Ian Boomer

Palaeolimnological responses of nine North African lakes in the CASSARINA Project to recent environmental changes and human impact detected by plant macrofossil, pollen, and faunal analyses

This paper presents multi-proxy palaeolimnological analyses from recent sediments in the nine CASSARINA lakes in northernmost Africa, three from each of Morocco, Tunisia, and Egypt. The lakes are diverse, ranging from hypersaline to brackish lagoons and fresh-water lakes from high to low conductivity and pH. The macrofossils analysed include fruits, seeds, and vegetative remains of plants, lagoon and fresh-water Mollusca, a range of other aquatic animals, and from one site in each country, Ostracoda and Foraminifera. The diverse macrofossils are multi-proxy indicators of environmental change, and demonstrate changes in response to human activities in the catchments of all the lakes. The three Egyptian Nile Delta lakes have received massive inputs of fresh-water due to modifications of the flow of the R. Nile culminating in the Aswan High Dam built in 1964. Elsewhere, water withdrawal is frequently a serious threat. One lake with high biodiversity in Morocco has been drained and cultivated, and a rare acid-water lake in Tunisia is in danger of drying up. The internationally famous Garaet El Ichkeul in Tunisia, which was so important for birds, has become permanently saline with a loss of diversity. All the lakes are affected by agricultural and/or urban run-off and are experiencing changes as a result of human activities. Several are in a marginally sustainable condition, whereas others are permanently damaged.

LATE CRETACEOUS AND CAINOZOIC BATHYAL OSTRACODA FROM THE CENTRAL PACIFIC (DSDP SITE 463)

Cainozoic deep-sea ostracod assemblages from the summits of Mid-Pacific guyots point to high levels of endemism possibly as a result of their bathymetric separation from the surrounding sea floor. However, the interpretation of these fossil assemblages is hampered by the paucity of comparative material from surrounding non-guyot sites. Fifteen ostracod assemblages from DSDP Site 463 (Late Cretaceous-Pleistocene) were studied to compare with those from nearby guyots. Three distinct faunal assemblages are recognised at Site 463: Assemblage A (Maastrichtian-Eocene), Assemblage B (Oligocene-Upper Miocene) and Assemblage C (Upper Miocene-Pleistocene) although the palaeoenvironmental significance of these units is unclear. Sixty-two ostracod species are identified, the thirteen most abundant are discussed in the taxonomic section, five of which are described as new. Between 30 and 100% of the species encountered in each sample are considered as endemic to Site 463, while some of the remaining species were previously thought to be endemic to individual guyots. Similarly high levels of endemism on nearby guyots probably reflect an incomplete knowledge of deep-sea ostracod faunas rather than the establishment of geographically or bathymetrically restricted populations. The presence of globally pandemic and geographically widespread taxa on sites such as the Mid-Pacific Mountains, surrounded by abyssal depths which lie below the CCD, indicates that some faunal exchange or migration of ostracods does take place. This must be achieved within the intermediate waters and probably occurs passively.

An Early Jurassic oligohaline ostracod assemblage within the marine carbonate platform sequence of the Venetian Prealps, NE Italy

Boomer, I., Whatley, R., Bassi, D., Fugagnoli, A., Loriga, C. (2001). An Early Jurassic oligohaline ostracod assemblage within the marine carbonate platform sequence of the Venetian Prealps, NE Italy. Palaeogeography Palaeoclimatology Palaeocology, 166(3-4), 331-344.

Systematic review and evolution of the early Cytheruridae (Ostracoda)

A review of the literature on the taxonomy of Triassic and Early Jurassic cytheracean Ostracoda reveals that the validity of many genera is questionable. A number of studies of the Triassic microfaunas from eastern European sequences have, in particular, obscured the true generic and suprageneric classification of many ostracod taxa. The present study concentrates on the diverse extant cytheracean family the Cytheruridae, whose origins are in the earliest Mesozoic–latest Palaeozoic, but it is clear that many contemporary cytheracean families present similar problems. This review clarifies the previous taxonomic confusion and obfuscation by demonstrating that many of these genera are spurious having been erected on specific rather than generic morphological criteria. Many of them are best accommodated within the extant genus Eucytherura Müller, 1894. Most of the cytherurid genera known from the Liassic deposits of NW Europe can be traced back to these Triassic assemblages. In considering the origin and earliest evolution of the Cytheruridae, we note that some Triassic taxa share characteristics typical of both the Cytheruridae and the Bythocytheridae and it is suggested that the former may have arisen from the latter family during the latest Permian or earliest Triassic. We also note that the palaeoenvironmental interpretation of many of the Triassic deposits is brackish-water, marginal marine.

Holocene evolution of the Blakeney Spit area of the North Norfolk coastline

Blakeney Spit extends more than 12 km along the North Norfolk coast, from its origin near Weyboume in the east, to a location opposite a point halfway between Morston and Stiffkey in the west. Borehole investigations landward of the spit have revealed remarkably uniform sequences of intertidal sediments, sometimes passing from lower intertidal muds into upper intertidal saltmarsh, sometimes being rather uniform upper saltmarsh throughout. Similar intertidal sediments are found landward of an inter-tidal barrier extending from off Stiffkey to off Wells. The thickness of these deposits, resting either on glacial deposits or directly on Chalk, reaches over 15 m in places, along the line of an original E-W trough or channel. Adequate radiocarbon and other reliable dating of these deposits has proved somewhat difficult to determine, but the earliest are Post-Glacial non-marine deposits as old as 10 000 years bp , with the initiation of marine deposition at c . 7500-6500 years bp at the eastern end of the sector. Apart from the Stiffkey and Morston mainly gravel and sandy ‘Meals’ barriers, which are resting on top of saltmarsh deposits and probably date back to no more than 670-900 years bp , there are no other sand or shingle deposits, except in drainage channels, anywhere landward of Blakeney Spit. The spit itself is being produced by the erosion of the cliffs east of Weybourne, and the entire Holocene and glacial sequences on its seaward side, rolling the sand and shingle body over landward (at about 1 m per annum), and prograding westward, (at c . 3.5 m per annum) - as indicated by accurate maps constructed over the last 400 years.