Calcareous nannofossil stratigraphy of ODP Holes 173-1065A and 173-1069A

Upper Jurassic calcareous nannofossil assemblages have been studied from strata cored over basement blocks now buried under the Iberia Abyssal Plain (Ocean Drilling Program Leg 173 Sites 1065 and 1069). The youngest Jurassic assemblages at each site are Tithonian in age, the same as those at nearby Leg 149 Site 901, an age that predates the breakup of the Iberia continental margin. The paucity of the assemblages, the prevalence of coccospheres, and the relatively high organic contents of the fine clastic sediments in which they occur are characteristic of a restricted interior basin that had little communication with the open ocean. During the major rifting episode (a Berriasian event), the Jurassic sequences were dispersed along with their underlying blocks of presumed continental crust across the ocean-continent transition of the Iberia Abyssal Plain, probably as a result of detachment faulting.

Benthic foraminifera and ostracoda in ODP Hole 107-650A

Twenty-three sediment intervals from top of Site 650 down to 510 m below seafloor have been studied. Their thicknesses vary between 0.25 m and about 40 m. The studied deposits are turbidites or parts of them except one which is interpreted as an ash-fall layer. The composition of the turbidites signalizes sources from shallow water/coastal areas as well as from deep water levels. Repeated mobilization and displacement seems to have been common. Volcaniclastic material is the dominant component of the whole studied part of Site 650 sedimentary sequence. Ashfall deposits as well as normal open marine sediments are rare.