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Evidence for Gloeocapsomorpha prisca in Late Devoniansource rocks from Southern Alberta, Canada
Martin G. Fowlera,*, Lavern D. Stasiuka, Mark Hearnb, Mark Obermajera
aGeological Survey of Canada Calgary, Natural Resources Canada, 3303-33rd Street NW, Calgary, Alberta, Canada T2L 2A7bShell Canada Ltd., 400-4 Avenue S.W., Calgary, Alberta, Canada T2P 2H5
Abstract
Organic-rich intervals within the Late Devonian Camrose Member of southern Alberta, Canada show opticaland chemical characteristics very similar to those of Ordovician samples whose organic matter is dominated byGloeocapsomorpha prisca-derived alginite. This includes saturate fraction gas chromatograms dominated by n-alkanes
with a pronounced odd carbon number up to C19, and much lower abundances of C19+ n-alkanes, acyclic isoprenoidsand biomarkers. Microscopy reveals these samples contain G. prisca-like alginite with a morphology that previouslyhas been suggested for the growth of this organism under higher salinity conditions which is in agreement with the
depositional environment of the Camrose Member. One unusual feature of the G. prisca-rich samples is the very highconcentration of C21 and C23 n-alkylnaphthalenes and n-alkylbenzenes in the aromatic fractions of their extracts. Theorigin of these compounds is not known but their occurrence could be related to the high concentrations of C21 and C23
n-alkyl phenols that have been noted in pyrolysates of Estonian kukersites by previous workers. Other CamroseMember extracts show very different distributions that are more typical for carbonates deposited under anoxic, highersalinity conditions. Many oils that occur in Nisku Formation reservoirs in the Enchant-Hays field in southern Albertashow saturate fraction gas chromatograms and other evidence that indicate an important contribution to these oils
from the G. prisca-rich intervals. These are thought to have a contribution from Camrose Member source rocks.Hence, caution should be used in only attributing G. prisca geochemical characteristics to Cambro-Ordovician oils as,on rare occasions, they can also occur in younger source rocks and their derived oils.
Crown Copyright # 2004 Published by Elsevier Ltd. All rights reserved.
1. Introduction
Gloeocapsomorpha prisca is the main contributingorganism to many Cambro-Ordovician hydrocarbon
source rocks where it can make up to greater than 90%of the organic matter (e.g. Reed et al., 1986; Hoffman etal., 1987; Fowler, 1992). Such source rocks are often
called kukersites (Hutton, 1987) after the OrdovicianEstonian kukersites in which Zalessky (1917) firstrecognized G. prisca. Kukersite-type deposits often
make excellent source rocks with high TOC (totalorganic carbon) contents and HI (Hydrogen Index)
values indicating Type I organic matter. In other Cam-
bro-Ordovician sediments, the contribution from G.prisca is diluted by input from other organisms andthese have been termed diluted kukersites (Fowler,
1992). There has been considerable dispute over whattype of organism G. prisca was (e.g. Reed et al., 1986;Hoffman et al., 1987; Foster et al., 1989; Fowler, 1992;
Stasiuk and Osadetz, 1990; Derenne et al., 1992;Wicander et al., 1996; Blokker et al., 2001). Mostauthors now favour that it was a probable photo-
synthetic coccoidal cyanophyte, possibly related to theextant Entophysalis major, that had both planktonic andbenthic life habits although some still believe it is relatedto the extant green algae, Botryococcus braunii (e.g.
Derenne et al., 1992).G. prisca-rich rocks and their derived oils show a
number of distinctive geochemical characteristics. This
0146-6380/$ - see front matter Crown Copyright # 2004 Published by Elsevier Ltd. All rights reserved.
doi:10.1016/j.orggeochem.2004.01.017
Organic Geochemistry 35 (2004) 425–441
www.elsevier.com/locate/orggeochem
* Corresponding author. Tel.: +1-403-292-7038; fax: +1-
403-292-7159.
E-mail address: [email protected] (M.G. Fowler).
is best displayed by their saturate fraction gas chroma-tograms which are dominated by n-alkanes up to C19
with a pronounced odd carbon number predominance.C20 and higher molecular weight n-alkanes are in much
lower concentrations and tend to show no or a veryslight odd over even carbon number preference. Whileimmature samples have low to moderate concentrations
of acyclic isoprenoids, higher maturity source rockextracts and oils show extremely low concentrations ofacyclic isoprenoids. Polycyclic biomarker compounds
are also present in very low concentrations. However,monocyclic alkanes are present in higher abundancethan in most other oils, with n-alkylcyclohexanes often
the second most abundant group of compounds afterthe n-alkanes. ‘Diluted kukersites’ differ from these byshowing a less pronounced odd carbon number pref-erence of the C13–C19 n-alkanes and greater amounts of
C19+ n-alkanes and acyclic isoprenoids (e.g. Fowler,1992). Pyrolysates of G. prisca rich sediments also show
distinctive characteristics. Some are heavily dominatedby n-alkyl species, often showing an odd carbon numberpreference with a low abundance of C19+ compounds(Douglas et al., 1990; Derenne et al., 1992; Blokker et
al., 2001), while Estonian kukersite pyrolysates appearto contain a higher abundance of phenols which byanalogy with extant Botryococcus braunii could be G.
prisca adapting to more saline conditions (Derenne etal., 1992).G. prisca was widespread in tropical epi-continental
seas during Cambro-Ordovican time with kukersites ordiluted kukersites known to occur on five present daycontinents (Fowler, 1992). There are very few reports of
G. prisca occurring in post-Ordovician sediments (e.g.Cramer and Diez de Cramer, 1972) with most olderreports that suggested a range in age up to Tertiaryappearing to be erroneous (Fowler, 1992; Wicander et
al., 1996). This led Fowler (1992) to suggest that G.prisca was part of the Ordovician-Silurian extinction
Fig. 1. Map showing location of Camrose Member/Nisku Formation source rocks in southern Alberta and the location of the
Enchant-Hays oil field. Note each township is 6�6 miles square so the same rocks occur roughly over a 120�70 mile (200�120 km)
area.
426 M.G. Fowler et al. / Organic Geochemistry 35 (2004) 425–441
event that is often linked with a major glaciation.However, in recent years there have been crediblereports of G. prisca in post-Ordovician sediments.Abrams et al. (1999) found Silurian and Lower
Devonian intervals showing geochemical characteristicssimilar to those of Ordovician kukersites in the north-eastern Timan Pechora Basin of Russia, although the
presence of G. prisca was not visually confirmed. Inaddition, oils found in Lower Devonian-Carboniferousreservoirs in part of this basin have characteristics simi-
lar to kukersite derived oils and were thought to bepossibly sourced from these units. Abrams et al. (1999)also report J.M. Moldowan (personal communication,
1996) finding G. prisca characteristics in rock extracts asyoung as Middle Devonian. G. prisca has been recog-nized microscopically in Middle Devonian Elk PointGroup and Upper Devonian Woodbend Group rocks in
eastern Alberta, generally as a minor component oforganic-rich intervals (Nowlan et al. 1998a,b; Chow etal., 1995; Stasiuk, 1999a).
During the course of our study of Devonian Petro-leum Systems of the WCSB (Western Canada Sedimen-tary Basin), units enriched in G. prisca were also noted
in Late Devonian units, especially in the CamroseMember of the Winterburn Group, southern Alberta(Figs. 1 and 2), some of which gave extracts with char-
acteristics similar to those of Ordovician kukersites(Fowler and Stasiuk, 1999). It is these samples and theirderived oils that are the subject of this paper.
