II - geochemie.ifg.uni-kiel.de · Exkursion in diesem Modul ... • Praktikum semesterbegleitender...

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Kapitel 3 – Organofaziesanalyse

Organisation Vertiefungsmodul Geochemie der Sedimente

Exkursion in diesem Modul (MWGS4) nur bei BedarfPfingstwoche 10.6. – 15.6.2019,

Anmeldung bei Dr. Rübsam, R. 108 bis zum 12.12.2018

Prüfungswochen: 6.2.-20.2.2019

Laborpraktikum in diesem Modul (MWGS3)

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Das obligatorische Laborpraktikum in diesem Modul (MWGS3) ist entweder semesterbegleitend für

Montags 9 bis 16 vorgesehen oder findet als Block statt:

• Praktikum Blockkurs voraussichtlich 11.03.-15.03.2019, Raum 563, LMS 10

Verbindliche Anmeldung bis 02.11.2018, 9:00 Uhr bei Herrn Dr. W. Rübsam, Raum 108, LMS 10. Vergabe der Teilnahmeplätze am 02.11.2018 um 09:00 Uhr bei Herrn Dr. W. Rübsam, Raum 108. Abgabe der Praktikumsprotokolle bis 22.03.2019 an [email protected]. Weitere Informationen zur Veranstaltung auf der Webseite der AG „Organische Geochemie“.

• Praktikum semesterbegleitender Kurs voraussichtlich 5.11.-17.12.2018:

Verbindliche Anmeldung bis 02.11.2018, 9:00 Uhr bei Herrn Dr. W. Rübsam, Raum 108, LMS 10. Vergabe der Teilnahmeplätze am 02.11.2018 um 09:00 Uhr bei Herrn Dr. W. Rübsam, Raum 108. Abgabe der Praktikumsprotokolle bis 10.01.2019 an [email protected]. Nähere Informationen zur Veranstaltung auf der Webseite der AG „Organische Geochemie“.

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• Vorbereitung und Nachbereitung der Vorlesung:

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Repetitorium Organofaziesanalyse

Kenntnisse in folgenden Analysentechniken und Interpretationsverfahren sinderforderlich oder werden falls erforderlich wiederholt:

- Elementaranalyse und abgeleitete Proxies

- Rock Eval Analyse und abgeleitete Proxies

- 13C-Isotopie des Organischen Materials

- Lipid/Bitumenextraktion und Stoffgruppentrennung

- GC/MS-Analyse aliphatischer/aromatischer Kohlenwasserstoffe

- Identifizierung von Biomarkern über Massen-Spektren/Fragmentogramme

- Interpretation von Biomarkerverteilungen über Massenfragmentogramme

- Integrierte Organofaziesinterpretation über Pauschal- und Biomarkerdaten

- Berücksichtigung von Matrix/Störeffekten (Diagenese, Kontamination, etc.)

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Organic Facies

Organic facies differentiation based on elemental analysis (van Krevelen plot)and Rock Eval analysis (pseudo- van Krevelen plot). Changes in elementalcomposition reflect organic facies as well as maturity of organic matter.Rock Eval may overestimate hydrogen content of humic coals (Black Hawk,Utah) and their generative potential.

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Organic facies indicators always have to be viewed in conjunction with effects of thermal maturity on organic matter composition. Idealized geochemical log, zone:

a) (sub)recent organic biomass or c) non-source interval, oxidized volatile OM eventually d) mature source rock, due to drilling additive, type I/II kerogen,

b) immature potential source rock, e) reservoir rocktype II/III kerogen, f ) postmature source rock.

Organic Facies

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Organic Facies

Composite well log of Devonian to Early Carboniferous strata in the in Bolivian Madre de Dios Basin, giving organic facies, sequence stratigr.,sedimentology, and thermal maturity information.Oil is produced from a Devonian sst at 1266 m. Source is suspected to be Late Devonian laminated, prasinophyte-rich marine shale at 1510 m, corresponding to the MFS. Tricyclics confirm prasinophyte(tasmanite) input.

