Application of tetracyclic polyprenoids as indicators of input from fresh-brackish water environments

Organic Geochemistry 34 (2003) 441–469 www.elsevier.com/locate/orggeochem

Application of tetracyclic polyprenoids as indicators of input from fresh-brackish water environments A.G. Holbaa,g,*, L.I. Dzoub,g, G.D. Woodc, L. Ellisd,g, P. Adame, P. Schaeffere, P. Albrechte, T. Greenef, W.B. Hughesg a

Phillips Petroleum Co., 670H Plaza Office Building, Bartlesville, OK 74004, USA b BP-AMOCO UTG, 501 Westlake Park Boulevard, Houston, TX 77079, USA c irf Group, Inc., 23222 Willow Pond Place, Katy, TX 77494-3566, USA d Terra Nova Technologies, 18352 Dallas Parkway, Dallas, TX 75287, USA e Laboratoire de Geochimie Organique, Institut de Chimie, Universite´ Louis Pasteur 1, rue Blaise Pascal, 67000 Strasbourg, France f Stanford University, School of Earth Sciences, Stanford, CA 94305, USA g ARCO Exploration Research and Technical Services, Plano, TX 75075, USA Received 22 August 2001; accepted 2 October 2002 (returned to author for revision 25 January 2002)

Abstract C30 tetracyclic polyprenoids (TPP) are most prominently observed in samples derived from low salinity, i.e. fresh to brackish lacustrine environments, and are generally present in low levels in samples derived from saline, i.e., marine and saline lacustrine, environments. A near-shore facies of the Chonta Formation, Peru, that has no marine palynomorphs but abundant Chlorococcalean (Green) algal nonmarine palynomorphs, has high levels of TPP, suggesting Green algae (or Chlorophyta) are a possible source for the TPP compounds. The ratio between a C30 TPP compound and 27-norcholestanes is useful for assessing this nonmarine algal input. Moderate elevations of TPP, above what is common in marine derived samples, were found in ostensibly marine source rocks and oils from certain basins of western and northern South America (Middle Magdalena, Colombia; Maracaibo, Venezuela; and Trinidad basins). This is likely due to transport from the nonmarine to the marine environment because of an influx of fresh water into the near-shore marine environment. Alternatively, oils from these basins may have inputs from near-shore shallow marine algae with chemistry similar to that found in lacustrine settings. The TPP ratio, in conjunction with other environmental indicators such as 4-methyl steranes or hopane/sterane ratio, is useful for differentiating marine and nonmarine influences in pre-salt oils and source rocks of West Africa. The TPP ratio, used with other environmental indicators (gammacerane, C29 steranes, C30 steranes) and age diagnostic biomarkers (dinosteranes, 4-methylsteranes), can be useful in differentiating among nonmarine source facies. For example, in the Turpan-Hami basin, China, Permian saline lacustrine and Jurassic lacustrine deltaic facies can be discriminated. # 2002 Elsevier Science Ltd. All rights reserved.

* Corresponding author. Present address: ConocoPhillips, 3004 Permian Building Houston, TX 77079, USA. Tel.: +1918-661-4701; fax: +1-918-661-5250. E-mail addresses: [email protected] or agholba@bartnet. net (A.G. Holba).

1. Introduction The characterization of lacustrine systems is more complex, when compared to marine systems, because they have a wider range of depositional conditions. Few

0146-6380/03/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved. PII: S0146-6380(02)00193-6

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geochemical indicators of lacustrine systems are universal because of the wide variety of controlling factors: salinity, redox chemistry, water depth, latitude, altitude, temperature, rainfall/runoff, nutrient supply, inorganic ion speciation, organic matter input, and geologic age (Katz, 1990, 1995). Numerous biomarkers generally related to algal input but of a nonspecific nature are available to the geochemist: Distributions of n-alkanes, highly branched isoprenoids, C37–C39 unsaturated alkyl ketones, C27 and C28 steranes, methyl steranes, and pigments (Meyers and Ishiwatari, 1993a, b; Volkman, 1988). The exception, botryococcane, is a specific indicator of the fresh water alga Botryococcus braunii (Cox et al., 1973; Volkman, 1988), but it is rarely found outside SE Asia. Other parameters reported as indicative of lacustrine depositional environments, including elevated 4-methyl steranes from dinoflagellate algae (Summons, et al., 1987; Goodwin et al., 1988; Murray et al., 1994), tricyclic terpane C26/C25 ratio >1 (Zumberge, 1987), and b-carotane (Jiang and Fowler, 1986; Fu et al., 1990), are not universal. Conversely, in marine systems C30 24-n-propylcholestanes (and especially their diasterane isomers) are specific, reliable biomarkers for marine algae and, therefore, depositional environments affected by marine organic input (Moldowan et al., 1990). Novel specific indicators of fresh/brackish water algal organic input in the form of tetracyclic polyprenoid (TPP) compounds have recently become available (Holba et al., 1999, 2000). These studies have observed C30 tetracyclic polyprenoid (C30TPP) isomers in elevated concentrations relative to algal steranes in fresh/ brackish water source rocks and oils derived from these sources. The observed isomers are part of a homologous series of tetracyclic polyprenoids (Holba et al., 2000; Li et al., 1996). This homologous series is one of several series of alkyl cyclized polyprenoids of three to seven rings with saturated and aromatic analogs identified and characterized by Schaeffer et al. (1994). Two related cyclic sulfide analogues have been identified and characterized in a wide variety of sedimentary environments (Poinsot et al., 1997, 1998). Related polycyclized-polyprenoid hydrocarbons have also been observed in source rocks and oils of the Ostracod Kill Zone of Western Canada Basin, an inferred brackish water depositional environment (Riediger et al., 1993; Li et al., 1996). The TPP compounds were also observed as an unknown doublet in Early Cretaceous lacustrine oils from West Africa (Schiefelbein et al., 2000) and far eastern lacustrine oils (Schiefelbein et al., 1997). With respect to the C30TPP, this paper, through a series of case studies, describes the following: (1) compound identification, (2) application as indicators of fresh/brackish water depositional environments, (3) application as specific indicators of input of fresh/ brackish water algal organic matter to marine and

transitional depositional environments, and (4) inferred biological provenance.

2. Samples and methods 2.1. Experimental Sample preparation, GC/MS and GC/MS/MS analytical conditions are outlined elsewhere (Dzou et al., 1999; Holba, et al., 1998). All analyses were performed at the former ARCO lab (Plano, TX) or at Baseline Resolution Inc. (The Woodlands, TX), with the exception of synthesis and co-elution experiments at the Laboratoire de Geochimie Organique (Universite´ Louis Pasteur, Strasbourg, France). C30TPP in lacustrine

Fig. 1. GC/MS/MS parent to daughter mass chromatograms of key biomarker types. (a) 414!259 for a lacustrine Triassic rock extract from Cuyo Basin, Argentina; (b) 414!259 for a Jurassic marine oil from Ekofisk Field, North Sea, Norway; and (c) 358!217 from a Jurassic marine oil, Cook Inlet, Alaska. Peaks are identified in Table 1. The inset shows the structure for the C30 tetracyclic polyprenoid (TPP).

A.G. Holba et al. / Organic Geochemistry 34 (2003) 441–469 Table 1 Peak identifications Peak

Identification

Ta Tb PS PBR PBS PR a b c d e f

C30 TPP 18a(H), 21R C30 TPP 18a(H), 21S 14a, 17a, 20S-3b-propylcholestane 14b, 17b, 20R,-3b-propylcholestane 14b, 17b, 20S,-3b-propylcholestane 14a, 17a, 20R,-3b-propylcholestane 13b, 17a, 20S-27-nordiacholestane 13b, 17a, 20R-27-nordiacholestane 5a, 14a, 17a, 20S-27-norcholestane 5a, 14b, 17b, 20R-27-norcholestane 5a, 14b, 17b, 20S-27-norcholestane 5a, 14a, 17a, 20R-27-norcholestane

(Fig. 1a) and marine (Fig. 1b) oils and source rocks are best analyzed by GC/MS/MS parent to daughter 414!259 (Fig. 1). C30TPP may be observed in the GC/ MS m/z=259 eluting approximately (depending on temperature program) one minute after the elution time of the 20R-24-ethylcholestane on a DB-1 column. TPP does not have an m/z=191 response. Peak identification for Fig. 1 is given in Table 1. Note, the identification of the 3-propylcholestane is tentative, as standards of 3b-propylcholestanes were not available. However, they exhibit a major cleavage of m/z 414!259, and a Bring cleavage of m/z 414!262. A linear n-propyl moiety is inferred, but has not been verified. Peak areas of compounds used for calculation of ratios are derived from GC/MS/MS parent to daughter transitions as follows: C30 methyl steranes (m/z 414!231); C27–C30 desmethyl steranes (m/z 372!217, 386!217, 400!217, and 414!217); C26 27-norcholestanes (m/z 358!217), and hopane (m/z 412!191). Absolute concentrations are the preferred input to calculating ratios, but for this paper all ratios are calculated from GC/MS/MS peak areas. 2.2. Samples A calibration set of nonmarine and marine oils was used to test the parameters discussed in this paper (Appendix A). The oil suite represents diverse source origins: 50 lacustrine, 26 terrigenous-rich, 140 marine, and 30 other oils. Oils were used for the calibration set, as they tend to summarize all possible facies contributors in the drainage area of an oil accumulation. Discussion of samples used in case studies will be done later with the geologic setting for each individual case study. 2.3. C30 Tetracyclic hydrocarbon standards (TPP) Following unambiguous structural characterization of the two C30 polyprenoid sulfides 1a,b (Appendix B)

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derived from the cyclization of regular polyprenoids (Poinsot et al., 1997, 1998), a fraction containing a 1:1 mixture of these sulfides was desulfurized using lithium in ethylamine (Hoffmann et al., 1992), yielding two tetracyclic hydrocarbon epimers (2a,b) (Appendix B) at C-21 in a 1:1 ratio (Fig. 2). Both compounds show identical mass spectra, which are also very close to those of the C30 TPP from the geological samples.