2. Methodology
Aliquots of possible source rocks were dried andpowdered for Rock-Eval/TOC analysis. The instrumentused was a Delsi Rock-Eval II pyrolysis unit equipped
with a total organic carbon (TOC) analysis module.Duplicate or muliple analyses of the core samples weremade. Rock samples selected for extraction were pow-dered and extracted using azeotropic chloroform:
methanol (87:13) mixture for 24 h. Rock extracts andoils were treated with approximately 40 volumes ofn-pentane to precipitate the asphaltenes. The deasphalted
extracts and oils were fractionated using open columnchromatography (3/4 activated alumina and 1/4 acti-vated silica gel with an adsorbent:sample mass ratio of
100:1). Saturates were recovered by eluting with 3.5 mlof pentane/g of adsorbent. Aromatics were recovered byeluting with 4 ml of 50:50 pentane-dichloromethane/g
adsorbent and the resins were recovered with 4 ml ofmethanol/g adsorbent.The gasoline range hydrocarbons (iC5–nC8) in the oils
were analyzed on a HP5890 gas chromatograph con-
nected to an OI Analytical 4460 Sample Concentrator.A small amount of the whole crude oil was mixed withdeactivated alumina and transferred to the Sample
Concentrator. The gasoline fractions were then passedonto the Gas Chromatograph equipped with a 50 mHP-1 column, with siloxane gum used as a fixed phase.The initial temperature was held at 30 �C for 10 min and
then programmed to 45 �C at a rate of 1 �C/min. Thefinal temperature was held for 25 min. The elutinghydrocarbons were detected using a flame ionization
detector. Saturate fractions were analyzed using gaschromatography (GC). A Varian 3700 FID gas chro-matograph was used with a 30 m DB-1 column. The
temperature was programmed from 60 to 300 �C at arate of 6 �C/min and then held for 30 min at 300 �C. Theeluting compounds were detected and quantitatively
determined using a hydrogen flame ionization detector.Gas chromatography–mass spectrometry (GC–MS) wasperformed on a VG 7070 mass spectrometer with a gaschromatograph attached directly to the ion source. The
Fig. 2. Stratigraphic nomenclature for Late Devonian units in
southern Alberta.
M.G. Fowler et al. / Organic Geochemistry 35 (2004) 425–441 427
instrument was controlled by an Alpha Workstationusing Opus software. A 30 m fused silica column (DB-5,J&W Scientific) was used for GC separation. The temp-erature was initially held at 100 �C for 2 min and then
programmed at 40 �C/min to 180 �C and at 4 �C/min to320 �C. After reaching 320 �C the temperature was heldfor 15 min. The mass spectrometer was operated with a
70 eV ionization voltage, 100 mA filament emissioncurrent and interface temperature of 280 �C. Massfragment ions monitored during single ion monitoring
experiments included m/z 177.1638, 191.1794, 217.1950,218.2028, 231.2106 and 259.2262. GC-MS analyses ofaromatic hydrocarbons were performed with a HP 6890
Series GC coupled to a HP 5973 Series Mass SelectiveDetector operated in selective ion monitoring (SIM)mode. The GC was fitted with a 30 m�0.25 mm i.d. DB-5column. The temperature was initially held at 100 �C for
2 min and then programmed at 3 �C/min to 300 �C andheld for 10 min. The mass spectrometer was operatedwith a 70 eV ionization voltage, 100 mA filament emis-
sion current and an interface temperature of 280 �C.Identification of peaks was aided by full scan GC–MSanalyses of selected samples using a Micromass Auto-
spec-TOF instrument in normal GC–MS mode. Py-rolysis-gas chromatography (py-GC) was achieved usinga Horizon Instrument Curie Point Pyrolyzer with a wire
with a Curie temperature of 610 �C on the injector ofa HP5890 gas chromatograph. The products wereseparated on a 30 m DB-1 column using a temperatureprogram of 0–300 �C at 6 �C/min.
Organic-rich core samples were prepared for incidentlight microscopy of dispersed organic matter by mount-ing rock fragments in epoxy resin. Prior to mounting,
small saw-cut core fragments (�1 cm cubes) were initi-ally hand polished while drill cuttings were crushed to1–5 mm particulates. Prepared as such, samples were
then put into 1 inch diameter circular plastic moldsensuring, where required, perpendicular to bedding,parallel to bedding or random orientation of the parti-culates. The moulds were filled with epoxy (cold setting
epoxy consisting of 2:1 resin and hardener) and left tocure for 24–48 h. The pellets were ground and polishedon a Buehler Ecomet IV polishing machine.
Dispersed organic matter (macerals) was analyzedand classified using white and fluorescence incident lightmicroscopy. Three reflected light microscope systems
were used for organic petrologic analysis: a Leitz MPVII system, a Zeiss UMP system, and a Zeiss Axioplan IIsystem. Fluoresence microscopy was done using water
immersion objectives with total magnification up to1200�. A Zeiss Invert 410 confocal laser scanningmicroscope equipped with 488, 543, and 633 nm lasersare also used, particularly for studying detailed maceral
morphology (2D and 3D perspectives) of liptinite andamorphinite macerals under magnification up to 8000�(see Stasiuk, 1999b).
3. Results
3.1. Geology
The regional geology of the Winterburn Group insouthern Alberta is summarized in Kissling (1996). Inthe area that extends from Townships 1 to 15 and Ran-
ges 1 to 25W4 (Fig. 1), over which we sampled 22 cores,the Frasnian-aged Camrose Member/Nisku Formationstrata (Fig. 2) are represented by a �30 m thick
sequence that displays a shallowing-upward profile, withdolomitized marine shelf facies to peritidal, lagoon andtidal flat facies. Three mappable, potential source rock
units have been identified within the Camrose Member/Nisku Formation section in this area, two in the Cam-rose Member and one in the Nisku Formation (Fowleret al., 2001). Here we concentrate on the evidence for G.
prisca within the Camrose Member potential sourcerock intervals as there was little or no evidence for G.prisca within the Nisku Formation potential source
interval in this area.
3.2. Optical evidence for the occurrence of G. prisca
Macerals within potential source rocks of the Cam-rose Member/Nisku Formation in southern Alberta are
derived from both marine and terrestrial sources andsuggest variable and fluctuating paleodepositional con-ditions (Fowler et al., 2001). Coccoidal alginite maceralsand shallow water organic facies are an important
component of some Camrose Member potential sourcerocks (Fig. 3). Several varieties of coccoidal alginitemacerals appear to be present in these rocks (e.g. G.
prisca, Botryococcus, Pediastrum-like?), but the majorityhave morphological features consistent with G. prisca(Fig. 3) and are hereafter referred to as G. prisca. G.
prisca alginites are very abundant and dominant in theCamrose Member at 10-4-1-9W4 (1185.75 and 1185.95m), at 15-35-7-22W4 (1942.5 m) and at 13-32-7-20W4(especially at 1665.9 m) (Fig. 3). Similar G. prisca-
dominated organic facies also occur in the CamroseMember at 16-31-10-4W4 (1379.37 and 1379.58 m) and6-22-6-23W4 (2324.9 and 2325.8 m), although the algi-
nites at these locations, and particularly the latter, are‘softened’ and largely ‘altered’ due to thermal alterationand probable S-enrichment (Fig. 3). Petrographic evi-
dence for in situ oil generation from G. prisca alginite isparticularly clear at the 7-22W4 location where solidbitumen and crude oil inclusions are abundant (Fig. 3).
