New age estimates for the Palaeolithic assemblages and Pleistocene succession of Casablanca, Morocco

Marine and aeolian Quaternary sediments from Casablanca, Morocco were dated using the optically stimulated luminescence (OSL) signal of quartz grains. These sediments form part of an extensive succession spanning the Pleistocene, and contain a rich faunal and archaeological record, including an Acheulian lithic assemblage from before the Brunhes–Matayama boundary, and a Homo erectus jaw from younger cave deposits. Sediment samples from the sites of Reddad Ben Ali, Oulad J’mel, Sidi Abderhamane and Thomas Quarries have been dated, in order to assess the upper limits of OSL. The revision of previously measured mammalian tooth enamel electron spin resonance (ESR) dates from the Grotte des Rhinocéros, Oulad Hamida Quarry 1, incorporating updated environmental dose rate measurements and attenuation calculations, also provide chronological constraint for the archaeological material preserved at Thomas Quarries. Several OSL age estimates extend back to around 500,000 years, with a single sample providing an OSL age close to 1 Ma in magnetically reversed sediments. These luminescence dates are some of the oldest determined, and their reliability is assessed using both internal criteria based on stratigraphic consistency, and external lithostratigraphic, morphostratigraphic and independent chronological constraints. For most samples, good internal agreement is observed using single aliquot regenerative-dose OSL measurements, while multiple aliquot additive-dose measurements generally have poorer resolution and consistency. Novel slow-component and component-resolved OSL approaches applied to four samples provide significantly enhanced dating precision, and an examination of the degree of signal zeroing at deposition. A comparison of the OSL age estimates with the updated ESR dates and one U-series date demonstrate that this method has great potential for providing reliable age estimates for sediments of this antiquity. We consider the cause of some slight age inversion observed at Thomas Quarries, and provide recommendations for further luminescence dating within this succession.

Invertebrate food supply and breeding success of Mallards Anas platyrhynchos at flooded gravel quarries in southern Britain

Reproductive parameters of Mallard Anas platyrhynchos were investigated in relation to vegetative development, physical characteristics and invertebrate food abundance of a complex of flooded gravel quarries in southern Britain. Breeding pair density over the study area was particularly high with 2.2 pairs km(-1) of shoreline. Across all lakes breeding success was limited to an average of 0.9 ducklings fledged pair(-1), yet an associated study showed that very little of the mortality could be attributed to predation. The results of stepwise multiple regressions indicated that the availability of emerging insects was important in determining the breeding density and breeding success of Mallards rather than habitat structure. We suggest that the overall great availability of suitable nest-sites combined with the variable but unmeasured stocking densities of fish may explain the lack of the latter correlations.

Field meeting: Romney Marsh - its churches and geology, 22 May 2004

The building fabrics of seven churches situated either on Romney Marsh or the marshland fringe were examined briefly. These revealed important differences in the relative abundance of the two principal building stones. Ragstones from the Hythe Formation occurred more frequently in the northeast, while sandstones from the Ashdown 'Beds' were more common in the west. In the Romney Marsh area, both stones were quarried mainly from their adjoining coastlines, with, up to the thirteenth century, opportunist collection of beach boulders generally preceding the exploitation or hewn stone. Other building stones, possible distribution routes and impacts of the quarrying upon coastline development were also discussed.