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doi:10.2204/iodp.proc.329.102.2011 Paleontology and biostratigraphyThe primary scientific objectives of Expedition 329 demanded a higher number of shipboard geochemists and microbiologists and a lower number of core describers (and no paleontologists) than a usual IODP expedition. Therefore, only very preliminary biostratigraphic and paleontological determinations at selected sites were carried out on board. We primarily examined planktonic and benthic foraminifers, ostracods, and, to a lesser extent, ichthyoliths (fish teeth) and radiolarians. Preliminary biostratigraphic determinations were based on fish teeth and radiolarians at Site U1365, where the dominant lithology is zeolitic metalliferous clay, and on planktonic foraminifers at Sites U1367, U1368, and U1370, where carbonate ooze was recovered. More detailed postexpedition examination will be necessary to better characterize microfossil assemblages and refine biostratigraphic assignments. Sediment sample processingThe major biogenic components found in the sediments of the Expedition 329 sites were assessed by analyzing smear slide (see “Lithostratigraphy, igneous petrology, alteration, and structural geology”) and sieved core catcher samples. Core catcher samples were processed following routine methods for the study of foraminifers. Core catcher samples were dried and weighed. Dry sediment was washed with tap/distilled water over a 63 or 38 µm wire-mesh sieve. Indurated samples were soaked in water for a short time prior to washing to promote disaggregation. Once sieved, all samples were dried on filter papers in a low-temperature oven at ~50°C and weighed and subsequently examined under a binocular light microscope. To minimize contamination of foraminifers between samples, the sieve was placed into a sonicator for several minutes and thoroughly checked between samples to enable identification of contaminants from previous samples. Planktonic foraminifer species distributions are presented for Sites U1367, U1368, and U1370. Species identification for planktonic foraminifers were generally made on the >250, >125, and >63 µm size fractions, with the exception of Site U1370, from which the >38 µm size fraction was also scanned for distinctive taxa. Benthic foraminifer assemblage compositions were based on counts of ~200 specimens from the >250, >125, and >63 µm size fractions, when possible. In the case of ostracods, all specimens per sample were picked and counted. Relative percentages of benthic to planktonic tests were determined by counting specimens in four adjacent quadrants in three different locations on the picking tray. Relative and absolute abundances were based on the overall counting of all the specimens found in each sample analyzed. The preservation, abundance, and zonal assignment for selected samples and for each microfossil group described were entered through DESClogik into the LIMS database. Paleontological and biostratigraphic analyses focused on the stratigraphy-dedicated hole, usually Hole B, at each site (see “Introduction, operations, and curation”). ForaminifersPlanktonic foraminifer zonal schemeand taxonomyThe planktonic foraminifer zonal scheme for the Paleocene (P zones) follows Olsson et al. (1999). The Eocene and Oligocene (E and O zones, respectively) scheme follows Berggren and Pearson (2005) and Wade et al. (2010). The Neogene (M, PL, and PT zones) scheme follows Berggren et al. (1995) and Wade et al. (2011). The biostratigraphy is tied to the geomagnetic polarity timescale (GPTS) used for IODP Expedition 320/321, which is based upon a composite of several timescales (Cande and Kent, 1995; Lourens et al., 2004; Pälike et al., 2006b). Ages and calibration sources of planktonic foraminifer datums are presented in Table T5. 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). Benthic foraminifer taxonomyTaxonomic assignments follow Tjalsma and Lohmann (1983), Miller and Katz (1987), Thomas (1990), Katz and Miller (1991), Jones (1994), Nomura (1995), and Holbourn and Henderson (2002). The generic classification of Loeblich and Tappan (1988) was used. Abundance and preservationRelative percentages of benthic to planktonic tests were determined by counting specimens in four adjacent quadrants in three different locations on the picking tray during Expedition 329.The following abundance categories were estimated from visual examination of the dried sample for planktonic and benthic foraminifers and ostracods:
The preservation status of planktonic and benthic foraminifers was estimated as follows:
OstracodsOstracods, calcareous bivalve microcrustaceans, are the only metazoan organisms commonly preserved as microfossils in deep-sea sediments. Similar to benthic foraminifers, ostracods have limited biostratigraphic use, but they can provide important environmental information and are valuable proxies in paleoceanographic studies (Dingle and Lord, 1990; Corrège 1993; Ayress et al., 1997; Didié and Bauch, 2000; Cronin et al., 2002; Alvarez Zarikian et al., 2009). Ostracod taxonomic concepts selectively follow Ayress (1995), Ayress et al. (1995), Boomer and Whatley (1995), Whatley and Boomer (1995), Boomer (1999), Zhao (2005), Alvarez Zarikian (2009), and Yasuhara et al. (2009). Ostracods were picked and identified from the examined samples following the same methodology as for benthic foraminifers (see above). RadiolariansRadiolarian identification was carried out postexpedition by C. Hollis (GNS Science, New Zealand). Radiolarian taxonomic assignments follow Sanfilippo and Riedel (1985). Age assignments are based on Hollis and Kimura (2001). |
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