Maastrichtian Heterohelicidae (Planktonic Foraminifera) from the North West Atlantic

Abstract. Relative frequencies of heterohelicid species in the Maastrichtian of DSDP Site 605, DSDP Hole 111A and Imperial Oil/Amoco core hole C23 on the Grand Banks have been estimated to show temporal and geographic variation patterns in terms of Cretaceous faunal provinces. Heterohelix globulosa and H. planata dominate the shallow marine heterohelicid faunas of core hole C23. Together with H. dentata and H. glabrans they are the most common forms in the temperate faunas from Hole 111A. Pseudoguembelina spp are common in the Tethyan faunas from Site 605 but are rare in Hole 111A. Racemiguembelina spp and fully developed Pseudotextularia spp exclusively occur at Site 605. A distinct but unexplained faunal boundary within the Site 605 section involves frequency shifts of three “relatively cold” species. H. dentata, H. glabrans and H. planata. Dissolution effects, expressed in changes in the relative frequencies of H. globulosa and Pseudotextularia elegans, are present in several intervals across the section. H. globulosa is the most sensitive for dissolution. Pst. elegans is resistant, as are to a lesser extent, Gublerina cuvillieri, Pseudoguembelina excolata, Psg. palpebra, and Planoglobulina acervulinoides.