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This study presents the results of a taxonomical investigation of deep-sea benthic foraminifera from Cretaceous-Paleogene boundary (K-PgB) strata at Deep Sea Drilling Project (DSDP) Sites 525 and 527 from the Walvis Ridge area, South Atlantic Ocean. Sites 525 (Walvis Ridge) and 527 (Angola Basin) represent different palaeodepths, which were estimated to be about 1,100 and 2,700, respectively, at the time of the K-PgB event. A total of 36 samples were analyzed across the K-PgB; 12 samples are from the lowermost Danian and 24 from the uppermost Maastrichtian. The sections from the sites studied represent about 400 ka (about 200 ka before and after the K-Pg transition, respectively). The faunas at Sites 525 and 527 contain both calcareous and agglutinated benthic foraminifera, and they are dominated by the suborder Rotaliina. A total of 132 taxa were identified at the generic or specific level, and about 8% of the specimens encountered were not possible to identify, mostly because of their poor state of preservation.
The benthic foraminiferal faunas at Sites 525 and 527 are very similar to the Paleocene 'Velasco-type' fauna (Berggren & Aubert 1 975), which is characterized by, among others, GavelinelIa beccariiformis (White), Cibicidoides rubiginosus (Cushman), C. velascoensis (Cushman), Nuttallides truempyi (Nuttall), Nuttallinella florealis (White), Osangularia velascoensis (Cushman), Aragonia velascoensis (Cushman), nodosariids (Nodosaria velascoensis Cushman, Dentalina limbata d'Orbigny), various agglutinated forms (Gaudrina pyramidata Cushman, Tritaxia aspera (Cushman), Marssonella trinitatensis Cushman & Renz), and various gyroidinoids and buliminids, ofwhich most are 'relict' upper Maastrichtian species that survived the K-PgB. The Maastrichtian faunas at Sites 525 and 527 are dominated by GavelinelIa beccariiformis (White) and Nuttallides truempyi (Nuttall), which maintained their dominance also in the lowermost Danian.
The total faunal diversity (number of taxa) at the shallower Site 525 on the Walvis Ridge is somewhat higher (116 taxa) than the fauna (109 taxa) at the deeper Site 527 in the Angola Basin. The faunal difference between the two sites is probably palaeobathymetrically controlled, and it is more pronounced in the Maastrichtian than in the Danian. Some Maastrichtian species that disappeared at the K-PgB [Eouvigerina subsculptura (McNeii & Caldwell), Tritaxia aspera (Cushman), Loxostomum sp., Bolivinoides draco (Marsson), B. decoratus (Jones), Pseudouvigerina plummerae Cushman, Stensioeina pommerana Brotzen, and Sliteria varsoviensis Gawor-Biedowa] occur at the shallower Site 525 only. On the other hand, four species that survived the K-PgB (Globorotalites sp. B, Nuttallides sp. A, Nuttallides sp. B, and Pullenia cf. cretacea Cushman) are common at the deeper Site 527 but absent at the shallower Site 525.
With regard to the K-PgB event recently reported about in the literature, it is generally agreed that benthic foraminifera were not severe!y affected by this transition, compared to the mass mortality in other (planktic) marine organisms. Nevertheless, data in the literature suggest that benthic foraminiferal paleocommunities responded differently to this transition depending on paleobathymetric gradients, which influence interrelated ecological parameters such as the food fux to the sea floor and oxygen leveIs at the water-sediment interface and within the sediment itself.
