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doi:10.2204/iodp.proc.342.102.2014 BiostratigraphyPreliminary age assignments were based on biostratigraphic analyses of calcareous nannofossils, planktonic foraminifers, and radiolarians. Paleodepth interpretations were based on benthic foraminifers. The biostratigraphy is tied to the geomagnetic polarity timescale (GPTS) used for Expedition 342, which is based upon the timescale of Gradstein et al. (2012) (Fig. F5). The age of events based on the previous timescales of Gradstein et al. (2004), IODP Expedition 320 (Pälike, Lyle, Nishi, Raffi, Gamage, Klaus, and the Expedition 320/321 Scientists, 2010), and Cande and Kent (1995) are also shown in Tables T1, T2, and T3. Calcareous nannofossil, planktonic and benthic foraminifer, and radiolarian data were collected from core catcher samples. Where possible, an additional sample was analyzed from each working section half in Hole A. At critical levels, extra samples from section halves were also analyzed. Sample depths are cited in the text as midpoint depths within the sample interval, where appropriate. Datum and zone boundary levels are cited as the midpoint between the datum level and the nearest sample without the datum taxon. Microfossil preservation, abundance, preliminary assemblage composition, datum level, and zonal assignment data were entered through DESClogik into the LIMS database (www.iodp.tamu.edu/UWQ). Biostratigraphic analyses focused on Hole A. In this Expedition Report, we present the biostratigraphic data for each site in datum tables, stratigraphic distribution charts, integrated biozonation figures, age-depth plots, and microfossil group abundance and preservation figures. It should be noted that the distribution charts are based on shipboard study only and are, therefore, biased toward age-diagnostic species. Calcareous nannofossilsCalcareous nannofossil zonal scheme and taxonomyThe zonal scheme of Martini (1971), zonal code numbers NP and NN, was used for Cenozoic calcareous nannofossil biostratigraphy. The zonal scheme of Burnett (1998), zonal code numbers UC, was used for Cretaceous calcareous nannofossil biostratigraphy. These zonations represent a general framework for the biostratigraphic classification of middle- to low-latitude nannofossil assemblages and are presented in Figure F5. The age estimates presented are based on the Gradstein et al. (2012) timescale (Table T1). We have added several additional secondary nannofossil marker species not included in Gradstein et al. (2012) to our datum table and also provide revised calibration ages for several existing datum levels; references for these calibrations are provided in Table T1. Nannofossil taxonomy follows Bown (1998, 2005) and Perch-Nielsen (1985a, 1985b), in which full taxonomic lists can be found. A taxonomic list of nannofossil datums is given in Table T4. Critical boundaries tend not to coincide precisely with nannofossil datum levels but may be approximated by the closest events, as follows:
Methods of study for calcareous nannofossilsCalcareous nannofossils were examined in smear slides using standard light microscope techniques under crossed polarizers, transmitted light, and phase contrast at 1000× magnification. Total calcareous nannofossil abundance within the sediment is recorded as
Abundance of individual calcareous nannofossil taxa is recorded as
For selected age-diagnostic species, abundance is presented as specimens counted. Preservation of the calcareous nannofossils is recorded as
ForaminifersPlanktonic foraminifer zonal scheme and taxonomyThe zonal scheme of Berggren and Pearson (2005) as modified by Wade et al. (2011) was used for the Paleogene (zonal codes P, E, and O), and Berggren et al. (1995) as modified by Wade et al. (2011) was used for the Neogene (zonal codes M, PL, and PT). The planktonic foraminifer zonal scheme used during Expedition 342 is illustrated in Figure F5. The Cretaceous planktonic foraminifer zones are based on the tropical zonal schemes of Caron (1985) and Sliter (1989), with modifications by Hardenbol et al. (1998). Age estimates for planktonic foraminiferal datums follow Gradstein et al. (2012) (Table T2). Planktonic foraminifer taxonomic concepts in the Cenozoic selectively follow those of Jenkins (1971), Blow (1979), Kennett and Srinivasan (1983), Bolli and Saunders (1985), Toumarkine and Luterbacher (1985), Scott et al. (1990), Spezzaferri (1994), Pearson (1995), Chaisson and Pearson (1997), Olsson et al. (1999), and Pearson et al. (2006). The Cretaceous taxonomic concepts are based on Robaszynski et al. (1979, 1984), Leckie (1984), Caron (1985), Nederbragt (1990), and data at services.chronos.org:9090/resources/interactiveforams.html. A taxonomic list of planktonic foraminifer datum species is given in Table T5. Benthic foraminifer taxonomy and paleodepth determinationTaxonomic assignments mainly follow Pflum and Frerichs (1976), Tjalsma and Lohmann (1983), van Morkhoven et al. (1986), Miller and Katz (1987), Thomas (1990), Katz and Miller (1991), Kaminski et al. (1993), Jones (1994), Nomura (1995), and Holbourn and Henderson (2002). The generic classification of Loeblich and Tappan (1988) was used and updated in some instances, in particular for uniserial taxa (Hayward, 2002). Species identification was made routinely on core catcher samples and on selected working section halves. Additional samples taken from working section halves are utilized for the description of relative abundance of individual morphogroups and preservation. Paleodepth estimates are based on van Morkhoven et al. (1986) using the following categories:
