21. PRELIMINARY LIPID ANALYSES OF TWO QUATERNARY SEDIMENTS FROM THE MIDDLE AMERICA TRENCH, SOUTHERN MEXICO TRANSECT, DEEP SEA DRILLING PROJECT LEG 661
S. C. Brassell, G. Eglinton, and J. R. Maxwell, School of Chemistry, University of Bristol, Bristol, United Kingdom
ABSTRACT
We investigated the solvent-extractable hydrocarbons, ketones, alcohols, and carboxylic acids of two Quaternary sediments from the Middle America Trench (Sections 487-2-3 and 491-1-5). These lipids are derived from a mixed input of autochthonous and allochthonous materials, with minor contributions from thermally mature sources. Their com- positions are typical of those of immature Quaternary marine sediments, and their lipid distributions show many similarities to those of Japan Trench sediments.
INTRODUCTION RESULTS The solvent-extractable lipids of two Quaternary sed- The distributions of aliphatic hydrocarbons, ketones, iments (Sections 487-2-3 and 491-1-5) from the oceanic alcohols, and carboxylic acids and of aromatic hydro- plate and central slope of the Middle America Trench carbons are reported herein. In addition, other suites of were investigated by gas chromatography and comput- components such as a, co-dicarboxylic acids and numer- erized gas chromatography-mass spectrometry. The sec- ous minor or unrecognized compounds were detected, tions were chosen to permit the comparison of environ- but are not included. ments on either side of the trench. This preliminary re- port describes the lipid compositions of these two sam- Aliphatic Hydrocarbons ples and interprets them in terms of their input sources, conditions of deposition, and extent of diagenesis. We Acyclic Components also make a brief comparison of their lipid distributions The n-alkanes of Sections 487-2-3 and 491-1-5 both with those of Quaternary sediments from the Japan ranged from C14 to C35 with «-C29 dominant. The con- Trench. centrations of individual homologues are shown in Fig- Table 1 summarizes the lithological characteristics of ure 1A and the CPI values in Table 2. Both distributions the samples and includes their weights. Organic carbon are dominated by the odd-numbered w-alkanes in the determinations were not made for these samples, but the C25 to C35 range, but in Section 491-1-5 the C17 to C22 values of adjacent sections are given (site chapters, this homologues are also prominent. No «-alkenes were de- volume). tected in either sample. Iso- and anteiso- alkanes in the C17 to C23 range were recognized as minor components EXPERIMENTAL (<0.5 ng/g) of Sections 487-2-3 and 491-1-5. No other The experimental procedures for Leg 66 samples generally follow simple branched alkanes or alkenes were found in either those of our earlier DSDP investigations (Barnes et al., 1979; Brassell sediment. et al., 1980a, 1980b). Gas chromatographic (GC) analyses were per- formed on a 20m OV-1 WCOT capillary column fitted in a Carlo Erba Seven isoprenoid alkanes were found in both samples; 2150 instrument. Computerized gas chromatography-mass spectrom- the concentrations of five of them, 2,6,10-trimethylpen- etry (C-GC-MS) was used to achieve compound identification. The tadecane, pristane (2,6,10,14-tetramethylpentadecane), Finnigan 4000 system with INCOS 2300 data system has been de- phytane (2,6,10,14-tetramethylhexadecane), 2,6,10,15, scribed elsewhere (Brassell et al., 198Od), but for these analyses a 20-m 19-pentamethyleicosane (I), and squalane (2,6,10,15,19, fused silica column coated with methyl silicone fluid led through to the ion source was used. Compound assignments were made from in- 23-hexamethyltetracosane, II), recognized by compari- dividual mass spectra and GC retention times, with reference to son with literature spectra (e.g., Holzer et al., 1979), are literature spectra and authentic standards, where possible. Mass frag- shown in Figure 1A. For Section 487-2-3 the identifica- mentography (MF) was used extensively to characterize homologous tion of 2,6,10,15,19-pentamethyleicosane is tentative; and pseudohomologous series and to aid in compound identification. Individual components were quantitated from their GC response, the mass spectrum suggested a contribution to the GC where possible, from their C-GC-MS response or by MF. For particu- peak from another acyclic isoprenoid alkane, perhaps lar compound classes either the small quantities or problems with 2,6,10,14,18-pentamethyleicosane (III, Holzer et al., component coelution prevented absolute quantitation. In such in- 1979). The presence of the two other acyclic isoprenoid stances, a semiquantitative estimate of their relative abundances is alkanes was suggested by the enhanced response of the given. m/z 183 MF (Albaiges, 1980) for the «-C34 and «-C35 peaks in GC-MS. From these mass spectral data the acyclic isoprenoid alkanes coeluting with these /z-al- kanes are probably 2,6,10,14,17,21,25,29-octamethyl- Initial Reports of the Deep Sea Drilling Project, Volume 66.
557 S. C. BPvASSELL, G. EGLINTON, J. R. MAXWELL
Table 1. Sample descriptions and lithological characteristics.
Sub-bottom Organic Weight (g) Sample Depth Carbon Site Location (interval in cm) (m) Age Lithology (%) Weta Dryb
oceanic plate 487-2-3, 135-150 5.2 middle-late Pleistocene mud 83 47 central trench slope 491-1-5, 110-135 7.2 Quaternary muddy silt 162 108
a Weight prior to extraction. All lipid concentrations are quoted in ng/g dry weight of sediment. c Value for Section 487-2-2, 40. d Value for Section 491-1-5, 101. hentriacontane (IV) and lycopane (2,6,10,14,19,23,27, trienes preclude their quantitation from a single MF. 31-octamethyldotriacontane, V), since both possess Hence, Table 3 gives only approximate concentration prominent m/z 183 ions (Moldowan and Seifert, 1979; values derived from the total ion intensities of individ- Kimble et al., 1974) and appropriate retention times. ual sterene mass spectra. Ster-2-enes (XII) and stera- Trace concentrations (<0.7 ng/g) of two phytene iso- 3,5-dienes (XIII) were recognized by comparison with mers with mass spectra similar to that of phyt-2-ene (3, standard spectra; the nuclear positions of unsaturation 7, 11, 15-tetramethylhexadec-2-ene, VI; Urbach and of the other components are uncertain. Three of the Stark, 1975) were found in Section 491-1-5. sterenes with nuclear triunsaturation are thought to pos- sess aromatic A or B rings (XIV or XV); Spyckerelle, Cyclic Components 1975; Rullkötter et al., in press). Their mass spectral A series of cyclohexylalkanes ranging from C16 to C26 similarities to D ring aromatic hopanes (Greiner et al., was recognized by MF (m/z 83 and 82) in Section 491- 1977) suggest that B ring aromaticity (XV) is the more 1-5. The concentration of the major homologue, cy- probable. The distributions and approximate concentra- clohexyldodecane (VII), was approximately 0.8 ng/g. tions of sterenes in Sections 487-2-3 and 491-1-5 are These components were not detected in Section 487-2-3. generally similar. Section 487-2-3 appears to contain Fichtelite (VIII) was detected as a minor component greater relative amounts of nuclear triunsaturated ste- (approx. 0.3 ng/g) of Section 487-2-3 but was not pres- renes, whereas Section 491-1-5 possesses higher abun- ent in Section 491-1-5. Section 487-2-3 also contained dances of stera-3,5-dienes. compounds with mass spectra similar to published spec- A wide range of triterpenoid hydrocarbons was tra of a C25H44 bicyclic alkadiene (Mt 344, Farrington found in both samples, although as with the sterenes, et al., 1977; Boehm and Quinn, 1978) and a C3OH52 their absolute quantitation was not possible. The abun- bicyclic alkatriene (M1412,12558 of Prahl et al., 1980). dances given in Table 4 are therefore approximate values Of the three major fragment ions in the spectra, two calculated from the total ion signal of individual mass (m/z 231 and m/z 259) are common to both compo- spectra. The intensities for each component's m/z 191 nents, whereas the third occurs at 68 amu higher (m/z response, relative to that of the major triterpenoid, are 315 rather than m/z 247) in the spectrum of the C30 also given. The majority of compounds were recognized compound, suggesting that the two hydrocarbons share from their mass spectra by comparison with those of a common bicyclic skeleton and differ by one isoprene standards or by MF. Two components with mass spectra (C5H8) unit. The mass spectral data do not, however, and GC retention times similar to those of two of the permit unambiguous assignment of the structure of three unknown triterpenoid hydrocarbons—those as- these C25 and C30 compounds, which are present in con- signed as C30 triterpenes in Table 4—were previously centrations of 6.5 ng/g and 4.6 n/g, respectively. found in Section 481-2-2 (Thomson et al., in press b); Steranes (IX) and diasteranes (X) were recognized by their structures have not been characterized. The rela- MF (m/z 217) as minor components of both samples. tive abundances of hop-22(29)-ene (diploptene, XVIIIf) The distributions of these compounds in the two sedi- and homohop-29(31)-ene (XVIIIi) are markedly higher ments were similar, but their low concentrations (<0.5 in Section 487-2-3 than in Section 491-1-5, whereas the ng/g and <0.3 ng/g for Sections 487-2-3 and 491-1-5, latter sample contains a greater abundance of fernenes respectively) prevented component identification from and αß-hopanes, notably the C31 to C35 homologues. In individual mass spectra. Hence, an accurate assessment other respects the distributions and approximate con- of the maturity of the steranes from specific stereoiso- centrations of triterpenoid hydrocarbons in the two meric ratios (Mackenzie et al., 1980) was not possible, sediments are generally similar. Neither triterpanes nor although the apparent proportions of 20S- and 14ß(H)- triterpenes with 6-membered E rings, such as gamma- steranes and diasteranes, as seen from MF, were com- cerane (XXVI) and olean-18-ene (XXVII), were de- parable in both samples with those in petroleums and tected in the samples. Both sections, however, contained mature sediments (Seifert and Moldowan, 1979; Mac- a suite of eight C24 components that were tentatively kenzie et al., 1980). Sterenes were significant compo- assigned as tetracyclic degradation products of 3-oxytri- nents of both sections, but the complexity of the poly- terpenoids (Fig. 2). The mass spectrum of component D cyclic region of the hydrocarbon fractions prevented is the same as that of a compound originally found in their absolute quantitation. In addition, the mass spec- the Messel shale (Kimble, 1972), which has been charac- tral differences between sterenes, steradienes, and stera- terized as a tetracyclic alkane (XXVIII) related to
558 LIPID ANALYSES
34
487-2-3 487-2-3
C18'
III 13 .1.11 | | 1.5
491-1-5 491-1-5
tmpd
. • I. 1 1 . . 1 . 1 1 1 | 15 20 25 30 35 20 25 30 Carbon No. Carbon No.
