ K⁻¹. The standard molar entropy of formation of the clay mineral from the elements is −2169.4 (±4.0) J mol⁻¹ K⁻¹.