Morphodynamic response of a meso- to macro-tidal intermediate beach based on a long-term data set

Four years of bi-monthly topographic surveys have been conducted on a 350 m stretch of the meso- to macro-tidal Truc Vert beach, France. Here we study the dynamics of both the inner bar and the upper part of the beach where a berm can develop in the presence of fair weather conditions. For the inner bar, the occurrences of the different states within the intermediate classification, following that of Wright and Short (Wright, L.D., Short, A.D. 1984. Morphodynamic variability of surf zones and beaches: a synthesis. Marine Geology 56, 93–118), are presented and compared to other sites in both micro- and meso-tidal environments. The results show a similar frequency of occurrence of the Transverse Bar and Rip (TBR) state, while the more dissipative states, Rhythmic Bar and Beach (RBB) and Longshore Bar and Trough (LBT), are less regularly observed despite the high wave energy levels. The LBT and RBB states are also observed in the presence of fair weather conditions and the TBR state can persist during very energetic events. Similar results are also observed with the upper beach dynamics. Very energetic events are not necessarily associated with erosion while and low-energy events are not necessarily accompanied by accretion. The conditions given here indicate, that berm development occurs preferentially when the beach morphology exhibits a TBR or a LTT state. Apart from the control exerted by offshore wave conditions, the beach state and berm development patterns exhibited by Truc Vert beach are also discussed within the framework of possible morphological (morphodynamic) feedback and of the influence of the meso- to macrotidal range which modulates the type, intensity and duration of the wave processes operating on the cross-shore profile.     

Field observations of an evolving rip current on a meso-macrotidal well-developed inner bar and rip morphology

The Aquitanian Coast (France) is a high-energy meso-macrotidal environment exhibiting a highly variable double sandbar system. The inner and the outer bar generally exhibit a bar and rip morphology and persistent crescentic patterns, respectively. In June 2007, an intense five-day field experiment was carried out at Biscarrosse Beach. A large array of sensors was deployed on a well-developed southward-oriented bar and rip morphology. Daily topographic surveys were carried out together with video imaging to investigate beach morphodynamic evolution. During the experiment, offshore significant wave height ranged from 0.5 to 3 m, with a persistent shore-normal angle. This paper identifies two types of behavior of an observed rip current: (1) for low-energy waves, the rip current is active only between low and mid tide with maximum mean rip current velocity reaching 0.8 m/s for an offshore significant wave height (H_s) lower than 1 m; (2) for high-energy waves (H_s≈ 2.5–3 m), the rip current was active over the whole tide cycle with the presence of persistent intense offshore-directed flows between mid and high tide. For both low and high-energy waves, very low-frequency pulsations (15–30 min) of the mean currents are observed on both feeder and rip channels.A persistent slow shoreward migration of the sandbar was observed during the experiment while no significant alongshore migration of the system was measured. Onshore migration during the high-energy waves can be explained by different sediment transport processes such as flow velocity skewness, wave asymmetry or bed ventilation. High-frequency local measurements of the bed evolution show the presence of significant (in the order of 10 cm) fluctuations (in the order of 1 h). These fluctuations, observed for both low- and high-energy waves, are thought to be ripples and megaripples, respectively and may play an important but still poorly understood role in the larger scale morphodynamics. The present dataset improves the knowledge of rip dynamics as well as the morphological response of strongly alongshore non-uniform meso-macrotidal beaches.     

Coloring and preservation state of faunal remains from the neanderthal levels of Kůlna Cave,Czech republic

The preservation process of faunal remains from the Middle Paleolithic levels of Kůlna Cave was studied within a taphonomic and palaeodietary framework. A visual examination of bones and teeth showed that they display a wide variety of colors. Chemical analyses (C, N, Fe, Mn) and a combination of analytical techniques, such as Fourier transform infrared (FT‐IR), X‐ray diffraction (XRD), and electron spin resonance (ESR) spectrometry, were conducted on 13 fossil remains. The crystallinity indexes, IR‐SF, XRD‐CI, XRD‐L200, the IR area band (Amide I), and the ESR analyses showed that the bones were not burned at a temperature higher than 200°C. This implies that the bone remains were not used as fuel by Neanderthals at Kůlna Cave. Coloring in these bones is largely due to the presence of Mn and Fe. © 2006 Wiley Periodicals, Inc.