FTIR absorbance signals in kerogens and macerals were evaluated as indices for thermal maturity. Two sets of naturally matured type-II kerogens from the New Albany Shale (Illinois Basin) and the Exshaw Formation (Western Canada Sedimentary Basin) and kerogens from hydrous pyrolysis artificial maturation of the New Albany Shale were characterized by FTIR. Good correlation was observed between the aromatic/aliphatic absorption ratio and vitrinite reflectance R0. FTIR parameters are especially valuable for determining the degree of maturity of marine source rocks lacking vitrinite. With increasing maturity, FTIR spectra express four trends: (i) an increase in the absorption of aromatic bands, (ii) a decrease in the absorption of aliphatic bands, (iii) a loss of oxygenated groups (carbonyl and carboxyl), and (iv) an initial decrease in the CH2/CH3 ratio that is not apparent at higher maturity in naturally matured samples, but is observed throughout increasing R0 in artificially matured samples. The difference in the CH2/CH3 ratio in samples from natural and artificial maturation at higher maturity indicates that short-term artificial maturation at high temperatures is not fully equivalent to slow geologic maturation at lower temperatures. With increasing R0, the (carboxyl+carbonyl)/aromatic carbon ratio generally decreases, except that kerogens from the Exshaw Formation and from hydrous pyrolysis experiments express an intermittent slight increase at medium maturity. FTIR-derived aromaticities correlate well with R0, although some uncertainty is due to the dependence of FTIR parameters on the maceral composition of kerogen whereas R0 is solely dependent on vitrinite.

The origin of sedimentary organic matter (kerogen) has been attributed to random recombination reactions of biological components in sediments or to selective preservation of decay-resistant macromolecules. Neither hypothesis explains the aliphatic composition of the cuticle of fossil arthropods. Thermal maturation experiments on modern arthropods, involving confined pyrolysis at 250-360 degrees C, degrade the chitin-protein complex of the cuticle and transform free aliphatic components into a polymeric structure. The results of the application of electron microscopy and spectroscopic methods to modern, thermally matured, and fossil arthropod cuticles indicate that in situ polymerization of free and ester-bound cuticular lipids can lead to kerogen formation. Thus, fossil arthropod fragments can contribute to sedimentary organic matter.

Tidal rhythmites are vertically stacked small-scale sedimentary structures that record daily variations in tidal current energy and are known to overlie some low-sulfur coals in the Illinois Basin. Tidal rhythmites from the Pennsylvanian Brazil Formation in Indiana have been analyzed sedimentologically, petrographically, and geochemically in order to understand the character and distribution of organic matter (OM) preserved in an environment of daily interactions between marine and fresh waters. The concentration of organic matter (TOC) ranges from traces to 6.9% and sulfur rarely exceeds 0.1% in individual laminae. Angular vitrinite is the major organic matter type, accounting for 50–90% of total OM. The C/S ratio decreases as the vertical distance from the underlying coal increases. A decreasing C/S ratio coupled with decreases in Pr/Ph, Pr/n-C17, Ph/n-C18 ratios and a shift of carbon isotopic composition towards less negative values suggest an increase in salinity from freshwater in the mudflat tidal rhythmite facies close to the coal to brackish/marine in the sandflat tidal rhythmite facies further above from the coal. Within an interval spanning one year of deposition, TOC and S values show monthly variability. On a daily scale, TOC and S oscillations are still detectable but they are of lower magnitude than on a monthly scale. These small-scale variations are believed to reflect oscillations in water salinity related to tidal cycles.

This study focuses on the different precursors of simple alkylphenols in pyrolyzates of different types of organic matter. Several organic matter samples were studied, i.e. dissolved organic matter (DOM), particulate organic matter (POM), sediments, polysaccharide/protein standards, algae, hydrolyzable tannins, lignins, lignites, coals, soils and insect cuticles. Most samples were subjected to saponification and some to hydrolysis using hydrochloric acid. Distribution patterns of the alkylphenols in the pyrolyzates were compared with those in pyrolyzates of natural samples. To some extent, the distribution patterns of these alkylphenols can be used to discriminate their precursors, lignins, protein and transformed protein. Alkylphenols in pyrolyzates of samples like DOM, POM and sediments are probably reflecting polymers which are formed by cross-linking of protein units (tyrosine) forming non-amide bonds on hydrolysis of polysaccharide/protein material in the water column. The polysaccharide part plays a major role in the formation of these polymers.

