Diagenesis

This research demonstrates the value of laser scanning confocal microscopy (LSCM) as a research tool in osteological studies, and diagenetic studies in particular.  LSCM combines properties of light and scanning electron microscopy by using laser light to excite fluorophores throughout the z-axis, developing a 3-D image.  Using differential staining and selecting for specific wavelengths of light, one can image targeted materials.  This research is divided into two parts: visualizing bone structures such as proteins and their decompositional products, and visualizing diagenesis.  Part one of this study utilized pig bones as a means of testing the overall ability of LSCM to fluoresce bone.  Twenty-three samples were imaged, including 13 samples from a decompositional study conducted 5 years previous, and 10 “fresh” samples collected from a commercial butcher.  This part of the study determined protein and organic components of the bone could be fluoresced and diagenetic alteration could be imaged.  The second part of the study used human samples as a means of imaging and mapping diagenetic alterations.  The second part of the study used 13 samples, including 4 clinical, 7 ancient, and 2 modern controls.  The pig study used Basic Fuchsin and SlowFade Gold stains, while the human study used Toluidine Blue.  Images were also taken with unstained elements.  The results of the non-human study found that a fresh bone fluoresced differently than that of a five-year subset while, the results of the human study confirmed these findings and determined that bone diagenesis can be mapped using LSCM.

We here report the discovery of unusual distributions of long-chain alkenones (C,,+) in two Cretaceous black shales from the Blake-Bahama Basin, western North Atlantic. These sediments are Cenomanian (c. 95 Ma) and mid-Albian (c. 105 Ma) in age, thus significantly extending the geological range of these compounds. The precise source of these lipids is, as yet, unknown, although they may derive from an ancient ancestor of Emiliania huxleyi.

The Hermod sand of the Stine Segments, Siri Field, Danish North Sea, displays large permeability variations (1-600 mD). These permeability variations represent horizontal layering in the reservoir, largely formed by diagenetic processes. They have a significant impact on reservoir performance, because horizontal producers in fairly thin reservoirs ($30 m) are protected against bottom-water influx and can produce water-free for long periods of time. This paper presents the results of a detailed multidisciplinary study where the observed variation in permeability can be explained by two main diagenetic phases: silica, as opal cement and microquartz, and berthierine, a serpentine mineral that is closely related to chlorite. Opal/microquartz and berthierine cements dominate in separate parts of the reservoir bodies. Opal/ microquartz cemented sands have high permeability (typically 500-600 mD). Berthierine cement has a different growth pattern in the oil and water zones, resulting in intermediate permeability in the oil zone (typically 50-100 mD) and very low permeability in the water zone (typically 1-10 mD).

The Tournasian age Pekisko carbonates in the Normandville Field (northwestern Alberta) form waulsortian-like, bryozoan/crinoid mounds that developed in fairly deep, low energy, cool water systems, close to the ramp margin. Three main depositional environments occur: (1) crinoidal apron with wackestone, grainstone and floatstone facies; (2) mound flank with grainstone, wackestone, packstone and floatstone facies dipping $351; and (3) bryozoan mound core, composed of rudstone and floatstone facies with fenestrate bryozoa, minor crinoids and carbonate mud. Local highs due to fault-bounded blocks, created from the collapse of the Devonian Peace River High, may have controlled the location of mound nucleation.

1] A rock magnetic study of the upper 40 m of the Ocean Drilling Program Site 133-820A recovered at the outer edge of the northeastern Australian continental margin shows that downcore variations in magnetic parameters are diagenetically driven and correlate with the changes in global sea level. We identified intervals enriched in single-domain (SD) magnetite in the studied section. Unlike previous studies that postulated a detrital source, we show that the bulk of the SD fraction is biologically produced and is likely to be authigenic. The abundance of SD magnetite thus cannot be used as an indicator for provenance or sediment transport mechanisms. The biogenic magnetite was preserved during the high sedimentation rate periods, likely due to a short residence time in the corrosive zone of active iron reduction. The presence of the biogenic magnetite thus can be used as an indicator for a low degree of reductive dissolution. More advanced dissolution during the periods of slow sedimentation, coincident with sea level highstands, resulted in significant changes in the composition of the detrital assemblage, particularly in relative abundances of different mineral phases. The overall stability of the detrital magnetic minerals toward dissolution varies in the studied section as hematite > magnetite > goethite. Due to the higher stability of hematite, reductive diagenesis in general will lead to the lowering of the goethite/hematite (G/H) ratio, which can be mistaken for an increased aridity in the sedimentary source areas in the conventional interpretation for this proxy. The sensitivity of the G/H proxy to diagenesis should be taken into account in paleoenvironmental studies.

