Chapter 4: Paleoplant Communities in New Zealand Coal Swamps As Revealed by Terpenoid Hydrocarbons

CHAPTER 4: PALEOPLANT COMMUNITIES IN NEW ZEALAND COAL SWAMPS AS REVEALED BY TERPENOID HYDROCARBONS

Both results presented in the previous chapter and in the publications of KILLOPS ET AL.

(1995; 2003), WESTON ET AL. (1988; 1989), WOOLHOUSE ET AL. (1992), BLUNT ET AL. (1988), ALEXANDER ET

AL. (1983B), NOBLE ET AL. (1985) have demonstrated that the organic matter of New Zealand coals consists of mostly higher land-plant material with additional bacterial biomass. In order to build a more detailed insight into the occurrences of angiosperms and gymnosperms surrounding the coal swamps, this chapter presents results on the composition and occurrences of sesquiterpanes and sesterterpanes, diterpanes and triterpanes.

The relative contribution of angiosperms and gymnosperms has been evaluated by the ratio of diterpenoids to non-hopanoid triterpenoids biomarkers in the aliphatic and aromatic fractions as established by BECHTEL ET AL. (2002). This ratio was then modified and denoted as di-/ (di- plus triterpenoids) ratio that is defined as the concentration of saturated plus aromatic diterpenoids divided by the sum concentration of diterpenoids plus angiosperm-derived triterpenoids (BECHTEL ET AL., 2005). Recently, the angiosperm-gymnosperm aromatic ratio (AGAR), that is the proportion of aromatic diterpenoids in the sum of aromatic di- plus triterpenoids, has been established to investigate the plant communities in the Mallik site, a gas hydrate production research well in Mackenzie Delte, Canada by HABERER ET AL. (2006). It means that either both the aliphatic and aromatic biomarkers or only the aromatic ones were considered to estimate the relative contribution of angiosperms and gymnosperms into organic matter. The plant communities of the New Zealand coals in this study were observed using both di-/ (di-plus triterpenoids) and AGAR ratios.

90 4.1 SESQUI- AND SESTERTERPENOID HYDROCARBONS

Aliphatic sesquiterpenoid hydrocarbons

The identification of aliphatic sesquiterpanes in this study was mostly based on the published mass spectra of PHILP (1985), which shows that they include mostly C14- C16 bicyclic sesquiterpanes [S1, S2, S7; FIGURE 4-1; TABLE 4-1]. Their appearances are indicative of higher plants contributing to the organic matter of the studied coals. Furthermore, 4α(H)- and 4ß(H)- eudesmane [S3, S4; FIGURE 4-1 TABLE 4-1] were also detected: ALEXANDER ET AL. (1983B) have shown that these compounds were found in sediments with a significant contribution of terrigenous source material and undoubtedly reflect their higher plant origins. The content of total higher plant sesquiterpanes was calculated, and shown to fall in the range from 2 to 25 µg/g TOC

(TABLE 4-2). There were some samples with a high abundance of sesquiterpanes, e.g. G001989, G001990, G002585, G002587 (West Coast Basin) and G001994 (Taranaki Basin). One specific sample (G002611, Eastern Southland) had a particularly high concentration of C15 bicyclic compounds (c.a. 40 µg/gTOC), this being the only detectable sesquiterpane.

Additionally, 8α(H)- and 8ß(H)-drimanes [S5-S6; FIGURE 4-1; TABLE 4-1] were found, possibly associated with a microbial contribution in New Zealand coals. In this regard,

ALEXANDER ET AL. (1983B) reported that 8ß(H)-drimane was found both in all sixteen worldwide crude oils. These oils range from Cambrian to Tertiary and represent a wide-varying types, and bitumen extracts from drill-hole cuttings of wells in Carnarvon and Canning basins (W. Australia; varying in age from Ordovician to Early Cretaceous and spanning a wide range of maturity levels) whereas the 8α(H)-drimane was present in undetectable amounts. The widespread geological and geographical occurrence of 8ß(H)-drimane suggests its ubiquitous source. Additionally, this compound was also found in Cambrian-Ordovician samples, where land plant input was absent, rules out the possibility of its being derived from higher plant precursors. Because of that, the authors concluded that 8ß(H)-drimane is most likely of microbial origin. The microbial degradation of higher terpenes such as hopanes, or from direct formation of a compound or compounds containing the bicyclic ring system was suggested as the possible precursor of these compounds. Even so, it does not exclude the possible origin from land plants for 8α(H)- and 8ß(H)-drimanes that are also found in young sediments, like the investigated samples are (C.F. PHILP, 1994). In fact, ALEXANDER ET AL. (1984) have also shown

91 ISD 100 D9 G002590-West Coast

Rank(Sr) = 7.4 Late Eocene 75

D6 50

D13 25 S8

S7 D1 S6 { D2 D3 S2 S1 0 30 35 40 45 50 55 60 65 70

D9 100 G001990- West Coast

Rank(Sr) = 10.8

Relative Abundance Relative Late Cretaceous 75

50 ISD

25 D2 20 C

0 30 35 40 45 50 55 60 65 70 75 Time (min) Figure 4-1: GC/MS chromatograms (m/z 123) of representative aliphatic fractions of samples G002590 (upper) and G001990 (below) originated from West Coast basin. Compound names are listed in Table 4-1.

