Geneviève Cambon

Evolution of the Messinian Mediterranean environments: the Tripoli Formation at Capodarso (Sicily, Italy)

Abstract New field data have been collected from the Capodarso section (Caltanissetta basin, Sicily); 48 samples from the Tripoli Formation were analysed for foraminifera, dinocysts, palynofacies, CaCO 3 , pollen grains and clay minerals. The uppermost clays of the Terravecchia Formation are clearly the result of deeper deposition than those corresponding to the lowermost analysed samples within the overlying Tripoli Formation. So, the general evolution of the basin was from normal marine conditions to confinement, during which the sedimentation of diatomite vs. clay was mainly controlled by relative sea-level changes. Three successive types of processes are considered to have generated the diatomites: 1. (1) in the lower part of the section, the sea level was relatively high and deposition of diatomites was aided by sea-level rises of unequal importance and variations of continental precipitations and run-off; 2. (2) then, relatively minor sea-level oscillations prevailed; however, the second part of the sequence is characterized by a generally strong shallowing trend leading to basin confinement; 3. (3) the explanation for diatomites during the last member does not rely as much on the occurrence of substantial sea-level rises in an increasingly desiccated basin; on the other hand, an increased number of rivers reached the central area of the basin, which helped to produce the youngest diatomites. The warm (subtropical to tropical) and xeric climate predisposed to such an evolution, inducing continuous high salt-concentration of marine waters; so, the smallest influx of less saline (oceanic) waters and/or continental freshwater (run-off) could produce water-mass stratification and diatomite deposition. However, not all lithologic breaks are likely to correspond to recorded environmental transitions. Bio- and magnetostratigraphy of the section allow consistent relationships between the sea-level curve at Capodarso and the δ 18 O curve at Site 588 (southwest Pacific), attesting global eustatic control on the sedimentation of the Caltanissetta basin up to the beginning of the Messinian salinity crisis.

Modern pollen deposition in the Rhone delta area (Lagoonal and marine sediments), France

The investigation identifies the two main types of pollen sedimentation in the Rhone delta, and presents synthetic pollen spectra in terms of ecological groups in order to predict the pollen source areas. Two different domains are studied: the lagoonal zone occupied by the Vaccares where atmospheric pollen imput predominates and the Rhone mouth area (river delta and prodelta) where fluvial pollen influx prevails. The reflection of local and regional vegetation in the surface sediment pollen spectra is carefully discussed with reference to atmospheric pollen records and to water sample analyses. This work is designed to help the interpretation of past pollen spectra and paleovegetation and through them also paleoclimate reconstructions.

Present-day rhythmic deposition in the grand Rhone prodelta (NW Mediterranean) according to high-resolution pollen analyses

Abstract A high-resolution pollen study (136 samples) has been performed on the KTR05 core (738 cm long) located in the modern Grand Rhône prodelta. The objectives were (1) to evaluate the palynological and sedimentological record quality of a prodelta in comparison with fluvial inputs (2) and to quantify lost sediment (resuspensions) in this area. The core covers more than the last thirty years. By comparison with the modern pollen rain both in the Rhône delta and in the mid-drainage basin (Lyon), a seasonal forcing in pollen deposition has been demonstrated. Monthly pollen successions can be evidenced in a well preserved sequence, providing an estimate of the true sedimentation rate (60 cm.yr−1). Importance of disturbed or incomplete sequences suggests that most of the sediment first deposited in the prodelta (around ⅔) has been resuspended. Sedimentological and palynological data record not only seasonal but fluvial impact. The progressive shift of the prodelta has been evidenced firstly with sedimentology and secondly with palynology. Despite high fluvial impact, pollen grains in the KTR05 core are representatives of the vegetation of the Rhône drainage basin. The apparent homogeneity of the pollen spectra evidences the high reliability of palynology applied on prodeltaic area, at least in a microtidal environment.