Samples of Recent Ginkgo biloba, two Cretaceous Ginkgo and two Cretaceous conifer cuticles from different enclosing lithologies but with similar thermal maturity of the fossils, have been analysed by scanning and transmission electron microscopy (SEM, TEM), Fourier transform–infrared spectroscopy (FT–IR), and pyrolysis–gas chromatography/mass spectrometry (Py–GC/MS). Recent and fossil Ginkgo cuticles under SEM reveal sheets, similar in appearance, varying in the abundance and texture of the cuticular papillae. TEM of the Recent Ginkgo shows an outer amorphous cuticle layer, a structured middle layer and an inner laminated layer of cell wall. The Cretaceous Ginkgo cuticles retain the amorphous layer and a modified structured layer. SEM of Cretaceous Abietites and Frenelopsis also shows preservation of cuticle sheets but each has distinctive morphology. These conifer cuticles are very thick (TEM), Frenelopsis cuticle has remarkable multilaminar ultrastructure whilst Abietites is amorphous. G. biloba cuticle consists mainly of the natural polyester, cutin, as revealed by FT–IR and pyrolysis, indicated by an abundance of saturated, unsaturated and hydroxy fatty acids. IR spectra of fossil cuticles, like modern cuticles, show aliphatic C–H, hydroxyl and carbonyl functions. However, in fossils, the carbonyl ester is transformed to carboxylic acid or ketone groups. Pyrolysates of fossils show phenolic constituents like modern cuticles but loss of cutin fatty acid monomers and an increased prominence of an homologous series of n-alkene and n-alkane fragments up to n-C30. Since most Recent cuticles, including those of conifers and Ginkgo biloba which we have studied, do not yield a non-saponifiable highly resistant residue it is proposed that organic preservation of fossil species investigated involves the diagenetic stabilisation of chemically-labile aliphatic cutin constituents along with incorporation of waxes. These general chemical modifications characterise all fossil Ginkgo and conifer cuticles, irrespective of their enclosing lithology, systematic affinity, external morphology or internal ultrastructural preservation. However there are also clear chemical differences between the fossil samples which may relate to their systematic affinity (ginkgos vs Abietites and Frenelopsis).

The environmental setting and taphonomy of the insect fauna of the Insect Bed, Bembridge Marls (late Eocene; 36 Ma) of the Isle of Wight is described. Cluster analysis of taxonomic data on the insect fauna of a diversity of modern tropical environments, together with that of the Bembridge Marls, shows that the insects of the latter are characteristic of a primary sub-tropical/tropical forest subject to significant seasonal rainfall. A similar approach indicates that the sample of taxa preserved in the Insect Bed is biased toward insects from leaf litter and lower herbage microhabitats. External ornamentation of the cuticle is preserved on a micron scale, and the individual microfibrils of the procuticle can be distinguished. The insects of the Bembridge Marls are remarkable in preserving cuticle and mineralized internal tissues in a largely uncompacted state. Chemical analysis (py-GC/MS) reveals that the cuticle is composed of an aliphatic polymer, possibly due to polymerization of cuticular waxes during diagenesis. No chitin was detected. The soft tissues, which include sarcolemma and muscle fibres, are preserved through replacement in calcite.

The morphological preservation of fossils in amber is remarkable, but their chemical composition is largely unknown. The likelihood of DNA preservation in amber has been questioned but, surprisingly the fate of more decay-resistant macromolecules such as ligno-cellulose in plants or the chitin-protein complex in insect cuticle has not been investigated. Here we report the results of investigations using pyrolysis-gas chromatography/mass spectrometry (py-GC/MS) of the tissues of insects and the plant Hymenaea from ancient and sub-fossil resins (2-20 ka) from Kenya, and from Dominican amber (25-30 Ma). The volatile components of the resin have penetrated even the internal tissues, resulting in the exceptional three-dimensional preservation of amber inclusions. Chitin is preserved in the bee and ligno-cellulose in the Hymenaea leaf from the Kenyan resins. There was no trace, however, of these macromolecules in tissues in Dominican amber. The presence of aliphatic polymer and sulphur-containing moieties in these tissues indicates that they have undergone diagenetic alteration; in view of this, the preservation in Dominican amber of a macromolecule as labile as DNA would be extraordinary .

