Late Paleocene to middle Miocene planktonic foraminifer biostratigraphy of the Ceara Rise

Abstract

During Ocean Drilling Program Leg 154, Þve sites (Sites 925, 926, 927, 928, and 929) were drilled as a depth transect on the Ceara Rise in the western Atlantic Ocean. Each site consists mainly of pelagic carbonate sediments. Planktonic foraminifers are abundant throughout the sequences except in intervals of intense dissolution at the bathymetrically deeper sites. Faunas are typical of the low latitudes, and they are diverse and reasonably well preserved for much of the record. Recrystallization is mostly moderate, but it is severe at the greater burial depths.A biostratigraphic framework is presented for the lower part of the stratigraphic interval, from Subzone P4c in the upper Paleocene to Zone N12 immediately below the most intensely dissolved level in the middle Miocene. This study replaces the previously published shipboard planktonic foraminifer biostratigraphy. It contains many additional datums and some revisions. Complete range charts of all the species recognized are also presented for the entire stratigraphic interval on the Ceara Rise.Sedimentation on the plateau was almost continuous from the Paleocene to the Holocene. Although several small hiatuses are identiÞed at individual sites, none extends across the whole plateau, so a remarkably complete geological history can be constructed. Much of this record is characterized by sedimentary cyclicity on Milankovitch time scales. This suggests that the Ceara Rise will be a key area for future advances in orbital-based chronology in which planktonic foraminifer biostratigraphy will be an important component.

Review and revision of Cenozoic tropical planktonic foraminiferal biostratigraphy and calibration to the geomagnetic polarity and astronomical time scale

“…5). We have found this scheme to provide excellent biostratigraphic control in the tropical Pacific and Atlantic Oceans Pearson and Chaisson, 1997).…”

“…The enhancements in deep sea drilling recovery, multiple coring, high resolution sampling both offshore and onshore, has improved the calibrations with the magnetostratigraphy and/or modified the species ranges and allowed many of the planktonic foraminiferal bioevents to be revised. For example, detailed biostratigraphic investigations from Ceara Rise Pearson and Chaisson, 1997;Turco et al, 2002), equatorial Pacific Ocean (Wade et al, 2007), Indian Ocean (Hancock et al, 2002) and the Gorrondaxte and Agost sections in Spain (Payros et al, , 2009Larrasoaña et al, 2008;Ortiz et al, 2008) have resulted in revision of the calibrations of numerous bioevents. Most of these changes are small and incremental in nature, but some (e.g., the revision of the lower-middle Eocene by Payros et al, 2007) are major developments.…”

“…It is unfortunate that no magnetostratigraphy is available for the sites. Nevertheless a very complete series of foraminifera and nannofossil biohorizons was recorded (Backman and Raffi, 1997;Chaisson and Pearson, 1997;Pearson and Chaisson, 1997;Turco et al, 2002). Datums that are derived from Leg 154 sites are indirectly calibrated to the geomagnetic time scale by interpolation between other well calibrated events and through linear interpolation with the astro-chronology of Lourens et al (2004).…”

“…Datums that are derived from Leg 154 sites are indirectly calibrated to the geomagnetic time scale by interpolation between other well calibrated events and through linear interpolation with the astro-chronology of Lourens et al (2004). To ensure consistency we have also recalculated bioevents from Ceara Rise Pearson and Chaisson, 1997;Turco et al, 2002) and converted them to the magnetochronology of Cande and Kent (1995) (Table 1, Fig. 2).…”

Methods

“…The age estimates presented are adjusted to the timescale of Expedition 320/321. Planktonic foraminifer taxonomic concepts selectively follow those of Bolli and Saunders (1985), Spezzaferri and Premoli Silva (1991), Chaisson and Leckie (1993), Leckie et al (1993), Spezzaferri (1994), Chaisson and Pearson (1997), Pearson and Chaisson (1997), Olsson et al (1999), and Pearson et al (2006).…”