3. Results 3.1. Identification of C30 TPP Based upon the mass spectrum of the C30TPP compounds, a tetracyclic polyprenoid structure was anticipated (Schaeffer et al., 1994) and subsequently confirmed by mass spectral comparison with two authentic synthesized reference compounds (2a,b) (described in the Experimental). Gas chromatography/ mass spectrometry (GC/MS) co-elution experiments (Fig. 3) were performed using the reference compounds with the hydrocarbon fraction from a lacustrine-derived oil (Sunda Basin, Indonesia) containing a 1:1 mixture of two isomers of C30 TPP. Co-elution of the synthesized compounds with the compounds observed in geological samples unambiguously established that the two naturally-occurring compounds correspond to an epimeric mixture at the C-21 chiral carbon of the tetracyclic hydrocarbons 2a,b formed by cyclization of regular polyprenoids (Poinsot et al., 1998). 3.2. Design of TPP ratio Oils derived from source rocks deposited in fresh/ brackish water depositional environments tested in this study show elevated C30TPP compounds relative to steranes. A biomarker parameter that indicates fresh/ brackish water organic input was sought, which was applicable to a wide range of depositional environments, geographic locations, and thermal maturities. A ratio with the 3b-propylcholestanes, which also appear in the GC/MS/MS parent to daughter m/z 414!259, proved to be inconsistent due to maturity and source input effects. Ratios constructed using the C30TPP and diasteranes in the GC/MS m/z=259 are also useful at times, but are subject to interferences. Fresh/brackish water derived oils and source rocks tend to have high hopane/sterane ratios due to low sterane contents (usually lacustrine samples have substantially lower concentrations of steranes than marine samples), thus suggesting a ratio of C30TPP with a sterane may be suitable. Experiments with C26, C27, C28, and C29 steranes identified that a parameter using TPP with the C26 27-norcholestanes as the most consistent parameter representing fresh/brackish water organic input. The

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Fig. 2. Synthesis of C30 tetracyclic polyprenoid hydrocarbons (TPP) from unambiguously identified polyprenoid sulfides.

C26 27-norcholestanes are probably derived from diagenetic processes upon C27 steroids; thus, they are low to exceptionally low in lacustrine samples and prominent in marine samples. We propose the following ratio: TPP ratio ¼ ð2  peak TaÞ=½ð2  peak TaÞ þ ð 27-norcholestanesÞ ð1Þ Peak Ta is the resolved C30TPP isomer in Fig. 1b and the  27-norcholestanes are peaks a through f in Fig. 1c, Table 1, and Appendix B (3, 4). The factor of 2 was used to allow for one C30TPP isomer co-eluting with a 3-propylcholestane. Note, when a DB-5 rather than DB-1 column is used with our GC program, then peak Ta co-elutes with peak PBS and peak Tb is the cleanly resolved peak, and should be substituted into Eq. (1). Preliminary data suggests that the C30TPP isomers are extremely stable to both thermal and microbial degradation. Thus, samples that are of exceptionally high maturity or severely biodegraded may have uncharacteristically high TPP ratios and misrepresent their original source provenance. 3.3. Application of TPP ratio A well characterized set of 220 oils derived from lacustrine (50), marine (140), mixed marine-lacustrine (4) and terrigenous-deltaic (26) depositional environments were used to define and calibrate plots for depositional environment determination (Fig. 4). A crossplot of TPP ratio and%C30 24-n-propylcholestanes (a specific indicator of marine algal input) is given in Fig. 4a. Lacustrine oils from fresh-brackish water environments have high TPP ratio (i.e., TPP ratio >0.40) and no detectable 24-n-propylcholestanes. Conversely, marine oils typically have detectable marine biomarkers and low values of the TPP ratio. An oil from the Green River Formation, Uinta Basin, Utah

(Appendix A, 86X0255) contains contributions from both saline (dominant) and fresh/brackish lacustrine facies. It has a relatively low value among the lacustrine oil sample set (TPP=0.33) probably because of a lower input of fresh/brackish water algal organic matter during periods of elevated salinity. The%C30 24-n-propyldiacholestanes is generally preferred for use in this plot because the diasterane peaks are most readily and most cleanly detected and integrated above possible background noise. The percentage regular C30 24-propylcholestanes generally give the same result, are best used for carbonate or low maturity sources, and are used in Fig. 4a. Marine oils contain variable %C30 24-n-propylcholestanes (0.5–12%), but, as expected, always have a positive measurable presence of the marine algal biomarkers (Fig. 4a). The exceptions are some high maturity or Paleozoic oils in which the C30 steranes are below detection limit due to thermal destruction. Terrigenous-rich samples from deltaic shales and coaly type sources commonly are low in both algal indicators. Nonmarine coaly and marine influenced deltaic oils may have 0–2% C30 steranes. When the source input of an oil sample or source rock is exclusively derived from organisms of fresh/brackish water or marine environment, conventional indicators of marine or lacustrine input often effectively discriminate the depositional environment. However, when mixed oils representing two different source facies (one marine and one lacustrine) occur, or when a vertical source package is predominantly a lacustrine formation with marine incursions, positive specific indicators of each type of input are necessary to clearly identify variable contributions from different depositional environments. Another powerful tool for discerning organic inputs in oils or rock extracts is a plot of TPP Ratio with a ratio using 4-methyl steranes. We recommend either a ratio of 4-methyl/(3-methyl+4-methyl)-24-ethylcholestanes or C30 4a-methyl-20R, 24-ethylcholestane/[C29 20R-24-ethylcholestane+4a-methyl-20R-24-ethylcho-

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Fig. 3. Co-elution experiments of synthesized TPP with the naturally occurring compounds in a lacustrine crude oil: (a) m/z 259 mass chromatogram of synthesized TPP standards; (b) m/z 259 mass chromatogram of Sunda Basin, Indonesia oil; and (c) co-injection of synthesized standard with geologically occurring TPP.

lestane] (Fig. 4b) after Murray et al., (1994). As before, samples from terrigenous-rich environments have low values as both ratios have algal derived components in the numerator. Typical marine oils give low TPP ratios and

low to moderate 4-methyl sterane ratios. Commonly, fresh/brackish water lacustrine derived samples of Cretaceous or younger age give high values for both ratios and plot in the zone labeled ‘‘Lacustrine I’’ in Fig. 4b.

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Fig. 4. Plots of biomarker indicators of depositional environment and biological input. (a) Plot of TPP ratio (indicator of fresh/ brachish water algal input) and%C30 24-propylcholestanes (indicator of marine algal input). (b) Plot of TPP ratio with a dinoflagellate biomarker indicator (4a-methyl-20R-24-ethylcholestane/(C29 20R-24-ethylcholestane+the numerator).

The zone in Fig. 4b labeled ‘‘Lacustrine II’’ contains oils of diverse description; they include older pre-Cretaceous samples, some richer in terrigenous biomarkers,

and others that are derived from source rocks deposited under more saline conditions. Other samples are of uncertain affinity. The 4-methyl steranes are most likely

A.G. Holba et al. / Organic Geochemistry 34 (2003) 441–469

derived from lacustrine and marine dinoflagellates (Robinson et al., 1984; Wolff et al., 1986; Goodwin et al., 1988). Dinoflagellate cysts (Tappan, 1980, p. 351) and generally their 4-methyl sterane chemistry (Summons et al., 1987, 1992; Moldowan et al., 1996) appear in the fossil record in the earliest Mesozoic. Thus, Paleozoic lacustrine samples (e.g., Permian Turpan and Devonian Orcadian Basin oils in Fig. 4b) and some Early Mesozoic samples tend to have high TPP ratios (> 0.4) and low 4a-methyl sterane ratios (< 0.25). In general, any depositional environment that tends to have low dinoflagellate biomass abundance, i.e., the more terrigenous-rich lacustrine settings (e.g., some Bohai Basin oils, Fig. 4b), may also have high TPP ratios (> 0.4) and low 4a-methyl sterane ratios (< 0.25). The general ‘‘rule of thumb’’ for samples derived from nonmarine algal-rich systems (limnic, lacustrine) is to expect an elevated TPP ratio ( >0.4), especially for Mesozoic and younger samples. Data from lacustrine oils representing 51 different fields or wells from 23 different basins (5 continents and 12 countries) support this statement (Fig. 4, Appendix A). Only a few Paleozoic lacustrine samples were available, but older lacustrine samples also appear to have elevated TPP relative to marine samples of the same age. We now turn to the occurrence of elevated TPP ratios in initially unexpected sample types, and the geochemistry of transitional environments where mixing of inputs may occur. The following case studies examine the data for transitional environments, restricted marine environments which potentially may receive elevated fresh water runoff, and a Paleozoic basin with a range of nonmarine depositional environments. 3.4. South American Late Cretaceous case study 3.4.1. Geologic setting Foreland basins are found along the perimeter of western and northern South America, ranging from Trinidad in the north to the southern tip of the continent. Stratigraphic sections contain sediments from Ordovician to Recent age. Earliest source rock deposition is pre-Andean including Ordovician (Contaya), Devonian (Cabanillas), Carboniferous (Ambo) and Permian (Copacabana and Ene) formations. These formations are thickest and are most likely petroleum sources in basins in Bolivia and Peru, e.g., Madre De Dı´os or Ucayali Basins (Pindell and Tabbutt, 1995; Mathalone and Montoya, 1995). The Late TriassicEarly Jurassic marine transgressive Pucara Group is also a significant source in the Maran˜on and Ucayali basins of Peru (Pindell and Tabbutt, 1995; Mathalone and Montoya, 1995; Holba et al., 1998). It is widely accepted that major petroleum contributors to sub-Andean and Caribbean Margin basins are marine Late Cretaceous source formations, particularly in

