Neogene and Quaternary Planktonic Foraminifer Biostratigraphy and Biochronology in Baffin Bay and the Labrador Sea

Abstract

During Ocean Drilling Program Leg 105, 11 holes were drilled in the Labrador Sea and Baffin Bay. Site 645 in Baf­ fin Bay was drilled to a depth of 1147 meters below seafloor (mbsf); planktonic foraminifers were recovered in the upper 110.3 m and in a short interval between 283.8 and 293.5 mbsf. Low species diversity and the lack of species with short stratigraphic ranges inhibited establishment of a planktonic foraminifer biostratigraphic framework at Site 645. Holes 646B and 647A in the Labrador Sea were drilled to depths of 766.7 and 716.6 mbsf, respectively. Although the observed assemblages in the Labrador Sea holes were of low diversity, the first and last occurrences of several age-diagnostic spe­ cies, when integrated with paleomagnetic stratigraphy, allowed the establishment of a high-latitude Miocene to Holo­ cene planktonic foraminifer biochronology. To determine the relative timing of planktonic foraminifer datum events in the eastern North Atlantic and the Labrador Sea, this biochronology is compared with the temperate-subpolar biozona­ tion of Weaver and Clement (1986). The late Miocene dextral-to-sinistral coiling change in Neogloboquadrina atlantica was observed -1.6 m.y. earlier at Site 646 than at any other site in the Atlantic. The first appearance datums (FAD) of Globorotalia margaritae, Glo­ borotalia puncticulata, Globorotalia inflata, and the last appearance datum (LAD) of N. atlantica are isochronous with their reported ages in the eastern North Atlantic, but the FADs of Globorotalia truncatulinoides and the modern, en­ crusted form of Neogloboquadrina pachyderma are diachronous.