Arthropod cuticles consist predominantly of chitin cross-linked with proteins. While there is some experimental evidence that this chitin-protein complex may resist decay, the chemical changes that occur during degradation have not been investigated in detail. The stomatopod crustacean Neogonodactylus oerstedii was decayed in the laboratory under anoxic conditions. A combination of pyrolysis-gas chromatography/mass spectrometry and FTIR revealed extensive chemical changes after just 2 weeks that resulted in a cuticle composition dominated by chitin. Quantitative analysis of amino acids (by HPLC) and chitin showed that the major loss of proteins and chitin occurred between weeks 1 and 2. After 8 weeks tyrosine, tryptophan and valine are the most prominent amino acid moieties, showing their resistance to degradation. The presence of cyclic ketones in the pyrolysates indicates that mucopolysaccharides or other bound non-chitinous carbohydrates are also resistant to decay. There is no evidence of structural degradation of chitin prior to 8 weeks when FTIR revealed a reduction in chitin-specific bands. The chemical changes are paralleled by structural changes in the cuticle, which becomes an increasingly open structure consisting of loose chitinous fibres. The rapid rate of decay in the experiments suggests that where chitin and protein are preserved in fossil cuticles degradation must have been inhibited.

Analyses of identifiable organic fossil remains of animals and plants have considerable potential to resolve conflicting models of organic matter diagenesis and kerogen formation (e.g. selective preservation versus random polymerization). Fossil cuticles of arthropods (scorpion, eurypterid) and plants (cordaite, pteridosperm) from Upper Carboniferous strata of Lone Star Lake, Kansas, USA and Joggins, Nova Scotia, Canada were analysed by pyrolysis–gas chromatography/mass spectrometry and examined by electron microscopy. Recent Pandinus (scorpion) and Araucaria (conifer) provided a basis for comparison. Pyrolysis of Recent dewaxed scorpion cuticle yielded products derived from chitin and proteins. These products were absent in the fossil arthropod cuticles, however, which yielded an homologous series of alkanes and alkenes, together with phenolic and other aromatic constituents. Recent dewaxed plant cuticle yielded fatty acids, phenols and carbohydrate-derived compounds indicative of cutin polyester and associated lignocellulose. The pyrolysates of the fossil plant cuticles, on the other hand, were dominated by alkane–alkene doublets, with minor phenolic and other benzenoid components. There is no evidence that the preservation of these cuticles as particulate organic matter in kerogen is simply a result of selective preservation. Nonetheless, the chemistry and morphology remain characteristic of a particular taxon, thereby eliminating the possibility of incorporation of randomly repolymerized materials or the transfer of material between plant and animal residues. The aliphatic moieties in the fossil cuticles are thought to be the result of polymerization of the associated epicuticular, cuticular and/or tissue lipids during diagenesis.

A colorimetric assay and pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) were used to study chitin in a variety of fresh, laboratory decayed and fossil arthropod cuticles, the last ranging in age from Upper Cretaceous (approximately 65 Ma) to Holocene, The results of the colorimetric assay of chitin in fresh arthropod cuticle are consistent with values reported in the literature, Py-GC-MS, although non-quantitative, yields pyrolysis products characteristic of chitin and other constituents of the cuticle, Both the colorimetric and Py-GC-MS methods demonstrate that chitin is preserved in Quaternary and some Tertiary specimens, In some fossil cuticles the colorimetric assay gave a positive response even though pyrolysis products characteristic of chitin were not detected, Py-GC-MS revealed the presence of non-chitinous carbohydrates in these cuticles, which presumably accounts for the positive result obtained from the colorimetric assay, The results show that analytical methods are required to provide reliable quantitative and qualitative information on chitin in fossil specimens, This investigation establishes the utility of this approach to the study of chitin in the geosphere, and where chitinous material has been degraded or chemically modified in modern environments.