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northern basins of South America (Talukdar and Marcano, 1994; Talukdar et al. 1986; Zumberge, 1984; Ramon and Dzou, 1999; Mello et al., 1995; Salas, 1991; Eisner et al., 1996; Requejo et al., 1994). These include the La Luna Formation of Maracaibo Basin, Venezuela; La Luna equivalent formations; Middle Magdalena Basin, Colombia; Napo Formation, Oriente Basin, Ecuador; Chonta Formation: Maran˜on Basin, Peru; and Gautier Formation/ Naparima Hill Formation, Southern and Columbus basins, Trinidad. The more northerly Late Cretaceous sources (e.g., La Luna, Gautier) were deposited on thermally subsiding passive margin sections that developed during periods of slow sediment accumulation, and high long-term relative sea level, where the oxygen-minimum zone intersected the shelf favoring organic preservation (Pindell and Tabbutt, 1995). The more southerly Late Cretaceous sources (e.g., Chonta) were deposited in tectonically flexurally subsiding foredeep basins east of the developing Andes at times of high long-term eustatic sea level. Common elements include Late Cretaceous source rock deposition associated with long, narrow, seaways with restricted marine circulation, and significant fluvial input off the land mass of South America (K. Meisling, personal communication; Erlich et al., 1999a,b). 3.4.2. Nonmarine-transitional facies of Marine Chonta Formation, Peru The Chonta Formation, an important marine source in northern Peru, was deposited during a ConiacianSantonian marine transgression (Mathalone and Montoya, 1995). However, marine formations may also contain transitional or near-shore facies that were deposited under conditions that are not typical of distal marine source facies. A near-shore transitional facies of the Chonta Formation (Maran˜on Basin, Peru) with no observable marine palynomorphs and with abundant freshwater Chlorococcalean algal palynomorphs has been documented in outcrop and core samples (Wood and Miller, 1997). This facies of the Chonta Formation is dominated by the freshwater Chlorococcalean alga Pediastrum (Family Hydrodictyaceae) and Botryococcus (Family Botryococcaceae) (Wood and Miller, 1997). The formation ranges in organic richness from source to nonsource quality facies (Table 2). Based on the presence of palynomorph assemblages in the horizons above and below the samples discussed here the interval ranges from brackish water to near-shore marine (Wood, unpublished). Not surprisingly, several of the transitional environments had insufficient preservation or productivity to be petroleum source rocks, although one core sample of the Nueva Esperanza 88X well that yielded an essentially monospecific assemblage of Pediastrum, has sufficient richness to contribute petroleum upon maturation (TOC 1.89, HI=602). General basin locations are shown in a map (Fig. 5) and more

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Table 2 South American Cretaceous source rock samples with total organic carbon, Rock-Eval, and GC/MS/MS data %C30 dia

%C30 reg

Peru Nueva Esperanza 88-X, Chonta Fm. Core 98R01874 0.39 182 437 0.71 98R01875 1.89 602 440 0.61

0.0 0.0

0.0 0.0

Rio Alto-Inambari, Chonta Fm. Outcrop 98R01873 0.30 20 422 0.14 98R01876 0.29 17 430 0.09

1.7 1.5

0.3a 0.4a

Trinidad Solado-189, Gautier Fm. 98Z00049 3.97 471

Sample

TOC

HI

Tmax

TPP

441

0.59

2.2

2.6

Solado-189, Naparima Hill Fm. 98Z00048 4.60 540 435

0.68

2.9

3.5

%C30 dia=C30 diasteranes/( C27+C28+C29+C30). %C30 reg=C30 regular steranes/( C27+C28+C29+C30). a Possibly low due to weathering.

specific locations may be found in Wood and Miller (1997). A plot of a marine indicator with a fresh water algal indicator, %C30 24-n-propyldiacholestanes vs. TPP ratio, reveals that the Nueva Esperanza Chonta samples show strong correspondence to the palynological data (Fig. 6). The Nueva Esperanza samples have no detectable marine C30 24-n-propylcholestanes (0%), and have elevated TPP ratios (0.61–0.71) consistent with no marine palynomorphs and the strong presence of freshwater algal palynomorphs. The Rio Alto-Inambari outcrop samples reveal a low%C30 24-n-propylcholestane (0.3–1.7%), and have low TPP ratios (0.09–0.14). The latter samples represent facies with poor preservation of algal organic matter (TOC < 0.3) and biomarkers either during original deposition or due to intense weathering in outcrop. Since the Chonta Formation sample suite from Nueva Esperanza 88x are interpreted as a transitional facies it is not surprising that they have higher inputs of C29 steranes (41 and 47%) and C29 diasteranes (45 and 46%) than the Chonta oils which receive a stronger marine contribution; C29 steranes (29 and 26%) and C29 diasteranes (24 and 22%). The agreement of the biomarker data with the palynological data emphasizes the application of TPP ratio as an indicator of fresh/brackish water algal input into marine/transitional environments. The strong presence of freshwater Chlorococcalean alga Pediastrum and Botryococcus in association with the elevated TPP ratio in the Nueva Esperanza 88X samples suggests that Chlorococcalean (Hydrodictyacean) alga may be considered as candidates for a biological source for the TPP biomarkers.

3.4.3. Trinidad source facies Characteristics of Trinidad oil source rocks range from a high-sulfur organic facies to those of clastic organic facies (low sulfur) exhibiting variable contributions of terrestrial organic matter. Examples include oils derived from clastic-starved source facies from the Gulf of Paria and West Trinidad (e.g., Soldado Complex). Oils from south-central and eastern onshore Trinidad were generated from a source facies that shows a mixture of marine and terrestrial organic matter (Rodrigues, 1988; Requejo et al., 1994). All Trinidad source facies are expected to be from a marine depositional environment (Requejo et al., 1994). Interestingly, Requejo et al. (1994) show m/z 191 mass chromatograms with elevated C20 and C21 tricyclic terpanes, relative to the C23 tricyclic terpane; a characteristic found in marine samples rich in Tasmanites, a marine Prasinophyte alga (Aquino Neto et al., 1992). Examination of the depositional environment indicators in two source rock samples from the Gautier (Cenomanian age) and Naparima Hill (Turonian-Campanian age) formations surprisingly reveals a mixed input of biomarker indicators. The TPP ratio is high (0.59–0.67) while%C30 steranes (2–3%) low (Table 2, Fig. 6a) suggesting that there has been a contribution from fresh water algae into the near-shore marine environment causing dilution of the marine biomarkers in these two selected samples. Recent work supports significant fresh water input into the offshore setting of Trinidad and Venezuela during deposition of Late Cretaceous source packages based on geological considerations as well as organic richness and inorganic geochemical data (Erlich et al., 1999a,b). The Gautier and Naparima Hill rock samples are not expected to represent near-shore environments, but appear to be marine sediments that have received nonmarine input. This phenomenon is not limited to the Trinidad samples. Cretaceous source rock samples from Middle Magdalena Basin, Colombia (Simiti, La Paja, and Tablazo Formations) also have modest%C30 steranes (2.5–3.0%) and moderately elevated TPP ratio (0.28–0.47) (Fig. 6a). These formations are also generally regarded as representing marine deposition (Ramon and Dzou, 1999). Cretaceous source rock extracts from Peru, Colombia, and Trinidad show variable enhancements of the TPP compounds that are more commonly found in lacustrine oils. 3.4.4. South American Late Cretaceous oils Biomarkers indicative of depositional environment (Table 3) were also examined in Late Cretaceous oils from sub-Andean Basins (Middle Magdalena Basin, Colombia; and the Chonta derived oils of the Maran˜on Basin, Peru) and from a Caribbean Margin basin (La Luna oils of Maracaibo Basin, Venezuela). Based on the literature, all are expected to be derived from marine

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Fig. 5. Map showing the Sub-Andean basins of South American sampled in this study.

shale and/or carbonate source facies (Talukdar and Marcano, 1994; Talukdar et al., 1986; Zumberge, 1984; Holba et al., 1998; Ramon and Dzou, 1999; Mello et al., 1995; Salas, 1991; Eisner et al., 1996; Requejo et al., 1994). All of these Late Cretaceous oils contain moderate

to high%C30 marine steranes (Fig. 6b) and low to moderate TPP ratios, the latter generally above that typically observed for marine source rocks and oils (Fig. 4a). This indicates that the elevated TPP ratios observed in source rock facies samples shown are also

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Fig. 6. Plot of TPP ratio vs.%C30 24-propylcholestanes, specific indicators for fresh water algal vs. marine algal input. (a) South American Cretaceous source rock samples include Chonta from Maran˜on Basin, Naparima Hill and Gautier of Trinidad, and several Cretaceous formations from Middle Magdalena Basin, Colombia. (b) South American Late Cretaceous derived oil samples from Maracaibo Basin, Venezuela; Middle Magdalena Basin, Colombia; and Maran˜on Basin, Peru.

observed in the Late Cretaceous oils in South American basins. Reservoired oils are a summation of all source facies in the kitchen area; thus, the Late Cretaceous

derived oils contain molecular indications of marine algal inputs (likely type II and IIS kerogens) and fresh water algal inputs (likely type I kerogen).

