Serravallian Shales in the Monte dei Corvi Pelagic Sequence (Ancona, Italy): An Organic Geochemical Perspective

In addition to the predominant marly lithologies, the Serravallian-Tortonian sequence at Monte dei Corvi (MDC), south of Ancona, Italy, contains at least 85 thin, dark calcareous shales. Such shales, averaging 14 cm in thickness, comprise 9% of the total Serravallian sequence. Sixteen of them were sampled for a preliminary organic geochemical evaluation. All the MDC shales appear to have been deposited during periodic anoxic events, as demonstrated by the presence of significant quantities of organic matter and authigenic pyrite. The degree of anoxicity (and thus the amount of organic matter preserved) appears to have differed from one event to the next. The quantity of organic matter preserved is highly variable, with Rock Eval S2 ranging from 0.4 to 27.6 mg/g. However, the type is remarkably consistent from sample to sample, as evidenced both by analytical pyrolysis-gas chromatography/mass spectrometry (GC/MS) of the solid organic matter and by the GC/MS analysis of the extractable material. This implies a regeneration of similar microfloral/microbial assemblages and depositional conditions during each anoxic event. The dominant organic matter types are marine, including several types of fossil algae and amorphous material (largely the product of bacterial reworking of organic matter). There is evidence of minor terrestrial input. The presence of isoprenoid hydrocarbons (prist-1-ene) in the pyrolyzates and 17β(H),21β(H) hopanes in the extractable organic matter attest to the low level of thermal alteration of the MDC shales. The MDC organic matter appears to be partially oxidized, probably from weathering at the outcrop, which partly obscures its original nature. To avoid this problem in any future organic geochemical study of the MDC sequence, the authors recommend that fresh, unweathered samples be obtained, preferably by coring

Geochemical Characterization of Maceral Concentrates from Herrin No. 6 Coal (Illinois Basin) and Lower Toarcian Shale Kerogen (Paris Basin)

Density gradient centrifugation (DGC) is a physical method for the separation of sedimentary organic matter into its constituents. Using DGC, it is possible to prepare maceral concentrates from a single sample, which are amenable to microanalysis. DGC fractions from a coal sample from the Illinois Basin (Herrin No. 6, Upper Carboniferous) and from the kerogen of a marine shale sample from the Paris Basin (Lower Toarcian) were analyzed by flash pyrolysis-gas chromatography-mass spectrometry, after extraction by CH2Cl2. Chemical differences between the coal DGC fractions are the easiest to recognize, indicating very distinctive biological precursors. For example, the liptinite fraction ( = 1.12 g ml-1) is dominated by long-chain aliphatic compounds (n-alkanes and n-alkenes) along with alkylbenzenes and alkylphenols. Vitrinite (1.29 g ml-1) shows a predominance of alkylbenzenes and phenolic compounds. Polyaromatic hydrocarbons (especially naphthalene, phenanthrene, anthracene and their pseudohomologues) are major compounds in the pyrolyzate of fusinite (1.45 g ml-1). In contrast, there is less variety of organic compounds in the Toarcian sample. Petrographically, this kerogen is primarily amorphous. However, a main DGC peak ( = 1.18 g ml-1) with two shoulders (1.15 and 1.23 g ml-1) is resolved using multi-step centrifugation. The chemical differences between these fractions are subtle but significant. Concentrations of alkylbenzenes, alkylthiophenes, alkylpyrroles and phenolic compounds increase with density, relative to the aliphatics. This indicates that this kerogen, probably of algal and bacterial origin, is partially separable by DGC

Organic Geochemistry and Petrology of Oil Source Rocks, Carpathian Overthrust Region, Southeastern Poland — Implications for Petroleum Generation

The organic matter rich Oligocene Menilite black shales and mudstones are widely distributed in the Carpathian Overthrust region of southeastern Poland and have excellent hydrocarbon generation potential, according to TOC, Rock-Eval, and petrographic data. Extractable organic matter was characterized by an equable distribution of steranes by carbon number, by varying amounts of 28,30-dinor-hopane, 18α(H)-oleanane and by a distinctive group of C24 ring-A degraded triterpanes. The Menilite samples ranged in maturity from pre-generative to mid-oil window levels, with the most mature in the southeastern portion of the study area. Carpathian petroleum samples from Campanian-Oligocene sandstone reservoirs were similar in biomarker composition to the Menilite rock extracts. Similarities in aliphatic and aromatic hydrocarbon distributions between petroleum asphaltene and source rock pyrolyzates provided further evidence genetically linking Menilite kerogens with Carpathian oils