Table 4-1: The sesqui- and sesterterpenoid hydrocarbon biomarkers found in aliphatic and aromatic fractions from extractabl e organic matters of New Zealand coals

Peak N0 Aliphatic Compounds Formular Mol. W. References (m/z 123) S C bicyclic sesquiterpane C H 194 1 14 14 26 Philp, 1985 S2 C15 bicyclic sesquiterpane C15H28 208

S3 4α(H)-eudesmane C15H28 208 S 4ß(H)-eudesmane C H 208 4 15 28 Alexander et al., 1983b S5 8α(H)-drimane C15H28 208

S6 8ß(H)-drimane C15H28 208 S C bicyclic sesquiterpane C H 222 7 16 16 30 Philp, 1985 S8 Des-A-lupane C24H42 330

Peak N0 Aromatic Compounds Formular Mol. W References

S9 5,6,7,8-tetrahydrocadalene C15H22 202 Wang & Simoneit, 1991; S10 Calamene C15H22 202 Weston et al., 1989; Philp, 1985 S11 Cadalene C15H18 198

92 Table 4-2: The concentrations of aliphatic and aromatic sesqui-, sester-, di- and triterpenoid hydrocarbon biomarkers (µg/g TOC) originated

from micro-organisms, higher land plants (gymnosperms, angiosperms, or not specific). The relative contribution of gymnosperms and

angiosperms are shown. Higher land plant Gymnosperms/ Microorganisms Gymnosperms Angiosperms (not specific) Angiosperms Samples Rank(Sr) Ali.Sesq. Aro.Tri. Hopanoids Ali.Sesq. Aro.Sesq. Ali.Sest. Ali.Di. Aro.Di. Ali.Tri. Aro.Tri. AGAR di/(di+tri)

G001985 0 -- 37.7 166.32 ------1.0 -- -- 37.7 -- 0.03 G001988 0 -- 49.2 119.25 ------4.8 -- -- 49.2 -- 0.09 G001979 0.1 -- 382.8 330.94 ------0.6 -- -- 382.8 -- 0.00 G001987 0.4 -- 78.9 288.17 ------2.1 0.5 -- 78.5 0.01 0.03 G001986 0.6 -- 50.8 200.54 ------50.8 -- -- G001976 1.6 -- 864.9 84.77 ------4.8 4.6 -- 860.4 0.01 0.01 G001978 3 -- 696.7 112.87 ------87.6 28.8 -- 667.9 0.04 0.15 G001975 3.4 -- 740.4 180.75 ------99.8 43.0 7.3 697.4 0.06 0.17 G001983 4.7 -- 615.2 19.12 ------20.6 40.6 27.7 574.6 0.07 0.09 G001977 5.4 -- 615.3 16.58 ------54.1 36.0 44.7 579.3 0.06 0.13 G001982 5.6 -- 90.2 60.63 ------7.7 33.9 82.5 0.09 0.06 G001984 6.1 0.7 465.7 22.20 0.5 -- -- 4.8 30.4 37.8 435.3 0.07 0.07 G001981 6.6 -- 719.8 31.22 ------29.9 55.2 11.2 664.7 0.08 0.11 G001992 6.9 -- 182.4 30.39 ------5.0 -- 7.7 182.4 -- 0.03 G001980 7 0.3 333.3 52.89 2.1 -- -- 17.4 51.2 35.4 282.1 0.15 0.18 G001989 11.6 -- 115.4 157.70 22.7 -- -- 18.1 28.4 -- 87.0 0.25 0.35 G001990 10.8 -- 155.0 94.38 13.7 -- -- 260.4 -- -- 155.0 -- 0.63 G001993 10.1 1.9 79.9 68.17 10.4 -- -- 19.3 21.3 -- 58.6 0.27 0.41 G001995 7.4 -- 249.8 28.68 -- 3.2 -- 7.7 38.8 -- 207.9 0.16 0.18 G001996 8.3 1.3 266.0 71.97 4.4 -- -- 10.5 69.7 -- 196.3 0.26 0.29 G001997 7.8 -- 211.5 39.03 2.7 -- -- 10.3 42.0 7.0 169.6 0.20 0.23 G001991 11.8 2.5 47.9 144.70 16.6 -- -- 1.6 -- -- 47.9 -- 0.03 G001994 9.5 1.0 431.2 81.62 5.0 -- -- 12.4 55.8 -- 375.4 0.13 0.15

Table 4-2 (continue)

Higher land plant Gymnosperms/ Microorganisms Gymnosperms Angiosperms (not specific) Angiosperms Samples Rank(Sr) Ali.Sesq. Aro.Tri. Hopanoids Ali.Sesq. Aro.Sesq. Ali.Sest. Ali.Di. Aro.Di. Ali.Tri. Aro.Tri. AGAR di/(di+tri)

G002610 1.6 -- 1801.9 42.51 4.5 2.3 1.0 4.2 66.8 5.6 1732.7 0.04 0.04 G002611 1.7 -- 267.4 23.77 40.6 2.5 1.4 4.3 44.7 4.3 220.1 0.17 0.18 G002595 2.2 -- 1026.4 281.77 -- 7.0 0.9 2.6 19.5 -- 999.9 0.02 0.02 G002600 2.3 -- 2131.8 87.97 -- 9.9 -- -- 64.1 -- 2057.8 0.03 0.03 G002596 2.5 -- 2372.5 409.04 ------619.9 -- 1752.6 0.26 0.26 G002570 5.3 -- 925.6 102.69 -- -- 1.3 20.7 30.4 70.6 895.2 0.03 0.05 G002580 5.6 0.7 1475.8 61.40 3.0 3.5 1.4 11.7 43.1 74.3 1429.1 0.03 0.04 G002573 5.7 -- 959.8 115.52 -- -- 1.9 18.1 39.8 179.2 920.0 0.04 0.05 G002582 6.4 -- 1467.0 58.77 4.0 -- 2.0 3.6 138.7 80.7 1328.3 0.09 0.09 G002590 7.4 0.8 703.0 44.68 2.0 -- 2.1 27.3 208.0 14.1 495.1 0.30 0.32 G002606 7.5 -- 222.3 64.41 ------155.7 51.3 -- 171.0 0.23 0.55 G002604 8.0 -- 960.4 83.00 -- 4.3 -- 4943.7 476.9 -- 479.2 0.50 0.92 G002592 10.3 -- 520.1 205.59 ------2874.4 186.8 -- 333.3 0.36 0.90 G002587 10.5 3.9 78.2 167.08 26.3 -- 2.9 11.1 21.8 -- 56.4 0.28 0.37 G002585 10.6 3.0 114.2 97.96 20.3 -- -- 7.2 22.6 -- 91.6 0.20 0.25