100 80
487-2-3 487-2-3
18
16:1
14:1 18:2 illi n 23 ill: .11 I 1 14
ph
491-1-5 491-1-5
18:1 115. ". I 1 . ,1 15 20 25 30 15 20 25 30 Carbon No. Carbon No. Figure 1. Concentrations (ng/g dry sediment) of acyclic hydrocarbons, ketones, alcohols, and acids in Sections 487-2-3 and 491-1-5. A. n-alkanes. (tmpd = 2,6,10-trimethylpentadecane; pr = pristane; ph = phytane; pme = 2,6,10,15,19-pentamethyleicosane; sq =
squalane; * = n-alkane peaks enhanced by coelution of acyclic isoprenoid alkanes [see text].) B. n-alkan-2-ones. (C18i = 6,10,14-tri- methylpentadecan-2-one.) C. n-alkanols. (i = wo-alkanols; a = αntewo-alkanols; dhp = dihydrophytol; ph = phytol; 22:1, 24:1, 26:1 = alkenols.) D. n-alkanoic acids, (i = iso-alkanoic acids; a = ante/5θ-alkanoic acids; 14:1, 16:1, 18:1, 18:2 = alkenoic acids.)
559 S. C. BRASSELL, G. EGLINTON, J. R. MAXWELL
Table 2. Carbon preference indices of normal components in the sam- Table 4. Abundance of triterpenoid hydrocarbons in Sections 487-2-3 ples. and 491-1-5.
a Section Abundance in Section Odd/Even or Compound Class C No. Range 487-2-3 491-1-5 Even/Odda Assignment Structure 487-2-3 491-1-5 18αH-22,29,30-trisnorneohopane XVI n.d. + (9) (14-33 3.5 2.5 o/e 17αH-22,29,30-trisnorhopane XVIIa + (5) + (20) π-alkanes <14-21 1.2 1.2 o/e 17ßH-22,29,30-trisnorhopane XVlIIa + + (25) + + (26) (22-33 4.1 3.7 o/e C30 triterpene ?b + + + (58) n.d. /i-alkan-2-ones 16-33 4.5 2.8 o/e α/3-30-norhopane XVIIb + + + (72) + + + (61) n-alkanols 11-30 5.7 7 4u e/o hop-17(21)-ene XIX + + + (15) + + + (14) (12-34 6.3 5.5b e/o unknown 7 + + (19) + + (21) /i-alkanoic acids {12-21 11.7 12.2C e/o α/3-hopane XVIIc + + + (65) + + + (100) (22-34 4.7 4.9 e/o fern-8-ene XX n.d. + (-)d neohop-13( 18)-ene XXI + + + (20) + + + (34) a Odd/even predominance o/e; even/odd predominance e/o 0/3-30-norhopane XVIIIb + + + (49) + + (14) b fern-9(ll)-ene XXII + + (-) + + (-) CPI for C14_34 range. c c C30 triterpene ? n.d. + (4) CPI for C14.21 range. neohop- 12-ene XXIII + + (8) + + (12) fern-7-ene XXIV + + (-) + + (-) 22S α/3-homohopane XVIId + (16) + + (19) Table 3. Abundance of sterenes in Sections 487-2-3 and 491-1-5. 22R αß-homohopane XVIIe + (15) + + (17) /3/3-hopane XVIIIc + + + (57) + + + (56) hop-22(29)-ene XVIIIf + + + (100) -t- (4) Abundance in hop-21-ene XXV + + (26) + + (12) Section 22S α/3-bishomohopane XVIIg + (6) + (10) 22R α/3-bishomohopane XVIIh + (10) Assignment Structure 487-2-3 491-1-5 + (6) homohop-29(31)-ene XVIIIi + (9) n.d. /3/3-homohopane XVIIIe + + + (50) + + + (47) cholesta-n,24-dienea Xlb + + 22S α/3-trishomohopane XVIIj n.d. + (6) cholest-2-ene Xlla + + + + 22R αiβ-trishomohopane XVIIk n.d. + (5) cholesta-3,5-diene XHIa + + + + ftß-bishomohopane XVIIIh n.d. + (2) 24-methylenecholestene Xld + + + + + 22S α/3-tetrakishomohopane XVIK n.d. + (3) 24-methylenecholest-2-ene XIIc + + + 22R α/3-tetrakishomohopane XVIIm n.d. + (3) 24-methylenecholestene Xld \ 22S α/3-pentakishomohopane XVIIn n.d. + (1) a 22R α/3-pentakishomohopane XVIIo n.d. 24-ethylcholesta-n,22-diene Xle / + + + + + + + (1) 24-methylcholestatriene XIc + + + Note: Section 487-2-3: + + + = approx. 5 ng/g; + + = approx. 2 ng/g; + = 24-methylcholesta-3,5-diene XIIIc n.d. + + approx. < 1 ng/g. Section 491-1-5: + + + = approx. 4 ng/g; + + = ap- 24-methylcholestatriene XIc + + + prox. 1 ng/g; + = <0.5 ng/g. n.d. = not detected. 23,24-dimethylcholest-2-ene Xllf + + + a Values in parentheses are the m/z 191 intensities relative to the major compo- 24-ethylcholest-2-ene Xllg + + + + nent of that MF. The variability in the intensity of m/z 191 fragmentation for cholestatriene XlVa or XVa + n.d. the different triterpenoids (e.g., Barnes et al., 1979) restricts the use of these 24-ethylidenecholestene Xlh + + + + + + values for quantitation purposes. b C30 triterpene also found in Section 481-2-2 (component D of Thomson et 24-ethylcholesta-3,5-diene XIIIc + + + al., in press b). 24-ethyldenecholestadiene Xlh + + + + + c C30 triterpene also found in Section 481-2-2 (component J of Thomson et 24-methylcholestatetriene XlVd or XVd + + al., in press b). 24-ethylcholestatriene XlVg or XVg + n.d. d m/z 191 is an insignificant ion in fernene mass spectra.