A.G. Holba et al. / Organic Geochemistry 34 (2003) 441–469 Table 3 South American Cretaceous oils and GC/MS/MS data TPP

%C30 dia

%C30 reg

Lake Maracaibo, Venezuela 90x2500 Centro 90x2504 Tia Juana 90x2507 Langunillas 90x2512 Lama

0.29 0.43 0.45 0.40

2.90 3.34 3.57 5.77

2.68 3.49 3.32 3.35

Middle Magdalena, Colombia 95x3879 Agua Caliente 95x3899 Caipal 95x3905 Colorado 95x3912 La Cira 95x3919 Peroles 95x3928 Bonanza

0.33 0.46 0.46 0.46 0.43 0.44

3.37 3.81 3.11 3.82 4.22 2.87

3.55 4.04 3.46 4.60 5.73 4.18

Maran˜on, Peru 93x3412 Shiviyacu 93x3377 Dorissa 93x3392 Capahuari S. 93x3576 Bartra

0.45 0.26 0.19 0.51

2.79 na 2.51 na

3.84 na 3.11 na

Number

Field

%C30 dia=C30 diasteranes/( C27+C28+C29+C30). %C30 reg=C30 regular steranes/( C27+C28+C29+C30). na=Not available.

3.5. West Africa case study 3.5.1. Geologic setting The southwestern coast of Africa, from Cameroon to Angola, has a series of basins formed during the rifting between South America and Africa in the Early Cretaceous (Brice et al., 1982; Burwood et al., 1992; Mello and Katz, 2000; Schiefelbein et al., 2000; Henry et al., 1998) that generally contain a series of three identifiable geologic sequences. The earliest represents a pre-salt sequence largely of Neocomian-Aptian lacustrine clastic sediments. Subsequently, a Late Aptian evaporitic sequence of salt, anhydrite and occasional interbedded shales and carbonates was deposited. The third post-salt sequence is composed of dominantly marine AlbianTertiary clastics and carbonates. Pre-salt source rocks are deposited in a series of large lakes of variable water depth, salinity, and paleo-climate (Wiles et al., 1998; Brice et al., 1982). Thus, the pre-salt lacustrine source rocks of Gabon and Congo have a high degree of lateral and vertical heterogeneity (Burwood et al., 1992; Kuo, 1994). The Walvis Ridge generally served as a barrier to invasion of marine waters from the early South Atlantic into the pre-salt rift basins of Gabon, Congo, and Angola. Pre-salt lacustrine formations (i.e., Bucomazi, Melania, Kissenda, Cocobeach, or Pointe Noire) are prolific petroleum sources containing primarily type I kerogens (Amaral et al., 1998; Wiles et al., 1998; Wood et al., 1997). Evaporitic source facies include the

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Madiela and Cap Lopez formations (Mello and Katz, 2000). Two types of source rocks contribute to post-salt petroleum systems: (1) Late Cretaceous marine sources containing mainly type II kerogens (i.e., Anguille, Iabe, or Azile, formations) and (2) Late Cretaceous through Tertiary deltaic-basinal facies containing types II–III kerogens (i.e., Malembo Formation) (Amaral et al., 1998; Wiles et al., 1998). 3.5.2. Marine vs. lacustrine oils Pre-salt lacustrine oils and source rocks from Congo and Gabon and post-salt marine oils from Gabon studied by biomarker geochemistry are listed in Table 4 and their locations are shown in a map (Fig. 7). A plot of TPP ratio with hopane/sterane ratio, a common geochemical parameter, is provided in Fig. 8. Hopane/sterane ratio is generally highest in nonmarine samples (dominated by terrigenous or lacustrine organic matter) and lowest in marine samples (Mackenzie et al., 1984; Mello et al., 1988; Isaksen, 1991). Although a variety of methods are used to calculate this ratio in the literature, we prefer to use the ratio of hopane to the normalized sum of the 20R-steranes (C27 30) from GC/MS/MS data. The plot (Fig. 8) shows excellent discrimination of the marine and lacustrine oils. Pre-salt lacustrinederived oils exhibit high hopane/sterane and TPP ratios. Marine oils are richer in steranes from marine algal input; thus, they have lower hopane/sterane and TPP ratios. The normalized ratio of C30 20R-4-methyl-24-ethylcholestane to C29 20R-24-ethylcholestane generally discriminates lacustrine-derived oils from marine-derived oils (Table 4), but there is considerable variability in 4-methyl sterane content, probably due to locally variable lacustrine conditions. Regular 4-desmethyl sterane distributions (aaa + abb) show that most of the lacustrine oils tend to be rich in algal-derived C27 28 steranes (Gabon: %C27=32–60%,% C28=12–25%, %C29=24– 53%; Congo: %C27=39–50%, %C28=14–25%, %C29= 31–37%). All lacustrine oils have no detectable C30 24-propylcholestane marine indicators (Table 4). The Gabon marine oils are also derived from algalrich kerogens, but relative to other marine-derived oils worldwide have low amounts of the marine indicator, C30 24-propylcholestane (Table 4). Like the lacustrine oils, they are not rich in terrigenous organic matter; the regular 4-desmethyl sterane distributions indicate a largely algal organic input (%C27=31–38%, %C28=24– 31%, %C29=31–39%). TPP and hopane/sterane ratios easily discriminate oils from lacustrine and marine algalrich kerogens. Note that some of the marine oils have slightly elevated TPP ratios relative to marine oils worldwide (Fig. 1) reminiscent of the South American oils discussed in the previous section. The Late Cretaceous source rocks of South America, and West Africa as well as Late Jurassic Egret Member-derived oils from

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Table 4 West African samples and GC/MS/MS data Number

Well (field)

Formation

TPP ratio

H/S

Gabon Lacustrine oils 89X02212 (Gamba) 89X02234 (Moubenga) 96X04248 Lum-23 96X04249 Rabi-53 96X04250 Echira-3 96X04251 Onal-1 96X04253 Onal-11 96X04255 Abre-2

Gamba Dentale Lucina na na Ivinga na Melania

0.92 0.93 0.92 0.79 0.74 0.96 0.80 0.87

0.87 0.81 0.85 0.88 0.80 0.80 0.95 0.77

Gabon Marine oils 95X04062 Konzi MA-1 95X04063 Konzi MA-6 95X04064 Konzi MB-1 96X04299 (Oguendjo) 96X04295 Mandji Sud N0 Tchengue-1 96X04297 (Gombe South) 97X06877 PO-6 97X06878 PSM-3 98X07400 Padouck-1

Azile Azile Azile Batanga (Miocene) (Paleo-Eocene) Anguille Anguille Madiela

0.39 0.35 0.30 0.22 0.26 0.17 0.29 0.28 0.17

Congo lacustrine oils 94x03649 Kouakoula-1 94X03709 TNB-1 94X03710 (Mengo) 94X03711 (Bindi) 94X03712 (Pointe Indienne) 94X03713 Pointe Indienne Marine 1

Basal Sand Mengo Ss. Mengo Ss. Mengo Ss. Toca Carbonate Djeno Ss.

Congo pre-salt source rock extracts 94R03539 Bindi-1 94R03560 Bindi-1 94R03568 Bindi-1 94R03580 Bindi-1

Point Noir Point Noir Djeno Djeno

4Me/29R

%30 dia

%30 reg

0.87 1.44 0.88 0.66 0.40 0.74 0.80 0.25

0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

0.19 0.15 0.14 0.14 0.20 0.19 0.20 0.29 0.30

0.20 0.20 0.21 0.23 0.24 0.23 0.21 0.20 0.15

1.63 2.53 3.22 1.92 1.88 1.28 2.36 3.95 1.31

2.99 3.78 4.48 2.08 2.40 1.88 2.96 3.95 1.53

0.84 0.87 0.92 0.91 0.92 0.75

0.93 0.92 0.94 0.94 0.93 0.81

1.09 0.86 1.12 1.42 1.26 na

0.0 0.0 0.0 0.0 0.0 0.0

0.0 0.0 0.0 0.0 0.0 0.0

0.90 0.61 0.86 0.43

0.95 0.91 0.93 0.65

1.55 0.57 1.12 0.28

0.0 0.0 0.0 2.35

0.0 0.0 0.0 1.93

H/S=hopane/[hopane+( 20R-steranes C27+C28+C29+C30)]. 4Me/29R=C30 (20R-4-methyl-24-ethylcholestane) / C29 (20R-24ethylcholestane).%C30 dia=C30 diasteranes / ( C27+C28+C29+C30).%C30 reg=C30 regular steranes/( C27+C28+C29+C30). na=Not available. All data by GC/MS/MS.

Jeanne d’Arc Basin (Butterworth et al., 1999) are the most prominent examples of moderately elevated TPP ratio in ostensibly marine oils (see Section 4.3). 3.5.3. Marine incursion in lacustrine section Four Congo source rock samples from pre-salt source rock formations were expected to be nonmarine in character (Brice et al., 1982; Schiefelbein et al., 2000; Henry et al., 1998). Two Point Noir and a Djeno rock extracts plot with the lacustrine oils when the parameters in Table 4 are used (Fig. 8). However, one of the Neocomian Djeno rock extracts contains the marine indicator C30 24-propylcholestane. It also has intermediate values for hopane/sterane ratio and the C30 20R-4-methyl-24-ethylcholestane to C29 20R-24-ethylcholestane ratio. This is most likely an indication of an

early marine incursion affecting this source horizon in the Congo basin. This represents an earlier occurrence of a marine incursion than has been previously proposed for late pre-salt formations of Angola (Burwood et al., 1992). The limited sample suite in this study can not confirm the observation by Burwood et al. (1992) that the marine incursions into the late pre-salt sequence may have been relatively frequent, even if short-lived. However, oils represent the sum of important contributing source facies and the oils analyzed here do not support a significant marine contribution to the pre-salt oils of Gabon and Congo. The combination of parameters reveals an event in the geohistory of the basin and assist in stratigraphic discrimination of facies and processes occurring in the basin.

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Fig. 7. Map of offshore Congo and Gabon areas showing locations of well samples.