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Kopplung Gaschromatographie (GC) mit Massenspektroskopie (MS) = GC/MS

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Kopplung Gaschromatographie (GC) mit Massenspektroskopie (MS) = GC/MS

Massenspektrometer mit Direkteinlass ausreichend für Analyse von Reinsubstanzen. Substanzgemische sind aber infolge der Signalkomplexität schlecht interpretierbar. Trennung der Gemische in Einzelkomponenten durch Gaschromatographie.

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Massenspektren Isoalkane

Unterschiede in den C-C-Bindungsenergien innerhalb des Isoalkan-Moleküls favorisieren die Abspaltung neben der Verzweigungsstelle im C-Gerüst. Es werden Isopropyl- (M+-43) und Methlyreste (M+-15) abgespalten und so die Intensitäten der Massenfragmente m/z = 43 und m/z = 71 erhöht.

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Organic Facies

Organic facies discrimination can be performed via simple elemental analysis.Results are, however, often ambiguous and should be verified by using additional and independent facies parameters, e.g. isotopes, Rock Eval, biomarkers, microfossils, etc. . Samples are from Tertiary Enspel oil shale.

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Organic Facies

All Tertiary lake sediments from the Westerwald/Rhinegraben volcanic province exhibit C/N ratios of app. 30, indicative of transport fractionation, preferentially acculumating lipidic terrestrial (wood-lean) organic matter.

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TN

TOC

PvH shallow

Enspel

Norken

Eckfeld

Lake Messel

PvH deep

PvH coal

Stoss

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Organic Facies Maar Lakes

Maar lakes have extremely small catchment areas, with very local and constrained organic matter input. Most maar lakes are nutrient depleted (oligotrophic) due to the lack of riverine input. Young maar lakes are oversteepend and due to sluggish circulation anoxic deep water causes preservation combined with low sedimentation.

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Organic Facies

Tertiary lake sediments from the Westerwald/Rhinegraben volcanic province exhibit high HI but moderate OI values upon Rock Eval analysis. This indicates dominantly lipidic terrigenous organic matter with few samples enriched in woody material (OI > 100).

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0 50 100 150 200

HI

OI

Eckfelder Maar

PvH shallow

Enspel

Norken

Lake Messel

Messel JR

PvH deep

PvH coal

Stoss

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Organic Facies

Tertiary lake sediments from the Westerwald/Rhinegraben and Eifel volcanic provinces allow for OM source differentiation in a HI vs. d13C discrimination plot. Higher HI indicates more lipidic source (cuticles, waxes) and better preservation. Heavier d13C values may indicate C4-plant input, lighter d13C microbial biomass.

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-36 -34 -32 -30 -28 -26 -24 -22 -20

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d13C-org

Eckfelder Maar PvH shallow Enspel

Norken Lake Messel Messel JR

PvH deep PvH coal Stoss

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d13Corg

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20

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60

-36 -34 -32 -30 -28 -26 -24 -22 -20

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increasing carbon recycling

Lacustrine OM source discrimination: C/N vs. d13Corg

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Organic Facies

Enspel Maar Organic Facies, long-chain alkyl lipid biomarkers confirm preponderance of terrigenous origin of OM, with algal OM occuring predominantly ester-bond.

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Organic Facies

Enspel Maar Organic Facies, long-chain alkyl lipid biomarkers confirm preponderance of terrigenous origin of OM, with algal OM occuring predominantly ester-bond.

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Organic Facies

Relationship among common depositional environments and tectonic settings with their

associated lithofacies and organic matter (kerogen type) composition.

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Organic Facies – Actualistic Approach

Production, Preservation, and Accumulation in Recent marine meso-and bathypelagic depositional environments. The case study from theArabian Sea includes an oxygen minimum zone OMZ shaded in grey.

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In the Arabian Sea a pronouncedoxygen minimum zone extendsfrom app. 200 m till 1100 m.