Nesting Biology and Foraging Ecology of the Wood-boring Bee Lithurgus chrysurus (Hymenoptera: Megachilidae)

Abstract The biology of the wood-boring bee Lithurgus chrysurus Fonscolombe, 1834 is described and the biology of the genus Lithurgus is summarized. Lithurgus chrysurus is univoltine and over-winter as prepupae inside cocoons. The females excavate their own burrows in various dead woods and they do not reuse burrows. The cells are separated by partitions composed of cut wood pieces. To assess the diet breadth of L. chrysurus, pollen analyses were conducted on 8 samples of provisions from 3 nests and 2 feces samples from one nest. The provisions averaged 30,600 pollen grains per mg of dry matter. The proportion of broken pollen grains averaged 3.3% and was consistent among nests and for provisions and feces. Centaurea (Asteraceae, tribe Cynareae) was the dominant pollen type found in all provisions and feces, accounting for 98.0 to 99.9% of the pollen based on the number of grains. This proportion was similar among nests for both provisions and feces. These results indicate that, at the study site, L. chrysurus was strictly oligolectic on Centaurea pollen while nectar was probably collected on other plant species as well.

Modern pollen spectra and vegetation in southern Ontario, Canada

Abstract A weekly census of air borne pollen grains was conducted for three years (1983–1985) at four sampling stations (from north to south: Sudbury, Peterborough, Toronto and London) in the Great Lakes region, southern Ontario, Canada. A Cour volumetric vane sampler was used at each site, located at the respective meteorological station, providing pollen spectra from an area of surrounding vegetation with an estimated radius of 40 km. Filter samples were processed by a standard, established procedure. The study area forms part of the Upper Canada Peninsula vegetation region. Two sites, Sudbury and Peterborough, occur in one of the two major vegetation zones, the Mixed-Hardwood; the others, Toronto and London, are located in the second zone, the Deciduous Forest. Previous studies of pollen-vegetation relations in this region were based on analysis of moss polsters. The pollen trap method used here provides a more sensitive registration of regional pollen and while the seven most important taxa quantitatively are found in the both data sets, such important taxa as Cupressaceae and Populus are under-represented or absent in polster data because of poor preservation, but well represented in the trap analyses (Cupressaceae at 9% and Populus at nearly 3%). Similarly, some spore taxa that are absent from previously published results occur in the present data in significant frequencies ( Lycopodium at 4% from Sudbury and Sphagnaceae from all stations). The results of statistical analyses show the predictable major change in the regional pollen spectra between Sudbury and Peterborough.

Biology of Nomioides variegatus (Olivier) (Hymenoptera: Halictidae)

Abstract The nesting biology, life history and pollen foraging of the minute Nomioides variegatus (Olivier) is described and illustrated. All Nomioides biological studies are reviewed. Nesting and foraging were observed over two years in a sandy natural area in the Rhône River delta region of southern France. Nest and cell structure was obtained from soil blocks removed from the nesting area and examined in the laboratory. Females, which were on average only 4.2 mm long, nested solitarily in loose aggregations in areas free of vegetation. Cells were placed from 6 to 12 cm deep, each terminating a lateral burrow off the main burrow. Cell walls were lined with a water proof wax-like lining. The pollen-nectar provision was a flattened sphere. The posterior end of the egg was embedded on the dorsal surface of the provision. Larval and pupal development was rapid, proceeding to adults by August, the over-wintering stage. Pollen foraging patterns were analyzed from both pollen provisions and fecal material for different nests (3) and cells (8). Nomioides variegatus is polylectic, but individuals bees exhibited a high degree of foraging consistency for the provisioning of single cells. Eleven different pollen types representing 10 plant families were found. In 1996, Ecballium elaterium (Cucurbitaceae) was the dominant pollen present in all samples but it was absent in 1997. Tamarix gallica (Tamaricaeae) was the dominant pollen type in 1997 and absent in 1996. A third pollen, Centaurium (Gentianaceae) was present in both years and represented 70% of some samples.