3.6. Turpan-Hami basin case study 3.6.1. Geologic setting The Turpan-Hami basin is a petroliferous nonmarine basin in NW China that has been physiographically isolated since the Late Permian and episodically was characterized by interfingering fluvial, swamp and lacustrine environments (Greene et al., 2001; Wartes et al., 2000; Wu and Zhao, 1997; Cheng et al., 1996a; Wang et al., 1996; Huang et al., 1991). Of importance to this study is the diverse range of documented terrestrial

and lacustrine depositional environments contained within the main source rock intervals of the Upper Permian and Lower/Middle Jurassic mudrocks and coals (Wu and Zhao, 1997). Upper Permian source facies of Turpan-Hami are stratigraphically and geochemically akin to southern Junggar’s Upper Permian world-class lacustrine oil shales (Wartes et al., 2000; Carroll 1998; Greene et al., 1997; Clayton et al., 1997; Cheng et al., 1996b; Mu, 1994; Hendrix et al., 1992). Recent studies of this large Upper Permian Junggar-Turpan-Hami lacustrine system report

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Fig. 8. Cross plot of TPP ratio with hopane/sterane ratio for Congo and Gabon oils and four Congo source rocks.

the existence of a 200,000 km2 areally extensive lake system that accounts for nearly 5 km of deposition in a rapidly subsiding basin. Wartes et al. (1998) stratigraphically correlated the more marginal lacustrine facies of the Turpan-Hami basin to the more basinal source facies of the Junggar basin and provided a paleogeographic reconstruction divided into three main phases. The three main phases of lacustrine development during this 40–50 million year period include: (1) relatively saline conditions with regional partitioning of sub-lake basins, (2) a period of decreasing salinity through time grading up to deeper basinal laminated facies, and (3) shallower freshwater lakes with extensive fluvial/deltaic influence. In addition, based on diterpane biomarker distributions, Greene (1997) geochemically correlated Upper Permian lacustrine mudstones to produced oils from the southern and western Turpan-Hami basin (Yudong-1 oil of this study). The Lower/Middle Jurassic strata are by far the thickest and most organic-rich deposits in TurpanHami, thereby representing the dominant source rock intervals for the basin (Li et al., 2001; Chen et al., 2001; Greene, 1997; Qiu et al., 1997; Wu and Zhao, 1997; Wu et al., 1997; Wang et al., 1996; Hendrix et al., 1995; Huang et al., 1991). During the Early and Middle Jurassic, temperate humid climates persisted throughout NW China, producing abundant run-off available for freshwater environments (Zhao et al., 1992). Consequently, Lower/Middle Jurassic source facies are represented by coaly swamp/marsh environments, to

meanderbelt fluvial systems interwoven with equivalent downdip deltaic and marginal fresh/brackish lacustrine environments (Greene et al., 2001; Wu and Zhao, 1997; Hendrix et al., 1995). Lower/Middle Jurassic coals and mudrocks have been loosely correlated to produced oils in the main producing region in north-central TurpanHami basin (Wang et al., 1998; Greene, 1997; Cheng et al., 1996a; Wang et al., 1996; Huang et al., 1991). However, due to spatial and temporal variability of depositional facies, precise identification of contributing source rock facies remains poorly determined. Recent publications suggest that either the terrigenous-dominated Lower-Middle Jurassic lacustrine mudstones (Chen et al., 2001) or the combination of the Upper Paleozoic and the Lower-Middle Jurassic lacustrine mudstones are the main source of the oils (Li et al., 2001). Li et al. (2001) suggest ‘‘coaly’’ biomarker signatures may result from migration contamination or from hydrocarbon mixing. 3.6.2. Discrimination between nonmarine facies One Permian and three Jurassic oils derived from nonmarine source facies together with three Jurassic source rock samples were examined using a variety of biomarker parameters (Table 5); their location in the basin is shown in a map (Fig. 9). A plot of TPP ratio with an age-diagnostic parameter, dinosterane ratio, readily differentiates the Permian from Jurassic nonmarine samples (Fig. 10). Dinosteranes are derived from dinoflagellates (Summons et al., 1987; Moldowan

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A.G. Holba et al. / Organic Geochemistry 34 (2003) 441–469 Table 5 Turpan-Hami Basin, China samples and GC/MS/MS data Number

Location

Fm.

TPP ratio

H/S

Gam

Dino

T2k

0.42

0.49

0.16

0.08

K1 J2s J2s

0.30 0.36 0.05

0.66 0.71 0.75

0.03 0.04 0.01

Turpan-Hami Basin, Middle Jurassic Rock Extracts Jurassic 99R00305 Taican-2** J2q 0.37 99R00306 Sandaoling Mine*** J2x 0.24 99R00307 Mi-1**** J2q 0.06

0.60 0.69 0.67

0.09 0.01 0.01

Turpan-Hami, Basin oils Permian 97X07103 Yudong-1 Jurassic 97X07105 Lian-2 97X07106 Sheng-26 97X07104 Wenxi-1

%27 reg

%28 reg

%29 reg

%30 reg

8

34

58

0

0.34 0.36 0.19

21 25 5

20 23 17

59 52 78

0 0 0

0.71 0.22 0.23

31 48 12

29 20 17

41 32 71

0 0 0

H/S=hopane/[hopane+( 20R-steranes C27+C28+C29+C30)]. Gam=Gammacerane Index=gammacerane/(hopane+gammacerane). Dino=( 20R Dinosteranes)/[20R-3-methyl-24-ethylcholestane+( 20R dinosteranes)]. %27reg=( C27 steranes) *100/( C27+C28+C29+C30 steranes) using aaa + abb isomers.%28reg=( C28 steranes) *100/( C27+C28+C29+C30 steranes) using aaa + abb isomers. %29reg=( C29 steranes) *100/( C27+C28+C29+C30 steranes) using aaa + abb isomers. %30reg=( C30 steranes) *100/( C27+C28+C29+C30 steranes) using aaa + abb isomers. ** Mudstone from fresh water environment (TOC=4%, Ro0.6–0.7). *** Coal from anastomosing braided plain-lake environment (TOC=64%, Ro0.5–0.8). **** Deltaic mudstone with numerous coalified plant fragments (TOC=2%, Tmax=436).

et al., 1996), whose cysts first became common in the Triassic. The Yudong-1 oil is reported to be derived from a Permian age source (Greene, 1997) and has the highest TPP ratio among Turpan-Hami samples. The measured TPP ratio is somewhat low relative to other lacustrine oils (Fig. 4), but its value is higher than that of the typical marine shale derived oil. A high gammacerane index and relatively abundant b-carotane in the Yudong-1 oil suggests elevated saline conditions during at least a portion of deposition of the Permian TurpanHami source rocks, similar to that in nearby Junggar basin (Carroll, 1998; Clayton et al., 1997). Like other oils of Late Paleozoic age that predate the evolution of modern dinoflagellates, it has no (or at best trace) levels of dinosterane and other 4-methyl steranes (e.g., C30 4-methyl-24-ethylcholestane). A Jurassic mudstone extract (Taican-2, 99R00305) and an extract from a deltaic/coaly source facies (Sandaoling Mine sample, 99R00306) show a correlation with two oils, Lian and Sheng (97X07105 and 97X07106) in having both elevated (moderate) TPP and dinosteranes. These samples also have elevated 4-methylsteranes consistent with Mesozoic lacustrine input in contrast to the Permian derived sample. The lower TPP ratio may stem from the higher deltaic input such that their nonmarine algal source (possibly Chlorococcalean algae) is not as dominant a biotic contributor to the depositional environment. The remaining two samples, Mi-1, a vitrinitic rock extract (99R00307), and the Wenxi oil (97X07104), are from the same geographic

area within the basin and have very low TPP ratios and relatively low dinosterane ratio. The hopane/sterane ratios remain high and they both have a very high percentage of C29 steranes. These latter traits are characteristic of high terrigenous plant input. These geochemical traits are consistent with the observations that the Mi-1 core is bounded above and below by 5–10 cm coal horizons, and contains abundant coalified plant fragments. The combination of specific environmental-diagnostic and age-diagnostic biomarker indicators provides a powerful tool for discrimination of source facies and parent source formations. The use of multiple age and depositional environment specific biomarkers adds further support and new insights to geochemical interpretation from more traditional biomarker and isotopic approaches. In this case, a Paleozoic lacustrine oil has a relatively moderate to high TPP ratio consistent with lacustrine algal input. A sub-group of lacustrine deltaic samples (including a coal extract) have moderate TPP ratios with elevated 4-methylsteranes. A second Jurassic sub-group of samples with hydrocarbons derived from terrigenous organic matter have very low values of both ratios because both ratios are reflecting lower lacustrine algae input.

4. Discussion Oils and source rocks from fresh to brackish water, algal-rich, lacustrine depositional environments were

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Fig. 9. Map showing sample locations from Turpan-Hami Basin, northwest China.