Epipelagic: 0-200m (photic zone)Mesopelagic: 200-1000m (twilightzone with bioluminescence usingblue light that penetrates deepest)Bathypelagic: 1000-4000 (dark)

In the OMZ oxygens drops below 5mM allowing putative aerobicarchaeal ammonium oxidation tooccur at the upper and lower OMZtransitions and putative anaerobicanammox in the central OMZ.


aerobic annamox

aerobic annamox

anaerobic annamox

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Accumulation rates of organic carbon (CA) drop with increasing bottom water oxygen (BWO) due to increasing aerobic mineralization. CA may depend on minerogenic dilution though Site 451 characterized by highest CA also shows exceptionally high MAR, arguing against minerogenic dilution. At Site 451 fast burial may move OM quickly out of the near-surface active degradation zone.

OMZ


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Averages for sediments deposited during the last 1000 years. Grey = below, black = within OMZ.

Stable d13C and C/N values argue against a mixing of terrigenic and marine derived OM typical for coastal setting with strong allochthonous OM influx. d13C values about 20 permil are typical for Recent to Tertiary marine OM.

The compositional changes observed are primarily due to differential preservation.


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Rock Eval analysis of theimmature marine organicmatter gives HI values ofapp. 330 mg HC/gTOC.This value is indicative ofmarine organic matter in agood to excellent stage ofpreservation.Changes in organic mattercomposition are notrecognizable through theOMZ.

OMZ


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Different Regimes of TOC accumulation for aerobic sediments and OMZ. Surfaceproductivity (P) estimates are empirically based on TOC and sedimentation rate(S) relation : TOC ~ P x S0.3 (Mueller and Suess, 1979). Surface productivitydoes not vary in the area, and differences in TOC must derive from preservation.


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Export productivities (Pexp) of organic carbon calculated from accumulation rates of organic carbon using a transfer function proposed by Sarnthein et al. (1992).

Grey aerobic regime and black = OMZ. The arrow indicates the adopted value of the export productivity in the whole region.

Export productivity in the OMZ is twice as high as in adjacent regions.


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Enhanced TOC accumulation has been attributed to the availablility of minerogenic sorption and protection sites, determined by average surface area of sediments (i.e. grain size). Mineral sorption effects is not a critical factor in the study area, where OMZs with high TOC accumulation do not reveal high surface areas.


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Accumulation rates (CA) of organic carbon versus the bioturbation depth estimated on the basis of differences in AMS-14C ages between organic carbon and foraminiferal carbonate.The grey envelope suggests the best relation. Shallow bioturbation depths minimize exposure times towards aerobic degradation and thus enhance OC accumulation. Note that BD of 10 cm may correspond to >1000 years of sedimentation and thus integrates environmental change over such intervals.


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In the present day Arabian Sea only a small proportion of the entiresea floor provides OM accumulation suitable to form source rocks.These areas are limited to OMZs, stressing preservation as regulator.


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Biomarkers as Organic Facies Indicators over Time

Facies recognition via biomarkers does have to consider evolutionary trends andappearance of new species and their respective biomolecules.

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Acyclic Biomarkers as Organic Facies Indicators

Compound Biological origin Environment

nC15, nC17, nC19 Algae Lacustrine or marine

nC19 >> nC17, nC15 Ordovician G. prisca Tropical marine

nC27, nC29, nC31 Land plant waxes Terrigenous

nC23 - nC31, max. nC23+25 Limnic algae Lacustrine

2-Methyldocosane Bacteria Hypersaline/Extreme

Mid-chain methylalkanes Cyanobacteria, Sponges Marine hot vents

Pristane/phytane Phototrophs, archaea Anoxic, salinity

PMI, bisphytanes Archaea, methanogen Anoxic, hypersaline

Crocetane Archaea, methanogen Methane seeps/PZE?

C20 or C25 HBI Diatoms, Rhizoselenia Marine (lacustrine?)

Squalane Archaea Hypersaline/Extreme

C31-40 irregular isoprenoids Archaea Unspecified

Botryococcane Green algae, Botryococcus Lacustrine (saline)

Polymethylsqualenes Green algae, Botryococcus Lacustrine (saline)

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Organic Facies

Abundance

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Prista

ne

Phyta

ne

nC

25

nC

27

nC

29

GC/MS trace (m/z 85) of an aliphatic hydrocarbon fraction obtained from aCarboniferous coal seam, Rietspruit Basin, RSA. High pristane/phytane ratioand high CPI indicates terrigenous and aquatic macrophyte organic matterinput into a highly productive oxic depositional environment.

