Planktonic foraminiferal stratigraphy of sediments from ODP Leg 173 sites

Planktonic foraminifers recovered from five sites drilled off western Portugal during Ocean Drilling Program Leg 173 are documented. Hole 1065A yielded planktonic foraminifers from Miocene sediments in Sections 173-1065A-1R-1 through 6R-2. Hole 1067A penetrated middle Eocene sediments containing planktonic foraminifers in Section 173-1067A-1R-1 through Lower Eocene planktonic foraminiferal horizons to Section 12R-CC. Hole 1068A yielded planktonic foraminiferal assemblages from middle Eocene sediments at Section 173-1068A-1R-1 to Maastrichtian sediments at Section 173-1068A-15R-3, whereas Hole 1069A contained middle Eocene taxa in Section 173-1069A-1R-1 through Campanian/Maastrichtian forms in Section 173-1069A-15R-2. All of the planktonic foraminifers recovered from these sites are of poor to moderately good preservation and are variable in abundance. Hole 1070A yielded only six planktonic foraminifers, with the assemblages being dominated by benthic foraminifers and fish teeth. The co-occurrence of other microfossil groups, including benthic foraminifers, are only briefly discussed here. The lower Miocene biosiliceous facies recorded in Hole 1065A is considered to be coeval with a similar facies found in onshore sections farther to the east, in southern Spain.

Petrology of ODP Leg 210 and Leg 173, and DSDP Leg 47 sites

Sand detrital modes of Albian-Eocene clastic gravity-flow deposits cored and recovered at Ocean Drilling Program Site 1276 reflect the postrift geologic evolution of the Newfoundland passive continental margin. Cretaceous sandstone compositions (average: Q57F23L20; Ls%Lsc = 35; total%bioclasts = 3) are consistent with a source on Grand Banks such as Avalon Uplift. Their relatively low potassium feldspar (Qm71K8P21) contents distinguish them from Iberian sandstones and appear to preclude an easterly source during the early history of the ocean basin. Isolated volcaniclastic input near the Paleocene/Eocene boundary (~60 Ma) at Site 1276 is also present in Iberian samples of this age, suggesting that magmatism was widespread across the North Atlantic during this time frame; the source(s) of this volcanic debris remains equivocal. In the Eocene, the development of carbonate bank facies on the shelf marks a profound compositional change to calcareous grainstones (average: Q27F11L62; Ls%Lsc = 82; total%bioclasts = 55) in basinal gravity-flow deposits at Site 1276. This calcareous petrofacies is present on the Iberian margin and in the Pyrenees, suggesting that it was a regional event. The production and downslope redistribution of carbonate debris, including bioclastic and lithic fragments, was likely eustatically controlled. The Newfoundland (Site 1276 and Jeanne d'Arc Basin) sandstones are mainly quartzolithic. Their composition and the contrast in composition between them and more quartzofeldspathic sandstones from the Iberian margin are likely a product of rifting along a Paleozoic suture zone separating distinct basement terranes. This prerift geologic setting contrasts with that of rifts developed within other cratonic settings with variable amounts of synrift volcanism. When synthesized, the spectrum of synrift and postrift sand compositions produces a general model of passive margin (rift-to-drift) sandstone provenance.