Stasiuk et al. (1993) described three G. prisca ‘micro-facies’ in Late Ordovician rocks of the Saskatchewanportion of the Williston Basin, two disseminated (A andB) and a stromatolitic facies. Disseminated A micro-
facies consists of small (generally <5 to 20 mm), thin-walled G. prisca alginite colonies typically consisting ofno more than 12 individual cells. Disseminated B
428 M.G. Fowler et al. / Organic Geochemistry 35 (2004) 425–441
Fig. 3. Photomicrographs of dispersed organic matter within Ordovician kukersites, Williston Basin (a–c) and Nisku Formation/
Camrose Member source units (d–l), Alberta. Incident, conventional fluorescent light (a, d–k), and laser scanning fluorescence
microscopy (LSM; b,c); water immersion. Scale on photo a is for all photos except b and c (scale on photo b). (a). G. prisca showing
mainly open cell morphology (o) but also some closed (c) morphology. (b, c). LSM image of open and closed cellular morphology in
G. prisca. (d). Solid bitumen (b) associated with G. prisca enriched organic facies. (e–h). Abundant small to medium colonies of coc-
coidal G. prisca alginite (Gp) associated with intense yellow-fluorescing Prasinophyte alginite (p) in photo e. (i–l). Thermally mature G.
prisca alginite (Gp) associated with abundant bitumen. Low (k) and high (l) magnification images showing thermally mature G. prisca
associated with abundant bitumen (b) and crude oil inclusions (hcfi) in late calcite cements from 7-20W4 location. Note the ‘softening’
of G. prisca with closed cellular structure resulting from thermal maturity effects.
M.G. Fowler et al. / Organic Geochemistry 35 (2004) 425–441 429
microfacies is similar although it consists of larger G.prisca colonies (up to 100 mm) with much thicker cellwalls and development of the colony by a thickened‘sheath’. Disseminated A is thought to represent the
earlier growth stage of G. prisca, while disseminated B isa more advanced growth stage under more stressfulconditions, probably related to the development of algal
blooms (Stasiuk and Osadetz, 1990; Stasiuk, 1999a).The stromatolitic G. prisca microfacies are characterizedby algal mats with upper surface microtextures, such as
domes, pinnacles, pustules or phototactic structures(Stasiuk, 1999a). This could form via the disseminated Bstage or directly at the sediment–water interface. The dis-
seminated B and stromatolitic microfacies are the mostvolumetrically important in the Ordovician of theWilliston Basin (Stasiuk and Osadetz, 1990).The cell size, cellular organization and shape of the G.
prisca colonies observed in the Camrose Member aresimilar to those previously described for the Ordovician(e.g. Stasiuk and Osadetz, 1990) (Fig. 3). However, there
are some notable differences. Only the disseminated Aand B G. prisca microfacies were observed while thestromatolitic microfacies rarely occurs in the Camrose
Member/Nisku Formation samples or any other Devo-nian samples where we have noted G. prisca. A closedand open morphology characterizes disseminated B G.
prisca alginites in Ordovician sediments of the WillistonBasin but almost all the disseminated B alginite noted inthe Upper Devonian rocks is characterized by a closedmorphology (Fig. 3). Closed and open cellular mor-
phology can easily be distinguished using both conven-tional fluorescence microscopy and confocal laserscanning fluorescence microscopy (Fig. 3a–c), the latter
is within the same range of magnification as used byDerenne et al. (1992) to demonstrate the two morpho-types of G. prisca alginite. The alginite colonies in the
Upper Devonian samples also tend to be considerablysmaller than those found in Ordovician sediments,ranging from �5 to 50 mm in diameter (Fig. 3).
3.3. Extract characteristics
Camrose Member extracts show variable saturate
fraction gas chromatogram (SFGC) characteristics.These range from a sample (Fig. 4a) that gave a SFGCclosely resembling those from Ordovician G. prisca rich
samples to those that show no odd or even carbonnumber preference with high abundances of acyclic iso-prenoids and biomarkers (Fig. 4c) and those that show
intermediate characteristics (Fig. 4b). The samples withhigher concentrations of higher molecular weight n-alkanes and biomarkers in their SFGCs have biomarkerdistributions characterized by low pristane/phytane
ratios, a relatively high abundance of C20+ acyclic iso-prenoids and a m/z 191 mass chromatogram (Fig. 5c)that shows a pronounced C34 homohopane prominence,
a relatively high abundance of gammacerane and lowamounts of tricyclic and tetracyclic terpanes. These arecharacteristics that are generally associated with car-bonate and elevated salinity depositional environments
(e.g. Peters and Moldowan, 1993, pp. 141–142, 209)which is in agreement with those interpreted for theCamrose Member (Fowler et al., 2001). Sterane carbon
number distributions vary from a slight C27 pre-dominance to a pronounced C29 predominance. Micro-scopic examination of these samples indicates little to no
contribution from G. prisca to their organic matter.As noted earlier, some samples have organic matter
dominated by G. prisca and hence resemble Ordovician
kukersite deposits. The location that showed the bestcombined optical and chemical evidence of a G. priscacontribution in this study was the lower potential sourceinterval of the Camrose Member at 13-32-7-20W4.
Fig. 4. Saturate fraction gas chromatograms of Camrose
Member extracts from southern Alberta. C15, C20 and C25 are
the C15, C20 and C25 n-alkanes, respectively; Pr and Ph
are pristane and phytane; H is 17a(H)-hopane, and peak
indicated with an asterisk is C17 n-alkylcyclohexane.
430 M.G. Fowler et al. / Organic Geochemistry 35 (2004) 425–441
Three samples of interlaminated organic-rich mudstoneswere taken between 1665.0 and 1665.90 m depth. Thisinterval contains abundant shell fragments (brachiopodand bivalve) and fish fragments (e.g. fish bones). The
maceral assemblage for this interval (Fig. 3) is domi-nated by G. prisca disseminated A and B alginite withvery minor amounts of Prasinophyte alginite and acan-
thomorphic acritarchs. The depositional environment isthought to have had oxygenated surface waters withperiodically more restricted anoxic bottom water condi-
tions, possibly related to times of increased G. priscaproductivity. These samples have TOC contents rangingfrom 10.60 to 16.76% and HI values from 797 to 864
mg HC/g TOC. Their Tmax values are 439–441�C which
are higher than might be expected for the level ofmaturity at this location (�0.70% vitrinite reflectance
equivalent: Stasiuk and Fowler, 2002) but not for Type Iorganic matter.The SFGC of the sample from 1665.9 m (8842) is very
similar to those of Ordovician kukersites (Fig. 4a). It
shows a pronounced odd carbon number predominanceof the C17 and C19 n-alkanes and low amounts of C20+
n-alkanes, acyclic isoprenoids and biomarkers. It also
has relatively high concentrations of n-alkylcyclohex-anes with the peaks of these compounds clearly appar-ent in the SFGC (Fig. 4a). A m/z 82 mass
chromatogram (Fig. 6a) shows an odd carbon numberpredominance of these compounds over the C15-C23
range with an abrupt decrease in concentration after
C23. This is a somewhat different distribution for thesecompounds compared with other North Americankukersite extracts and derived oils which usually show a
Fig. 5. m/z 191 and m/z 217 mass chromatograms showing the distributions of terpanes and steranes, respectively, for Camrose
Member organic-rich samples from southern Alberta. Peaks identified in Table 2.
M.G. Fowler et al. / Organic Geochemistry 35 (2004) 425–441 431
distribution similar to that of the n-alkanes (Fowler etal., 1986; Fowler, 1992). An extract of the Late Ordovi-cian Collingwood Member from southern Ontario hasbeen reported with a predominance of C23 and C25 n-
alkylcyclohexanes but with C14–C31 homologues alsopresent in moderate to high abundance (Fowler, 1992).The biomarker distribution of sample # 8842 (Fig. 5,
Table 1) is different to most of the other CamroseMember/Nisku Formation organic-rich intervals thatshow no optical or chemical evidence of a major G.
prisca contribution. This includes higher abundances ofC27 and C29 17a(H)-hopanes relative to C30 17a(H)-hopane, lower gammacerane and C34 homohopane prom-
inence, lower Ts/Tm, much higher diasterane/regularratio and a higher abundance of short-chain steranes(Fig. 5a, Table 1). Steranes are in much lower abun-dance than hopanes. While these characteristics cannot
be attributed to a G. prisca contribution with any cer-tainty, some of these characteristics have been pre-viously noted for Ordovician kukersites and their
derived oils, including the predominance of diasteranesover regular steranes (Longman and Palmer, 1987;Fowler, 1992), a relatively higher abundance of C27 and
C29 hopanes (Zumberge, 1987) and the large pre-dominance of hopanes over steranes (Fowler, 1992). It isnoteworthy that the Family C oils of Abrams et al.