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GC/MS trace (m/z 85) of an aliphatic hydrocarbon fraction obtained from amarine Jurassic source rock (Kimmeridge Clay = Spekk Formation) from theNorth Sea. Low pristane/phytane ratio and low CPI indicates marine algalinput into a highly productive anoxic depositional environment.

nC

Organic Facies

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Abundance

Prista

ne

Phyta

ne

nC

27

nC

35

nC

15

nC

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Organic Facies

GC/MS trace (m/z 83) of an aliphatic hydrocarbon fraction obtained from amarine Jurassic source rock (Kimmeridge Clay = Spekk Formation) from theNorth Sea. Distribution of alkyl-cyclohexanes mimics distribution of n-alkanes indicating an input from marine algae.

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Time-->

Abundance

cycC

15 +

nC

26

nC

31n

C17n

C15

cycC

17

cycC

15

cycC

30

cycC

20

cycC

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nC

23

cycC

27

cycC

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GC/MS trace (TIC) of an aliphatic hydrocarbon fraction obtained from amarine carbonate source rock. Distribution of n-alkanes is domiated by long-chain even-numbered homologues, indicating deposition under conditions ofenhanced salinity and/or alkalinity. Note presence of nor-oleanane, a markerof angiosperm input indicating deposition in a near-shore environment.Pristane/phytane ratio is low, pointing to hypersaline and anoxic conditions.

Abundance

Time-->

Organic Facies

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GC/MS trace (TIC) of an aliphatic hydrocarbon fraction obtained from amarine carbonate platform sediment (Monte Bolca). Presence of HBIsindicates diatoms as major producers in a nearshore anoxic and alkalineshallow environment receiving substantial terrigenic input. Note CPI, Pr/Ph.

Abundance

Time-->

Organic Facies

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GC/MS trace (m/z 117) of a fatty acid fraction obtained from a marinecarbonate platform sediment (Monte Bolca). Importance of terrigenic run-offand nutrient influx is documented by long chain fatty acids derived from landplant waxes. Short chain fatty acids are of algal/cyanobacterial origin.

Organic Facies

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Organic Facies

TIC-trace of an aliphatic hydrocarbon fraction obtained from a Pleistocene (YoungerDryas chronozone) limnic sediment from SW-Germany. Distribution of branched (HBI)and cyclic alkanes (Cheilanthanes) indicates dominant algal input. Alkane/alkenedoublets and low abundance of phytol derivatives are due to low maturity and lowredox potential. Cylcic diterpanes originate from resinous plants (gymnosperms).

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HB

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ane

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ane

hex

adec

ene

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yta

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no

nad

ecan

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ico

scan

e

docoscane

HBI-25-

monoene

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I-2

5-d

ien

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C21-c

hei

lanth

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C20-c

hei

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ane

resinous diterpanes

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Steisslinger See, BW

Younger Dryas 11700 BP

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Organic Facies

Complex TIC-trace of TLE obtained from a Pleistocene (Younger Dryas chronozone)limnic sediment from SW-Germany. Long chain alkanes/alkenes derive from landplants, whereas the C28 and C29 a,w-dienes originate from algae. Hopanoids derivefrom hetero- and phototrophic bacteria, steroids from land plants and algae.

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Time

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opan

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chole

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opan

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opan

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ohopan

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ohopan

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hom

ohop(2

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ne

hen

tria

conta

ne

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b-

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hh

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ohopan

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tria

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iaco

nta

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trit

riac

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tri

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7)d

iene

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,22)d

ien

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tri

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GC/MS traces of aliphatics, fatty acids and alcohols yield coherent land plant signature dominating in a freshwater lake. Recalcitrant components like n-alkanes may deviate in biomarker signatures due to an origin from „older“ or more remote sources.

Organic Facies

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Chemotaxonomic value of n-alkanes for paleobotanical reconstruction. In land plants n-alkane distribution is genetically determined but may be adapted to environmental constraints (temperature, humidity, wind strength).

Organic Facies

Birch

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Biomarkers as Organic Facies Indicators

Chain length preferences of n-alkanes is expressed as CPI (carbonpreference index) and allows to indentify terrigenous input (fluvial or eolian)into marine depositional environments. High CPI thus correlates with low HI.