A brief overview of our current understanding of nitrogen-containing macromolecules and their fate in the bio- and geosphere is presented in the context of their significance in the N cycle. The major biological macromolecular sources, such as amino sugars, proteins and nucleic acids, as well as abiogenic forms of N, are briefly reviewed. The analytical techniques and methods used in studies of nitrogen in the bio- and geosphere are also summarized.

The Pliocene lake sediments at Willershausen, Germany, have yielded a diversity of remarkably preserved fossils, including crayfish and insects. The internal structure of the cuticle of the crayfish Astacus and of insects is preserved, but shows evidence of some degradation. Chitin and amino acids survive, although the quantity that remains is variable. The proportion of chitin in the cuticle of the modern crayfish Pacifastacus (12.2%) is higher than that in Astacus from shallow depths in the Willershausen paleolake (5%), indicating that the fossils have undergone degradation. Analyses of the cuticles of these crayfish following demineralization show that some chemical components, which were presumably bound to the carbonate, are lost. The proportion of chitin (40%) in the cuticle of a weevil from the deeper part of the stratified paleolake (below the chemocline) is comparable to that in the cuticle of modern beetles. A much lower proportion of chitin (2-5%) survives in the cuticle of insects from the shallower oxygenated part of the paleolake, indicating that intensive degradation has occurred. Thus depositional setting, and biomineralization, influence the preservation of the organic constituents of fossil arthropod cuticles.

Chitin is one of the most abundant biopolymers on earth. It occurs in a range of organisms but is particularly important as a constituent of arthropod cuticles. Experiments have demonstrated that chitin is more resistant to degradation than protein, but it is rarely preserved in the fossil record. The chitin content of beetle cuticles from 11 Quaternary deposits in Canada, UK and USA was estimated using pyrolysis-GC/MS and quantitative colorimetric assay. The proportion preserved ranged from 3 to 37 dry weight %. Analyses of insects and fresh-water crustaceans from several European Tertiary biotas revealed that the chitin biopolymer is preserved at levels varying from 2 to 38%. Chitin can survive, even for millions of years, in non-marine elastic sediments that provide favourable environmental conditions, but it is much more susceptible to degradation in marine settings. The 25 Ma lacustrine deposit of Enspel, Germany, preserves the oldest reliable evidence of chitin reported to date. The differences in the proportion of chitin preserved in fossils reflect the environment of deposition more than their age. Chitin is more likely to be found in fossils preserved in terrestrial than in marine strata.

DNA from excrements can be amplified by means of the polymerase chain reaction. However, this has not been possible with ancient feces. Cross-links between reducing sugars and amino groups were shown to exist in a Pleistocene coprolite from Gypsum Cave, Nevada. A chemical agent, N-phenacylthiazolium bromide, that cleaves such cross-links made it possible to amplify DNA sequences. Analyses of these DNA sequences showed that the coprolite is derived from an extinct sloth, presumably the Shasta ground sloth Nothrotheriops shastensis. Plant DNA sequences from seven groups of plants were identified in the coprolite. The plant assemblage that formed part of the sloth's diet exists today at elevations about 800 meters higher than the cave.

A wide range (16) of synthetic polymers, biological and organic geochemical samples was chosen to compare the performance of filament and Curie-point pyrolysis devices in combination with gas chromatography/mass spectrometry (py-GC/MS). The pyrolysis results were compared qualitatively, quantitatively and using statistical data visualization methods. Multivariate visualization methods showed a good reproducibility between consecutive runs of the same sample. Statistical analyses of processed py-GC/MS data and qualitative comparison of total ion and mass chromatograms revealed a high degree of comparability between the data obtained from the two pyrolysis devices. This investigation constitutes the first systematic comparison of the two most widely used pyrolysis devices and demonstrates that their results can be confidently cross-referenced providing that all other analytical variables, e.g. sample size, GC column stationary phase, carrier gas, etc. are strictly controlled.