Flexural isostatic response of the Alps to increased Quaternary erosion recorded by foreland basin remnants,SE France

We test the hypothesis that flexural isostatic compensation of the mass removed by enhanced Quaternary erosion is responsible for uplift of the Western European Alps and their forelands. We use two well‐preserved and well‐dated (1.8 Ma) abandonment surfaces of foreland basin remnants in SE France (the Chambaran and Valensole plateaux) as passive benchmarks for tilting of the foreland. Estimating their initial slope from morphometric scaling relationships, we determine bulk post‐depositional tilting of 0.5–0.8% for these surfaces. The calculated isostatic response of the Alpine lithosphere to erosional unloading, using the method recently proposed by Champagnac et al. [Geology 35 (2007) 195–198] , yields a predicted tilting of 0.3–0.4% in the considered areas, explaining approximately half of the determined post‐depositional tilting. Such long‐term deformation being insensitive to cyclic loading/unloading because of glaciations, we suspect the other half to be related to as yet undetermined long‐wavelength and long‐lived tectonic process(es).     

The delay between solar activity and density changes in the upper atmosphere

Since 1958 it is known that there exists a response time of the upper atmosphere to changes in solar activity. This response time is best described as the lag between the 27-day variation of solar decimeter flux and the observed density changes of the upper atmosphere. Roemer obtained as a mean observational value for this lag 1.0 ± 0.12 days. Volland's simplified version of the Harris-Priester model of the upper atmosphere is used to calculate the delay which can be expected from theory. Only the effect of solar EUV radiation is taken into account. A possible influence of the corpuscular component of the solar radiation is not included in our estimate.

The calculations are carried out for the Harris-Priester model with solar activity index and a variation of . The resulting delay is 0.6 days. The calculated amplitude of the variations of the diurnal average temperatures during the solar 27-days cycle is in very good agreement with Jacchia's empirical formula.     

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A sonic well log of the basement complex of the Walvis Ridge

A sonic well log was obtained within the basement complex of the Walvis Ridge during Deep Sea Drilling Project Leg 74. The top of the basement complex is characterized by smooth acoustic reflectors. The rocks recovered within the basement complex consist of basalts with intercalated sediments. According to the log ～-50% of the upper 75 m of basement are igneous rocks and the other 50% sedimentary. Sonobuoy results indicate that the ratio of sediments to basalt increases with depth for an additional 225 m until a typical oceanic velocity structure is observed. Paleontological results suggest that the processes forming this upper 300 m of the basement complex was accomplished within a short time interval.     

Unusual large-scale phytoplankton blooms in the equatorial Pacific

Unusual large-scale accumulations of phytoplankton occurred across 10,000 km of the equatorial Pacific during the 1998 transition from El Niño to La Niña. The forcing and dynamics of these phytoplankton blooms were studied using satellite-based observations of sea surface height, temperature and chlorophyll, and mooring-based observations of winds, hydrography and ocean currents. During the bloom period, the thermocline (nutricline) was anomalously shallow across the equatorial Pacific. The relative importance of processes that enhanced nutrient flux into the euphotic zone differed between the western and eastern regions of the blooms. In the western bloom region, the important vertical processes were turbulent vertical mixing and wind-driven upwelling. In contrast, the important processes in the eastern bloom region were wave-forced shoaling of nutrient source waters directly into the euphotic zone, along-isopycnal upwelling, and wind-driven upwelling. Advection by the Equatorial Undercurrent spread the largest bloom 4500 km east of where it began, and advection by meridional currents of tropical instability waves transported the bloom hundreds of kilometers north and south of the equator. Many processes influenced the intricate development of these massive biological events. Diverse observations and novel analysis methods of this work advance the conceptual framework for understanding the complex dynamics and ecology of the equatorial Pacific.     

Fracture activity: A possible triggering mechanism for slope instabilities in the Eastern Atlantic?

The largest known submarine slope instabilities occur on gently inclined slopes or in the deep sea. The sedimentation rates are mostly too low to induce an excess pore-water pressure sufficient to create failure. A possible triggering mechanism for these instabilities is additional horizontal ground acceleration caused by earthquakes. Old zones of weakness, represented by fracture zones, can be reactivated by isostatic movements and induce seismic activity. The distribution of some major slope instabilities and the trend of fracture zones in the Eastern Atlantic are compared and Fracture activity is suggested as the main triggering mechanism for these slope instabilities.     

The Biology of Upogebia pusilla (Petagna) (Decapoda, Thalassinidea) I. The Burrows

Abstract. The biology of the thalassinidean shrimp Upogebia pusilla was studied on a tidal flat in the Lagoon of Grado (Northern Adriatic). Burrows were investigated using in situ resin casting and with additional in situ and laboratory observations. Burrows show a basic pattern consisting of a U or a double U with turning chambers and a vertical shaft. Mean burrow diameter depends on animal size, it is smaller than the rigid carapace of the animal. Dimensions, distance between openings, depth of U, total depth, volume and surface are size dependent. The burrow wall is smooth and oxidized. Burrows are always inhabited by a single shrimp. Although they overlap, they are never interconnected. They are mainly constructed by compression of the sediment and are relatively permanent structures. A comparison of the burrows of Thalassinidea with regard to shape, number and appearance of openings, dimensions, properties of the burrow wall and dynamics is given.