Figure
3 illustrates the variations of alkenone unsaturation indices.
Paleotemperature estimated from 
varies from 8.5° to
17.5°C. The
temperature of the top 54 cm of core ranges between 13.8°
and 14.5°C, which
agrees with the present mean annual SST at this site (Robinson, 1976). This
result is concordant with the recent observation that core-top -derived
temperatures represent the mean annual SST along the California margin (Herbert
et al., 1998).
The variations of 
and K37:4/K37 are very similar to that of
. A good correlation (r
= 0.92) exists between
and . This
suggests a single source of C37:2-4 alken-2-one and C37:2-3
methylalkenoates in Core 167-1016C-1H.
The variation of
at Site 1016 is also similar to both 
18O
profiles of planktonic and benthic foraminifers (Kennett et al., Chap.
21, this volume) and
variation (Shipboard Scientific Party, 1997b) at the adjacent shallower Site
1017. Comparison with the oxygen isotope stratigraphy of Site 1017 (Kennett et
al., Chap. 21, this
volume) enables us to make a preliminary -based
stratigraphy of Site 1016, as shown in Figure
3. This preliminary age-depth model implies that Core 167-1016C-1H
covers oxygen isotope Stages 1-6, with the average linear sedimentation rate of
6.4 cm/k.y. The precise age-depth model needs future investigations such as the
analyses of 14C of foraminifers, radioactive elements, and amino acid
racemization.
Figure 4 illustrates the variations of total organic carbon (TOC), total nitrogen (TN), and calcium carbonate (CaCO3) contents, and the TOC/TN value of Core 167-1016C-1H.
TOC varies between 0.8% and 2.3%, with an average of 1.3%. High TOC contents (>1.5%) occur in the core-top interval (0-0.12 mbsf), at 5.1-6.2 mbsf (Peaks D, E, and F in Fig. 4), 7.3 mbsf (Peak G), and 8.2 mbsf (Peak H). TOC/TN values range between 5.4 and 10.0, with an average of 7.5, indicating predominantly marine origin of the organic matter supplied to this site. CaCO3 content varies between 0% and 13.7%, with an average of 2.5%. Maxima of CaCO3 content (>10%) occur around 0.5 mbsf (Peak I in Fig. 4), 5.2 mbsf (Peak J), and 7.2 mbsf (Peak K). The background value of CaCO3 contents is nearly 0%, which indicates the dissolution of calcium carbonate below the carbonate compensation depth.
The F1 (hydrocarbon) and F3 (alkenone) fractions were analyzed by gas chromatography and gas chromatography-mass spectrometry. Figure 5 and Figure 6 illustrate the reconstructed ion chromatograms and mass fragmentograms of the F1 fraction from representative samples. Figure 7 illustrates the reconstructed ion chromatograms of the F3 fraction. The compounds identified in Core 167-1016C-1H are listed in Table 1 and Table 2, and most of them were already reported by previous workers including Venkatesan et al. (1980), McEvoy et al. (1981), Simoneit and Manzurek (1981), Rullkötter et al. (1981), and Hinrichs et al. (1995). Concentrations of selected biomarkers and indices are shown in Appendix A, Appendix C, Appendix D, and Appendix E.
Long-chain n-alkanes (LNAs) occur as a major component of the F1 fraction in all investigated samples and maximize at C29 (Fig. 5). Their homologous distribution is typical of terrestrial higher plant waxes (Eglinton and Hamilton, 1967). The concentration of LNAs (n-C25, n-C27, n-C29, and n-C31) varies between 0.94 and 1.83 µg/g sediment, with an average of 1.43 µg/g sediment (Fig. 8). The variation with depth is small, but concentration minima occur at the warming intervals (0.6 and 8 mbsf). Their odd/even carbon number preference index (CPI) values (Bray and Evans, 1961) vary between 3.5 and 8.2, with an average of 5.4. The ratio of C31/C27 of n-alkanes ranges between 1.3 and 2.7, with an average of 1.8. The small changes in CPI and C31/C27 ratio suggest a homogenous source of n-alkanes.