Molecular Composition of the Louse Sheath

Flash pyrolysis-gas chromatography/mass spectrometry was used to assess the chemical composition of the head louse\u27s nit sheath. The pyrolyzate of the female insect\u27s secretions, which form a cement-like cylinder holding the egg onto the hair, is dominated by amino acid derivatives and fatty acids. No chitin-specific compounds were detected in the sheath. These results, contrary to previous reports, show that the polymeric complex of the sheath is composed of proteinaceous moieties, possibly cross-linked to aliphatic components. This study constitutes the first chemical characterization of the pyrolysis products of insect (louse) glue and unequivocally confirms that louse sheaths are not chitinous, as suggested by earlier histochemical studies. Development of agents that might loosen nits from the hair shaft is dependent on research that addresses the chemical composition of the nit sheath

Separation and Artificial Maturation of Macerals from Type II Kerogen

Immature Type II kerogen (HI= 660 mg/g) from the Lower Toarcian of the Paris Basin was separated into an alginite concentrate (HI = 952 mg/g) and an amorphous organic matter (AOM) concentrate (HI = 573 mg/g) by density centrifugation. The flash pyrolyzate of the alginite is characterized by high relative concentrations of several series of n-alkanones and n-alkenones (including mid-chain alkyl ketones), in addition to n-alkanes, n-alk-1-enes and n-alkadienes. To our knowledge, this Toarcian alginite is the oldest example of marine organic matter whose pyrolyzate contains mid-chain alkanones in such high relative concentrations. In sharp contrast, the AOM produced predominantly alkylbenzenes, alkylthiophenes, n-alkanes and n-alk-1-enes upon pyrolysis. Micro-FTIR spectroscopy indicated that the alginite was enriched in aliphatic C-H (particularly CH2) and depleted in aromatic C=C, relative to the AOM, consistent with the pyrolysis results. Aliquots of the concentrates were heated separately in gold tubes (24 h, 70 MPa) at fixed temperatures ranging between 250 and 375°C. Yields of liquid products as a function of temperature were initially greater for the AOM, reaching a maximum at 325°C. In contrast, the alginite yielded little liquid product at low temperatures, attaining its maximum at 350°C, at which temperature its yield greatly surpassed that of the AOM. This kerogen is a heterogeneous assemblage of fossil organic matter, exhibiting different degrees of preservation and petroleum potential. The alginite is fossilized marine algaenans with alkyl chains cross-linked by ether bridges, while the AOM component is at least in part a geopolymer with thioether linkages, the thermally labile nature of which is responsible for its lower temperature peak liquid generation. It is evident that the alginite concentrate is chemically distinct from its companion AOM in this kerogen and that the full extent of its uniqueness would not have been revealed without the density separation step

Protein preservation and DNA retrieval from ancient tissues

The retrieval of DNA from fossils remains controversial. To substantiate claims of DNA recovery, one needs additional information on the preservation of other molecules within the same sample. Flash pyrolysis with GC and MS was used to assess the quality of protein preservation in 11 archaeological and paleontological remains, some of which have yielded ancient DNA sequences authenticated via a number of criteria and some of which have consistently failed to yield any meaningful DNA. Several samples, including the Neanderthal-type specimen from which DNA sequences were recently reported, yielded abundant pyrolysis products assigned to 2,5-diketopiperazines of proline-containing dipeptides. The relative amounts of these products provide a good index of the amount of peptide hydrolysis and DNA preservation. Of these samples, four stem from arctic or subarctic regions, emphasizing the importance of cooler temperatures for the preservation of macromolecules. Flash pyrolysis with GC and MS offers a rapid and effective method for assessing fossils for the possibility of DNA preservation

A Geochemical Study of Macerals from a Miocene Lignite and an Eocene Bituminous Coal, Indonesia

