Heat flow ratios of stations from the Iberian abyssal plain (Table 1)

New heat flow observations have been made in the Iberia abyssal plain off the Galicia margin along the transeat of Ocean Drilling Program Leg 149 drill sites. in order to investigate the nature of this unusually wide and deep continet-ocean transition region. Our results indicate the presence of three separate zones. Average values of 47.5 +/- 3 mW/m in the westernmost zone III agree with predictions of standard oceanic lithospheric models for its estimated age of 126 Ma. In contrast, the heat flow within zone II is 5-15 mW/m higher than predicted. assuming that the mantle heat flow remains constant across the basin. This region of high values is coincident with the location of a major intra-crustal "S"-type reflector east of ODP Site 900. and the anomaly is consistent with the presence of 2-3 km of primarily upper continental crust above the reflector, with concentrations of radiogenic components similar to those from granodiorite samplles dredged off Galicia Bank. It is not, however, consistent with the low values of heat production measured on gabbroic sanhples from its western end at ODP Site 900. In zone I, detailed measurements across the tilted fault block south of ODP Site 901 show consistent variations which closely match predictions due to the effects of basement structure and sediment deposition. There is no evidence for variations due to vertical convective transport along the dipping basement fault block. Once corrected for these variations. measurements in zone I yield average values that agree quite well with previous measurements across Calicia Bank. indicating no systematic landward increase in heat flow with decreasing amounts of continental, extension.

Absolute abundances of benthic and planktonic foraminifers in samples of ODP Hole 149-901A (Table 1)

Dark gray laminated silty claystones (Unit II) drilled at Site 901 contain Tithonian benthic foraminifer assemblages that indicate a neritic depositional environment and probably dysaerobic bottom-water conditions. Three benthic foraminifer zones are distinguished within Unit II. The upper part of the unit is dominated by Spirillina polygyrata, contains Globospirillina spp. (Samples 149-901A-3R-1, 10-12 cm, to 149-901A-3R-1, 75-77 cm) and is interpreted as late Tithonian. Samples 149-901A-3R-1, 87-89 cm, to 149-901A-6R-1, 74-76 cm, contain Epistomina uhligi and Lingulina franconica and are probably early Tithonian. The early Tithonian Neobulimina atlantica Zone is characterized by the occurrence of the zonal marker and Epistomina uhligi and reaches from Sample 149-901A-6R-1, 128-130 cm, to the base of the drilled-sequence. The sediments and benthic foraminiferal assemblage characteristics of the Tithonian-aged sequence in Hole 901A are unknown elsewhere in the Atlantic and may represent deposition in a marginal shelf basin with increased terrigenous and organic flux.