(1999), which have SFGCs suggesting that they have a
source rock containing a significant G. prisca contribu-tion, show many similar biomarker characteristicsincluding a C34 homohopane predominance, a muchgreater abundance of the C24 tetracyclic terpane than
the C23 tricyclic terpane and relatively high abundancesof diasteranes compared with the regular steranes.Evidence for a contribution from G. prisca to other
Camrose Member samples is less obvious. A samplefrom 10-4-1-9W4 (sample #8664, Table 1) that opticallyshowed a minor persistent contribution from G. prisca
has intermediate geochemical characteristics betweenthe 13-32-7-20W4 kukersite-like sample and samplesthat show no evidence of a G. prisca contribution. It has
a slight odd carbon number preference up to C19 andlower abundance of acyclic isoprenoids and biomarkers(Fig. 4b). This sample also has a higher concentration ofmonocyclic alkanes than most other samples showing a
pronounced odd carbon number preference up to C23
similar to the 13-32-7-20W4 sample (Fig. 6b). n-Alkyl-cyclohexanes are present in other samples (e.g. Fig. 6c)
but in much lower abundance and with a different car-bon number distribution. The 10-4-1-9W4 sample alsoshows intermediate biomarker characteristics including
only a minor C34 homohopane prominence, a high C29/hopane ratio, high diasteranes/regular steranes and C21
sterane/C29 sterane and low gammacerane/hopane
ratios (Fig. 5b, Table 1). A number of other samples
Table 1
Geochemical data for Camrose Member/Nisku Formation extracted samples and a typical crude oil from the Nisku Formation
reservoir (sample #2091)
GSC #
8664 8842 8686 8666 8685 2091Location
10-4-1-9W4 13-32-7-20-W4 6-29-12-12W4 11-27-8-17W4 6-29-12-12W4 3-18-13-14W4Depth (m)
1185.75 1665.90 1276.55 1418.06 1269.72 1331.5-1386.0TOC%
7.15 16.76 2.26 4.19 3.72 n/aHI
895 856 765 800 784 n/a%HC
21.71 23.35 40.85 17.87 25.46 76.48S/A
0.29 0.70 0.53 0.26 0.28 0.62Pr/Ph
1.20 n.d. 0.69 0.71 0.83 0.58Pr/17
0.27 0.02 0.21 1.14 0.27 0.12S/(S+R)
0.46 0.45 0.47 0.27 0.46 0.45dia/reg
0.61 1.94 0.75 0.10 0.68 0.8621/29
0.41 0.79 0.44 0.08 0.32 0.6827:28:29
47:10:43 43:13:44 33:14:53 38:11:51 15:15:70 37:16:47Ts/Ts+Tm
0.21 0.13 0.17 0.21 0.27 0.2829/hop
0.75 0.74 0.72 0.49 0.73 0.7623/hop
0.10 0.07 0.06 0.29 n/d 0.32g/hop
0.17 0.11 0.14 0.52 0.35 0.11alkylarom
high high high low high high21/21+23
0.56 0.74 0.69 0.98 0.98 0.77N/a—not applicable; TOC—% total organic carbon; HI—Hydrogen Index;%HC—weight percent hydrocarbons; S/A—saturated/
aromatic hydrocarbons ratio; Pr/Ph—pristane/phytane ratio; Pr/17—pristane/n-C17 ratio; S/(S+R)—5a(H),14a(H),17a(H) 20S/
(20S+20R)—C29 sterane; dia/reg- 13b(H),17a(H) 20S—C27 diasterane/5a(H),14a(H),17a(H) 20R—C27 sterane; 21/29—C21 sterrane/
5a(H),14a(H),17a(H) 20R—C29 sterane; 27:28:29—normalized relative abundance of C27, C28 and C29 regular steranes based on aaaisomers; Ts/Ts+Tm—18a(H)-trisnorhopane/(18a(H)-trisnorhopane+17a(H)-trisnorhopane); 29/hop—17a(H)-norhopane/
17a(H),21b(H)-hopane; 23/hop—C23 tricyclic terpane/17a(H),21b(H)-hopane; g/hop- gammacerane/17a(H),21b(H)-hopane;
alkylarom-relative abundance of n-alkylaromatics in aromatic fraction; 21/21+23—C21/(C21+C23) n-alkylnaphthalenes.
432 M.G. Fowler et al. / Organic Geochemistry 35 (2004) 425–441
have characteristics intermediate between those of thekukersite-like sample (sample #8842) and samplesinterpreted to have no or very little G. prisca contribu-tion (e.g. sample #8666). These were interpreted to have
a significant G. prisca contribution which is also sup-ported by their aromatic hydrocarbon distributions andpyrolysis-gas chromatography data discussed below.
The major compounds in the aromatic fractions ofmany of the rock extracts are C21 and C23 alkylatedaromatic hydrocarbons. This is shown for a lower
potential source rock sample from 6-29-12-12W4 (sam-ple #8686) in Fig. 7. The mass spectra of the majorcompounds are very simple with the two major peaks
being the base fragment ion (m/z 92, 141, 155) and aM+ ion. The C21 and C23 n-alkylbenzenes and n-alkyl-naphthalenes are the major compounds with loweramounts of C21 and C23 alkylmethylnaphthalenes. The
carbon number distributions of the n-alkylnaphthalenesand n-alkylbenzenes show a strong tendency to mirroreach other for this sample set (Fig. 8), suggesting these
compounds have a similar origin. The relative amountsof C21 and C23 compounds varies. All samples show apredominance of the C21 compounds except one which
shows a slight predominance of C23. Extracts of thepotential source rock at the base of the Camrose Mem-ber have lower values for the C21/(C21+C23)parameterthan other source rock intervals (Table 1). Thus there
could be a palaeoevironmental control on this pa-rameter. This could be related to the different, deeperwater organic facies previously noted for this interval
compared with other Camrose/Nisku organic-rich unitswhich were deposited under more restricted shallowerconditions (Fowler et al., 2001). The m/z 92 and 141
mass chromatograms show that lower homologues arein very low abundance with a slight odd carbon numberpredominance over the C15–C19 range. Sample #8842,
which is one of the higher maturity source rock samplesexamined here, shows greater amounts of C20 and loweralkyl aromatic compounds than the other samples withan odd carbon number preference (Fig. 8). These may
be derived from cracking of the C21 and C23 compoundsor their precursors. There is possible evidence in thesemass chromatograms of extremely low abundances of
C23+ homologues, up to C30 for the alkylbenzenes andup to C25 for the alkylnaphthalenes. The m/z 155 masschromatogram shows the presence of multiple isomers
for the alkylmethylnaphthalenes. Aryl isoprenoids (i.e.1-alkyl-2,3,6-trimethylbenzenes) which are thought tobe derived from photosynthetic green sulphur bacteria
(Summons and Powell, 1987; Hartgers et al., 1994) canonly be detected in low abundance in samples withlower concentrations of the C21 and C23 alkylbenzenesbecause these latter compounds usually dominate the
m/z 133 and 134 mass chromatograms due to their con-siderably higher abundance. This is in contrast to mostof the other Devonian source rocks the Western Canada
Sedimentary Basin, such the Duvernay Formation,which have much higher concentrations of aryl iso-prenoids (e.g. Requejo et al. 1992).