Note: Ali.Sesq. - Aliphatic sesquiterpanes Aro.Di. - Aromatic diterpanes AGAR - Angiosperm-Gymnosperm Aromatic Ratio (c.f. Haberer et al., 2006) Aro.Sesq. - Aromatic sesquiterpanes Ali.Tri. - Aliphatic triterpanes di/(di+tri) - diterpenoids/(diterpenoids+triterpenoids) (c.f. Bechtel et al., 2005) Ali.Sest. - Aliphatic sesterterpanes Aro.Tri. - Aromatic triterpanes Ali.Di. - Aliphatic diterpanes

94 that in certain cases there was a similarity between the distributions of the hopanes and the dirmanes supporting the idea that these sesquiterpanes may indeed be derived from the hopanes and formed via a microbial mechanism. The concentrations of 8α(H)- and 8ß(H)- drimanes were calculated, which were around 1 to 4 µg/g TOC (FIGURE 3-15 IN CHAPTER 3; TABLE

4-2). They were detected mainly in samples from the Waikato (Eocene-Oligocene), West Coast (Eocene) and Taranaki (Late Cretaceous- Eocene) basins. There is only one sample

G001984- Waikato basin (Rank(Sr) ~ 6; R0% ~ 0.45) having both 8α(H)- and 8ß(H)-drimane, others which have Rank(Sr) higher than 6 just contain 8ß(H)- drimane. It implies that 8α(H)- and 8ß(H)-drimane occurrences depend on not only the maturity but might also on the varying organofacies. This supports the research of WESTON ET AL. (1989) who pointed out that the less stable 8α(H)-epimers were almost completely converted to the 8ß(H)-isomers before the onset of oil generation, which means vitrinite reflectance is around 0.5%.

Aromatic sesquiterpenoid hydrocarbons

Aromatic sesquiterpanes were found in some samples from Waikato, Eastern

Southland and Central Otago basins. They were calamene [S10], cadalene [S11], and 5,6,7,8- tetrahydrocadalene [S9] (TABLE 4-1 AND TABLE 4-2), their total contents making up to 8 µg/g TOC. Cadalene and some related sesquiterpenoids have been known as the common constituents of conifer resins (WANG AND SIMONEIT, 1990; OTTO AND WILDE, 2001). According to the authors, cadalene and its congeners are found in Pinaceae, Cupressaceae s. str., Taxodiaceae and Podocarpaceae species, i.e. families of gymnosperms. However, it is reported that aromatic sesquiterpenoids could also be found in recent dammar resin, obtained from trees of the angiosperm family Dipterocarpaceae (VAN AARSSEN ET AL., 1990). For that, the detected aromatic sesquiterpenoids even present in minor amount appear to signal higher plant source input, with no specificity for gymnosperms or angiosperms, for the New Zealand coals.

Aliphatic sesterterpanoid hydrocarbons

Des-A-lupane (C24) was the only identifiable sesterterpane in the New Zealand coal, its content built up to c.a. 3 (µg/g TOC). This compound was found in G002570, G002573, G002580, G002582 (Waikato), G002587, G002590 (West Coast) and G002610, G002611

(Eastern Southland) (FIGURE 4-1; TABLE 4-1 AND TABLE 4-2). Similarly, this compound has also been found in a number of terrestrial oils (WOOLHOUSE ET AL., 1992) as well as in the Tertiary angiospermous lignite (STOUT, 1992). The des-A triterpenoid hydrocarbons are believed to be originally derived from the various (C3) functionalized triterpenoid precursors present in the plant via oxidative processes during early diagenesis. These compounds might be generated by microorganisms through biochemical reactions where the exciting-state 3-ketones are formed either by energy transfer or by oxidation of the 3-alcohol. TRENDEL ET AL. (1989) AND

STOUT (1992) have stated that the presence of this compound not only testifies to the input of angiospermous organic matter but also tends to confirm the loss of ring A as a common transformation pathway of higher plant triterpenoids (this pathway will be described in more detail in SECTION 4.3). Hence, in this study the occurrence of Des-A-lupane (C24), even in small amounts, still indicates higher plant source input, i.e. angiosperms, for these mentioned samples

4.2 DITERPENOID HYDROCARBONS

Aliphatic diterpenoid hydrocarbons

Tri- and tetracyclic aliphatic diterpanes with 19 or 20 carbon atoms have been identified by their key fragment ion m/z 123 from GC-MS analysis (FIGURE 4-1). They have long been known to be associated with resins and leaf waxes from higher plants, typically occurring in gymnosperms, mainly conifers (THOMAS, 1969). Nevertheless, diterpenoids have also been detected in bryophytes, pteridophytes and angiosperms, albeit in smaller amounts

(PETERS AND MOLDOWAN, 1993; OTTO AND WILDE, 2001). These compounds have been found in many oils and source rocks which are known to contain higher plant material from countries such as

Australia, New Zealand, Taiwan, Germany, Philippines, Israel, Canada (NOBLE ET AL., 1985;

SIMONEIT ET AL., 1986; BLUNT ET AL., 1988; WESTON ET AL., 1989; OTTO ET AL., 1997).

TABLE 4-3 shows the aliphatic diterpanes which are identified in this study. Their identifications were based on previous publications such as TUO & PHILP, (2005); BLUNT ET AL.,

(1988); NOBLE ET AL., (1985, 1986) AND PHILP, (1985). The peak named as D6 was a co-elution of n-C20 with C20-diterpane (C.F. PHILP, 1985; P.153; MASS SPECTRA N0.166) that could be tentatively identified as pimarane in this study (FIGURE 4-1). There were also some unidentifiable compounds showing as significant peaks in the m/z 123 ion trace.

Total aliphatic diterpane concentrations vary from 0.5 to 50 (µg/g TOC) and are given in TABLE 4-2. Aliphatic diterpenoids appear in lower content and diversity in samples from the Northland and Central Otago basins than in other basins. On the contrary, there were two samples from Eastern Southland (G002604; G002606) and two samples from West Coast basin (G001990; G002592) that had particularly high content of total aliphatic diterpenoid, which interestingly due to an unusual predominance of isopimarane, and these four samples are Late-Cretaceous. The isopimarane contribution as much as 85- 98% of the total aliphatic diterpenoid contents in some cases. This finding corroborates earlier studies of New Zealand coals (BLUNT ET AL., 1988; WESTON ET AL., 1989; NOBLE ET AL., 1986 AND KILLOPS ET AL., 1995). They showed that isopimarane is the major diterpane occurring in some New Zealand oils and coals, e.g. oil from West coast and Taranaki basins. This outstanding abundance of a single diterpane suggests a specific higher plant source contributing to the sediment or a broad distribution of this diterpane in higher plants. According to OTTO AND WILDE (2001) isopimarane is a common constituent and is found in all families of conifers.