Note: Section 487-2-3: + + + = approx. 3 ng/g; + + = approx. aromatic tetracyclic components (XXXIV to XXXVIII) 1.5 ng/g; + = approx. <0.5 ng/g. Section 491-1-5: + + + = approx. 3 ng/g; + + = 1 ng/g; + = <0.3 ng/g. n.d. = not were recognized by comparison with literature spectra detected. (Spyckerelle, 1975; Spyckerelle et al., 1977a, 1977b; a n designates nuclear double bond in an uncertain position. Laflamme and Hites, 1979; Wakeham et al., 1980a, 1980b). Assignments of the monoaromatic tetracyclic lupáne (XXIX, Corbet et al., 1980). The identities of the components (XXXII and XXXIII) were made by com- other components cannot be unambiguously assigned parison with a literature spectrum (Spyckerelle, 1975) from their mass spectra. The distributions of these com- and by spectral interpretation. In addition to the aro- pounds in the two samples are similar, but they are pres- matic hydrocarbons listed in Table 5 and the monoaro- ent in rather greater concentrations in Section 487-2-3 matic steroids just discussed, series of ring C aromatic than in Section 491-1-5. steroids (XL, Schaeffle et al., 1978) were found as trace components (<0.1 ng/g) of both samples. The major Aromatic Hydrocarbons difference between the two distributions of aromatic Aromatic hydrocarbons were minor components of hydrocarbons, which were present at similar concentra- both samples (approx. < 1 ng/g), with the exception tions in both sections, is the greater abundance of the of perylene (XXXIX) in Section 491-1-5. The small aromatic diterpenoids simonellite and retene in Section amounts of these compounds prevented their accurate 491-1-5. quantitation; hence, Table 5 gives approximate values for their concentrations, estimated from the total ion Ketones signal of their mass spectra or from MF of their molec- ular ions. Simonellite (XXX), retene (XXXI), and pery- Acyclic Components lene (XXXIX) were identified from C-GC-MS by com- In both samples the «-alkan-2-ones are dominated by parison with standard spectra, whereas the tri- and di- odd-numbered components as seen in their CPI values
560 LIPID ANALYSES
3.5 recognized in either sample. 6,10,14-trimethylpenta- decan-2-one was present as a prominent component of both sections (Fig. IB); indeed, in Section 491-1-5 it is 487-2-3 more abundant than the «-alkanones. No other acyclic isoprenoid ketone was found in the sections. Cyclic Components The minor components of both samples included steroidal ketones that were identified from standard or literature spectra (Gagosian and Smith, 1979; Withers et al., 1978), by spectral interpretation or from their GC retention times using MF. 5α- and 5ß-cholestan-3-one (XLIIIa and XLIVa), 24-ethyl-5α-cholestan-3-one 1 1 I 1 (XLIIIb), dinosterone (4α,23,24-trimethyl-5α-cholest- 22-en-3-one, XLVc), dinostanone (4α,23,24-trimethyl- 5α-cholestan-3-one, XLVd), and an isomer of dino- 491-1-5 stanone, probably differing in its side chain methylation (perhaps 4α,22,24-trimethyl, XLVe or 4α,22,23-tri- methyl, XLVf), were identified in the samples. Dino- sterone was the dominant component of both distribu- tions, found in minor amounts (
C37:2 methyl ketone (heptatriaconta-15,22-diene-2-one, The H-alkanols of Sections 487-2-3 and 491-1-5 range XLIa), which is the major ketone in these sediments. No from C12 to C30, with the even-numbered components other alkenones or simple branched acyclic ketones were dominant. Their concentrations are shown in Figure 1C,
Table 5. Abundance of aromatic hydrocarbons in Sections 487-2-3 and 491-1-5.
Abundance in Section Assignment Formula Structure 487-2-3 491-1-5
l,l-dimethyl-7-isopropyl-l,2,3,4-tetrahydrophenanthrene (simonellite) n.d. C19H24 XXX 1 -methyl-7-isopropylphenanthrene (retene) C18H20 XXXI a 3,4,7,10b,12a-pentamethyl-l,2,3,4,4a,4b,5,6,10b,ll,12,12a-dodecahydrochrysene C23H34 XXXII C H 3,3,7,10a,12a-pentamethyl-l,2,3,4,4a,4b,5,6,10b,ll)12,12a-dodecahydrochrysene 23 34 XXXIII 2,8-dimethyl-5' -isopropyl-1,2-cyclopentano-l ,2,3,4-tetrahydrophenanthrene C22H3O XXXIV 3,4,7,12a-tetramethyl-l, 2,3,4,4a, 11,12,12a-octahydrochrysene c22H30 XXXV 3,3,7,12a-tetramethyl-l ,2,3,4,4a, 11,12,12a-octahydrochrysene c22H30 XXXVI 3,4,7-trimethyl-l,2,3,4-tetrahydrochrysene C21H26 XXXVII 3,3,7-trimethyl-l,2,3,4-tetrahydrochrysene C21H26 XXXVIII perylene C20H12 XXXIX 7 ng/g
Note: Sections 487-2-3 and 491-1-5: + + + = approx. 1 ng/g; + + = approx. 0.2 ng/g; + = 561 S. C. BRASSELL, G. EGLINTON, J. R. MAXWELL 48 and αnte/so-alkanols ranging from Ci5 to C21 were found in both samples (Fig. 1C), but no n-alkan-2-ols (cf. Cranwell, 1980) were detected. Phytol (3,7,11,15- tetramethylhexadec-2-enol) was a prominent compo- nent of both samples (Fig. 1C) but dihydrophytol (3,7, 487-2-3 11,15-tetramethylhexadecanol) was only found in Sec- tion 487-2-3. Cyclic Components Sterols were major components of both sections; the concentrations of the 35 compounds characterized (Table 7) are shown in Fig. 4. Standard and literature spectra (Gaskell and Eglinton, 1976; Wardroper et al., 1 1 1 14 1978; Lee et al., 1979; Wardroper, 1979; Boon et al., 1979; Brassell and Eglinton, 1981; Brassell, 1980 and references therein) and GC retention times were used for most sterol identifications; other assignments are based on spectral interpretation (Table 7). 491-1-5 Dinosterol [4α,23,24-trimethyl-5α!-cholest-22(E)-en- 3j3-ol, LVIj] was the dominant sterol of both sections, which possessed similar distributions, except for the 22 greater prominence of 5α-stanols and C29Δ compo- nents in Section 491-1-5. No sterols with short side chains ( T /24-ethyl-5α-cholest-22(E)-en-3|8-ol LVk Note: Sections 487-2-3 and 491-1-5: + + =0.2 ng/g; + = \4α,24-dimethyl-5α!-cholest-22(E)-en-3|8-ol LVIg 562 LIPID ANALYSES 68 487-2-3 .1. 1. 1. ll.lll II ..1 . 21 491-1-5 . _ __ |.|| I M . ill • B CDE FGHI JKilL Ml N .hOPQ Ri S T UVW X Y ZAAABAC AD Figure 4. Concentrations (ng/g dry sediment) of sterols in Sections 487-2-3 and 491-1-5. (Assignments are given in Table 7.) 28 components were identified from their mass spectra by comparison with reference standards or literature spec- tra (Dastillung et al., 1980b) or from MF. The excep- tions were taraxer-14-en-3-ol and component D (Table 8). Diplopterol (ß|0-hopan-22-ol, XVIIIq) was not de- 487-2-3 tected in either sample (cf. Rohmer et al., 1980). Hydroxyalkanones Both samples contained C30 and C32 hydroxyalka- nones (LXIIIa and b; Table 8), compounds recently characterized by de Leeuw et al. (personal communica- tion); their concentrations are shown in Fig. 5. ., 1 1 I Carboxylic Acids Acyclic Components The concentrations of w-alkanoic acids in Sections 487-2-3 and 491-1-5 are shown in Figure ID; C16 and C26 491-1-5 are the major homologues of the respective distribu- tions, which are both dominated by even-numbered components, although they differ markedly in the rela- tive amounts of their short-chain (C12-C20) to long- chain (C20-C34) members. In addition to the compounds shown in Figure ID, Section 487-2-3 contained trace amounts of C35 and C36 «-alkanoic acids. /r-Alkenoic acids were recognized in both samples (Fig. ID), but a 1 l• | 1 rather greater range of these compounds was present in A B CDE H Section 487-2-3. Iso- and α/zte/so-alkanoic acids were Figure 5. Concentrations (ng/g dry sediment) of triterpenols and hy- also found in both samples, but the carbon number droxyalkanones in Sections 487-2-3 and 491-1-5. (Assignments are ranges varied (Fig. ID). In particular, C25, C27, and C29 given in Table 8.) components were detected only in Section 491-1-5. 563 S. C. BRASSELL, G. EGLINTON, J. R. MAXWELL Cyclic and Aromatic Components phytoplankton inputs. The short-chain n-alkanes of both samples possess similar low CPI values (Table 2), Dehydroabietic acid (LXIV) was detected only in Sec- but these compounds are present in greater concentra- tion 487-2-3 (approx. 