蓝色摩洛哥 混搭之城

多民族历史混搭和曾经的殖民统治,给摩洛哥留下的,就像一个混血大眼睛男孩迷人的神情,可以瞥见西班牙风情,又可以凝望撒哈拉的苍凉。     

Possible fossil impression in sandstone from the late Palaeoproterozoic-early Mesoproterozoic Semri Group (lower Vindhyan Supergroup), central India

The Lower–Middle Ordovician Zitai Formation of the South China palaeoplate consists of a succession of purple red, nodular argillaceous limestones. Palaeogeographically, it is distributed along the southeastern margin of the Yangtze Platform, and is of late Floian to Dapingian age, correlative with the Dawan Formation of the Middle and Lower Yangtze Platform. In Shitai County, Anhui Province, East China, the Zitai Formation is rich in conodonts, enabling the recognition of four biozones based on first appearance data. Detailed palaeontological and biostratigraphical study of these conodonts reveals that the Ordovician conodont radiation in the Lower Yangtze Platform attained its first diversity peak low in the Oepikodus evae Biozone. This diversification is generally consistent with macroevolutionary trends of brachiopods of South China and graptolites of the Upper Yangtze Platform, but was earlier than that of trilobites and acritarchs of the same palaeoplate. Correlation with the sea-level curve for South China suggests that conodont diversity change during the Ordovician radiation was mainly controlled by regional sea-level fluctuations.     

Pastoralism and Protected Area Management in Mongolia's Gobi Gurvansaikhan National Park

The Gobi Gurvansaikhan National Park was established in south central Mongolia in 1993 and is used by over 1100 families with pastoralism as their main means of livelihood. Research conducted in 1998–2000 to analyse grazing management problems identified a number of issues and concerns, including a significant increase in the number of herders and the size of the herd; variations in herd size reflecting differences in wealth; problems with marketing of livestock or livestock products; declining stock movements because of transportation costs and loss of water sources; and significant competition and conflicts for grazing areas. The socio‐economic problems associated with Mongolia's transition to a market system, coupled with the expansion of protected areas, mean that herders have to adapt to both the current economic system and changes in land use. Although some aspects of the development of the park can be seen as a positive influence on maintaining pastoral livelihoods in this area, the national goal of protecting 30 per cent of the country, doubling the area of Mongolia currently under protected area status, could have negative effects on pastoral livelihoods, unless ministry officials, protected area administrators and pastoralists can work effectively to solve resource problems.     

A Map Overlay Error Model Based on Boundary Geometry

An error model for quantifying the magnitudes and variability of errors generated in the areas of polygons during spatial overlay of vector geographic information system layers is presented. Numerical simulation of polygon boundary displacements was used to propagate coordinate errors to spatial overlays. The model departs from most previous error models in that it incorporates spatial dependence of coordinate errors at the scale of the boundary segment. It can be readily adapted to match the scale of error–boundary interactions responsible for error generation on a given overlay. The area of error generated by overlay depends on the sinuosity of polygon boundaries, as well as the magnitude of the coordinate errors on the input layers. Asymmetry in boundary shape has relatively little effect on error generation. Overlay errors are affected by real differences in boundary positions on the input layers, as well as errors in the boundary positions. Real differences between input layers tend to compensate for much of the error generated by coordinate errors. Thus, the area of change measured on an overlay layer produced by the XOR overlay operation will be more accurate if the area of real change depicted on the overlay is large. The model presented here considers these interactions, making it especially useful for estimating errors studies of landscape change over time.     

The ‘Sand-Bath’ and Lithic Heat Treatment in the South African Middle Stone Age: Myth or Reality?

When heat treatment of silcrete for stone knapping was first discovered in the South African Middle Stone Age (MSA), the procedure used for it was suggested to be similar to the one used for heat treatment of finer rocks in other parts of the world: slow sand-bath heating. This comparison may have been based on published data from the fields of ethnography, experimentation and archaeology, describing sand-bath like structures and processes. In this review, I discuss whether the available data from these three fields indeed justify the suggestions that sand-bath heating was used in the context of MSA silcrete heat treatment. A careful revaluation of the available data shows that, although sand-bath heating is a widely accepted procedure that is documented in other parts of the world, understanding the earliest known cases of heat treatment in the MSA calls for another technical procedure.