Methods of study for foraminifersSediments were washed with tap water over a 63 µm wire mesh sieve. For clay-rich sediments, samples were boiled in water with added Borax first. Subsequently, samples were washed and dried repeatedly until a clear residue formed. Lithified samples were treated with a 3% hydrogen peroxide solution for several minutes before washing. Planktonic foraminiferal age determination was initially established using the wet samples in sieves. Subsequently, all samples were dried in sieves or on filter papers in a low-temperature oven (~50°C) and then examined under a binocular light microscope for benthic and planktonic foraminiferal assemblages. To minimize contamination of foraminifers between samples, the empty sieves were placed in a sonicator for several minutes and thoroughly checked between samples to enable identification of contaminants from previous samples. Species identification for planktonic foraminifers was generally made on the >250 and >150 µm size fractions. The 63–150 µm size fraction was scanned for distinctive taxa. Planktonic foraminifer species distribution and range charts are presented in each site chapter. Benthic foraminifer assemblage composition, paleodepth estimates, and relative abundance of morphogroups were based on counts of ~150 specimens from the >150 µm size fraction, where possible. The preservation status of planktonic and benthic foraminifers was estimated as
Planktonic foraminifer abundance estimatesThe following planktonic foraminifer abundance categories relative to total sediment particles were estimated from visual examination of the dried sample in the >63 µm fraction as
The number of individuals of each planktonic foraminifer species was categorized as
Benthic foraminifer abundance estimatesThe following benthic foraminifer abundance categories relative to total sediment particles >150 µm were estimated from visual examination of the dried sample as
The number of individuals of each benthic foraminifer species was categorized as
The number of individuals of each benthic morphotype was counted for selected working half section samples and categorized as
RadiolariansRadiolarian zonal scheme and taxonomyThe radiolarian zonal scheme used during Expedition 342 is described in Sanfilippo and Nigrini (1998), Nigrini et al. (2006), and Kamikuri et al. (2012). Age estimates for radiolarian datums from the Quaternary to the lower Eocene are based on the magnetobiochronology established for equatorial Pacific Leg 199 and Expedition 320 (Nigrini et al., 2006; Kamikuri et al., 2012), complemented by earlier compilations (Sanfilippo and Nigrini, 1998; Nigrini and Sanfilippo, 2001). For the lowermost Eocene through Upper Cretaceous, age estimates are based on correlation with calcareous microfossil datums (Sanfilippo and Riedel, 1985; Sanfilippo and Nigrini, 1998). For Expedition 342, these age estimates were calibrated to four timescales, where possible (Cande and Kent, 1995 [CK95]; Berggren et al. 1995; Gradstein et al., 2004 [GTS2004]; Ogg et al., 2008; Pälike, Lyle, Nishi, Raffi, Gamage, Klaus, and the Expedition 320/321 Scientists, 2010; Gradstein et al. 2012 [GTS2012]) (Table T3). All ages cited in the text and shown in figures are based on GTS2012. The primary references for the taxonomy of radiolarians studied during Expedition 342 were Nigrini and Lombari (1984), Sanfilippo et al. (1985), Nishimura (1992), Nigrini and Sanfilippo (2001), Sanfilippo and Blome (2001), Nigrini et al. (2006), Funakawa et al. (2006), and Kamikuri et al. (2012). Additional sources are noted in the taxonomic list (Table T6). Methods of study for radiolariansSamples were disaggregated by warming in a solution of 10% H2O2 and a generous squirt of dilute Borax (laundry detergent, acting as a clay dispersant). After effervescence subsided, calcareous components were dissolved by adding a 10% solution of hydrochloric acid. The solution was then washed through a 63 µm sieve. Strewn slides were prepared by pipetting the residue onto a microscope coverslip that was then dried on a hot plate. Norland mounting medium was applied to the coverslip (8–10 drops) while the coverslip was still warm. The coverslip was then inverted and gently placed on the slide. The mounting medium was fixed by placing the slide under an ultraviolet lamp for 15 min. Abundance estimates of the radiolarian assemblage are qualitative estimates of the concentration of radiolarians in individual sediment samples, with the following categories:
Abundance of individual radiolarian species was based on a census of 300 specimens and recorded as
Preservation of the radiolarian assemblage was recorded as
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