0.5 ng/g); no other diterpenoid tions in Section 491-1-5 than Section 487-2-3, in contrast acids and no steroidal acids were found in either sample, to the overall abundance of n-alkanes in the two sam- ßß-bishomohopanoic acid (XVIIIu) was recognized in ples. In view of the evidence for thermally mature inputs Sections 487-2-3 and 491-1-5 at concentrations of ap- to the samples (see the following) it seems probable that proximately 1.6 ng/g and <0.2 ng/g, respectively. Sec- the short-chain n-alkanes of Section 491-1-5 are, at least tion 491-1-5 also contained traces of ßß-homohopanoic in part, derived from such a source. acid (XVIIIv). Nonhopanoid triterpenoid acids, pos- The n-alkan-2-one distributions resemble those of the sibly related to amyrin or friedelane skeletons (cf. Cor- n-alkanes, especially in Section 487-2-3 (cf. Fig. 1A and bet et al., 1980), were present in minor amounts in Sec- B). Such similarity suggests that the n-alkan-2-ones tion 487-2-3, but lack of standard mass spectra pre- originate from alkane oxidation rather than from ß-oxi- cluded their identification. dation of alkanoic acids (Brassell et al., 1980c and refer- ences therein), but it is unclear whether such oxidation DISCUSSION occurs at a pre- or postdepositional stage. In Section 491-1-5 the low relative abundance of short-chain n-al- Lipid Yields kan-2-ones, in contrast to the n-alkane distributions, Although the total lipid yields of Sections 487-2-3 suggests predepositional alkane oxidation. and 491-1-5 have not been determined, the concentra- Two possible sources of the n-alkanols and n-alke- tions of individual lipids provide a measure of their total nols in marine sediments are input from the wax esters lipid content. The abundances of the compound classes of marine organisms or lipid contributions from terrig- evaluated in the two samples are considerably lower enous higher plants. In higher plant waxes hexacosanol than those of other Quaternary marine sediments ana- is the dominant homologue (Eglinton and Hamilton, lyzed in our laboratory (e.g., Walvis Bay, Wardroper, 1967), whereas zooplankton wax esters contain C16 to 1979; Japan Trench, Brassell et al., 1980b, 1980c; C22 alkanol moieties (Benson and Lee, 1975), although California continental borderland, McEvoy et al., in their composition varies with growth conditions (Lee et press; Guaymas Basin, Thomson et al., in press b). Such al., 1971). The distributions of n-alkanols in Sections sediments, however, show greater variability in their 487-2-3 and 491-1-5 do not therefore correspond well concentrations of components of marine origin (e.g., with an origin from either source. Indeed, similar distri- sterols and alkenones) than of terrestrial origin (e.g., butions have been interpreted as both wax ester (Ikan et n-alkanes in all the samples except Walvis Bay). The al., 1975) and terrestrial input (Aizenshtat et al., 1973; lower abundances of marine components relative to ter- Brassell et al., 1980c). The presence of C22 to C26 restrial components in the Middle America trench n-alkenols in Section 487-2-3 further confuses the issue samples compared with the other sediments may there- in that C20:i and C22:1 are the major alkenoid moieties of fore, in part, reflect less intensive water column produc- calanoid copepods (Nevenzel, 1970) and higher plants tivity, although other environmental conditions are un- are not known to contain these compounds. These dis- doubtedly also important. crepancies between the biological and sedimentary dis- tributions of n-alkanols and n-alkenols precludes the Paleoenvironmental Assessment: Lipid Indicators unambiguous assignment of their biological origin. The distributions of n-alkanoic and n-alkenoic acids Straight-Chain Components suggest input from both autochthonous and allochtho- The distributions of saturated straight-chain compo- nous sources. The prominence of C22 to C34 n-alkanoic nents (n-alkanes, n-alkan-2-ones, n-alkanols, and n-al- acids with even/odd predominance (Table 2) is consis- kanoic acids) are consistent with a mixed input from tent with input from terrigenous plants (e.g., Simoneit, autochthonous and allochthonous sources. The n-al- 1978). The widespread occurrence of C16 and C18 n-al- kane distributions maximizing at n-C29 (Fig. 1A), with a kanoic acids in biota makes them nondiagnostic source prominent odd/even preference in the C22 to C33 range indicators, whereas the relative abundance of C12 and (Table 2), are similar to those of higher plant waxes C14 n-alkanoic acids in Section 487-2-3 suggests autoch- (e.g., Eglinton et al., 1962) and suggest that the n-al- thonous lipid inputs. It is not possible, however, to dif- kanes reflect terrigenous input (e.g., Simoneit, 1978; ferentiate between algal and bacterial autochthonous in- Brassell et al., 1978). Evidence of major autochthonous put of carboxylic acids without information regarding input is not reflected by the lower n-alkanes, especially the geometrical isomerism of the n-alkenoic acids (Volk- n-Cπ The mediety of n-C 1 may, however, be due to its man and Johns, 1977). The shorter-chain n-alkanoic preferential biodegradation relative to higher n-alkanes and n-alkenoic acids might also originate from marine (e.g., Johnson and Calder, 1973; Brassell et al., 1978) in wax esters (Boon and de Leeuw, 1979). both water column and sediment rather than to a low The only organism in which the C37 to C39 alkenones level of algal productivity in the euphotic zone. In addi- (XLI, XLII) have been recognized is Emiliania huxleyi tion, that higher plants possess greater concentrations (Volkman et al., 1980a, 1980b). Hence, these ketones of n-alkanes in their surface waxes than do algae makes have been ascribed to coccolithophore input 10 sedi- n-alkanes more sensitive indicators of terrestrial than of ments, even where deposition below the CCD has de- 564 LIPID ANALYSES stroyed any skeletal evidence of such organisms (Bras- bacterial inputs (Brassell et al., 1981) but is consistent sell et al., 1980b, 1980c; Volkman et al., 1980a). A ma- with a thermally mature source, which therefore seems jor difference between the distribution of alkenones in the most probable origin of these compounds. Sections 487-2-3 and 491-1-5 and in E. huxleyi is the ratio of di- to triunsaturated homologues. In E. huxleyi Acyclic Isoprenoid Components the alkatrienones are dominant, although analysis at the Despite the nonspecificity of its biological occur- motile, sessile, and Coccolith stages of growth shows rence, the lability of phytol means that its abundance in that the ratio of alkadienones to alkatrienones varies Sections 487-2-3 and 491-1-5 probably reflects autoch- throughout the growth cycle (Volkman et al., 1980a). In thonous marine inputs (Brassell et al., 1980c). In con- contrast, the alkenone distributions of sediments are trast, 6,10,14-trimethylpentadecan-2-one is less readily generally dominated by the alkadienones (di/tri ratios degraded and may derive from allochthonous sources range from 0.7 to 4; Volkman et al., 1980a; Brassell et and/or be generated from phytol within the water col- al., 1980b), but Sections 487-2-3 and 491-1-5 possess umn or sediment. There are two possible biological alkadienones/alkatrienones ratios an order of magni- sources for 2,6,10-trimethylpentadecane, pristane, phy- tude higher (33 and 57, respectively). This dissimilarity tane, the phytenes, and dihydrophytol: they may be in the alkenone ratios may reflect sediment contribu- degradation products of plant phytol and/or inputs tions from E. huxleyi that has grown under different en- from methanogenic sources (e.g., Holzer et al., 1979). vironmental conditions or an input from an organism In the absence of stereochemical analyses (e.g., Patience that biosynthesises these alkenones with a different et al., 1978) the three alkanes might alternatively origi- alkadienone/alkatrienone ratio. Alternatively, the alka- nate from mature allochthonous sources (see the follow- trienones may be more easily degraded relative to the al- ing). The recognition of 2,6,10,15,19-pentamethyl- kadienones in the Middle America Trench than in other eicosane (I) and squalane (II) in the samples provides sediments. evidence for methanogenic biological activity (Brassell Although the biological source of the hydroxyalka- et al., 1980c, 1981). Methanogens may also be the nones (LXIII) is uncertain because they have yet to be source of lycopane (V), although this compound has yet recognized in organisms, they are probably of marine to be recognized among their lipids (Brassell et al., origin in view of their geological occurrence (de Leeuw, 1980c, 1981). Similarly, the acyclic isoprenoids coelut- personal communication; Thomson et al., in press, b). ing with 2,6,10,15,19-pentamethyleicosane and «-C34, The absence of the C31 hydroxyalkanone is not unex- tentatively assigned as 2,6,10,14,18-pentamethyleico- pected, since this component is present in markedly sane (III) and 2,6,10,14,17,21,25,29-octamethylhentri- lower concentrations than the C30 and C32 homologues acontane (IV), respectively, are probably of methano- in other sediments (de Leeuw et al., personal communi- genic origin. cation; Thomson et al., in press b). Nonisoprenoidal Cyclic Components Branched-Chain Components Alkylcyclohexanes have yet to be found in organ- Short-chain iso- and αnte/so-alkanoic acids are con- isms, although α>-cyclohexylalkanoic acids (LXV) have stituents of bacteria (e.g., Parker et al., 1967; Cranwell, been recognized as lipid constituents of thermoacido- 1973), hence the occurrence of such C13 to C17 com- philic bacteria (e.g., De Rosa et al., 1972). Their occur- ponents (Fig. ID) in Sections 487-2-3 and 491-1-5 may rence in ancient sediments and petroleums (Johns et al., be attributed to input from bacteria (e.g., Simoneit, 1966; Speers and Whitehead, 1969) and their formation 1978; Brassell et al., 1980c). By analogy, the iso- and in simulated maturation experiments (Ishiwatari and anteiso-alkanols (C15-C2i, Fig. 1C) are also of bacterial Fukushima, 1979; Rubinstein and Strausz, 1979) sug- origin (Brassell et al., 1980c). In contrast, the C25, C27, gest that their presence in Section 491-1-5 reflects input and C29 iso- and α/ite/so-alkanoic acids are probably from thermally mature sources. derived from terrestrial sources in view of their relation- ship to the long-chain 2- and 3-methylalkanes found in Cyclic Diterpenoid Components higher plant waxes (Eglinton et al., 1962). The iso- and The four cyclic diterpenoids (fichtelite, simonellite, αwte/so-alkanes recognized in Sections 487-2-3 and retene, and dehydroabietic acid; VIII, XXX, XXXI and 491-1-5 are short-chain homologues, however, which LXIV) recognized in the sediments are all believed to be may be of direct bacterial origin (e.g., from methano- diagenetic products of abietic acid (Maxwell et al., 1971; gens; Holzer et al., 1979). Alternatively, the widespread Laflamme and Hites, 1978) and markers for terrigenous occurrence of such compounds in ancient sediments and input of resinous plants (Simoneit, 1977). petroleums (e.g., Tissot and Welte, 1978) suggests that they could be contributed by an input of thermally C25 and C30 Unknown Alkenes mature lipids—e.g., from an oil seep or other reworked The biological origins of the Q5H44 bicyclic alka- source. The uniformity of the carbon number distribu- diene and the C30H52 bicyclic alkatriene are uncertain. tions of the branched alkanes in Sections 487-2-3 and The mass spectral, and hence structural, similarities of 491-1-5 differs from the limited range found in bacteria the two compounds imply that they derive from a com- (Holzer et al., 1979) and in sediments thought to reflect mon source, which appears to be marine rather than ter- 565 S. C. BRASSELL, G. EGLINTON, J. R. MAXWELL restrial. Indeed, a planktonic source for the C30 compo- and a marker for dinoflagellate blooms (Boon et al., nent has been suggested (Prahl et al., 1980) but has yet 1979). Other sedimentary 4-methylstanols may also de- to be confirmed by its isolation from such an organism. rive from dinoflagellates (e.g., Withers et al., 1978, 1979), although methanotrophic bacteria contain such Steroidal Components compounds and have been suggested as their source The majority of the stenols of Sections 487-2-3 and (Dastillung et al., 1980b). On present evidence, how- 5 22 5 5 22 491-1-5—namely C26Δ ' and C27-C29Δ , Δ - , and ever, sediment inputs from these two types of organism Δ5,24(28) components (A, F, H, J, M, O, P2, R, S2, U2, cannot be distinguished, except that the abundance of and W in Table 7)—may be attributed to phytoplankton dinosterol in sediment traps in the equatorial Atlantic inputs (e.g., Boutry and Jacques, 1970; Boutry and Bar- Ocean (Wakeham et al., 1980c) indicates that it can orig- bier, 1974; Orcutt and Patterson, 1975; Ballantine et al., inate from a pelagic source. 1979; Volkman et al., 1980c), although they are not The stanones appear to represent direct biological in- uniquely biosynthesized by these organisms. For exam- puts to the sediment, although they are not widely re- ple, all of these Δ5-sterols occur in tunicata (Ballantine ported as constituents of organisms, with the exception et al., 1977), but previous investigations of sedimentary of dinosterone (4α, 23,24-trimethyl-5o;-cholest-22-en- sterol distributions (e.g., Lee et al., 1977, 1979; Ward- 3-one, XLVc), a known component of dinoflagellates roper et al., 1978; Wardroper, 1979; Brassell, 1980) have (Withers et al., 1978). The other 4α-methylstanones ap- ascribed them to phytoplankton or terrestrial higher pear to be the 3-oxy equivalents of sterols AB and dino- plant contributions (Huang and Meinschein, 1976). stanol (AC, LVI£), and may therefore be derived from In Sections 487-2-3 and 491-1-5, as in Japan Trench the same unknown sources. The overall dissimilarity of sediments (Brassell, 1980; Brassell and Eglinton, 1981), the sterol and sterone distributions seems to preclude a the inconsistency of the Δ5-stenol/5α-stanol ratios and diagenetic origin for the latter (cf. Gagosian and Smith, 1979; Edmunds et al., 1980). the occurrence of only C27 5/3-stanols argue against dia- genetic reduction of Δ5-stenols (Gaskell and Eglinton, Sterenes have not been detected among the lipids of 1975) as a major source of 5α-stanols. Hence, the 5α- any organisms and are regarded as microbial degrada- stanols probably originate from direct biological inputs tion products of sterols (e.g., Dastillung and Albrecht, to the sediment. 5α-Stanols are minor constituents of 1977; Gagosian and Farrington, 1978). In Sections 487- various organisms, including phytoplankton, zooplank- 2-3 and 491-1-5 the distribution and relative abundances ton, and higher plants (e.g., Nishimura and Koyama, of the sterenes do not parallel those of their presumed 1976, 1977); echinoderms (Goad et al., 1972); coelenter- precursor sterols, suggesting that their formation is ates (Kanazawa et al., 1977); and sponges (Nes and Mc- selective, affecting only specific individual sterols or Kean, 1977), which all might contribute lipids to the sources of sterols. In particular, the prominence of sediments. These Leg 66 sediments, like most others (cf. Δ24-sterenes is disproportionate to the relative abun- Wardroper et al., 1978), contain larger amounts of dance of Δ24-stenols and stanols, suggesting that Δ24- 5α-stanols relative to Δ5-stenols than do organisms, a sterols may be more susceptible to microbial dehydra- fact which may largely reflect a bias in the analyses of tion than other sterols, such as Δ22 components. Indeed biological sterols. In particular, stanols can be more the abundance and range of Δ22-sterols in the sediments prevalent at stationary growth phases than at exponen- (Table 7 and Fig. 4) are markedly greater than those of tial growth stages (Ballantine et al., 1979). The relative Δ22-sterenes (Table 3). Among the nuclear unsaturated abundance of sedimentary stanols compared with stenols sterenes, Δ2-sterenes (XII) and Δ3>5-steradienes (XIII) may therefore reflect direct lipid contributions from may originate from dehydration of stanols and Δ5- phytoplankton at their stationary rather than exponen- stenols, respectively (e.g., Dastillung and Albrecht, tial growth stages. Alternatively, Δ5-stenols may be 1977; Gagosian and Farrington, 1978). The recognition preferentially degraded relative to 5α-stanols in the of such sterenes in particle traps illustrates their rela- water column, but evidence for the Black Sea shows that tively fast formation associated with sinking particles this is not the case there (Gagosian et al., 1979). Wakeham et al., 1980c) and attests to their pelagic ori- The overall distribution of 4-desmethyl sterols and gin. The source of the steratrienes, thought to be mono- stanols suggests that they are largely of phytoplanktonic aromatic steroids (XIV or XV), is uncertain, but they origin, with the exception of components U2 and V! are probably microbial degradation products of sterols (24-ethylcholest-5-en-3/3-ol, LIVm and 24-ethyl-5α- (Gagosian and Farrington, 1978), perhaps stera-5,7- cholestan-30-ol, LVm; Table 7 and Fig. 4), which may dienols (LXIX) which are rarely found intact in sedi- derive from allochthonous inputs of higher plants ments (Brassell, 1980; Edmunds et al., 1980). (Huang and Meinschein, 1976). The absence of C21 to The absence of 4-methylsterenes in Sections 487-2-3 C25 stanols and other characteristic sponge and coelen- and 491-1-5, despite the abundance of 4-methylstanols, terate sterols (e.g., gorgosterol, LIVs; Wardroper et al., is consistent with results for other Quaternary marine 1978) argues against major lipid inputs from such or- sediments (Wardroper, 1979; Brassell, 1980; Gagosian ganisms (cf. Brassell, 1980; Brassell and Eglinton, et al., 1980; Thomson et al., in press b). It appears, 1981). therefore, that defunctionalization of 4-methylstan-3j8- The dominant sterol of both samples is dinosterol ols may be inhibited by the steric hindrance of a 4- (component X in Table 7 and Fig. 4, LVIj), which is the methyl substituent. Such discrepancy in the occurrence principal sterol of dinoflagellates (Shimizu et al., 1976) of sterenes and 4-methylsterenes compared to 4-des- 566 LIPID ANALYSES methyl- and 4-methylsterols suggests that microorgan- Table 8. Triterpenols and hydroxyalkanones identified in isms effect sterol to sterene conversions, since a geo- Sections 487-2-3 and 491-1-5. chemical transformation would be expected to be less dependent on sterol C-4 substitution (Thomson et al., in Peak press b; Gagosian et al., 1980). (Fig. 5) Assignment Structure The steranes (IX) and diasteranes (X) of Sections A taraxer-14-en-3 -ola LVIII 487-2-3 and 491-1-5 do not represent direct biological B olean-12-en-3-ol (/3-amyrin) LIX input but derive from an allochthonous thermally ma- _b urs-12-en-3-ol (α-amyrin) LX ture source (see the following). C ß,S-hopan-29-ol XVIIIp D hopan-3/3-ol or hopan-6α-ol?c LXI or LXII? E hydroxytriacontan-15 -one LXIIIa Triterpenoidal Components F /3|3-homohopan-31 -ol XVIIIr G hydroxydotriacontan-15-one LXIIIb Hopanoids H /3/3-bishomohopan-32-ol XVIIIs The majority of hopanoids in the two samples are b i3/3-trishomohopan-33-ol XVIIIt either direct bacterial inputs or diagenetic derivatives of a Assignment based on spectral interpretation by compari- bacterial lipids such as polyhydroxybacteriohopanes son with spectrum of taraxer-14-en-3-one (XLVII). (XVIIIw or x, De Rosa et al., 1971; Ourisson et al., ° Compounds present in minor amounts (< 1 ng/g for Sec- tion 487-2-3, <0.3 ng/g for Section 491-1-5). 