Table 4-3: The identified gymnosperm hydrocarbon biomarkers found in aliphatic and

aromatic fractions from extractable organic matters of New Zealand coals

Peak N0 Aliphatic compounds Formular Mol. W. References (m/z 123)

D1 C18-Diterpane C18H32 248 Philp, 1985

D2 4ß (H)-19-Norisopimarane C19H34 262 Noble et al., 1986

D3 4α (H)-18-Norpimarane C19H34 262 Philp, 1985; Tuo & Philp, 2005

D4 C19-Diterpane C19H34 262 Philp, 1985

D5 C19- tricyclicterpane C19H34 262 Philp, 1985- p.155

D6 C20 & C20-Diterpane or Pimarane C20H36 276 Philp, 1985; Tuo & Philp, 2005

D7 ent-Beyerane C20H34 274 Noble et al., 1985

D8 Norabietane C19H34 262 Philp, 1985

D9 Isopimarane C20H36 276 Blunt et al., 1988

ISD 5α-Androstane C19H32 260 Internal standard

D10 16ß(H)-Phyllocladane C20H34 274 Noble et al., 1985

D11 Abietane C20H36 276 Philp, 1985

D12 ent-16ß(H)-Kaurane C20H34 274

D13 16α(H)-Phyllocladane C20H34 274 Noble et al., 1985

D14 ent-16α(H)-Kaurane C20H34 274

Peak N0 Aromatic compounds Formular Mol. W. References

DI 18-norabieta-8,11,13-triene C19H28 256 Simoneit, 1977 DII 19-norabieta-8,11,13-triene C19H28 256

DIII 19- norabieta-3,8,11,13-tetraene C19H26 254 Philp, 1985

DIV 1-3,13-dimethylpodocarpa-8,11,13-triene C19H28 256 Wang & Simoneit, 1991

DV Dehydroabietane C20H30 270 Philp, 1985 D Simonellite CH Wakeham et al., 1980a; Tuo & VI 19 24 252 Philp, 2005

DVII 1,2,3,4-tetrahydroretene C18H22 238 Philp, 1985

DVIII Totarane C19H24 252 Tuo & Philp, 2005 DIX Semperivrane C19H24 252

DX Retene C18H18 234 Philp, 1985 ISTD Ethylpyrene Internal standard

Tetracyclic diterpanes (e.g. ent-beyerane, 16ß(H)-phyllocladane, 16α(H)- phyllocladane, ent-16α(H)-kaurane, ent-16ß(H)-kaurane) are the main compounds in aliphatic diterpanes in some case, e.g. G001981, G001982- Waikato (Eocene-Oligocene), G002590-

West Coast (Late Eocene) and G002606- Eastern Southland (Late Cretaceous) basins (FIGURE

4-1 AND TABLE 4-2). GC-MS analysis shows a base peak of m/z 123 and a molecular ion of m/z 274 for each compound. They were distinguished by comparison with mass spectral data previously reported by NOBLE ET AL. (1985). It is known that tetracyclic diterpanes originated from higher plant diterpenoids, which are found in leaf waxes of conifers, by diagenetic removal of their functional groups. Phylocladanes are frequently described in Podocarpus and Dacrydium genera (Podocarpaceae family), beyeranes are found in a few species of Cupressaceae s.str., Podocarpaceae and Araucariaceae, while kauranes are present in most conifer families (OTTO AND WILDE, 2001).

Briefly, it can be said that the appearance of aliphatic diterpanes not only indicates gymnosperms contributing as a part of the organic matter in New Zealand coals, but also give names of some possible conifer families, such as Podocarpaceae, Cupressaceae, Araucariaceae.

Aromatic diterpane hydrocarbons

Ten aromatic diterpane hydrocarbons belonging to the abietane group were detected

(TABLE 4-3 AND FIGURE 4-2). Most could be identified by comparison with the published results of

WAKEHAM ET AL. (1980A), PHILP (1985), WANG AND SIMONEIT (1991), OTTO ET AL. (1997) AND TUO AND PHILP

(2005).

100 G002595- Central Otago ISTD Rank(Sr) 2.2

25 VIII

S11 D DIX DX DV

0 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70

DX 100 G002596- Central Otago

Rank(Sr) 2.5 Relative Abundance Retene 75

ISTD VIII D 25

VI VII DIX D D

0 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 Time (m) Figure 4-2: GC/MS chromatograms (TIC) of sester-, ditriterpenoid aromatic hydrocarbons found in sample G002595 (upper) and G002596 (below) originated from Central Otago basin. Compound names are listed in Table 4-1.

Simonellite [DVI], totarane [DVIII] and semperivrane [DIX] having a similar mass spectra, with molecular ion of m/z 252 and base peak at m/z 237, were differentiated using the publication of TUO AND PHILP (2005). These compounds were found in predominant contributions. OTTO ET AL. (1997) suggested that totarol might be degraded by microbial or diagenetic processes to the proposed diaromatic structure of totarane. Totarol is abundant in

100 the resins of Taxodiaceae, Cupressaceae and Podocarpaceae, and may be used as the taxonomical marker for these conifer families (OTTO ET AL., 1997 AND REFERENCES THEREIN). The concentrations of total diterpenoid aromatics as a function of rank were illustrated in

FIGURE 4-3, which does not show any clear trend with increasing maturity. Samples from Northland basin (Pleistocene) had very low content of diterpenoid aromatics, their concentrations were just around 0.5µg/g TOC. In contrast, there were two samples with extremely high diterpenoid aromatic contents, one sample from Central Otago (G002596- Tertiary; ~ 600 µg/g TOC) and one from Eastern Southland basin (G002604-Late Cretaceous; ~ 480 µg/g TOC). Both of them have retene concentration up to 320- 330 µg/g TOC.