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Chain length preferences of n-alkanes from Jurassic Posidonia Shale (Luxembourg)

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Pristane/phytane ratio versus sum of pristane plus phytane versus sum ofnC17 plus nC18. Both parameters reflect redox conditions and biological input.Independent verification of applicability of this biomarker ratio is achieved bycalculating average ratios for sediments of consistent biofacies. Oxygendemands of biological assemblages agree well with biomarker ratios.

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Facies influence on pristane / phytane ratio. The ratio of diasteranes versusregular steranes depends on both, clay content (catalytic conversion) and redoxpotential of the sedimentary environment.

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The pristane/phytane redox indicators often correlate well with gammaceraneindex, indicative of intensive water column stratification. Stratification is oftenaccompanied by establishment of bacterial mat communities floating on thepycnocline/halocline and being grazed by ciliates.


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Facies influence on pristane / phytane ratio. Canonical variable (CV) describesvariation in isotopic difference between saturated and aromatic hydrocarbonfraction. High CV (>0.47) indicates non-marine depositional environment.

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Alicyclic Biomarkers as Organic Facies Indicators - I


C25-34 Macrocyclic alkanes Green algae, Botryococcus Lacustrine (saline)

C25-34 Cyclohexylalkanes Ordovician G. prisca Tropical marine

ß-Carotane Cyanobacteria, algae Hypersaline

Phyllocladanes/Kauranes Conifers Terrigenous

Pregnane, Homopregnane Unknown (diagenetic) Hypersaline

C27-29 Steranes Eukayrotic plants, algae Various

C26 Norcholestanes Diatoms, silicoflagellates Marine

C28 Steranes Coccoliths, prasinophytes Marine

C30 Steranes Marine Algae Marine

24-n-Propylcholestanes Chrysophytes Marine

24-Isopropylcholestanes Sponges Marine

4-Methylsteranes Algae (Bacteria?) Lacustrine, marine

Dinosterane Dinoflagellates Marine, (lacustrine?)

Diasteranes Algae, higher plants Clay-rich sediment

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Alicyclic Biomarkers as Organic Facies Indicators - II


C19-35 Tricyclic terpanes Algae, Tasmanites Cold marine, Latitude

C24 Tetracyclic triterpane Unknown Hypersaline

25,28,30-Trisnorhopane Bacteria Marine anoxic

28,30-Bisnorhopane Bacteria Marine anoxic

C35 Hopanes Bacteria Anoxic

C30 Norhopane Various bacteria Carbonate/evaporitic

2-Methylhopanes Cyanobacteria Enclosed basins

3-Methylhopanes Methanotrophes Lacustrine?

Hexahydrobenzohopanes Bacteria Carbonate/anhydritic

Bicadinanes Higher Plants Tropical terrigenous

28,30-Bisnorlupanes Higher Plants Terrigenous

Oleanane Angiosperm plants Terrigenous, paralic

Gammacerane Bacterivorous Ciliates Stratified, hypersaline

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Facies influence on sterane/hopane ratio. High ratio indicates predominance ofmarine algae, low ratios indicate either high abundance of cyanobacteriafavoured under nutrient limited conditions in semi-enclosed basins or presenceof heterotrophic bacteria in aerobic depositional environments.

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Correlation of sterane and tricyclic triterpenoid facies indicators. High abundanceof C28 steranes due to prasinophycean or to coccolithophorid input?

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Correlation of aliphatic and aromatic steroid facies indicators.

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Association of sterane distribution with biological input and facies regime. Theoverwhelming fraction of marine and lacustrine algae to not produce preservablehard-parts. Thus the principal composition of marine primary producers can onlybe investigated by their molecular biomarker composition.

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Characteristic major sterols (algae always produce a suite of steroids) inphytoplankton algal classes Positions of unsaturation are indicated in D

nomenclature.4Me = 4-methylsterols, dinos = dinosterol. The Prochlorophyceae and

Cyanophyceae do not appear to synthesize sterols but other triterpenoids.

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Influence of facies and biological input on sterane ratios in Toarcian Shale.