1979; Dastillung et al., 1980a, 1980b; Rohmer et al., c 1980). In particular, extended hopanols and hopanoic Tentative assignments suggested by mass spectral com- parison with standard and literature spectra (Rohmer, acids have not been found in organisms; their occur- 1975), respectively. rence in sediments is attributed to oxidation of poly- hydroxybacteriohopanes, which are the only extended hopanoids found in biota (Ourisson et al., 1979). Hop- source appears probable in view of the fact that the 17(21)-ene (XIX) and neohop-13(18)-ene (XXI) have other triterpenes are all attributed to bacterial lipid been assigned as isomerization products of hop-22(29)- inputs. ene (XVIIIf) in the Paris Basin (Ensminger, 1977) and as direct terrigenous inputs from ferns in immature sedi- Perylene ments from the Japan Trench (Brassell et al., 1980c). The origin of perylene is uncertain (Wakeham et al., The recent recognition of hop-17(21)-ene and neohop- 1979, 1980a), but it appears to be an early-stage dia- (18)-ene in an anaerobic photosynthetic bacterium (Ho- genetic product formed in situ from unknown pre- ward, 1980) suggests that these compounds may repre- cursors. The source of such precursors, i.e. whether sent direct sediment inputs of bacterial lipids (Brassell et marine or terrestrial, is also unclear (Wakeham et al., al., 1981). By analogy, neohop-12-ene (XXIII) may also 1979, 1980a). be derived from bacteria (Brassell et al., 1981) rather than from ferns (Brassell et al., 1980c and references Summary therein). The C and C hopanoid ketones (XLVI and 27 29 The lipid markers in the sediments provide evidence L), like n-alkan-2-ones, may be products of microbial for inputs of organic matter from both autochthonous oxidation of the corresponding hydrocarbons (Dastil- and allochthonous sources (Table 9). The autochtho- lung et al., 1980a), further illustrating the importance of nous indicators include components characteristic of bacteria in influencing sedimentary lipid compositions. algae and bacteria and of bacterial reworking within the water column or sediment. The lipids of allochthonous origin include compounds derived from higher plants Nonhopanoids and inputs from a thermally mature source. The lack of Until recently the occurrence of fernenes (XX, XXII, full quantitative data for all compounds complicates the XXIV) in a sediment was thought to reflect terrestrial assessment of the relative size of autochthonous and inputs, since these triterpenes had only been recognized allochthonous lipid inputs. On balance, however, the in ferns (Wardroper, 1979; Brassell et al., 1980c). The dominance of higher straight-chain compounds derived discovery of fernenes in a bacterium (Howard, 1980), from terrestrial sources suggests that the major lipid in- however, casts doubt on this interpretation and suggests put to both samples is of terrigenous origin, assuming that they may be of microbial origin (Brassell et al., that the C22 to C26 w-alkanols are derived from higher 1981). The other nonhopanoid triterpenones (Table 6) plants. The lipid contributions from algae are of a simi- and triterpenols (Table 8) are all components of higher lar order of magnitude, greatly outweighing the bacte- plants (e.g., Devon and Scott, 1972) and may therefore rial and thermally mature allochthonous inputs. There represent terrigenous inputs to the samples (Brassell et are, however, significant differences between Sections al., 1980c). Similarly, the tetracyclic aliphatic and aro- 487-2-3 and 491-1-5 in the relative sizes of their four ma- matic hydrocarbons recognized in Sections 487-2-3 and jor sources of lipids (Table 9). 491-1-5 (Fig. 2 and Table 5) are of allochthonous, terrig- enous origin because they appear to be photochemical Diagenetic Assessment or microbially induced photomimetic products of higher The dominant lipids of both sediments are func- plant triterpenoids (Corbet et al., 1980). tionalized compounds, namely alcohols, ketones, and The unknown triterpenes found in Sections 487-2-3 carboxylic acids; for example, sterols are markedly and 491-1-5 are of uncertain origin, but a bacterial more abundant than other steroidal lipids. Such dis- 567 S. C. BRASSELL, G. EGLINTON, J. R. MAXWELL Table 9. Lipid markers in Sections 487-2-3 and 491-1-5 indicative of autochthonous and allochthonous sources of organic matter. Allochthonous Compound Autochthonous Structural Class Marine (nonbacterial) Bacteriala Terrestrial (higher plant) Rederived (thermally mature) (i) straight-chain n-alkenoic acids n-alkanes; n-alkanes n-alkanols? (n-alkan-2-ones) n-alkan-2-ones; n-alkenones: rt-alkanols?; hydroxyalkanones n-alkanoic acids (ii) branched-chain iso- and anteiso- iso- and anteiso- alkanols and alkanoic acids alkanes (iii) acyclic isoprenoids phytol 2,6,10,15,19-pentamethyleicosane and squalane (iv) nonisoprenoidal cyclics alkylcyclohexanes (v) cyclic diterpenoids fichtelite, simonellite, retene, and dehydro abietic acid (vi) unknown alkenes C25H44 and C30H52 components (vii) steroids many sterols and (sterenes) 24-ethylcholesteroids steranes and diasteranes 4-methylstanols; stanones and 4-methylstanones (viii) triterpenoids a) hopanoids extended hopanoids and hopanes α/3-hopanes (in part) b) nonhopanoids fernenes? fernenes? triterpenones and (tetracyclic aliphatic and triterpenols; tetracyclic aromatic hydrocarbons) aliphatic and aromatic hydrocarbons (ix) perylene a Components in parentheses are assigned as products of bacterial reworking rather than direct input of bacterial lipids. tributions are characteristic of immature sediments in Hop-22(29)-ene (XVIIIf) originates from a direct which diagenetic processes, other than microbial degra- autochthonous input and undergoes diagenetic isomeri- dation, have not occurred to a marked extent. The lipid zation to hop-21-ene (XXV) and thence to hop-17(21)- analysis of two shallow samples from different sites ene (XIX; Ensminger, 1977; Brassell et al., 1980c). The precludes an evaluation of diagenetic trends in the Mid- presence of hop-22(29)-ene and hop-21-ene in the sam- dle America Trench, but the extent of microbial degra- ples is an indication of their immaturity, since these dation of lipids and other early-stage transformations compounds disappear at an early stage of diagenesis can be assessed. (Brassell et al., 1980c). On the basis of their hop-22(29)- The presence of diunsaturated carboxylic acids in ene/hop-21-ene ratios, Section 491-1-5 appears to be Section 487-2-3 is an indication of sample immaturity, more mature than Section 487-2-3, but differences in the as such compounds usually undergo rapid microbial clay content of the sediment or other lithological char- breakdown in sediments (e.g., Matsuda and Koyama, acteristics may also influence their rates of isomeriza- 1977). The occurrence of alkenes varies among com- tion. In addition, the recent recognition of hop-17(21)- pound classes: several sterenes derived from sterol pre- ene and neohop-13(18)-ene (XXI) in a bacterium (How- cursors were present in both samples, whereas phytenes ard, 1980) means that hop-21-ene may in fact originate formed from dehydration of phytol or contributed as as both a direct biological input and an isomerization direct input from methanogens (Tornabene et al., 1979; product of hop-22(29)-ene. Although both samples con- Holzer et al., 1979) were only recognized as trace com- tained ster-2-enes (XII), no Δ4- or Δ5-sterenes nor dia- ponents in Section 491-1-5. No rt-alkenes were detected. sterenes were detected, indicating that no isomerization These differences in the occurrence of alkenes suggest of sterenes has yet occurred (cf. Rubinstein et al., 1975; that alcohol dehydration is a microbially mediated pro- Wardroper, 1979; Brassell, 1980). cess rather than a physicochemical reaction in this in- Aromatization, presumably