The aromatic fraction of the Collingwood Membersample from southern Ontario mentioned earlier thathad a predominance of C23 and C25 n-alkylcyclohexaneswas also analyzed for comparison with the Camrose
Member extracts. C21 and C23 n-alkylnaphthalenes andn-alkylmethylnaphthalenes were not detected. Therewas a relatively high abundance of n-alkylbenzenes up
to C30 with the C23–C25 members in highest concentra-tions. Thus the distributions of the n-alkylcyclohexanesand n-alkylaromatics in the Ordovician Collingwood
sample are very different to the Upper DevonianCamrose Member samples.The concentration of the C21 and C23 benzenes and
alkylnapthalenes varies in the Camrose Member/NiskuFormation extracts. There does not seem to be anyobvious correlation with the source rock interval orproximity to anhydrite intervals. However, there does
seem to be some correlation with the presence of G.prisca alginite. A subjective assessment of the relativeabundance of these compounds is provided in Table 2.
Fig. 6. Representative m/z 82 mass chromatograms of Cam-
rose Member organic-rich samples.
M.G. Fowler et al. / Organic Geochemistry 35 (2004) 425–441 433
Fig. 7. Aromatic hydrocarbon data for an organic-rich Camrose Member sample from 6-29-12-12W4 (1276.55 m); (a) Total Ion
Chromatogram (TIC), (b) m/z 92 mass chromatogram, (c) m/z 141 mass chromatogram, (d) m/z 155 mass chromatogram.
434 M.G. Fowler et al. / Organic Geochemistry 35 (2004) 425–441
High abundance indicates that these are among themost abundant aromatic compounds in the extracts.Generally, these compounds are in either very high orvery low abundance. It is noticeable that the C21 and
C23 alkylaromatic species are more abundant in sampleswhere other geochemical characteristics suggested a sig-nificant G. prisca contribution based on SFGC char-
acteristics (n-alkane distributions, concentration ofacyclic isoprenoids and biomarkers) and biomarker fea-tures (e.g. minor C34 homohopane prominence, lower
gammercerane/hopane ratio). For example, these com-pounds are in high abundance in the kukersite-likesample #8842, but in much lower concentrations in a
sample such as #8666 which is believed to have little G.prisca contribution (Fig. 10).
High abundances of alkylated benzenes and naph-thalenes have been noted previously in sedimentsthought to be deposited under elevated salinity condi-tions or their derived oils (Connan et al., 1986; Williams
et al., 1988; Sinninghe Damste et al., 1993). They havebeen attributed a probable bacterial precursor. C21
compounds were found by Connan et al. (1986) and
Williams et al. (1988) to be in highest abundance in theirsamples. Sinninghe Damste et al. (1993) noted a varietyof alkylbenzene distributions in Mulhouse Basin sam-
ples including some that showed a large predominanceof C23 with the C25 also in much higher concentrationsthan other homologues. They did not observe the C21
and C23 predominance displayed by the CamroseMember samples.
Fig. 8. Aromatic hydrocarbon data for an organic-rich Camrose Member samples from 13-32-7-20W4 (1665.9 m) and 11-27-8-17W4
(1418.0 m).
M.G. Fowler et al. / Organic Geochemistry 35 (2004) 425–441 435
The C21 and C23 alkylaromatic compounds in the G.prisca-rich Camrose Member samples may have a simi-lar origin to the high concentrations of n-alkyl phenols,especially C21 and C23, that have been noted in some
Ordovician kukersite pyrolysates from Estonia(Derenne et al., 1990; Blokker et al., 2001). These alkylphenols occur in much lower concentrations in py-
rolysates from another Ordovician kukersite deposit,the GuttenbergMember (Derenne et al., 1990; Blokker etal., 2001). This was attributed to G. prisca growing
under conditions of higher salinity during deposition ofthe Estonian kukersite by Derenne et al. (1990, 1992)and/or due to the higher maturity of the Guttenberg
Member (Blokker et al., 2001). The Camrose Membersamples that have significant G. prisca contributionwere likely deposited under conditions of elevatedsalinity, considering their close association with evapo-
rites, and thus may be the source of the C21 and C23
alkylaromatics.The results of pyrolysis-gas chromatography also
appear to show the influence of a G. prisca contributionto some samples. As indicated in Fig. 9, both the #8842and #8664 samples show similar pyrograms to an
Ordovician Yeoman Formation kukersite pyrolysatefrom the Williston Basin, Canada. The Ordoviciansample shows a decrease in abundance after C17 for
alkene–alkane doublets which is also shown by the twoCamrose Member samples, suggesting that a large pro-portion of the organic matter of these samples is likely
Fig. 9. Whole-rock pyrograms of (a) Upper Ordovician Yeo-
man Formation kukersite interval from southeast Saskatch-
ewan portion of Williston Basin and (b–d) Late Devonian
Camrose Member organic-rich interval samples from southern
Alberta, (b) G. prisca-rich sample from 13-32-7-20W4 (1665.9
m), (c) Moderately-rich G. prisca sample from 10-4-1-9W4
(1185.75 m) and (d) G. prisca-poor sample from 11-27-8-17W4
(1418.06 m). 12 and 17 are the C12 and C17 alkene–alkane
doublets, TMB is tetramethylbenzene.
Table 2
Biomarker compounds identified in saturate fraction mass
fragmentograms shown in Figs. 5 and 10
Peak
Compound1
C23 tricyclic terpane2
C24 tetracyclic terpane3
18a(H),22,29,30-trisnorhopane(Ts)4
17a(H),22,29,30-trisnorhopane (Tm)5
17a(H),21b(H)-30-norhopane6
17a(H),21b(H)-hopane7
moretane8
17a(H),21b(H)-homohopanes (S & R)9
gammacerane10
17a(H),21b(H)-bishomohopanes11
17a(H),21b(H)-trishomohopanes12
17a(H),21b(H)-tetrakishomohopanes13
17a(H),21b(H)-pentakishomohopanesa
pregnaneb
diacholestane 20Sc
5a(H),14a(H),17a(H)-cholestane (20S)d
24-methyl-5a(H),14a(H),17a(H)-cholestanee
24-ethyl-5a(H),14a(H),17a(H)-cholestane (20S)f
24-ethyl-5a(H),14b(H),17b(H)-cholestane (20S & 20R)g
24-ethyl-5a(H),14a(H),17a(H)-cholestane (20R)h
24-propyl-5a(H),14a(H),17a(H)-cholestane (20S & 20R)436 M.G. Fowler et al. / Organic Geochemistry 35 (2004) 425–441
derived from G. prisca. Other Camrose Member/NiskuFormation samples that were thought not to have asignificant G. prisca contribution show very differentpyrograms (Fig. 9d) with much higher amounts of
higher molecular weight compounds. They all show arelatively large tetramethylbenzene (TMB) peak. Thiscompound is thought to be mostly derived from aryl
isoprenoids and their precursors found in Chlorobiacae(Hartgers et al., 1994). The #8664 sample shows a smallTMB peak that is not evident in the #8842 sample, once
again suggesting it was deposited in an intermediateenvironment between those of the G. prisca-rich and-poor intervals.