Peridinin, FucoxanthinL.

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Carbonate depositional environments show low C24 over C23 but high C22

over C21 ratios for tricyclic triterpenoids. Lacustrine and terrestrialenvironments are characterized by low relative abundance of C23 andC21 tricyclic triterpenoids.

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Carbonate depositional environments often lead to increasing C31 overC30 hopanes. Lacustrine settings are characterized by high abundance ofC26 over C25 tricyclic triterpanes (cheilanthanes). Marine shales plotintermittent in this discrimination diagram.

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Carbonate depositional environments often lead to increasing C29 overC30 hopanes and due to iron limitation promote early sulfurization andrelease of intact extended hopanes.


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Mass fragmentograms of m/z= 191 and 367 showing distribution of hopanes and hopenes for three lithofacies types marls, silicified carbonates and laminated marls. Filled triangles represent hop(17,21)enes, stars neohop(13,18)enes, open circles moretanes and filled circles ab-hopanes.


homo-geneous

marl

lami-natedmarl

silicifiedlimestone

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Relative distribution of extended hopanes allows differentiation of variation in biological input and in environmental conditions of sedimentation.


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64.00 66.00 68.00 70.00 72.00 74.00 76.00 78.00 80.00 82.00

C31 C33

2me-C332me-C31

C29

C27

2me-C27

Mass fragmentograms of m/z= 191 and 205 showing distribution of hopanes and 2-methylhopanes (cyanobacteria) for a well laminated black mudstone of Posidonia shale from SW-Germany.

2me-C34 2me-C35

m/z=205

m/z=191

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Mass fragmentograms of m/z= 191 and 205 showing distribution of hopanes and 2-methylhopanes (cyanobacteria) for a non-laminated grey mudstone of Posidonia shale from SW-Germany. Note lack of C33 predominance and constant decline of extended hopanes towards C35.


64.00 66.00 68.00 70.00 72.00 74.00 76.00 78.00 80.00 82.00

C31

C33

2me-C33

2me-C31

C29

C27

2me-C302me-C29

2me-C27

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Mass fragmentograms of m/z= 191 and 205 showing distribution of hopanes and 2-methylhopanes (cyanobacteria) for a poorly laminated black mudstone of Posidonia shale. Note lack of cyanobacterial 2-methylhopanes but for regular hopanes C33 predominance and extended hopanes up to C35 remain.


64.00 66.00 68.00 70.00 72.00 74.00 76.00 78.00 80.00 82.00

no methyl-hopanes present

C31 C33

C29

C27

C30

C35

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Arocyclic Biomarkers as Organic Facies Indicators - I


Benzothiophenes Unknown (diagenetic) Carbonate/evaporitic

Isoreniaratene Chlorobiaceae Photic zone euxinia

2,3,6-Trimethylaryl isoprenoids Chlorobiaceae Photic zone euxinia

Isobutyl maleimides Chlorobiaceae Photic zone euxinia

Trimethylchromanes Plankton? saline

Methylchromanes Plankton? hypersaline

Monoaromatic Steroids Eukayrotic plants, algae Various

Triaromatic 4-methylsteroids Algae (Bacteria?) Lacustrine, marine

Triaromatic dinosteroids Dinoflagellates Marine, (lacustrine?)

Benzohopanes Bacteria Anoxic, carbonate

8,14-Secohopanes Bacteria Anoxic, carbonate

Pimanthrene Conifers, (Araucaria) Terrigenous

Cadalene, Simonellite, Retene Gymnosperms Terrigenous

iC5-iC6-Methylnaphthalene Gymnosperms Terrigenous

Monoaromatic polyprenoids Ostracodes? Lacustrine, marine

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Hughes – Plot

Differentiation of organic facies according to the dibenzothiophene versus phenanthrene-ratio. In carbonatic environments iron is often limited. This favors incorporation of sulfur into organic matter and leads to formation of thiophenes.Higher pristane abundance in non-carbonates is due to decarboxylation of phytenic acid at low water table and high availability of free oxygen.

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Aromatic carotenoids derived from chlorobiacea are indicative of PZE.