According to the method of Prahl and Carpenter (1984), terrestrial organic carbon content (TROC) was calculated from LNA (n-C25, n-C27, n-C29, and n-C31) concentration (µg/g) using the following expression: TROC = LNA/(LNAr/TOCr), where LNAr and TOCr are the LNA and TOC of riverine sediments, respectively, that sourced terrigenous organic matter to the site. Because there are no available data for the LNAr/TOCr ratio of riverine sediments near Point Conception, we used the values from the Columbia River (Prahl and Carpenter, 1984). Based on this assumption, TROC (%) was expressed as LNA/2.77. Marine organic carbon content (MROC) was obtained by subtracting TROC from TOC. The estimated TROC is almost constant around 0.5%, whereas MROC varies between 0.4% and 2% (Fig. 8). The MROC decreases rapidly with depth in the top 9 cm, which reflects the degradation of metabolizable marine organic matter. MROC percentage of TOC ranges between 44.6% and 81.9%, with an average of 59.8%, which agrees with the low TOC/TN values of this core.
C25:4 and C25:1 highly branched isoprenoid (HBI) alkenes were found in the F1 fraction. They were identified by comparison of their mass spectra and retention times (Requejo and Quinn, 1983). C25 HBI alkenes were identified in a marine diatom Haslea ostrearia (Volkman et al., 1994), and the compounds in sediments are thought to derive from diatoms.
C25:4 HBI alkene decreases rapidly with increasing depth within top 60 cm of the core and is under the detection limit in the underlying horizons (Fig. 9). This implies that the C25:4 HBI alkene is highly unstable during early diagenesis (Requejo and Quinn, 1983). In contrast, the C25:1 HBI alkene seems more stable in the sediment column and has maximal concentrations in warming intervals (0.8 and 8 mbsf).
C37-C39 alkenones and C37-C38 alkenoates (C36 fatty acid-methyl and ethyl esters) were found in the F3 fraction (Fig. 7), and C37-C38 alkatrienes were found in the F1 fraction (Fig. 5). All of these in normal marine sediments are thought to derive from Genera Gephyrocapsa and Emiliania, Family Gephyrocasaceae, Class Haptophyceae (Marlowe et al., 1990).
Alkenones are most abundant in lipids extracted from Core 167-1016C-1H. Their concentrations vary between 2.0 and 16.5 µg/g sediment, with an average of 5.8 µg/g sediment, and have maximal values at 5.2, 6.2, and 7.4 mbsf (Fig. 10). Alkenoates have a similar variation with alkenones. Alkatrienes show a different variation with alkenones and alkenoates, and their concentrations are higher in a cooling interval (3.8-5.2 mbsf). Conte et al. (1994) compiled published and unpublished data for lipids in various strains of Emiliania huxleyi and found that the occurrence of alkatrienes is restricted to several strains from northern subarctic Oceans such as the northeast Pacific Ocean and the English Channel. This suggests that the alkatrienes from Site 1016 reflect the contribution of Emiliania and/or Gephyrocapsa species of subarctic origin.
In the F1 fraction, diploptene, neohop-13(18)-ene, and fern-7-ene were found, and hop-21(22)-ene and hop-17(21)-ene were detected in trace amounts (Fig. 6). All of these are thought to derive from eubacteria or cyanobacteria (Ourrison et al., 1979). Brassell et al. (1980) proposed a diagenetic isomerization of diploptene (hop-22(29)-ene) to neohop-13(18)-ene through hop-21(22)-ene and hop-17(21)-ene. There seems a trend that the relative abundance of neohop-13(18)-ene to diploptene increases with increasing depth (Fig. 9), which is consistent with the Brassell hypothesis. Both diploptene and neohop-13(18)-ene show similar variations with depth, but the amplitude is much higher in the variation of neohop-13(18)-ene concentration.
Hopanes, steranes, and
C-ring monoaromatic (MA) steroids were observed in the F1 fraction (Fig.
6). Their identification was achieved by comparison of their mass
spectra and retention times (Philp, 1995; Moldowan and Fago, 1986; Schouten et
al., 1994). Their isomeric pattern (e.g., the presence of thermally stable 22S-
and 17
(H),
21
(H)-hopanes
and 20S- and 5(H),
14(H),
17(H)-steranes)
is typical of matured organic matter (Seifert and Moldowan, 1980), and the
presence of 28, 30-dinorhopane (Seifert et al., 1978) implies that their source
is a weathered Miocene Monterey Formation source rock and/or Monterey oil. Figure
11 demonstrates the variations in the concentrations of these
petroleum-type compounds. All of these show parallel variations in
concentration, and they are most abundant in warming intervals at 0.8 and 8.2
mbsf. The concentration of 28,30-dinorhopane ranges between 3 and 13 µg/g TOC,
which is in the same order as that in Site 893 sediments in Santa Barbara Basin
(10-42 µg/g TOC; Hinrichs et al., 1995).