800 Northland Eastern Southland Waikato West Coast G002596 Taranaki Central Otago 600

G002604

400 omatics (µg/gTOC) omatics r penoid A r 200 Dite

0 04812 Rank (Sr)

Figure 4-3: Concentration of total gymnosperm aromatic biomarkers found in New Zealand coals presented as function of maturity. Sample G002596 (Central Otago) and G002604 (Eastern Southland) have significant diterpenoid aromatics due to the high content of retene.

101

It is well known that these identified aromatic diterpenoid hydrocarbons originate mainly from abietic acid as well as from pimaric acid which have been found in Podocarpaceae, Cupressaceae, Taxodiaceae, Pinanceae, and Araucariaceae conifer resin species. The degradation of abietic and pimaric acids has been studied and their diagenetic pathways have been suggested (SIMONEIT, 1977; SIMONEIT ET AL., 1986; LAFLAMME AND HITES, 1979;

WAKEHAM ET AL., 1980A; OTTO ET AL., 1997; OTTO & WILDE, 2001; OTTO AND SIMONEIT, 2001; 2002; TUO

AND PHILP, 2005). Various natural product abietenes and pimarenes undergo successive aromatization with minor reduction that is illutrated in FIGURE 4-4. It shows in this figure that tricyclic diterpenoids are transformed to phenanthrenes in several steps via the formation of simonellite and retene. Thus, the high contributions of retene as well as simonellite in immature samples confirm the occurrence of aromatization starting at the early stages of diagenesis. The rate governed by microbial activity and abiotic processes such as clay and acid catalysis (TAN AND HEIT, 1981; WAKEHAM ET AL, 1980A; LAMFLAMME AND HITES, 1979; SIMONEIT ET AL.,

1986; OTTO AND SIMONEIT, 2001; TUO AND PHILP, 2005).

102

COOH COOH Pimaric acid Abietic acid

Pimarane* COOH 18-norabietane-7,13-diene Dehydroabietic acid

Abietane* Dehydroabietane* 18-Norabietan-8,11,13- triene*

Beyerane * Simonellite* 1,2,3,4-Tetrahydroretene*

Retene* 7-Ethyl-1-Methyl-phenanthrene

Phenanthrene* Pimanthrene*

Figure 4-4: The diagenetic pathways of the abietane and pimarane type diterpenoids (c.f. Simoneit et al., 1986; Wakeham et al., 1980b; Otto and Simoneit, 2001, 2002; Otto and Wilde, 2001; Tuo and Philp, 2005). Compound with an asterisk (*) are detected in extractable organic matters of New Zealand coals

103

4.3 NON-HOPANOID TRITERPENOID HYDROCARBONS

Aliphatic triterpenoid hydrocarbons

The non-hopanoid triterpanes, which even appear in the key ion trace of hopanoids

(m/z 191), have been identified as olean-13(18)-ene [H4], olean-(12)-ene [H5], olean-18-ene

[H6] and urs-12-ene [H9]. They were found to contribute significantly to the organic matter of the Waikato Basin (TABLE 3.3 AND FIGURE 3-14 IN CHAPTER 3) suggestive of an abundance of higher vascular plant residues in samples from this basin. Since, triterpenoids can be tetracyclic or pentacyclic, among them pentacyclic tritepenoids are normally found in higher plants. In which they appear to belong to three major series: the oleanane (ß-amyrin); the ursane (α- amyrin) and lupane (lupeol). During diagenesis, ß-amyrin/ α-amyrin (the abundant constituents of angiosperms) are transformed into oleanane, ursane via oleanene/ ursine (PHILP,

1985; KILLOPS AND KILLOPS, 1993). The appearance of oleanene/ ursene, therefore, suggests an angiosperms input for these samples.

Aromatic triterpenoid hydrocarbons

The detected tetra- and pentacyclic aromatic triterpenoid hydrocarbons (FIGURE 4-5;

TABLE 4-4) comprised a main proportion of the aromatic fraction. They were mainly picene and chrysene groups, derived from oleanane, ursane or lupane precursors, at different stage of aromatization. Picene isomers include tetramethyloctohydropicene [14-17], dimethyl- [18, 19] and trimethyltetrahydropicene [23, 24]. In most samples, monoaromatic triterpenoid hydrocarbons were detected, such as, 24,25-dinoroleane-1,3,5(10),12-tetraene [8], 24,25- dinorursa-1,3,5(10),12-tetraene [10] and 24,25-dinorlupa-1,3,5(10)-triene [12]. Chrysene isomers include tetramethyloctohydro-, trimethyltetrahydrochrysene [2-6], and 1,2- (1´isopropylpropano)-7-methylchrysene [21]. Additionally, the C-ring cleavage skeletal structure [7] was also found. Rarely, tetracyclic-monoaromatic de-A-triterpenoid hydrocarbon

[1] (STOUT, 1992) appeared as a trace component.

104

100

ISTD G001986- Northland

Rank(Sr) 0.6

23 24 19 8 18 15

0 15 100 G002600- Central Otago

Rank(Sr) 2.3 12

50 1 17 23

8 16 18 24 ISTD Relative Abundance 11 22 2 3

0 11 12 100 G002573- Waikato 8 Rank(Sr) 5.7

ISTD 15

17 6 16 20 22 24 21 23

0 66 70 74 78 82 86 90 94 98 Time (min)

Figure 4-5: The GS/MS chromatograms (TIC) of representative triterpenoid aromatic hydrocarbons in sample G001986 (upper), G002600 (middle) and G002573 (below). Letters and numbers correspond to compound names listed in Table 4-4.