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Diagenetic fate of diaromatic carotenoids derived from chlorobiacea.

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Composition of aryl isoprenoids in Toarcian shales, marls, and carbonates of SW-Germany varies with organic facies and sea level stand.


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AIR increases with decreasing preservation of aryl isoprenoids. A plot of AIR versus pr/ph-ratios differentiates three groups. Group 1 contains samples from the lower TST deposited under intermediate sea level. Cluster 2 groups high sea level samples of upper TST, MFZ, and HST. Group 3 combines samples deposited under aerobic conditions during low sea level and intensive shelf water ventilation. Low AIR values indicate long-lived and permanent photic-zone anoxia (PZA) whereas high values indicate shortlived and episodic PZA.


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Salinity influence on pristane/phytane ratio discriminated by parallel application of MTTC-ratio.Low MTTC-ratio indicates presence of mono- and dimethyl-MTTC assumed to be characteristic for halophilic phototrophs.

MTTC-ratio has been questioned due to thepossibility of diagenetic origin of chromanes viacondensation of phytol with alky-substituted phenols.

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Crossplot of molecular paleo-salinity indicators ITR and pri/phy. Both ratios respond to salinity and anoxia, which develop parallel in most depositional environments.Open and black filled circles indicate different lithologies: laminated and non-laminated marls, circles filled grey represent silicified lithofacies types.Laminated marls show indications of slightly enhanced salinity (meso-saline) for both molecular parameters.

Abundant trimethylated chromans are considered to indicate a freshwater lense overlying saline bottom waters and thus indicate intensive water column stratification. Devonian Gogo Fm. Canning Basin Australia.

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Parameter Marine Terrigenic Lacustrine

C21-35 N-alkanes Low High High/Low

Pristane/phytane Low,<1.5 High,>3 High,~1-3

Pristane/nC17 Low,<0.5 High,>1.0 Intermediate

4-Methylsteranes High Low Low

C27-29 Steranes High C28 or C 27, High C29 High C27

24-n-Propylcholestanes Low Absent Absent

Steranes/hopanes High Low Low

Bicyclic sesquiterpanes Low High Low

Tricyclic diterpanes Low High High

Tetracyclic diterpanes Low High Low

Lupanes, bisnorlupanes Low High Low

28,30-Bisnorhopane High Low Low

Oleanane Low / Absent High Low

ß-Carotane Absent Absent High (arid)

Bottryococcane Absent Absent High

Pr/Ph and bulk lithology as Organofacies Indicators

Global map of petroleum source rock data point distribution for Pr/Ph-ratios and bulk lithology determined by XRD.


Organofacies types A,B,C, D/E/F as established by Pepper and Corvi (1995).Kerogen type III/IV is devided into hydrogen-rich terrigenic organic matter low in lignin (D/E) and type F, corresponding to lignin-rich humic input:P&C A = marine carbonate, iron-poor and sulfur –rich (type II-S)P&C B = marine siliciclastic to marl, pyrite-rich (type II)P&C C = lacustrine basins and lagoons (Type I)P&C D/E/F = terrigenic OM, humic, oxic environment (Type III/IV)


Frequency distribution for Pr/Ph ratios classified by P&C organofacies type.


Carbonate content vs. Pr/Ph ratios classified by P&C organofacies type.


Clay content vs. Pr/Ph ratios classified by P&C organofacies type. Discriminative power is lower than for carbonate and organofacies C reveals a large spread, diminishing its applicability in source assessment.


Quartz content vs. Pr/Ph ratios classified by P&C organofacies type. Discriminative power is poor compared to carbonate and clay (e.g. Pr/Ph ratios in the range of 1 to 3 may derive from all lithofacies types).


Ternary diagram of Carbonate/Clay/Quartz (CCQ) depicting organofacies via Pr/Ph ratios (discete datapoints) versus XRD-based organofacies type. Note matching colors in both discrimination schemes.


Ternary diagram of Carbonate/Clay/Quartz (CCQ) depicting organofacies exclusively by XRD-based separation.


Ternary CCQ-diagram showing contoured Pr/Ph values and color-coded organofacies interpretations demonstrates a good match and reasonable predictive power, in particular when using big data sets.

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