Paleointensity of various DSDP sites (Table 3)

The existing database for paleointensity estimates of the ancient geomagnetic field contains more than 1500 data points collected through decades of effort. Despite the huge amount of work put into obtaining these data, there remains a strong bias in the age and global distribution of the data toward very young results from a few locations. Also, few of the data meet strict criteria for reliability and most are of unknown quality. In order to improve the age and spatial distribution of the paleointensity database, we have carried out paleointensity experiments on submarine basaltic glasses from a number of DSDP sites. Of particular interest are the sites that provide paleointensity data spanning the time period 0.3-5 Ma, a time of relatively few high quality published data points. Our new data are concordant with contemporaneous data from the published literature that meet minimum acceptance criteria, and the combined data set yields an average dipole moment of 5.49 +/- 2.36*10**22 Am**2. This average value is comparable to the average paleofield for the period 5-160 Ma (4.2 +/- 2.3*10**22 Am**2) (Juarez et al., 1998, doi:10.1038/29746) and is substantially less than the value of approximately 8*10**22 Am**2 often quoted for the last 5 Myr (e.g. McFadden and McElhinny (1982) J. Geomagn. Geoelectr. 34, 163-189; Goguitchaichvili et al., 1999, doi:10.1016/S0012-821X(99)00010-2).

Dinoflagellate cysts in surface sediment samples of METEOR cruises M20/2, M23/1, M34/1, M34/2, M34/3 and M34/4

To enhance the limited information available about the palaeo-ecological significance of calcareous dinoflagellates, we have studied their lateral distribution in surface sediments of the equatorial and south Atlantic between 13°N and 36°S. Calcareous dinoflagellate cysts appear to be widely distributed throughout the studied area. In the surface sediments, concentrations (cyst per gram dry sediment) of the vegetative stage Thoracosphaera heimii are generally higher than that of the (presumably) calcareous resting cysts. Distribution patterns in surface sediments of Orthopithonella granifera (Fütterer) Keupp and Versteegh, Rhabdothorax spp. Kamptner., Sphaerodinella albatrosiana (Kamptner) Keupp and Versteegh S. albatrosiana praratabulated, Sphaerodinella tuberosa var. 1 (Kamptner) Keupp and Versteegh and S. tuberosa var. 2 and the ratios between these species have been compared with temperature, salinity, density and stratification gradients in the upper water column. Rhabdothorax spp. is characteristically present in sediments of more temperate regions characterized by high seasonality. Dinoflagellates producing these cysts are able to tolerate high nutrient concentrations, and mixing of the water column. S. albatrosiana is abundant in regions characterized by high sea surface temperatures and oligotrophic surface water conditions. In contrast, the distribution of S. tuberosa var. 2 is negatively related to temperature. The other cyst species did not show a characteristic pattern in relation to the studied environmental gradients. The ratio of Sphaerodinella tuberosa var. 2 to Orthopithonella granifera can be used for reconstructing the presence of stratification in the upper 50 m of the water column, whereas the ratios of S. tuberosa var. 2 to Sphaerodinella albatrosiana and of O. granifera to Rhabdothorax spp. might be used for palaeotemperature reconstructions. Calcareous dinoflagellate cysts are abundant in oligotrophic areas and may be useful for the reconstruction of palaeoenvironmental conditions.