105

Table 4-4: The identified triterpenoid biomarkers in aromatic fraction of extractable organic matter of New Zealand coals

Peak Compounds References No. ISTD Ethylpyrene 1 Monoaromatic- de A- triterpenoid IX 2 Tetramethyloctahydrochrysene I, VI, IX 3 3,3,7,12-Tetramethyl-1,2,3,4,4a,11,12,12a-octahydrochrysene II, IX 4 3,4,7,12-Tetramethyl-1,2,3,4,4a,11,12,12a-octahydrochrysene IX 5 3,4,7-Trimethyl-1,2,3,4-tetrahydrochrysene III, IX 6 3,3,7-Trimethyl-1,2,3,4-tetrahydrochrysene III 7 Isomer of tetracyclic triaromatic V 8 24,25-Dinoroleane-1,3,5(10)12-tetraene VIII 10 Triaromatic triterpenoid IX 11 24,25-Dinorursa-1,3,5(10)12-tetraene VIII 12 24,25-Dinorlupa-1,3,5(10)12-triene VIII 13 Triaromatic triterpenoid IX 14 2,2,4a,9-Tetramethyl-1,2,3,4,4a,5,6,14b-octahydropicene III, IX, X 15 Triaromatic oleane VI, IX 16 1,2,4a,9-Tetramethyl-1,2,3,4,4a,5,6,14b-octahydropicene II, X 17 Triaromatic lupane VI, VII, IX, X 18 1,2-Dimethyl.1,2,3,4-tetrahydropicene (?) II 19 2,2-Dimethyl.1,2,3,4-tetrahydropicene (?) II, III 20 Derivative of octahydropicene VII 21 1,2 (1´isopropylpropano)-7-methylchrysene IV, VII 22 7-Methyl-3´-ethyl-1,2-cyclopentenochrysene IV, VI, IX 23 1,2,9-Trimethyl-1,2,3,4-tetrahydropicene III, VII, IX 24 2,2,9-Trimethyl-1,2,3,4-tetrahydropicene IV, IX Note: I Spyckerelle et al., 1977b VI Philp, 1985 II Wakeham et al., 1980b VII Chaffee & Fookes, 1988 III Wakeham et al., 1980a VIII Wolff et al., 1989 IV Chaffee & Johns, 1983 IX Stout, 1992 V Chaffee et al., 1984 X Tuo & Philp, 2005

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One exception, the aromatic triterpenoid No. 22 was assigned as 7-methyl-3´-ethyl-

1,2-cyclopentenochrysene which has a hopene-type skeleton (WAKEHAM ET AL, 1980B- PEAK NO. 31;

PHILP, 1985- P188). STOUT (1992) has pointed out that this aromatic triterpenoid compound could also have a 24,30-bisnorlupanoid structure, but in considering with relative parallel abundance of hopanoids with this aromatic triterpenoid concentrations (FIGURE 3-15 IN CHAPTER 3), we prefer this compound would be 7-methyl-3´-ethyl-1,2-cyclopentenochrysene to 7-methyl-1´- ethyl-1,2-cyclopentenochrysene. Although samples from the Northland Basin conversely have low concentration of 7-methyl-3´-ethyl-1,2-cyclopentenochrysene despite of quite high in hopanoid concentrations. The concentration of this hopene skeleton aromatic is up to 80- 160 µg/g TOC in samples from the Central Otago Basin, but contributes in smaller concentration (e.g. up to 50 µg/g TOC) in other basins such as the West Coast and the Waikato Basins. This compound was found to be derived from the geochemically dominant hopanoid triterpenes, and considered as a good indicator for not only bacteria input but also important roles of microbiological factors during the early diagenesis (GREINER ET AL., 1976; SPYKERELLE ET AL, 1977A;

WAKEHAM ET AL, 1980A; LOUREIRO AND CARDOSO, 1990). Diploptene was thought to be its natural precursor, via a sequential aromatization process spreading from ring D to A (GREINER ET AL.,

1976).

2500 FIGURE 4-6 shows the Northland Eastern Southland concentrations of total Waikato West Coast aromatic triterpenoid 2000 Taranaki hydrocarbons against Central Otago

Rank(Sr), which are from 1500 40 to 2500 (µg/g TOC) and decrease with increasing 1000 maturity. However, within individual basins these concentrations were (µg/gTOC) Aromatics Triterpenoids 500 varying. These concentrations of samples 0 from the Northland Basin 04812 Rank (Sr) were around 40-380 (µg/g Figure 4-6: Concentration of triterpenoid aromatic TOC) that were very low in biomakers found in the aromatic fraction of New Zealand coals as a function of maturation

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comparison with other immature samples, even they have very “fresh” clear aromatic triterpenoid traces (SEE FIGURE 4-5).

The skeleton structures of triterpenoid aromatics suggest that their precursors are pentacyclic triterpenoids. The E-ring of these precursors may be either six-membered ß- amyrin/ α-amyrin (the abundant constituents of angiosperms) or five-membered (lupenol). These C-3 oxygenated pentacyclic triterpenes are subjected to bio- or geo-degradation processes during diagenesis following different pathways leading to the formation of different products. The aromatization pathways of angiosperm-derived triterpenoids have been widely investigated and reported by SPYKERELLE ET AL. (1977A, 1977B), LAFLAMME AND HITES (1979), WAKEHAM

ET AL. (1980A) TAN AND HEIT (1981), CHAFFEE AND JOHNS (1983), CHAFFEE ET AL. (1984), WOLFF ET AL.

(1989), CHAFFEE (1990), AND STOUT (1992). Generally, aromatic hydrocarbons are probably derived from 3-oxygenated pentacyclic triterpenes such as α-amyrin or ß-amyrin, by bio- or geo-degradation processes. The diagenesis pathways for higher plant triterpenoids and detected compounds are summarized in FIGURE 4-7. It shows the aromatization of triterpenoid aromatic hydrocarbons could be via one of several possible pathways. It could be (1) cleavage of the A-ring followed by progressive aromatization from the B to E rings ultimately resulting in chrysene-like compounds, (2) aromatization of the A-ring followed by progressive aromatization of the B- D rings ultimately resulting in picene-like compounds, or (3) cleavage of the C-ring resulting in aromatized seco-triterpanes. The high occurrence of identified- aromatized triterpenoid hydrocarbons in recent sediments obviously implies that these compounds should be produced at the earlier stages of diagenesis, the dehydrogenation processes occur rapidly and does not require such high temperature. Moreover, the possibility of the aromatization of triterpenoids via microbially mediated reactions is also suggested.

From FIGURE 4-7 and the concentrations of individual triterpenoid aromatics SHOWED IN APPENDIX

3D, it can be said that the aromatization of triterpenoid aromatic hydrocarbons in organic matter of New Zealand coals following the progressive aromatization of the A- D rings is more preferable in comparison with other aromatization pathways, resulting in the generation of more significance of picene-like compounds.