microbial, of diterpe- stance. Sedimentary ketones can come from direct con- noids, steroids, and triterpenoids can occur at an early tributions of biological lipids (e.g., sterones) or be de- stage of diagenesis or, especialy for compounds derived rived from the oxidation of input of alkanes, acids, or from allochthonous sources, prior to sediment deposi- alcohols (e.g., hopanones). In some instances (e.g., n- tion. Whether the aromatic diterpenoids (simonellite, alkan-2-ones) these two different modes of origin can- XXX and retene, XXXI) and the aromatic tetracyclic not be distinguished on the basis of compound distribu- components derived from nonhopanoid triterpenoids tions. Overall, the ketones recognized in Sections 487- (XXXII-XXXVIII) are formed in situ or predeposition- 2-3 and 491-1-5 suggests that their in situ formation by ally cannot be resolved from the analysis of an individual microbial degradation is not a significant process, as il- shallow sediment. The aromatization of such com- lustrated by the disparity of hopanone and other hopan- pounds may be a continuing process in the sediments, oid distributions. however, in view of the presence of incompletely aro- 568 LIPID ANALYSES matized components (e.g., dehydroabietic acid, LXIV). samples suggests that their microbial populations may The presumed precursor of one of the major tetracyclic differ, although it may also simply reflect lipid preserva- aromatic components (XXXIV) and the C24H32 alkane tion. The few compounds present in greater amounts in (XXVIII), lupan-3-one (LXVI), was not detected in either Section 491-1-5 than in Section 487-2-3 include those sample, suggesting that the microbial degradation of its components that are derived largely from thermally ma- A ring and subsequent saturation or aromatization ture sources (e.g., w-heptadecane in 491-1-5) and certain (Corbet et al., 1980) is well advanced. In contrast, the aromatic components (e.g., retene) and several ketones minor amounts of steratrienes with aromatic A or B (e.g., 22,29,30-trisnorhopan-21-one) thought to derive rings (XIV or XV) found in the samples (Table 3) sug- from allochthonous sources. The greater relative pro- gest that their formation by microbial dehydrogenation portion of lipids derived from thermally mature sources or dehydroxylation (e.g., Gagosian and Farrington, in Section 491-1-5 may reflect its proximity to such 1978) may not be favored in these sediments or that it sources. Similarly, consideration of the geographical has not yet proceeded far. The aromatic hopanoids location of the two sites suggests that the trench slope thought to be products of microbial action on other ho- sample (Section 491-1-5) should possess a higher pro- panoids (Greiner et al., 1977; Ourisson et al., 1979) were portion of lipids of terrestrial origin, which it does in not detected in the samples, although they have been terms of their relative abundance, although their abso- recognized in other marine sediments (e.g., Tissier and lute concentration is often lower in Section 491-1-5 than Dastillung, 1978). These results may reflect differences in Section 487-2-3. in sedimentary microbial populations or overall sample The lithological characteristics of the samples may immaturity, since few of the microbial degradation also bear on the relative size of their lipid input from products of lipids are present in any abundance. autochthonous and allochthonous sources, since higher The majority of lipids in the sections therefore repre- plant material may be concentrated in coarser-grained sent direct biological inputs or microbial degradation sediment fractions (Thompson and Eglinton, 1978). products of such inputs (e.g., sterenes). The exceptions are those compounds (steranes, αß-hopanes, etc.) de- rived from thermally mature sources whose recognition Comparison with Japan Trench Samples in shallow, immature DSDP sediments necessitates an Although a detailed comparison of the lipids of Sec- evaluation of the possibility of shipboard core contami- tions 487-2-3 and 491-1-5 with those of Pleistocene sedi- nation from drilling lubricants, principally pipe dope ment from the Japan Trench (Brassell et al., 1980b, (Brassell and Eglinton, 1980; Thomson et al., in press 1980c; Brassell, 1980) is not presented here, the con- a). There are, however, significant differences between siderable similarity that exists between some of their the thermally mature components of Sections 487-2-3 lipid distributions is illustrated in Figure 6. In addition, and 491-1-5 and the hydrocarbons of pipe dope sampled Table 12 provides a general comparison between these during Leg 59 (Brassell and Eglinton, 1980). These dis- sediments in terms of the distributions of specific lipid similarities include the distributions of n-alkanes, alkyl- classes. Both suites of samples contain similar series of cyclohexanes, extended diterpanes (which are absent in lipids derived from autochthonous (algal and bacterial) Leg 66 samples), and steranes and the Cmax unresolved and allochthonous (higher plant) sources, although in- complex mixture of hydrocarbons. They suggest that evitably there are minor differences in their distribu- pipe dope is not the source of the thermally mature lip- tions (Table 12). The more significant discrepancies be- ids in Sections 487-2-3 and 491-1-5, although the uni- tween the lipid distributions appear to reflect the variety formity of its composition cannot be guaranteed. Hence of biological input represented (e.g., sterol distributions these allochthonous lipids appear to represent a natural, are more complex in Japan Trench sediments), the ex- rather than contaminant, input of reworked material, tent of diagenesis (e.g., diasterenes occur only in Japan perhaps derived from oil seeps. On the evidence of the Trench sediments), the presence or absence of hydrocar- distribution of w-alkanes assigned as a thermally mature bons from thermally mature sources (e.g., branched input in Section 491-1-5 it appears that the input is of alkanes in the Middle America Trench sediments), and, relatively unbiodegraded material. possibly, environmental conditions (e.g., alkenone dis- tributions). It is significant, however, that the differ- Sample Comparisons ences in lipid composition between Sections 487-2-3 and A summary of the qualitative differences and similar- 491-1-5 are as great (or as small) as those between Leg ities between the lipid compositions of Sections 487-2-3 66 and 56/57 samples. and 491-1-5 is given in Table 10. In quantitative terms, The resemblance between the lipid distributions of the lipid content of Section 487-2-3 is generally higher the Middle America and Japan Trench sediments prob- than that of Section 491-1-5 (Table 11); a difference that ably reflects a general similarity in their autochthonous is probably a function of sediment inputs or of lipid and allochthonous lipid input, their conditions of depo- preservation, as seen in Table 10. The larger amounts of sition (especially their microbial populations), and their autochthonous lipids in Section 487-2-3 may reflect the diagenetic processes. The greater relative size of the magnitude of such input and/or their better preserva- autochthonous inputs in the Japan Trench sediment tion. The discrepancy in the apparent size of input of (Brassell et al., 1980b, 1980c) is probably a function of bacterial lipids (e.g., branched alkanoic acids) to the water column productivity. 569 S. C. BRASSELL, G. EGLINTON, J. R. MAXWELL Table 10. Qualitative differences and similarities between the lipid compositions of Section 487-2-3 and 491-1-5. Comparison between Sections Lipid Class 487-2-3 and 491-1-5 Comments Straight-Chain rc-alkanes The proportion of short-chain difference arises from thermally mature components is greater in 491-1-5 (Fig. 1A) inputs in 491-1-5 π-alkan-2-ones similar (Fig. IB) n-alkanols similar (Fig. 1C) n-alkanoic acids short-chain components are more larger autochthonous inputs in 487-2-3 prominent in 487-2-3 (Fig. ID) alkenones similar (Fig. 3) alkenols detected only in 487-2-3 (Fig. 1C) better lipid preservation in 487-2-3? alkenoic acids greater range present and more abundant autochthonous input larger and better in 487-2-3 (Fig. ID) preserved in 487-2-3? hydroxyalkanones similar (Fig. 5) Branched-Chain alkanes more prominent in 491-1-5 than 487-2-3 occurrence reflects thermally mature inputs alkanols similar (Fig. 1C) alkanoic acids short-chain homologues are more differences reflect greater autoch- abundant in 487-2-3, higher homologues thonous and terrigenous inputs, were found only in 491-1-5 respectively Acyclic Isoprenoids alkanes similar, except for the coeluting C25 differences may reflect variations in component in 487-2-3 (Fig. 1A) methanogen populations ketone 6,10,14-trimethylpentadecan-2-one