3.4. Southern Alberta oils
The Nisku reservoired oils at Enchant-Hays in
southern Alberta (Fig. 1) are thus far the only majorfield discovered in the Nisku Formation in this region.In total, 21 oils from Nisku Formation reservoirs from
the Enchant-Hays area were analyzed for this study.Most of these oils show features that allow them to bedifferentiated from all other Devonian oils of the
WCSB. This is most apparent in their SFGCs whichcommonly show a high abundance of n-alkanes up toC17, often with a distinct odd carbon number pre-
dominance over the C15–C19 range, followed by a rapid
decrease in concentration to C18 and then a moregradual decrease in abundance with no odd or evencarbon number preference (Fig. 10). The samples tendto show a low abundance of acyclic isoprenoids and
biomarkers relative to n-alkanes. Most oils share othercharacteristics in common including, low saturate/aro-matic (<0.76) and pristane/phytane ratios (<0.82), low
amounts of rearranged steranes and hopanes comparedto their unrearranged counterparts, a predominance ofthe C24 tetracyclic terpane over the C26 tricyclic terpanes
and a significant gammacerane peak (Fig. 10c). Somealso show a C34 homohopane prominence. Aryl iso-prenoids are present in these oils as relatively minor
components. The C21 and C23 n-alkybenzenes and n-alkylnaphthalenes are among the most abundant aro-matic hydrocarbons in these oils. The C21 compoundsare in much higher concentrations than their C23
homologues, often by a factor of two or more (Fig. 10b).Enchant-Hays oils also have gasoline range hydro-
carbon distributions that differ from almost all the other
Devonian oils analyzed from Western Canada. Theyshow a very high abundance of n-alkanes relative toother compounds, with aromatics such as toluene pre-
sent in very low concentrations. This leads to someunusual values for gasoline range parameters such as thevery high heptane values which are more typical of
supermature oils (i.e. heptane values >30) (Thompson,
Fig. 10. Geochemical data for a Nisku Formation oil from southern Alberta (Hays 3-18-13-14W4, 1331.5-1386.0 m). (a) Saturate
fraction gas chromatogram (annotation of peaks as in Fig. 4), (b) partial aromatic hydrocarbon TIC; MN—methylnaphthalenes,
MP—methylphenanthrene, 21B and 23B—n-alkylbenzenes, 21N and 23N—n-alkylnaphthalenes (c) m/z 191 mass chromatogram,
(d) m/z 217 mass chromatogram; peaks identified in Table 2.
M.G. Fowler et al. / Organic Geochemistry 35 (2004) 425–441 437
1983). While low concentrations of aromatics can beattributed to water-washing, in the case of these Niskuoils it is thought to relate to their source organic matteras these gasoline range characteristics are also similar to
those shown by Ordovician kukersite derived oils fromthe Williston Basin (Fowler et al., 1998).
4. Discussion
Both optical and chemical evidence indicate a sig-nificant contribution from G. prisca to the organic mat-ter of Camrose Member potential source rock intervals.
Organic petrological observations show that the mor-phology of G. prisca in these Late Devonian samples isvery similar to that observed in many Ordoviciankukersite deposits. However, there is a strong pre-
dominance of G. prisca with the ‘closed morphology’within the Camrose Member samples.The extract characteristics of the samples believed to
have a major G. prisca contribution are also similar tothose of Ordovician kukersites. For example, SFGCswith a predominance of odd numbered n-alkanes up to
C19 and lower abundances of C20 and higher n-alkanes,acyclic isoprenoids and biomarkers. Saturated hydro-carbon biomarker distributions, especially those of the
most G. prisca-rich sample (sample #8842), also havesimilar features to those reported for Ordoviciankukersite samples. However, there is a significant differ-ence in the aromatic hydrocarbons with the Camrose
Member samples having high concentrations of C21 andC23 n-alkylnaphthalenes and n-alkylbenzenes whichhave not been previously reported for Ordovician sam-
ples. The origin of these compounds is still uncertain buttheir empirical association with G. prisca-rich samplessuggest that their precursors are biochemical compo-
nents of this organism. They may have a similar originto the C21 and C23 n-alkylphenols that are abundant inthe pyrolysates of Estonian kukersite (Derenne et al.,1990, 1992; Blokker et al., 2001).
Derenne et al. (1992) showed that increasing salinityfrom 0 to 10 g/l of NaCl could influence the morphologyof extant Botryococcus braunii and its production of
phenols. By analogy, they suggested that variations insalinity could be the cause of similar changes observedfor G. prisca in different Ordovician rocks. The range of
salinity chosen by Derenne et al. (1992) for theirexperiments with Botryococcus braunii reflect those inwhich this organism mostly thrives (i.e. freshwater to
brackish) and did not range up to normal seawatersalinity. There is considerable geological evidence thatG. prisca lived mostly in normal marine environmentsduring the Ordovician including for example, the Middle
Ordovician Guttenberg Member of the Decorah For-mation in Iowa (Ludvigson et al., 1996) and UpperOrdovician kukersite intervals in the Williston Basin,
Saskatchewan (Kendall, 1976; Stasiuk and Osadetz,1990). The Camrose Member intervals enriched in G.prisca are always associated with interbedded evaporitesand dolomites suggesting that the organism was living in
conditions of higher than normal salinity. Thus,although G. prisca is likely a different type of organismto Botryococcus braunii, the adoption of the closed cel-
lular morphology and the high abundance of C21 andC23 alkylaromatic compounds may represent a similarresponse to growth under higher salinity conditions for
this organism.The saturate fraction gas chromatograms, aromatic
hydrocarbon distributions and gasoline fraction hydro-
carbons all suggest that the organic-rich intervals thatare the source of most of the Enchant-Hays oils had asignificant G. prisca contribution. The saturated hydro-carbon biomarkers give more ambiguous evidence for
the origin of the oils. This can be explained by theCamrose Member/Nisku Formation potential sourcerocks containing several different organic facies (Fowler
et al., 2001). Hence, any oils that are derived from themmight reasonably be expected to have contributionsfrom units with different geochemical characteristics,
some indicative of a significant G. prisca contributionand others not. The SFGCs of the Enchant-Hays oilsfrom Nisku Formation reservoirs with the pre-
dominance of odd number n-alkanes up to C19
(Fig. 10a), and the relatively high abundance of C21 andC23 n-alkylaromatics (Fig. 10b) strongly suggest that G.prisca-rich intervals were a major source of hydro-
carbons for these Late Devonian oils. These source rockintervals tend to contain much lower concentrations ofbiomarkers than intervals where G. prisca made a lesser
contribution to their organic matter. Hence, the dis-tribution of biomarkers in the Enchant oils would likelyshow a greater influence from the non-G. prisca source
intervals than other compound classes which mightexplain why they have intermediate characteristics.This paper conclusively demonstrates the presence of
G. prisca in Late Devonian sediments in southern
Alberta using both optical and chemical evidence. Inaddition, G. prisca-like coccoidal algae have also beenoptically distinguished as a minor contributor to the
organic matter in other Middle and Late Devonian unitswithin the Western Canada Sedimentary Basin (WCSB)that do not show the chemical fingerprint for G. prisca
(Stasiuk, unpublished results). These include theMiddle Devonian Keg River and Winnipegosis forma-tions and Late Devonian Duvernay Formation in
central and northern Alberta, and the WinnipegosisFormation and Late Devonian Birdbear Formation,that is equivalent in age to the Camrose Member/NiskuFormation intervals discussed in this paper, in southern
Saskatchewan. However, in all of the other WCSBDevonian units G. prisca is only rarely found as a minorcomponent in organic-lean intervals deposited under
438 M.G. Fowler et al. / Organic Geochemistry 35 (2004) 425–441
shallow water oxidizing conditions within carbonateplatform settings. This suggests that the precursor oftheir G. prisca alginite lived in the photic zone of mainlyshallow water depositional environments. Despite the
oxidative conditions and apparent low algae-biologicalproductivity within the water column during depositionof these sediments, some marine alginite macerals were
nonetheless preserved, probably as a result of selectivepreservation of highly resistant algaenan biomacro-molecules found in the outer cell walls derived from the
G. prisca precursor (e.g. Tegelaar et al., 1989). Prasino-phyte algae such as Tasmanites and Leiosphaeridia arethe main primary producers contributing to the organic
matter of the most of the Devonian source rocks in theWCSB such as the Duvernay and Keg River formations(Chow et al., 1995).The presence of G. prisca as a significant contributor
to Camrose Member potential source rocks and not toany of the several other Devonian source rocks in theWestern Canada Sedimentary Basin (Fowler et al.,
2001), allows us to speculate on the post-Ordovicianhistory of this organism. The geological record clearlyshows that G. prisca lost its position as a dominant
algae in the open marine tropical seas after the Ordovi-cian-Silurian extinction event. This probable cyano-phyte (Foster et al., 1989; Stasiuk and Osadetz, 1990;
Wicander et al., 1996) was replaced in this environ-mental niche by Prasinophytes and other green algae. Itsurvived in shallow water, near-shore environments thatare not typically considered conducive to source rock
development. It may also have had an ability to toleratehigher salinity conditions which are not as favourable toChlorophytes, and thus could have thrived in some of
these environments at least until the Late Devonianwhere it can be a major contributor to petroleum sourcerocks, such as those in the Camrose Member. This
speculation is obviously based on data from just onebasin but it will be interesting to see if other post-Ordovician occurrences of G. prisca are also associatedwith strata deposited under higher than normal salinity.
