A high-resolution, niultiproxy palaeolininological record frorn the Manga Grasslands, northeastern Nigeria, spanning the last 5500 calendar years, reveals the episodic deterioration in Sahelian climate as significant biogeophysical thresholes were crossed.. Desert-dust deposition began to increase -4700 cal. BP. Raintall during the AtLmmer-monsoon season declined permanently after 4100 cal. BP. A further significant change in atmospheric circulation, giving rise to multidecadal to centenniall-scale droughts and enhanced dust deposition.

A high-resolution 5500 year palaeolimnological record from Kajemarum Oasis, a closed basin in the Manga Grasslands of northern Nigeria, provides evidence of environmental change in Subsaharan Africa during the Holocene. Palaeohydrological variations, mainly changes in the balance between precipitation and evaporation, are recorded by stable oxygen isotope ratios in bulk carbonate and ostracod calcite and by the Sr/Ca ratio in ostracode shells. Variations in the carbon isotope ratios in carbonates indicate changes in primary productivity in the lake, whereas the carbon isotope composition of organic carbon reflects ecophysiological processes within the lake and its surrounding catchment. Results indicate that there have been marked environmental changes in the Manga Grasslands over the last 5500 years. A more variable climate set in around 1500 cal. a BP. A prolonged drought between 1200 and 1000 cal. a BP, with reduced aquatic productivity, was followed by a switch to a wetter, but still unstable climate: moist conditions prevailed during the Little Ice Age. The results indicate that drought has affected the Sahel episodically over the last 1500 years and is not solely a twentieth-century phenomenon.

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Excavations were undertaken in advance of construction work at Newbury Sewage Treatment Works on the outskirts of Thatcham in Berkshire, close to the sites of previous excavations undertaken by Wymer and by Peake and Crawford. Worked flint of Mesolithic date was recovered from a sandy layer overlying river gravel in two distinct concentrations suggesting two distinct episodes. Use wear analysis of the flint suggests that the sites were used as home bases at which a wide range of activities took place, with an emphasis on the processing of plant foods. A 14C date of 9100±80 BP was obtained from a sample of hazel-nut shells from within one of the concentrations. Analysis of the soil and sedimentary sequence as well as the pollen indicates constantly changing localised environments in the early Holocene in the Thatcham area, with sporadic occupation by Mesolithic communities on the drier areas at the edge of the floodplain.

The Neolithic round barrow at Duggleby Howe comprises a substantial mound surrounded by a large causewayed ditch. The mound covers a rich Middle Neolithic burial sequence, as revealed by Mortimer's nineteenth-century excavations, and occupies a position on the northern valley side of the Gypsey Race, near to the stream's source. Following the recent radiocarbon dating of the burial sequence and primary mound building, a small research excavation was undertaken across the ditch of the large, penannular causewayed enclosure that surrounds the mound primarily in order to obtain artefactual and ecofactual material from which to construct a relative and absolute chronology for the ditch sequence(s). INTRODUCTIONDuggleby Howe (SE 880669) is one of the most iconic monuments of the British Neolithic and comprises a substantial round mound surrounded by a large causewayed ditch (Illus. 1). The mound covers a rich Middle Neolithic burial sequence, as revealed by Mortimer's nineteenth-century excavations (Mortimer 1905), and occupies a position on the northern valley side of the upper Gypsey Race, near to the stream's source. The site has been reinterpreted on a number of occasions, most notably by Kinnes et al. (1983) and Loveday (2002), but both reconsiderations lacked an absolute chronology for either the mound sequence or its surrounding ditch. Following the dating of the burial sequence and primary mound building at Duggleby Howe (Gibson and Bayliss 2009), a small research excavation was undertaken across the ditch of the large, penannular causewayed enclosure that surrounds the mound in order to obtain artefactual and ecofactual material from which to construct a relative and absolute chronology for the ditch sequence(s). It was also designed to test the relationship of the causewayed ditch (Illus. 2, a) to other features and in particular a large circular pit (Illus. 2, b) on the inside of the causewayed ditch and a smaller linear ditch (Illus 2, c) which followed its outside edge. In collaboration with colleagues from the University of Vienna, Institute of Archaeological Sciences (VIAS), the excavation was also designed to test the suitability of laser-scanning recording within an excavation environment. The excavation lasted six weeks and was generously funded by English Heritage and the University of Bradford. PRELIMINARY SURVEYIn order to locate the trench exactly, non-invasive topographical laser-scanning, magnetometry and ground penetrating radar surveys were undertaken over the northern section of the field (Illus 3-5). This survey was undertaken by Dr Wolfgang Neubauer and his team from VIAS, and a detailed methodology is presented in the project archive.The combined results of the geophysical surveys were used to precisely locate the excavation trench to within 0.04 m in the national grid. It was also possible to pinpoint the features chosen for excavation and outlined above. The GPR (Illus. 5) and gradiometer (Illus. 6) surveys added detail to the aerial photographs and seemed to suggest that the main cause...