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Fig. 10. Cross plot of TPP vs.  20R-dinosteranes/20R-3-methyl-24-ethylcholestane for Turpan-Hami Basin Jurassic source rocks and Permian- and Jurassic-derived oils.

found to have high TPP ratios, particularly for Mesozoic and Tertiary settings (Fig. 4). Lacustrine rock extracts from Devonian/Early Carboniferous Burnt Island shale of the United Kingdom and the Permian of China, were also found to show elevated TPP ratios similar to those observed in younger lacustrine samples. The limited availability of Paleozoic and older samples restricts the ability to test the TPP ratio in older lacustrine sediments or oils. 4.1. TPP and hopane/sterane ratios The format of the TPP ratio is similar in format to other terpane/sterane ratios, especially the hopane/sterane ratio. However, the source of the C30 tetracyclic polyprenoid is distinctly different from the hopanes, which are dominantly from prokaryotic organisms, bacteria. A plot of TPP ratio and hopane/sterane ratio (Fig. 11) shows distinct clustering of (1) lacustrine nonmarine oils, (2) marine oils, and (3) oils from terrigenous-rich depositional environments; coals, deltaic shales, and paralic environments. Lacustrine and terrigenous-rich samples both tend to have high hopane/ sterane ratios, but only the lacustrine oils have high TPP ratio. The high TPP is most likely from nonmarine algal

input into lacustrine fresh-brackish water type-I kerogens. Marine type-II kerogens tend to generate oils that have high sterane contents. The steranes originate from marine eukaryotic organisms (algae) that contribute to marine type-II kerogens. Thus, marine derived oils have low values for both ratios in Fig. 11. Oils from terrigenous-rich kerogens are usually mixtures of type-III kerogens with lesser amounts of type-I or II inputs. Oils from terrigenous-rich kerogens have high amounts of hopanes from bacteria or plants and low amounts of algal steranes or tetracyclic polyprenoids. If TPP were from fresh water bacteria then it would be expected to be commonly prominent in coals and oils from terrigenous-rich carbonaceous shales deposited under freshbrackish water conditions. TPP can be quite variable in terrigenous-rich depositional environments but the ratio is not commonly high. The exceptions in Fig. 11 are of interest. The lone lacustrine oil plotting in the marine oil quadrant is a Carboniferous age oil from Moncton Basin, Canada. It is an atypical lacustrine oil. Oils classified as marine in origin that have low TPP and high hopane/sterane include several marine carbonate derived oils (three Late Jurassic Saudi Arabian and Qatar oils; and 2 Pennsylvanian oils); and four Carboniferous marine oils that

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Fig. 11. Cross plot of TPP vs. hopane/(sterane+hopane) ratio. Algal lacustrine oils have high hopane/sterane and TPP ratio. Marine oils tend to have low values for both ratios. Terrigeneous-rich oils (marine and nonmarine deltaic or coal sourced) have high values of hopane/sterane, but typically low values of TPP, consistent with a low algal content.

have extracted coal derived bitumen from nearby Westphalian coals (East Midlands, UK). Gulf of Mexico Eocene oils tend to plot in the high hopane/sterane, low TPP quadrant as well. Several oils from terrigenous-rich sources plot with the marine oils (Central Graben, Denmark; Gippsland basin, Australia; Taranaki basin, New Zealand; Sahkalin basin; and Khatyrka basin). 4.2. Potential diagenetic effects Diagenetic effects mediated by reduced sulfur likely modulate the final TPP hydrocarbon concentration in oils or source rock bitumens. Cyclic sulfide analogues of TPP compounds appear to be extremely stable to laboratory desulfurization techniques, implying strong sequestering may occur in the natural marine environment (Poinsot et al., 1997, 1998). It is proposed that the high sulfate concentrations in marine sediments could facilitate sulfurization in anoxic marine sediments and formation of recalcitrant stable sulfide analogues. Fresh/brackish water anoxic sedimentation (or any environment in which reduced sulfur species is low) would favor preservation of TPP as hydrocarbons or in a labile form that may subsequently be thermally liberated as hydrocarbons from the kerogen. Oils derived from more saline (low sulfate) lakes such as the Green

River oils (Appendix A, Fig. 4) appear to have much reduced TPP ratios suggesting that in more saline lacustrine conditions, the fresh-brackish water algal input of the TPP compounds is much less. The resulting oils are the sum of generation from source facies derived from relatively fresh water environments and more saline or even hypersaline lacustrine environments. Assuming the C30 TPP compounds are derived from a specific biotic type then it is important to emphasize that there are multiple possible reasons why that biotic type may not occur in a particular lacustrine system. The Turpan samples illustrate nonmarine examples that have moderate to low TPP ratios because either algalderived organic matter is diluted by elevated terrigenous input (Jurassic) or the oil is a mix of inputs from fresh and saline lacustrine facies (Permian). The TPP algal source may not have flourished in environments with higher sediment input or under higher salinities. 4.3. Elevated TPP in marine samples Marine source rocks and their derived oils from around the world typically have low values of TPP ratio (Fig. 4). The exceptions include the intermediate TPP ratios in the marine samples shown earlier from the Late Cretaceous of western and northern South America and

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some oils from marine post-salt Late Cretaceous sources of West Africa (see the last section of Appendix A). This pattern of intermediate TPP ratios (previously published as the proprietary ‘‘ARCO Lacustrine Indicator’’) was first reported in the Jurassic of the Jeanne d’Arc and Porcupine Basins along the North Atlantic Rift (Butterworth et al., 1999). There are several possible explanations for the observance of elevated TPP ratios in these source rocks and oils. Factors affecting the TPP ratios in marine or transitional source rock facies like the Egret Chonta, Gautier, and Naparima Hill rocks, and in oils such as the South American and West African Late Cretaceous marine oils could be due to the following: 1. During periods of high runoff, fluvial transport of freshwater algal organic matter (i.e., Chlorococcalean algae) from the nonmarine environment to the marine environment could take place in a similar manner as transport of terrigenous land-plant input into the marine environment (Fig. 12a). 2. Elevated freshwater flow into the transition water volume between marine and nonmarine environments could cause either a fresh water lens above more saline marine waters or upon mixing (e.g., in an estuary) a lowering of salinity such that a fresh/brackish water algal bloom could form in near-shore environments (Fig. 12b). 3. The fresh water algae that contribute TPP compounds could have evolved and adapted to shallow transitional marine environments and become tolerant of salinities ranging from marine to brackish conditions. These adapted organisms might also contribute the TPP compounds in the near-shore marine to transitional facies (Fig. 12c). The TPP source could be from marine adapted Chlorococcalean algae or from marine Prasinopytes. Prasinophytes are considered the most primitive of the green algae (Guy-Ohlson, 1996), but could be distantly related to Chlorococcalean algae, which are dominantly fresh water forms (Batten, 1996).

The transitional Chonta samples discussed earlier show a link between the microfossil record (high dominant Chlorococcalean algae, Pediastrum) and the molecular fossil chemistry in support of scenarios (1) and (2). The TPP ratio may thus reflect the nonmarine algal input where the morphological characteristics are not preserved in the geologic record. The Trinidad source rocks indicate that nonmarine and marine biomarkers may be deposited in the same source formation possibly reflecting disparate algal inputs. The chemical profile of the Trinidad samples support scenario (3) in which the

459

source of the compounds could be shallow-water, nearshore marine species. Paleozoic oils from sources rich in Tasmanites (Devonian, North America or Silurian, North Africa) have low TPP ratios and do not appear to support scenario (3). The phylogenetic relationship between Mesozoic and Paleozoic Tasmanites is not well established beyond the presence of similar morphological features (e.g., punctate cyst walls). In fact, there is a possibility that the different stages in the life cycle may generate a variety of organic compounds (Guy-Ohlson, 1996). Both scenarios (1) and (2) require climatic conditions to provide sufficient fresh water run-off to transport nonmarine algal material or a sufficient volume of fresh water to lower the salinity near the interface with the marine environment. However, slow moving or standing water bodies with some level of eutrophication favor the growth of Chlorococcalean algae (Batten, 1996; Batten and Grenfell, 1996). Algae from these latter environments could be flushed into the marine environment with the onset of the rainy season. West African, Late Cretaceous (post-salt) marine source rocks were deposited during a period of high fresh water runoff into the marine environment (P. Hoffman, T. Wagner, and B. Beckmann, personal communication), and are likely the reason that some West African Late Cretaceous derived oils have moderately elevated TPP ratios compared to other marine oils. Foerster (1973) reports the only known discussion of Chlorococcalean nonmarine algae entering a marine or near-marine environment. Foerster (1973) cultured green algae in different salinities and many survived and reproduced in salinities > 30 ppt. Pediastrum and Scenedesmus survived culturing under more saline conditions, but significantly changed their morphology (especially Scenedesmus) and are more difficult to recognize. Nonmarine algae may be absent from nearshore marine or transitional depositional environments, or they may not have been preserved in a recognizable form. Interestingly, Pediastrum and Scenedesmus are often the only nonmarine algae found preserved in the Mesozoic and Cenozoic fossil record of near-shore marine environments and may be particularly abundant in regressive phases (Wood, unpublished data). The absence of nonmarine algal fossils does not mean they were not present, and another line of evidence, like their biomarkers, can be used as a proxy showing an organic connection. Foerster (1973) indicates that freshwater algae may contribute up to 50–80% of the total biomass at the head of an estuary, but general data on the flux of nonmarine algal organic matter into these transitional environments remains unavailable. Elevated C20 and C21 tricyclic terpanes have been observed in high levels relative to the C23 analogues in some marine Tasmanites rich samples (Aquino Neto et al., 1992), but have also been observed in lacustrine

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A.G. Holba et al. / Organic Geochemistry 34 (2003) 441–469

Fig. 12. Cartoon showing the possible sources of nonmarine algal input into the near-shore marine environment. (a) Transport of nonmarine algal organic matter into the marine environment. (b) High fresh water input into the near-shore marine environment causes fresh water lensing or the freshening of marine waters such that nonmarine algae may bloom, and (c) near-shore, shallow-water marine algal variants may also synthesize the TPP compounds thus mimicking the chemistry in nonmarine systems.

samples (Zumberge, 1987; Kuo, 1994; Holba, et. al., 1999). The occurrence of a tricyclic pattern consistent with Tasmanites (marine Prasinophycean, Green, algae)

in Trinidad supports scenario (3). These marine algae may produce the TPP compounds in near-shore marine conditions or when the near-shore salinity is possibly

A.G. Holba et al. / Organic Geochemistry 34 (2003) 441–469

lowered by fresh water inputs. Prasinophycean algae, like Tasmanites and their modern analogs, are primarily marine but may tolerate brackish conditions and produce morphological varieties that display differing chemical structure during ontogeny (Guy-Ohlson, 1996). Cases with low marine indicators (C30 24-propylcholestanes) and elevated TPP, e.g., Trinidad, could be explained by either of the scenarios outlined above. Much more information with present-day transitional systems is required before these issues can be fully resolved.

