Dating sediments in coastal areas and potential applications for constraining the palaeo-environmental context of an archaeological site at Vohemar

We present an overview on different environmental zones within coastal areas and summarise the physical basis behind the three most important methods that are available to date Holocene coastal sediments. Besides radiocarbon and uranium series dating, Optically Stimulated Luminescence (Osl) has increasingly been applied for dating in coastal settings over the past decade. This is illustrated by a number of case studies showing that Osl can be applied to sediments from almost any kind of coastal environment, covering a potential dating range from some years up to several hundred thousand years. Osl dating may hence be the method of choice for deciphering natural environmental change along coasts as well as the presence and the impact of human occupation in such areas. In addition, we briefly show how and where these dating methods could be applied to constrain the palaeo-environmental context of an archaeological site at Vohemar in north-eastern Madagascar.

Mid-Holocene Climate and Culture Change in the South Central Ande

This chapter reviews the history of study and the current status of Mid-Holocene climatic and cultural change in the South Central Andes, which host a wide range of different habitats from Pacific coastal areas up to extremely harsh cold and dry environments of the high mountain plateau, the altiplano or the puna. Paleoenvironmental information reveals high amplitude and rapid changes in effective moisture during the Holocene period and, consequently, dramatically changing environmental conditions. Therefore, this area is suitable to study the response of hunting and gathering societies to environmental changes, because the smallest variations in the climatic conditions have large impacts on resources and the living space of humans. This chapter analyzes environmental and paleoclimatic information from lake sediments, ice cores, pollen profiles, and geomorphic processes and relates these with the cultural and geographic settlement patterns of human occupation in the different habitats in the area of southern Peru, southwest Bolivia, northwest Argentina, and north Chile and puts in perspective of the early and late Holocene to present a representative range of environmental and cultural changes. It has been found that the largest changes took place around 9000 cal yr BP when the humid early Holocene conditions were replaced by extremely arid but highly variable climatic conditions. These resulted in a marked decrease of human occupation, “ecological refuges,” increased mobility, and an orientation toward habitats with relatively stable resources (such as the coast, the puna seca, and “ecological refuges”).

On the seasonal variations of salinity of the tropical Atlantic mixed layer

The physical processes controlling the mixed layer salinity (MLS) seasonal budget in the tropical Atlantic Ocean are investigated using a regional configuration of an ocean general circulation model. The analysis reveals that the MLS cycle is generally weak in comparison of individual physical processes entering in the budget because of strong compensation. In evaporative regions, around the surface salinity maxima, the ocean acts to freshen the mixed layer against the action of evaporation. Poleward of the southern SSS maxima, the freshening is ensured by geostrophic advection, the vertical salinity diffusion and, during winter, a dominant contribution of the convective entrainment. On the equatorward flanks of the SSS maxima, Ekman transport mainly contributes to supply freshwater from ITCZ regions while vertical salinity diffusion adds on the effect of evaporation. All these terms are phase locked through the effect of the wind. Under the seasonal march of the ITCZ and in coastal areas affected by river (7°S:15°N), the upper ocean freshening by precipitations and/or runoff is attenuated by vertical salinity diffusion. In the eastern equatorial regions, seasonal cycle of wind forced surface currents advect freshwaters, which are mixed with subsurface saline water because of the strong vertical turbulent diffusion. In all these regions, the vertical diffusion presents an important contribution to the MLS budget by providing, in general, an upwelling flux of salinity. It is generally due to vertical salinity gradient and mixing due to winds. Furthermore, in the equator where the vertical shear, associated to surface horizontal currents, is developed, the diffusion depends also on the sheared flow stability.

Isotope Study of Moisture Sources, Recharge Areas and Groundwater Flowpaths within the Eastern Batinah Coastal Plain, Sultanate of Oman

Oxygen and hydrogen isotope analyses of rainfall samples collected on the eastern Batinah coastal plain of northern Oman between 1995 and 1998 indicate two different principal water vapor sources for precipitation in the area: a northern, Mediterranean source and a southern, Indian Ocean source. As a result, two new local meteoric water lines were defined for the study area. Isotopic analyses of groundwater samples from over 200 springs and wells indicate that the main source of water to the Batinah coastal alluvial aquifer is high-altitude rainfall from the adjacent Jabal Akhdar Mountains, originating from a combination of northern and southern moisture sources. The groundwater recharged at high-altitude forms two plumes of water which is depleted in the heavy isotopes 18O and 2H and stretches from the mountains across the coastal plain to the sea, thereby retaining a chemical homogeneity horizontally and vertically down to a depth exceeding 300 m. In contrast, in areas adjacent to these two plumes the alluvial aquifer is geochemically stratified. Near the coast, saline intrusion results in abrupt changes in chloride concentrations and isotope values.