During Leg 185 calcareous nannofossils and radiolarian assemblages were studied to provide biostratigraphic constraints on the sedimentary section at Site 1149. Clays at Sites 801 and 1149 were sampled to study ichthyolith (fish debris) assemblages. The reference time scale adopted for Leg 185 follows Gradstein at al. (1995) for the Late Cretaceous and part of the Early Cretaceous and Channell et al. (1995) for the Late Jurassic and part of the Early Cretaceous. The nannofossil biozonations adopted for the Lower and Upper Cretaceous during Leg 185 are mainly that of Thierstein (1973, 1976), Sissingh (1977), and Roth (1978) and are regarded as standards as summarized in Perch-Nielsen (1985). Additional useful bioevents as shown by Erba et al. (1995) for Leg 144 and by Erba et al. (in press) for the Cismon Apticore were also used.
INTERRAD Jurassic-Cretaceous Working Group radiolarian biochronology (1995) was adopted for Leg 185. The INTERRAD Jurassic-Cretaceous Working Group (1995) provided a synthesis of the systematics, occurrences, and biochronology of radiolarians of Middle Jurassic to Early Cretaceous age from the low-latitude Tethyan realm. Twenty-two radiolarian zones were defined by means of Unitary Associations (Guex, 1977, 1991). These zones were correlated to the standard stages using other fossil groups reported from the same sections, such as ammonites, nannofossils, calpionellids, and dinoflagellates. In particular, Upper Jurassic-Lower Cretaceous radiolarian Unitary Association zones were correlated with calpionellid and calcareous nannofossil bioevents and magnetic chrons (Jud, 1994; Dumitrica-Jud, 1995). Figure F5 shows a tentative correlation between calcareous nannofossil and radiolarian biozonations based on magnetic chrons.
Age determinations of ichthyoliths were based on Doyle et al. (1974), Doyle and Riedel (1979, 1985), and Kozarek and Orr (1979).
Radiolarians from siliceous sediments were extracted with a standard hydrofluoric (HF) acid method, by reacting samples in 5% diluted HF acid for 12-24 hr. Carbonate-rich samples were first decalcified in 10% hydrochloric (HCl) acid. The samples were sieved and the >46-µm fraction was examined.
Preservation was defined as follows:
Abundance of radiolarian specimens has been defined as follows:
Samples for calcareous nannofossil biostratigraphic analysis were prepared using standard techniques in order to retain the composition of the original assemblage. Smear slides were examined using standard light microscope techniques under crossed polarizers and transmitted light at 1000× magnification. Because of calcite dissolution or overgrowth, preservation and abundance of calcareous nannofossil species may vary significantly. Thus, to characterize preservation a simple code system, which follows the shipboard ODP-PAL (paleontology analysis log) program, has been adopted and is listed below:
Estimates of the total calcareous nannofossils abundance (group abundance in PAL) were recorded as follows:
Estimates of the relative abundance of calcareous nannofossil species in pelagic assemblages, according to those suggested in the PAL program, were determined as follows:
During Leg 185, data entry to the Janus database was performed with the ODP-PAL program. Data input and data query in PAL were performed in a user-friendly working window very similar to most commercial spreadsheets. The program links the data input to the scientist and the fossil group in order to retrieve the appropriate spreadsheet every time the data input or the data query are performed by the same scientist. The scientist selects the appropriate fossil group and creates a personal taxa dictionary. This can be performed either by selecting different species names from the main taxa dictionary, or adding new relevant taxa, together with their authorship, to the main dictionary. Datum events, biozones, and geologic ages can be selected and recorded as well. Data input of micropaleontological analysis records the biozone, age, preparation technique, preservation, group abundance, and bathymetry of all samples. Moreover, presence/absence, reworking/contamination, and relative abundance are recorded for every species belonging to a given sample. Queries can be performed in the Janus database to produce reports (range charts, age models, etc.) and perform data correlation between different sites.
Samples were disaggregated in a mixture of water and hydrogen peroxide (H2O2) for 1 day then sieved and washed through 250- and 64-mesh sieves. The residues were dried and the >250- and >64-µm fractions were examined. The fish remains were picked from the residue, first studied under reflected light and then permanently mounted on glass slides with Norland Optical Adhesive for detailed description of structural patterns under transmitted light.