Reports to date such as that of Abrams et al. (1999) donot provide enough data to verify this.
5. Summary and conclusions
Some Late Devonian Camrose Member potentialsource rock samples show characteristics that suggest acontribution to their organic matter by the organism G.
prisca whose presence is very rarely noted in post-Ordovician strata. G. prisca characteristics are bestdemonstrated by a lower Camrose Member sample from13-32-7-20W4 that shows a saturate fraction gas chro-
matogram very similar to Ordovician kukersite samples,including an odd/even predominance of n-alkanes up toC19, much lower abundances of C19+ n-alkanes, acyclic
isoprenoids and biomarkers, and relatively highconcentrations of n-alkylcyclohexanes. Other samplesshow a range of characteristics intermediate between thekukersite and those more typical for carbonate envir-
onments. Microscopy confirms that G. prisca alginite isthe dominant component of the 13-32-7-20W4 sampleand major constituent of many other samples that show
the G. prisca chemistry. The morphology of the LateDevonian G. prisca is generally similar to that observedin Ordovician samples although the ‘closed’ cellular
morphology is more common which could be related togrowth of this organism under elevated salinity condi-tions. An unusual feature of many of the Camrose
Member/Nisku Formation extracts is the very highconcentrations of C21 and C23 n-alkylaromatic com-pounds, especially n-alkylnaphthalenes and n-alkylben-zenes in their aromatic fractions. This distribution does
not seem to have been previously reported and the originof these compounds is still uncertain. However, the C21
and C23 n-alkylaromatics are in higher concentrations in
those samples with a high G. prisca contribution to theirorganic matter and hence their occurrence could be rela-ted to the biochemistry of this organism. The n-alkylaro-
matics may have a similar origin to the C21 and C23
n-alkylphenols that have been noted in high concentrationsin some kukersite pyrolysates from Estonia that could
be due to G. prisca growing under higher salinity con-ditions (Derenne et al., 1990, 1992; Blokker et al., 2001).Thermally mature equivalents of the Camrose Mem-
ber/Nisku Formation potential source rocks are con-
sidered the source of the oils that occur in NiskuFormation reservoirs in the Enchant-Hays field ofsouthern Alberta. Saturate fraction and gasoline range
gas chromatograms, and the presence of the n-alkylaro-matics in the Enchant-Hays oils in relatively high con-centrations indicates an important contribution from G.
prisca-rich intervals.We have demonstrated conclusively using both opti-
cal and chemical evidence that G. prisca was a con-tributor to some very organic-rich intervals within the
Late Devonian Camrose Member. We have alsoobserved G. prisca optically as an occasional, minorcomponent in organic-lean intervals in other Middle
and Late Devonian units of the Western Canada Sedi-mentary Basin where its presence is not readily chemi-cally evident. Hence, G. prisca did survive the
Ordovician-Silurian extinction event but appears to losemuch of its ecological niche to prasinophytes and othergreen alga that dominate most of the organic-rich
Devonian intervals within the Western Canada Sedi-mentary Basin. These data and other reports (e.g.Abrams et al., 1999) indicate that caution should beused in unequivocally attributing a Cambro-Ordovician
age to sediments and oils having G. prisca geochemicalcharacteristics, as these can also occur in rocks as youngas the Late Devonian.
M.G. Fowler et al. / Organic Geochemistry 35 (2004) 425–441 439
Acknowledgements
We acknowledge the excellent technical support ofSneh Achal, Kim Dunn, Laura Mulder, Rachel Robin-
son and Ross Stewart at the NRCan GSCC OrganicGeochemistry and Organic Petrology Laboratory. Wethank Roger Summons and Sylvie Derenne for their
very helpful comments on an earlier version of thispaper. We also thank the GSC and the oil and gascompanies that financially supported the Devonian Pet-
roleum Systems of Western Canada Project for enablingus to undertake this research. This is Geological Surveyof Canada Contribution 2002251.
References
Abrams, M.A., Apanel, A.M., Timoshenko, O.M., Kosenkova,
N.N., 1999. Oil families and their potential sources in the
Northeastern Timan Pechora Basin, Russia. American
Association of Petroleum Geologists Bulletin 83, 553–577.
Blokker, P., van Bergen, P., Pancost, R., Collinson, M.E., de
Leeuw, J.W., Sinningh Damste, J.S., 2001. The chemical
structure of Gloeocapsomorpha prisca microfossils: implica-
tions for their origin. Geochimica et Cosmochimica Acta 65,
885–900.
Chow, N., Wendte, J., Stasiuk, L.D., 1995. Productivity versus
preservation controls on two organic-rich carbonate facies in
the Devonian of Alberta: sedimentological and organic pet-
rological evidence. Bulletin of Canadian Petroleum Geology
43, 433–460.
Connan, J., Bouroullec, J., Dessort, D., Albrecht, P., 1986. The
microbial input in carbonate-anhydrite facies of a sabka
palaeoenvironment from Guatemala: a molecular approach.
Organic Geochemistry 10, 29–50.
Cramer, F.H., Diez de Cramer, M.D.C.R., 1972. North
American Silurian palynofacies and their spatial arrangment:
acritarchs. Palaeontographica Abt. B 138, 107–180.
Derenne, S., Largeau, C., Casadevall, E., Tegelaar, E.W., de
Leeuw, J.W., 1990. Characterisation of Estonian kukersite
by spectroscopy and pyrolysis: evidence for abundant alkyl
phenolic moieties in an Ordovician, marine, type II/I
kerogen. Organic Geochemistry 16, 873–888.
Derenne, S., Metzger, P., Largeau, C., van Bergen, P.F.,
Gatellier, J.P., Sinninghe Damste, J.S., de Leeuw, J.W.,
Berkaloff, C., 1992. Similar morphological and chemical
variations of Gloeocapsomorpha prisca in Ordovician
sediments and cultured Botryococcus braunii as a response to
changes in salinity. Organic Geochemistry 19, 299–313.
Douglas, A.G., Sinninghe Damste, J.S., Fowler, M.G.,
Eglinton, T.I., de Leeuw, J.W., 1990. Unique distributions of
hydrocarbons and sulphur compounds released by flash
pyrolysis from the fossilised alga Gloeocapsomorpha prisca, a
major constituent in one of four Ordovician kerogens.
Geochimica et Cosmochimica Acta 55, 275–291.
Foster, C.B., Reed, J.D., Wicander, R., 1989. Gloeocapsomor-
pha prisca Zalessky 1917: a new study part 1: taxonomy,
geochemistry, and paleoecology. Geobios 22, 735–759.
Fowler, M.G., 1992. The influence of Gloeocapsomorpha prisca
on the organic geochemistry of oils and organic-rich rocks of
Late Ordovician Age from Canada. In: Schidlowski, M. et al.