461

between fresh and marine conditions (high freshwater input in the Chonta rock extracts), or even into some marine environments (e g., Trinidad rock extracts). 5. Low values of TPP ratio may occur in some lacustrine source rocks and oils when the algal source of the TPP compounds is sufficiently diluted by other organic inputs (e.g., terrigenous plant matter), or if the environment is not conducive to the growth of the algae responsible for biosynthesizing the TPP compounds (saline to hypersaline conditions).

5. Conclusions Acknowledgements 1. TPP ratio is a powerful tool for recognition of fresh/brackish water algal input into the depositional setting of oil source rocks, especially when used in conjunction with other geochemical indicators. 2. Fresh/brackish water algal input may now be recognized in some lacustrine shale, lacustrine deltaic or coaly (e.g., Turpan-Hami samples), marine/nonmarine transitional rock facies and even in transitional marine source rocks (e.g., the Chonta samples). 3. Potentially, the TPP ratio may be useful in sorting out stratigraphic relationships and in recognizing changes in depositional environment and water chemistry. TPP used in conjunction with marine indicators can give new insights into the geologic history of a basin or area (e.g., the pre-salt rocks of Gabon). 4. Furthermore, the TPP ratio may be an indicator of Chlorococcalean, green algal input into the nonmarine environment (freshwater lacustrine oils and source rocks), transitional environments

This work was done at ARCO Exploration Research & Technical Services. The authors thank ARCO management for support and approval to release the work. We thank British Petroleum and Phillips Petroleum for their cooperation in the completion of the work. The suggestions of referees H. P. Nytoft, J. Zumberge, and M. Fowler substantially improved the manuscript and are appreciated. The authors thank Erik Tegelaar, Susan Singletary, Dave Roper and the staff of Baseline Resolution Inc. for their analytical assistance. The authors thank Ann Fincannon and Nicole Baptista (ARCO) for their assistance throughout the study. We thank Pierre Zippi for helpful conversations. We thank the following for contributing samples: J. C. Ramon, D. Wavrek, B. Huizinga, J. M. Moldowan, B. Ritts, B. Mei, J. A. Bojesen-Koefoed, H. P. Nytoft, L. R. Russell, M. Fowler, A. Wilhelms, N. Telnæs, C. Guzman-Vega, and N. Goodwin. Antenor M. Alema´n provided the Chonta Formation rock samples from Peru.

Associate Editor—M. Fowler

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Appendix A Number

Source age

Lithology

Basin

Country/state

TPP

Lacustrine samples 89X2301 89X2302 89X2306 89X2307 89X2308 89X2185 89X2218 89X2220 95X3799 95X3811 95X3800 95X3802 95X3801 94X3595 94X3596 94X3601 94X3623 94X3628 98X7437 86X0987 86X0255 97X4619 95X3981 98X7312 89X2212 96X4249 96X4250 96X4251 96X4253 96X4255 89X2234 96X4248 94X3649 94X3709 94X3710 94X3711 94X3712 94X3713 98X7127 98X7128 98X7129 98X7130 97X4617 98X7135 92X3079 97X04622 97X04623 92R0642py 97X7103 98X7296

Oligocene Oligocene Oligocene Oligocene Oligocene Oligocene Eo-Oligocene Eo-Oligocene Oligocene Oligocene Oligocene Oligocene Oligocene Eocene Eocene Eocene Eocene Eocene Eocene Eocene Eocene L. Cretaceous E. Cretaceous E. Cretaceous E. Cretaceous E. Cretaceous E. Cretaceous E. Cretaceous E. Cretaceous E. Cretaceous E. Cretaceous E. Cretaceous E. Cretaceous E. Cretaceous E. Cretaceous E. Cretaceous E. Cretaceous E. Cretaceous E. Cretaceous E. Cretaceous E. Cretaceous E. Cretaceous Jurassic E.-M. Jurassic E. Jurassic Triassic Triassic Triassic E. Permain Mississippian

Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale marl marl Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale marl marl Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale

Sunda Sunda Sunda Sunda Sunda Lombok Central Sumatra Central Sumatra Mekong Mekong Song Hong Song Hong Con Son Bohai (offshore) Bohai (offshore) Bohai (offshore) Bohai (onshore) Bohai (onshore) Liaohe Uinta Uinta Songliao Songliao Muglad Gabon Coastal Gabon Coastal Gabon Coastal Gabon Coastal Gabon Coastal Gabon Coastal Congo Congo Congo Congo Congo Congo Congo Congo Campos Campos Reconcavo Reconcavo Sichuan San Jorge Tacatu Mid Caspian Mid Caspian Cuyo Turpan-Hami Moncton

Indonesia Indonesia Indonesia Indonesia Indonesia Indonesia Indonesia Indonesia Viet Nam Viet Nam Viet Nam Viet Nam Viet Nam China China China China China China Utah Utah China China Sudan Gabon Gabon Gabon Congo Congo Congo Gabon Gabon Congo Congo Congo Congo Congo Congo Brazil Brazil Brazil Brazil China Argentina Guyana Kazakhstan Kazakhstan Argentina China Canada

0.88 1.00 0.73 0.65 0.71 0.83 0.98 0.97 1.00 1.00 0.37 1.00 1.00 0.50 0.60 0.46 0.31 0.63 0.71 0.79 0.33 0.62 0.50 0.88 0.92 0.79 0.74 0.96 0.80 0.87 0.93 0.92 0.84 0.87 0.92 0.91 0.92 0.75 0.82 0.85 0.85 0.94 0.60 0.74 1.00 0.55 0.35 0.82 0.42 0.17

mix mix mix

North China Neuquen Cuyo

China Argentina Argentina

0.24 0.26 0.31

Mixed Marine-Lacustrine samples 89X2230 Eocene 93X3517 E. Jurassic+? 98X7134 Triassic+?

(continued on next page)

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A.G. Holba et al. / Organic Geochemistry 34 (2003) 441–469 Appendix A (continued) Number

Source age

Lithology

Basin

Country/state

TPP

95X3942

Dev.+Jur.

mix

Orcadian

U.K.

0.55

Nonmarine Coal-Marine Deltaic samples 90X2436 Miocene 86X0777 Oligocene 89X2180 Oligocene 89X2181 Oligocene 86X0246 Oligocene 86X0232 Oligocene 86X1568 Oligocene 95X4013 Oligocene 90X2391 Oligocene 86X1240 L. Eocene 86X1252 L. Eocene 86X1995 L. Eocene 89X2293 Eocene 96X4454 Eocene 94X3573 Eocene 86X2078 Eocene 89X2222 Paleocene 97X7014 Paleocene 97X7015 Paleocene 94X3567 Paleocene 98Z0016 Tertiary 96X4490 Jurassic 97X04633 Jurassic 98X7524 Mid Jurassic 98X7525 Mid Jurassic 97X7104 E.-M.Jurassic

Shale Coal Coal Coal Coal Coal Coal Coal Coal Paralic Paralic Paralic Shale Coal Coal Coal Coal/shale Coal Coal Shale Shale/coal Shale/coal Shale Coal/shale Coal/shale Coal/shale

Khatyrka Ardjuna Ardjuna Ardjuna Ardjuna Ardjuna Kangean NW Java North Taiwan Gulf Coast Gulf Coast Gulf Coast Mackenzie Delta Pacific Rim Sakhalin Taranaki Gippsland Svalbard Svalbard Niger Delta Nussuaq Qaidam N.E. Mid. Caspian Central Graben Central Graben Turpan-Hami

Russia Indonesia Indonesia Indonesia Indonesia Indonesia Indonesia Indonesia Taiwan Texas Texas Texas Canada na Russia New Zealand Australia Norway Norway Nigeria Greenland China Kazakhstan Denmark Denmark China

0.11 0.12 0.00 0.09 0.13 0.13 0.17 0.08 0.11 0.20 0.31 0.36 0.06 0.06 0.07 0.13 0.06 0.03 0.02 0.24 0.03 0.09 0.36 0.15 0.12 0.05

Marine samples 95X3869 95X3870 95X3871 95X3995 94X3609 94X3612 94X3615 94X3616 86X1384 90X2612 91X2820 94X3656 95X3839 96X4455 94X3742 94X3744 94X3617 86X1116 91X2810 98X7380 98X7460 93X3427 95X3882 95X3872 92X3049 96X4299

Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Marl Marl Marl Shale Shale Shale Marl Shale

Santa Barbara Santa Barbara Santa Barbara San Joaquin San Joaquin San Joaquin San Joaquin San Joaquin S. Cuyama Black Sea Black Sea Black Sea Pacific Rim Pacific Rim Sakhalin Sakhalin San Joaquin Gulf Coast Pelagian Pelagian Pelagian Talara Llanos Llanos Oriente Gabon coastal

California California California California California California California California California Romania Romania Bulgaria na na Russia Russia California Louisiana Tunisia Tunisia Tunisia Peru Colombia Colombia Ecuador Gabon

0.11 0.22 0.17 0.24 0.20 0.13 0.26 0.26 0.17 0.04 0.22 0.30 0.10 0.14 0.12 0.16 0.14 0.25 0.16 0.08 0.12 0.27 0.25 0.16 0.05 0.22

Miocene Miocene Miocene Miocene Miocene Miocene Miocene Miocene Miocene Eo.-L.Miocene Eo.-L.Miocene Eo.-L.Miocene Oligocene Oligocene Oligocene Oligocene Eocene Eocene Eocene Eocene Eocene Eocene L. Cretaceous L. Cretaceous L. Cretaceous L. Cretaceous

(continued on next page)