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E E R= O or OH C D C D

B AB A α-amyrin ß- amyrin R R

1. Progressive 2. Loss of A-ring followed by aromatization aromatization

3. C-ring cleavage with aromatization

C2 C2 *

8,14- seco tetracyclic triaromatic* of C2 pentacyclic tetraaromatic

Tetramethyloctohydropicene* C2

Tetramethyloctohydrochrysene*

C2 Trimethyltetrahydropicene*

Dimethyltetrahydropicene*

C2 Trimethyltetrahydrochrysene*

Figure 4-7: The diagenetic pathways of aromatic triterpenoid formation starting form α-amyrin or ß-amyrin (c.f. Wakeham et al., 1980b; Tan and Heit, 1981; Chaffee, 1984; 1990; Chaffee and Fookes, 1988; Chaffee and Johns, 1983; and Stout, 1992). Compounds with an asterisk (*) are reported here for New Zealand coals.

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4.4 THE RELATIVE CONTRIBUTION OF GYMNOSPERM AND ANGIOSPERM BIOMARKERS IN NEW ZEALAND COALS

4.4.1 GENERAL OBSERVATION AND CONCLUSIONS

The contribution of gymnosperms versus angiosperms in sediments generally is estimated based on the relative proportions of diterpanes and triterpanes. KILLOPS ET AL. (1995) have created an angiosperm/ gymnosperm index (AGI) to investigate the contribution of angiosperms and gymnosperms into the sediments of Taranaki basin. The relative abundance of aliphatic biomarkers was calculated from peak height in m/z 123 (diterpane) and m/z 191 (triterpane) mass chromatograms. They showed that gymnosperms, especially podocarps, were the main members of coastal plan swamp flora during the late Cretaceous, and contributed significant quantities of diterpanes, dominated by isopimarane, to organic rich sediments. Angiosperms increased in relative abundance through the Paleocene and became the dominant higher plant in the Eocene. However, the authors pointed out that the AGI values of four samples, mid-Cretaceous, were relatively high, but both DT/H (gymnosperm- derived diterpane/ hopane) and TT/H (angiosperm-derived triterpane/ hopane) values were low, leading to possibly significant errors in the AGI calculation.

Recently, a ratio namely di-/ (di- plus triterpenoids) was defined as the concentration of saturated plus aromatic diterpenoids divided by the sum concentration of diterpenoids plus angiosperm-derived triterpenoids (BECHTEL ET AL., 2005). This ratio varies between 0 and 1, allowing the easy comparison of relative contribution of gymnosperms and angiosperms into organic matter of different depositions (BECHTEL ET AL., 2005). Another ratio, a modification of the above, the so-called angiosperm/gymnosperm- aromatic- ratio (AGAR), has been developed to investigate the gymnosperms versus angiosperms (HABERER ET AL., 2006). However, one should work with caution because these above ratios indicating the relation of diterpenoids and angiosperm-derived triterpenoids in sediments may not properly reflect the proportion of organic matter from angiosperms and conifers (OTTO ET AL., 2005). Because, OTTO

AND OTHERS pointed out that diterpenoids are probably trapped in the resinous and woody tissue of the conifers and are thus dispersed less in small-sized sediment particles. Conversely, the angiosperms contribute higher amount in leaves and other microscopic particles (leaf detritus, wax) that are easily broken and shredded into small pieces. To date, these ratios are nevertheless still considered as the best quantitative indicators for estimating gymnosperms versus angiosperms contribution in sediment.

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The ratios of aliphatic plus aromatic diterpenoids divided by the sum of diterpenoids plus angiosperm derived aliphatic biomarker triterpenoids, denoted as gymnosperms angiosperms ratio-GAR, vary mostly around 1, except samples from the Waikato Basin which have this ratio around 0.25- 0.75 (FIGURE 4-8, UPPER). This means that gymnosperms would be the most abundant land plant contributed into New Zealand coals generally, while angiosperms contributed as main part into samples originated from the Waikato Basin only. This observation is caused by the appearance of angiosperm-derived triterpenoids only dominantly found in coals from the Waikato Basin (SEE SECTION 4.1). However, this result would be not so precise, because as described in SECTION 4.1, angiosperm-derived aromatic hydrocarbon biomarkers are not only found in the Waikato Basin but also in other basins, such as Central Otago and Eastern Southland basins (FIGURE 4-6). Thus, the contribution of triterpenoid aromatic hydrocarbons must be taken into account to estimate the relative contribution of gymnosperms and angiosperms. The observations from AGAR value (FIGURE

4-8, MIDDLE) as well as di/(di- plus triterpenoids) (FIGURE 4-8, BELOW) ratio, which was obtained from both aromatic and aliphatic biomarkers, are more or less the same. These figures show in contrast that angiosperms are the main type of higher land plant contributed into New Zealand coals, since these ratios range mainly from zero to 0.4. However, there are four samples appearing differently in FIGURE 4-8 (BELOW). They are two samples from the Eastern Southland Basin- coal field Ohai, formation Morley Coal Measures (G002604; G002606) and two samples from the West Coast Basin- coal field Greymouth, formation Paparoa Coal Measures (G001990; G002592) whose di/(di- plus triterpenoids) values ~ 0.55- 0.9, but their AGAR values are not so different in comparison with those of the remaining samples. The high values of di/(di- plus triterpenoids) are caused by the high content of aliphatic diterpenoid biomarkers, particularly isopimarane (SEE SECTION 4.2) in these four samples and imply that gymnosperms contributed in higher proportion in these samples than in other ones. Meanwhile using AGAR values to evaluate the relative contribution of gymnosperms and angiosperms does not point out this information.