(Eds.), Early Organic Evolution: Implications for Mineral
and Energy Resources. Springer-Verlag, Berlin, Heidelberg,
pp. 336–356.
Fowler, M.G., Stasiuk, L.D., 1999. Presence of Gloeocapso-
morpha prisca in Devonian sediments of the Western Canada
Sedimentary Basin. In: 19th International Meeting on
Organic Geochemistry, September 1999, Istanbul, Turkey,
Abstracts Part 1, pp.163–164.
Fowler, M.G., Abolins, P., Douglas, A.G., 1986. Monocyclic
alkanes in Ordovician organic matter. Organic Geochemistry
10, 815–823.
Fowler, M.G., Stasiuk, L.D., Li, M., Obermajer, M., Osadetz,
K.G., Idiz, E., 1998. Reexamination of the Red River Petro-
leum System, southeastern Saskatchewan, Canada. In:
Christopher, J.E., Gilboy, C.F., Paterson, D.F., Bend, S.L.
(Eds.), Eighth International Williston Basin Symposium,
Saskatchewan Geological Society Special Publication No. 13,
pp. 11–13.
Fowler, M.G., Stasiuk, L.D., Hearn, M., Obermajer, M., 2001.
Devonian hydrocarbon source rocks and their derived oils
in the Western Canada Sedimentary Basin. Bulletin of
Canadian Petroleum Geology 49, 117–148.
Hartgers, W.A., Sinninghe Damste, J.S., Requejo, A.G., Allan,
J., Hayes, J., Ling, Y., Xie, T.-M., Primack, J., de Leeuw,
J.W., 1994. A molecular and carbon isotopic study towards
the origin and diagenetic fate of diaromatic carotenoids.
Organic Geochemistry 22, 703–725.
Hoffmann, C.F., Foster, C.B., Powell, T.G., Summons, R.E.,
1987. Hydrocarbon biomarkers from Ordovician sediments
and fossil alga G. prisca Zalessky 1917. Geochimica et
Cosmochimica Acta 51, 2681–2697.
Hutton, A.C., 1987. Petrographic classification of oil shales.
International Journal of Coal Geology 8, 203–231.
Kendall, A.C., 1976. The Ordovician Carbonate Succession
(Bighorn Group) of Southern Saskatchewan. Saskatchewan
Department of Mineral Resources, Report 180.
Kissling, D.L., 1996. The Nisku Formation of south Alberta
and northwest Montana: birth to burial of an Upper Devo-
nian barrier-lagoon complex. In: Longman, M.W., Sonnen-
field, M.D. (Eds.), Paleozoic Systems of the Rocky Mountain
Region. Society for Sedimentary Geology, Rocky Mountain
Section, pp. 97–116.
Longman, M.W., Palmer, S.E., 1987. Organic geochemistry of
Mid-Continent Middle and Late Ordovician oils. American
Association of Petroleum Geologists Bulletin 71, 938–950.
Ludvigson, G.A., Jacobson, S.R., Witzke, B.J., Gonzalez,
L.A., 1996. Carbonate component chemostratigraphy and
depositional history of the Ordovician Decorah Formation,
Upper Mississippi Valley. In Witzke, B.J., Ludvigson, G.A.
and Day, J. (Eds.) Paleozoic Sequence Stratigraphy: Views
from the North American Craton. Geological Society of
America Special Paper 306.
Nowlan, G.S. (Compiler and editor), 1998a. The Lower Paleo-
zoic: A New Frontier in the Western Canada Basin, Part 1,
Report to Partners 1993–1994. Geological Survey of Canada
Open File Report #3416.
Nowlan, G.S. (Compiler and editor), 1998b. The Lower Paleo-
zoic: A New Frontier in the Western Canada Basin, Part 2,
Report to Partners 1994–1995. Geological Survey of Canada
Open File Report #3603.
440 M.G. Fowler et al. / Organic Geochemistry 35 (2004) 425–441
Peters, K.E., Moldowan, J.M., 1993. The Biomarker Guide.
Prentice Hall, New Jersey.
Reed, J.D., Illich, H.A., Horsfield, B., 1986. Biochemical
evolutionary significance of Ordovician oils and their
sources. Organic Geochemistry 10, 347–358.
Requejo, A.G., Allan, J., Creaney, S., Gray, N.R., Cole, K.S.,
1992. Aryl isoprenoids and diaromatic carotenoids in Paleo-
zoic source rocks and oils from the Western Canada and
Williston Basins. Organic Geochemistry 19, 245–264.
Sinninghe Damste, J.S., Keely, B.J., Betts, S.E., Baas, M.,
Maxwell, J.R., de Leeuw, J.W., 1993. Variations in abun-
dances and distributions of isoprenoid chromans and long-
chain alkylbenzenes in sediments of the Mulhouse Basin: a
molecular sedimentary record of palaeosalinity. Organic
Geochemistry 20, 1201–1215.
Stasiuk, L.D., 1999a. Microscopic studies of sedimentary
organic matter: key to understanding organic-rich strata,
with Paleozoic examples from Western Canada. Geoscience
Canada 26, 149–172.
Stasiuk, L.D., 1999b. Confocal laser scanning fluorescence
microscopy of Botryococcus alginite from Boghead oil shale,
Ukraine: selective preservation of various micro-algal com-
ponents. Organic Geochemistry 30, 1021–1026.
Stasiuk, L.D., Fowler, M.G., 2002. Thermal Maturity
Evaluation (Vitrinite and Vitrinite Reflectance Equivalent) of
Middle Devonian, Upper Devonian and Mississippian Strata
in the Western Canada Sedimentary Basin. Geological
Survey of Canada Open File Report #4341.
Stasiuk, L.D., Osadetz, K.G., 1990. The life cycle and phyletic
affinity of Gloeocapsomorpha prisca Zalessky 1917 from
Ordovician rocks in Canadian Williston Basin. In: Current
Research, Part D, Geological Survey of Canada Paper
90-1D, pp. 123–137.
Stasiuk, L.D., Kybett, B.D., Bend, S.L., 1993. Reflected light
microscopy and transmission micro-FTIR of alginite in rela-
tion to petroleum generation, Upper Ordovician kukersites,
Saskatchewan, Canada. Organic Geochemistry 20, 707–719.
Summons, R.E., Powell, T.G., 1987. Identification of aryl iso-
prenoids in source rocks and crude oils; biological markers
for the green sulphur bacteria. Geochimica et Cosmochimica
Acta 51, 557–566.
Tegelaar, E.W., de Leeuw, J.W., Derenne, S., Largeau, C.,
1989. A reappraisal of kerogen formation. Geochimica et
Cosmochimica Acta 53, 3103–3106.
Thompson, K.F.M., 1983. Classification and thermal history of
petroleum based light hydrocarbons. Geochimica et Cosmo-
chimica Acta 47, 303–316.
Wicander, R., Foster, C.B., Reed, J.D., 1996. Chapter 7E—
Gloeocapsomorpha. In: Jansonius, J., McGregor, D.C. (Eds.),
Palynology: Principles andApplications. American Association
of Stratigraphic Palynologists Foundation, vol. 1, pp. 215–225.
Williams, J.A., Docater, D.L., Torkelson, B.E., Winters, J.C.,
1988. Anomalous concentrations of specific alkylaromatic
and alkylcycloparaffin components in West Texas and
Michigan crude oils. Organic Geochemistry 13, 47–59.
Zalessky, M.D., 1917. On marine sapropelite of Silurian
age formed by a blue-green alga. Izvestiia Imperatroskoi
Akademiia Nauk (IV) 1, 3–18. (in Russian).
Zumberge, J.E., 1987. Prediction of source rock characteristics
based on terpane biomarkers in crude oils: a multivariate
statistical approach. Geochimica et Cosmochimica Acta 51,
1625–1637.
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