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Appendix A (continued) Number

Source age

Lithology

Basin

Country/state

TPP

96X4295 96X4297 97X06877 97X06878 98X07400 94X3585 91X2805 98X7381 93X3377 93X3392 92X3060 92X3020 92X3027 91X2790 89X2227 96X4284 97X4690 86X1808 86X1771 86X1774 90X2522 96X4476 97X4615 90X2104 96X4477 97x4616 96X4472 96X4473 97X4612 97X4613 97X4614 96X4475 99X07568 98X07532 96R4025 96R4026 98X7565 98X7533 98X7520 98X7566 97X6933 95R5115 95R5143 96X4500 96X4501 98X7301 98X7302 98X7303 93X3093 98X7294 98X7295 98X7132 98X7131 95X4082 97X4598 92X2952 94X3787

L. Cretaceous L. Cretaceous L. Cretaceous L. Cretaceous Cretaceous L. Cretaceous L. Cretaceous L. Cretaceous L.Cretaceous L.Cretaceous L.Cretaceous Cretaceous Cretaceous E. Cretaceous E. Cretaceous E. Cretaceous E. Cretaceous L. Jurassic L. Jurassic L. Jurassic L. Jurassic L. Jurassic L. Jurassic L. Jurassic L. Jurassic L. Jurassic L. Jurassic L. Jurassic L. Jurassic L. Jurassic L. Jurassic L. Jurassic L-M. Jurassic L-M. Jurassic M. Jurassic M. Jurassic M. Jurassic M. Jurassic M. Jurassic M. Jurassic M-L Jurassic M-L Jurassic M-L Jurassic Jurassic Jurassic Jurassic Jurassic Jurassic L. Jurassic L. Jurassic L. Jurassic M.-L.Jurassic E.-M.Jurassic Jurassic Jurassic M. Jurassic M. Jurassic

Shale Shale Shale Shale Shale Limestone Shale Shale Shale Shale Shale Shale Shale Shale Limestone Shale Shale Shale Shale Shale Limestone Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Marl Marl Marl Shale Limestone Limestone Limestone Limestone Limestone Limestone Shale Shale

Gabon coastal Gabon coastal Gabon coastal Gabon coastal N. Gabon Dead Sea Pelagian Pelagian Maran˜on Maran˜on Gulf Coast Gulf Coast Gulf Coast Gulf Coast S. Florida North Slope North Slope Troms Haltenbanken Haltenbanken Solan East Shetlands Viking Graben East Shetlands East Shetlands Forties Forties S. Halibut Central Central Central Central W. Shetlands W. Shetlands W. Shetlands W. Shetlands W. Shetlands W. Shetlands W. Shetlands W. Shetlands Jeanne d’Arc Porcupine Porcupine Porcupine Porcupine na na na Neuquin Tampico Tampico East Platform East Platform Southern Gulf Southern Gulf Moesian Platform Moesian Platform

Gabon Gabon Gabon Gabon Gabon Jordan Tunisia Tunisia Peru Peru Louisiana Louisiana Louisiana Louisiana Florida Alaska Alaska Norway Norway Norway U.K. U.K. U.K. U.K. U.K. U.K. U.K. U.K. U.K. U.K. U.K. U.K. U.K. U.K. U.K. U.K. U.K. U.K. U.K. U.K. Canada Ireland Ireland Ireland Ireland na na na Argentina Mexico Mexico Saudi Arabia Saudi Arabia Qatar Qatar Romania Bulgaria (continued on next

0.26 0.17 0.29 0.28 0.17 0.15 0.25 0.26 0.26 0.19 0.04 0.09 0.11 0.13 0.11 0.03 0.07 0.05 0.05 0.05 0.12 0.08 0.04 0.16 0.10 0.04 0.11 0.02 0.13 0.07 0.07 0.11 0.12 0.13 0.17 0.18 0.15 0.24 0.13 0.06 0.23 0.22 0.17 0.23 0.12 0.07 0.07 0.08 0.24 0.13 0.19 0.22 0.21 0.24 0.21 0.05 0.13 page)

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465

Appendix A (continued) Number

Source age

Lithology

Basin

Country/state

TPP

86X1875 86X1916 86X0560 96X4287 97X7012 97X7013 89X2295 96X4498 96X4499 93X3388 95X3855 86X1294 93X3302 94X3697 90X2563 90X2565 98X7155 96X4496 86X0652 89X2278 89X2281 97X7027 97X7028 97X7083 97X4618 97X6941 97X6942 97X6945 90X2457 91X2728 89X2120 86X0398 97X4608 97X4609 97X4610 97X4611 86X0338 86X0041 86X0656 86X0983 93X3331 86X0983 86X1226 90X2477 86X1088 86X1210 89X2224 98X7126 93X3501 93X3502 98X7133 90X2432 91X2668 86X0085 86X0866 98X7313 98X7332

M. Jurassic M. Jurassic M. Jurassic M. Jurassic Jurassic Jurassic E. Jurassic E. Jurassic E. Jurassic E. Jurassic E. Jurassic E. Jurassic L. Triassic L. Triassic L. Triassic L. Triassic L. Triassic L. Triassic L. Triassic Triassic Triassic Triassic Triassic Triassic Triassic E. Triassic E. Triassic E. Triassic Permian Permian Permian Permian Pennsylvanian Pennsylvanian Pennsylvanian Pennsylvanian Pennsylvanian Pennsylvanian Pennsylvanian Pennsylvanian Pennsylvanian Pennsylvanian Mississippian Devonian Devonian Devonian Devonian Devonian Devonian Silurian Silurian Ordovician Ordovician Ordovician Ordovician Precambrian Precambrian

Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Marl Marl Marl Marl Marl Shale Shale Shale Shale Shale Shale Marl Marl Marl Limestone Marl Limestone Marl Shale Shale Shale Shale Limestone Limestone Limestone Shale Shale Shale Limestone Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale

Cook Inlet Cook Inlet Cook Inlet Cook Inlet Vienna Vienna Paris Hampshire Hampshire Maran˜on North Slope North Slope North Slope North Slope North Slope North Slope North Slope North Slope North Slope Sverdrup Sverdrup Western Canada Western Canada Barents Sea Sichuan Perth Perth Perth Southern Gas Permian Permian Big Horn E. Midlands E. Midlands E. Midlands E. Midlands Denver na na Paradox Anadarko Paradox Williston Permian Illinois Williston Alberta Illizi Ghadames Ghadames West Platform Anadarko Anadarko Williston Illinois na na

Alaska Alaska Alaska Alaska Austria Austria France U.K. U.K. Peru Alaska Alaska Alaska Alaska Alaska Alaska Alaska Alaska Alaska Canada Canada Canada Canada Norway China Australia Australia Australia UK Texas Texas Wyoming UK UK UK UK Colorado na na New Mexico Oklahoma New Mexico N. Dakota Texas Illinois N. Dakota Canada Algeria Algeria Algeria Saudi Arabia Oklahoma Kansas N. Dakota Illinois Oman Oman (continued on next

0.08 0.21 0.10 0.10 0.11 0.10 0.14 0.14 0.14 0.27 0.06 0.07 0.04 0.00 0.08 0.07 0.06 0.07 0.04 0.12 0.13 0.04 0.08 0.07 0.05 0.14 0.21 0.29 0.02 0.06 0.06 0.01 0.28 0.23 0.23 0.18 0.02 0.12 0.09 0.03 0.13 0.03 0.21 0.19 0.06 0.03 0.19 0.05 0.05 0.04 0.02 0.25 0.03 0.03 0.05 0.02 0.05 page)

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A.G. Holba et al. / Organic Geochemistry 34 (2003) 441–469

Appendix A (continued) Number

Source age

Marine oils (mixed input-elevated TPP) 95X04040 Oligocene 97X4650 Oligocene 91X2664 Eoc.-L.Miocene 92X3227 Eocene 95X4062 L. Cretaceous 95X4063 L. Cretaceous 95X4064 L. Cretaceous 91X2765 L.Cretaceous 90X2500 L.Cretaceous 90X2504 L.Cretaceous 90X2507 L.Cretaceous 90X2512 L.Cretaceous 95X3879 L.Cretaceous 95X3899 L.Cretaceous 95X3905 L.Cretaceous 95X3912 L.Cretaceous 95X3919 L.Cretaceous 95X3928 L.Cretaceous 93X3412 L.Cretaceous 93X3576 L.Cretaceous 97X6929 M-L Jurassic 97X6930 M-L Jurassic 97X6931 M-L Jurassic 97X6932 M-L Jurassic 97X6934 M-L Jurassic 96X4585 M-L Jurassic Na=Not available

Appendix B

Lithology

Basin

Country/state

TPP

Shale Shale Shale Shale Shale Shale Shale Shale Marl Marl Marl Marl Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale Shale

S. Caspian Fore Caucasus Black Sea Gulf Coast Gabon coastal Gabon coastal Gabon coastal Gulf Coast Lake Maracaibo Lake Maracaibo Lake Maracaibo Lake Maracaibo M. Magdalena M. Magdalena M. Magdalena M. Magdalena M. Magdalena M. Magdalena Maran˜on Maran˜on Jeanne d’Arc Jeanne d’Arc Jeanne d’Arc Jeanne d’Arc Jeanne d’Arc Jeanne d’Arc

Azerbaijan Russia Romania Louisiana Gabon Gabon Gabon Louisiana Venezuela Venezuela Venezuela Venezuela Colombia Colombia Colombia Colombia Colombia Colombia Peru Peru Canada Canada Canada Canada Canada Canada

0.35 0.32 0.32 0.36 0.39 0.35 0.30 0.31 0.29 0.43 0.45 0.40 0.33 0.46 0.46 0.46 0.43 0.44 0.45 0.51 0.31 0.34 0.35 0.47 0.28 0.29

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