is greater allochthonous input to or poor relatively more abundant in 491-1-5 lipid preservation in 491-1-5? (Fig. IB) alcohols similar, except that dihydrophytol was autochthonous inputs may differ recognized only in 487-2-3 (Fig. 1C) Nonisoprenoid Cyclics alkylcyclohexanes detected only in 491-1-5 components originate from thermally mature input Cyclic Diterpenoids alkane fichtelite was detected only in 487-2-3 feature of differences in allochthonous lipid input or lipid preservation? aromatic simonellite and retene are more abundant greater allochthonous input in 491-1-5 hydrocarbons in 491-1-5 acid dehydroabietic acid was recognized only better preservation of unaltered lipids in 487-2-3 in 487-2-3 Unknown Cyclics alkenes C25H44 and C30H52 components were autochthonous inputs more prominent observed only in 487-2-3 in 487-2-3 Steroids alkanes distributions differ in the relative size of components derive from separate input their C29 components and diasteranes of thermally mature lipids to each sample alkenes similar distributions except steratrienes sterenes may originate from different and stera-3,5-dienes are more abundant in sources or reflect variability 487-2-3 and 491-1-5, respectively (Table 3) in diagenesis. ketones similar alcohols similar, but 5α-stanols and C29Δ sources of sterols differ, in part components are more prominent in 491-1-5 (Fig. 4) Hopanoid Triterpenoids 491-1-5 contains a higher abundance of thermally mature inputs are greater in alkanes αß-hopanes, distributions are otherwise 491-1-5 similar (Table 4) similar, except for the prominence of autochthonous input or bacterial alkenes hop-22(29)-ene in 487-2-3 (Table 4) populations differ, or lipids of 491-1-5 are diagenetically more mature dissimilar; 22,29,30-trisnorhop-21-one, the greater allochthonous input to, or ketones major component of 491-1-5 was not poorer lipid preservation in, 491-1-5? detected in 487-2-3 (Table 6) similar, except for the absence of minor differences in autochthonous alcohols component D in 487-2-3 (Fig. 5) inputs similar acids Nonhopanoid Triterpenoids and Derivatives alkanes/alkenes fernenes are more prominent in 491-1-5 greater allochthonous inputs to tetracyclic alkanes and alkenes are 491-1-5, or different bacterial similar (Fig. 2) populations aromatic hydrocarbons similar (Table 5) ketones similar, except for the presence of reflects differences in lipid inputs or glutenone in 487-2-3 (Table 6) preservation? alcohols taraxerol is more prominent in 491-1-5 reflects differences in lipid inputs or (Fig. 5) preservation? Other perylene perylene is much more abundant in In 491-1-5 perylene precursors are 491-1-5 more abundant or depositional conditions are more favorable for perylene formation 570 LIPID ANALYSES Table 11. Quantitative comparisons of lipid compositions of Sections Ballantine, J. A., Lavis, A., and Morris, R. J., 1979. Sterols of the 487-2-3 and 491-1-5. phytoplankton-effects of illumination and growth stage. Phyto- chemistry, 18:1459-1466. Concentrations (ng/g)a Ballantine, J. A., Lavis, A., Roberts, J. C, et al., 1977. Marine Section 487-2-3/491-1-5 sterols V. Sterols of some tunicata. The occurrence of saturated Compound (structure) 487-2-3 491-1-5 Ratio ring sterols in these filter-feeding organisms. J. Exper. Mar. Biol. π-heptadecane 1.5 3 0.5 Ecol., 30:29-44. π-nonacosane 3.4 13 2.6 π-nonacosan-2-one 3 0.5 6 Barnes, P. J., Brassell, S. C, Comet, P. A., et al., 1979. Preliminary rt-tetradecanol 100 21 4.8 lipid analyses of core sections 18, 24, and 30 from Hole 402A. 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Thomson, I. D., Brassell, S. C, Eglinton, G., et al., in press b. Pre- Wardroper, A.M.K., Maxwell, J.R., and Morris, R. J., 1978. Sterols liminary lipid analyses of Section 481-2-2. In Curray, J. R., of a diatomaceous ooze with Walvis Bay. Steroids, 32:203-221. Moore, D. G., et al., Init. Repts. DSDP, 64: Washington (U.S. Withers, N. W., Kokke, W.C.M.C., Rohmer, M., et al.,1979. Isola- Govt. Printing Office). tion of sterols with cyclopropyl-containing side chains from the Thompson, S., and Eglinton, G., 1978. The fractionation of a Recent cultured marine alga Peridinium fociaceum. Tetrahedron Lett., sediment for organic geochemical analysis. Geochim. Cosmochim. 3605-3608. Acta, 42:199-207. Withers, N.W., Tuttle, R.C., Holz, G.G., etal., 1978. Dehydrodino- Tissier, M. J., and Dastillung, M., 1978. Inventaire et dynamique des sterol, dinosterone and related sterols of a non-photosynthetic lipides à 1'interface eau de mar-sediment V. Hydrocarbures poly- dinoflagellate, Crypthecodinium cohnii. Phytochemistry, 17:1987- aromatiques des sediments, de l'eau de mer et de l'eau intersti- 1989. 573 S. C. BRASSELL, G. EGLINTON, J. R. MAXWELL 50 440B-3-5 440B-3-5 440B-3-5 ..Illlllll 1 11.1 34 487-2-3 ,1 3.5 491-1-5 487-2-3 _ mill 11 I 1 1 II 15 20 25 30 ABC A BCDEFG H Carbon No. 390 440B-3-5 Ph 190 | Λ 440B-3-5 • 1. | 100 487-2-3 111, 48 487-2-3 Ph π 1 1 I.I.I I 1 • . • 15 .1, 30 AB CDEF GH 20 25 Carbon No. Figure 6. Comparison of lipid distributions of Quaternary Middle America and Japan Trench sediments. A. Concentrations (ng/g dry sediment) of «-alkanes in Sections 440B-3-5 and 487-2-3. B. Concentrations (ng/g dry sediment) of fernenes in Sections 440B-3-5 and 491-1-5. (A = fern-8-ene (XX); B = fern-9(ll)-ene (XXII); C = fern-7-ene (XXIV).) C. Concentrations (ng/g dry sediment) of C24 tetracyclic alkanes/alkenes, assigned as ring A degraded triterpenoids in Sections 440B-3-5 and 487-2-3. Formulae as in Figure 2. D. Concentrations (ng/g dry sediment) of alkadienones (solid bar) and alkatrienones (open bars) in Sections 440B-3-5 and 487-2-3. (A = heptatriaconta-8,15,22-trien-2-one (XLa); B = heptatriaconta-15,22-dien-2-one (XLIa); C = octatriaconta-9,16,23-trien-3-one (XLb); D = octatriaconta-9,16,23-trien-2-one (XLc); E = octatriaconta-16,23-dien-3-one (XLIb); F = octatriaconta-16,23-dien-2- one (XLIc); G = nonatriaconta-10,17,24-trien-3-one (XLd); H nonatriaconta-17,24-dien-3-one (XLId). The peak lettering differs from that of Fig. 3. E. Concentrations (ng/g dry sediment) of /j-alkanols and phytol in Sections 440B-3-5 and 487-2-3. (ph = phytol [open bar].) 574 LIPID ANALYSES Table 12. Qualitative differences and similarities between selected lipid distributions of Japan and Middle America Trench sediments. Lipid Structural Comparison between Middle America (Leg 66) and Class Japan (Legs 56/57) Trench Sedimentsa Comments on Differences straight-chain distributions of alkanes, alkan-2-ones, alkanols, alkenones may differ because of environmental conditions alkanoic acids, alkenols and alkenoic acids or diagenetic effects generally similar (Fig. 6); alkadienone/alkatrienone ratios much higher in Leg 66 (Fig. 6) branched-chain distributions of alkanols and alkanoic acids alkanes of Legs 56/57 are direct biological inputs; those similar; range of alkanes greater in Leg 66 of Leg 66 come from a thermally mature source acyclic isoprenoid distributions of alkanes, alkanones, and alcohols phytol diagenesis may be more advanced in Legs 56/57 similar; phytenes more abundant in Legs 56/57 or phytenes may reflect lipid inputs from methanogens cyclic diterpenoid distributions of acids similar; range of alkanes and inputs may be similar, but the extent of diagenetic aromatic diterpenoids greater in Legs 56/57 alteration varies steroids range of sterols and sterenes greater in Legs 56/57, a greater diversity of marine organisms (e.g., diatoms) although relative abundance of common may contribute sterols and thence their diagenetic components are similar; diasterenes only present products to Legs 56/57, which are also diagenetically in Legs 56/57; sterane distributions differ more mature, except in comparison to the thermally mature steranes of Leg 66 triterpenoids-hopanoid alkane, alkene, alkanol, and alkanoic acid minor differences reflect diagenetic discrepancies distributions generally similar; range of alkanones greater in Legs 56/57 nonhopanoid fernene distributions similar (Fig. 6), as are ranges minor differences reflect variations in sediment inputs of higher plant triterpenones, triterpenols, and and/or diagenetic processes their tetracyclic alkane, alkene, and aromatic derivatives (Fig. 6) Sections 487-2-3 and 491-1-5 of Middle America Trench (this chapter), Sections 440-5-6, 440A-7-6, 440B-3-5, and 440B-8-4 of Japan Trench (Brassell et al., 1980b, 1980c; Brassell, 1980; Brassell et al., 1981). 575 S. C. BRASSELL, G. EGLINTON, J. R. MAXWELL APPENDIX Compound Structures IV V VII XIII R= 576 LIPID ANALYSES R XVI XVII XVIII R = OH ,YY o OH OH OH OH OH r XXIV XXV XXVII 577 S. C. BRASSELL, G. EGLINTON, J. R. MAXWELL XXVIII XXIX XXX R n a H 4 bCH3 4 c H 5 dCH3 5 XLI 578 LIPID ANALYSES rrr " 579 S. C. BRASSELL, G. EGLINTON, J. R. MAXWELL LXIV LXIII an=11 bn=13 LXV LXVI LXV 11 LXVIII LXIX HO 580