Briefly, (1) it clearly shows that using relation of aromatic plus aliphatic diterpenoids divided by the sum of aromatic and aliphatic angiosperm-derived triterpenoids in sediments would give a more precise quantitative indication for gymnosperms versus angiosperms contribution in sediments. (2) Basing on the relation of diterpenoids and angiosperm-derived triterpenoids in extractable organic matters of New Zealand coals, it shows that angiosperms contributed higher proportion than gymnosperms in the investigated samples. Gymnosperms

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still dominated during the Cretaceous, particularly the Podocarpaceae, Cupressaceae, Taxodiaceae, Pinanceae and Araucariaceae conifer species. This observation is in agreement with previous publications (KILLOPS ET AL., 1995; MILDENHALL, 1980).

0.75

0.5 GAR

Northland Eastern Southland 0.25 Waikato West Coast Taranaki Central Otago 0 1 048122610 Rank (Sr)

0.75

0.5 AGAR

0.25

0 1 2610 04812G002604 Rank (Sr) G002592 0.75

G002606 G001992 0.5

0.25 di-/(di- plus triterpenoids) plus di-/(di-

0 048122610 Rank (Sr) Figure 4-8: The relative contribution of gymnosperms and angiosperms into New Zealand coals based on (1) the ratio of aromatic plus aromatic diterpenoids over the sum of diterpenoids plus aliphatic angiosperm-derived angiosperm triterpenoids (upper); (2) angiosperm-gynosperm aromatic ratio (c.f. Haberer et al., 2006; middle); and (3) diterpenoids/(diterpenoids plus triterpenoids) (c.f. Bechtel et al., 2005; below). 112

4.4.2 REGIONAL SYNTHESIS

Northland Basin (Pleistocene; Rank(Sr) ~ 0- 0.6)

This basin was characterized by the absence of sesquiterpane and diterpane hydrocarbons. Although, almost samples had very "clear" aromatic triterpenoid traces that have high concentration of picene compound, e.g. 8, 15, 18, 19, specially 23 and 24; TABLE 4-4. The organic matter is immature, characterized by the high contribution of recent higher land plants, e.g. angiosperms.

Central Otago Basin (Tertiary; Rank(Sr) ~ 2.5)

Aliphatic sesquiterpanes, diterpanes were found as trace in these samples. The aromatic sesquiterpane hydrocarbons were determined as traces meanwhile aromatic diterpanes appeared with "clean" peaks. Totarane, semperivrane, dehydroabietane and retene were particular high in comparison with other compounds. Triterpenoids consisted abundance of 3, 4 ring phentacyclic aromatics, e.g. compound 17, 18, 19, 22, 23, 24. Lupane monoaromatic [12] also contributed in a high concentration (TABLE 4-4). Angiosperms as well as gymnosperms (e.g. Taxodiaceae, Cupressaceae and Podocarpaceae conifer families) have contributed as the main organic matter source input. Besides, microbial mass (e.g. hopanoids, 7-methyl-3´-ethyl-1,2-cyclopentenochrysene) also appears as a considerable source.

Eastern Southland Basin (Late Cretaceous- Rank(Sr) ~ 7.5- 8.0; Oligocene-Miocene- Rank(Sr) ~ 1.6- 3.4)

As well as samples from Central Otago basin, gymnosperms and angiosperms both contributed within samples from Eastern Southland basin. These samples have abundance of

18-norabieta-8,11,13-triene [DI], 19-norabieta-8,11,13-triene [DII], 19-norabieta-3,8,11,13- tetraene [DIII], 1-3,13-dimethylpodocarpa-8,11,13-triene [DIV]. Aromatic tritepenoid hydrocarbons were characterized by the predominance of picene compound, e.g. 8, 12, 15, 16 and 23, 24, in some mature samples these have addition of tetramethyloctohydrochrysene isomer [1]. There was in common no significant amount of aliphatic diterpenoid hydrocarbons, but two samples (G002604, G002606) both contain isopimarane contributed as the only diterpane in such a superior content. Sample G002604 contains abundant amount of retene, it therefore can be said that gymnosperms play as the main proportion of input material of these two mentioned samples which are both late-Creataceous.

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Waikato Basin (Eocene-Oligocene; Rank(Sr) ~ 4.7- 7)

Aliphatic, aromatic diterpanoid hydrocarbons found in this basin are more diverse in type in comparison with three above basins. Almost of identifiable sesquiterpenoid and diterpanoid hydrocarbons were found, even so they occured in low amounts. Isopimarane and tetracyclic diterpanes, e.g. kaurane, phyllocladane and beyerane were found more frequently and in remarkable amounts. The Podocarpaceae, Cupressaceae s.str., and Araucariaceae conifer families are considered as the main constituent of organic matter source input in these samples.

Additionally, aromatic triterpenoids (TABLE 4-4) together with the “non hopanoid” triterpanes were found to significantly contribute into the organic matter of Waikato Basin indicating for higher vascular plant proportion within samples from this basin. Besides, aromatic hydrocarbon patterns interbedded by methylated aromatics are indicative for the stage where lots of molecular-alteration takes place.

West Coast Basin (Late Cretaceous; Eocene; Rank(Sr) ~ 7.4- 11.6)

As well as samples from Waikato basin, samples from West Coast basin contain most kind of identifiable diterpanoids. In addition, they have more abundance of methylated aromatics. Anthracene and its isomers were also detected but in smaller concentrations. In comparison with samples from other basins, West Coast basin samples have less abundance of triterpenoids, they mainly consisted of 12, 15, 16, 23, 24 (TABLE 4-4) and some other unknown compounds which appear in traces. Gymnosperms are known to be contributed in higher amounts than angiosperms, particularly in late-Cretaceous to Eocene samples. Gymnosperm biomarker contents of sample from West Coast basin are higher than these of other basins.

Taranaki Basin (Late Cretaceous; Eocene; Rank(Sr) ~ 9.5- 11.8)

Instead of biomarker aromatics, methylated aromatics appeared more predominantly (such as naphthalene, methylnapthalenes; methyldibenzothiophenes; phenanthrene, methylphenanthrenes). Some aromatic diterpenoids were still observed, such as 18-norabieta-

8,11,13-triene [DI], 19-norabieta-8,11,13-triene [DII], 19-norabieta-3,8,11,13-tetraene [DIII],

1,2,3,4-tetrahydroretene [DVII] and retene [DVIII]. Triterpenoids were found in very poor amounts, among these triterpenoids 15, 16, 19, 24 were the main components.

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