Optical and chemical studies of maceral concentrates from a Miocene lignite and an Eocene high-volatile bituminous C coal from southeastern Kalimantan, Indonesia were undertaken using pyro-Lysis, optical, electron microprobe and FTIR techniques Pyrolysis products of vitrinite from bituminous coal were dominated by straight-chain aliphatics and phenols. The huminite of the Miocene lignite produced mostly phenolic compounds upon pyrolysis. Differences in the pyrolysis products between the huminite and vitrinite samples reflect both maturation related and paleobotanical differences. An undefined aliphatic source and/or bacterial biomass were the likely contributors of n-alkyl moieties to the vitrinite. The resinite fraction in the lignite yielded dammar-derived pyrolysis products, as well as aliphatics and phenols as the products of admixed huminite and other liptinites. The optically defined resinite-rich fraction of the bituminous coal from Kalimantan produced abundant n-aliphatic moieties upon pyrolysis, but only two major resin markers (cadalene and 1,6-dimethylnaphthalene). This phenomenon is likely due to the fact that Eocene resins were not dammar-related. Data from the electron microprobe and Fourier transform infrared spectrometry strongly support the results obtained by Py GC MS and microscopy

Geochemistry of the Alginite and Amorphous Organic Matter from Type II-S Kerogens

Maceral fractions of the Type II-S kerogens from the Monterey Formation (Miocene. California. U.S.A.) and Duwi Formation (Campanian/Maastrichtian, Egypt) were separated by density gradient centrifugation. The Monterey Fm. kerogen sample was comprised chiefly of light red-fluorescing amorphous organic matter (AOM), the flash pyrolyzate of which was characterized by a predominance of alkylbenzenes, alkylthiophenes and alkylpyrroles. In contrast, the pyrolyzates of its alginite concentrate showed a highly aliphatic character, typical of this maceral, with the series of n-alkenes and n-alkanes (C6- C26) predominating. The pyrolyzate of the dominant light brown-fluorescing AOM of the Duwi Fm. kerogen had a relatively high concentration of alkylbenzenes and alkylthiophenes, while its elginite concentrate showed a more aliphatic character upon pyrolysis. There was a marked enrichment of thiophenic sulfur in the light-colored AOM of both samples (and also pyrrolic nitrogen in the case of the Monterey) relative to the alginite. The results support a bacterially-mediated, degradative origin for Type II-S amorphous organic matter, with algal remains as the primary source of the kerogen

Density Gradient Centrifugation: Application to the Separation of Macerals of Type I, II, and III Sedimentary Organic Matter

Samples of organic matter from nine well-known geological units (Green River Fm., Tasmanian Tasmanite, Lower Toarcian Sh. of the Paris Basin, Duwi Fm., New Albany Sh., Monterey Fm., Herrin No. 6 coal, Eocene coal, and Miocene lignite from Kalimantan) were processed by density gradient centrifugation (DGC) to isolate the constituent macerals. Optimal separation, as well as the liberation of microcrystalline pyrite from the organic matter, was obtained by particle size minimization prior to DGC by treatment with liquid N2 and micronization in a fluid energy mill. The resulting small particle size limits the use of optical microscopy, thus microfluorimetry and analytical pyrolysis were also employed to assess the quality and purity of the fractions. Each of the samples exhibits one dominant DGC peak (corresponding to alginite in the Green River Fm., amorphinite in the Lower Toarcian Sh., vitrinite in the Herrin No. 6, etc.) which shifts from 1.05 g mL-1 for the Type I kerogens to between 1.18 and 1.23 g mL-1 for Type II and II-S. The characteristic densities for Type III organic matter are greater still, being 1.27 g mL-1 for the hydrogen-rich Eocene coal, 1.29 g mL-1 for the Carboniferous coal and 1.43 g mL-1 for the oxygen-rich Miocene lignite. Among Type II kerogens, the DGC profile represents a compositional continuum from undegraded alginite through (bacterial) degraded amorphinite; therefore chemical and optical properties change gradually with increasing density. The separation of useful quantities of macerals that occur in only minor amounts is difficult. Such separations require large amounts of starting material and require multiple processing steps. Complete maceral separation for some samples using present methods seems remote. Samples containing macerals with significant density differences due to heteroatom diversity (e.g., preferential sulfur or oxygen concentration in the one maceral), on the other hand, may be successfully separated (e.g., coals and Monterey kerogen)