Diatomite with variable chemical and mineralogical composition occurs in the Komnina Lignite Basin. The diatomite layers, which overly lignite seams of Upper Miocene age, are rich in silica or calcium. These layers correspond respectively to quartz-rich and calcite-rich layers. The diatomite mainly consists of opal-A, while other minerals are quartz, feldspars, calcite, smectite, illite, kaolinite, chlorite, cristobalite, and muscovite. The well-preserved nature of the diatom species indicates a weak silica diagenesis. This is also indicated by the mineralogical composition of diatomite, especially the absence of opal-CT. The organic material present in the lake acted as coating and prevented diatom dissolution. The shallow lake, where the diatoms were deposited, did not allow diagenesis of diatomite. Diatoms were deposited in the Komnina Lake as a result of the acidic pH, the warm-humid conditions, and the silica-rich environment that occurred due to volcanic activity in the nearby area (Aridea). Remains of volcanic ash have been identified in the lignite deposits of the wider Ptolemais area. The association of diatomite with lignite was brought about by tectonic movements that occurred in the wider area of Monastir-Florina-Ptolemais-Kozani-Elassona-Sarantaporo in the Upper Miocene, resulting to the development of individual small shallow lakes. The paleoenvironment changed to acidic from the previous alkaline pH, the vegetation died off, the silica produced from the volcanic activity and the calm water conditions allowed the deposition of diatoms.

Cleats are natural opening-mode fractures in coal beds. They account for most of the permeability and much of the porosity of coalbed gas reservoirs and can have a significant effect on the success of engineering procedures such as cavity stimulations. Because permeability and stimulation success are commonly limiting factors in gas well performance, knowledge of cleat characteristics and origins is essential for successful exploration and production. Although the coal-cleat literature spans at least 160 years, mining issues have been the principal focus, and quantitative data are almost exclusively limited to orientation and spacing information. Few data are available on apertures, heights, lengths, connectivity, and the relation of cleat formation to diagenesis, characteristics that are critical to permeability. Moreover, recent studies of cleat orientation patterns and fracture style suggest that new investigations of even these well-studied parameters can yield insight into coal permeability. More effective predictions of cleat patterns will come from advances in understanding cleat origins. Although cleat formation has been speculatively attributed to diagenetic andror tectonic processes, a viable mechanical process for creating cleats has yet to be demonstrated. Progress in this area may come from recent developments in fracture mechanics and in coal geochemistry. q 1998 Elsevier Science B.V.

Ancient bone bioapatite is a potential source of diverse and
significant elemental and isotopic data that could be used to
provide  information  on  ancient  chronologies,
paleoenvironments,  and  paleodiets.  However,  buried  bone
bioapatite  often  undergoes  diagenesis  and  foreign
contaminants  alter  the  original  biogenic  signal.  Though
different  methods,  most  often  based  on  weak  acid
treatments,  have  been  proposed  for  the  cleaning  of  ancient
bone  bioapatite,  there  is  currently  no  universally  accepted
protocol.
Here, we propose an approach that explores the composite
nature of bone and is based on recent research that showed
an association between collagen and bioapatite preservation
at the micro-scale.
An  exploratory  study  was  made  on  a  small  number  of
ancient  bones  with  significant  collagen  content.  The  tested
protocols  involved  bone  powdering  to  the  osteon  scale,
without bleaching of collagen, and the use of acetic acid and
EDTA  solutions.  Comparison  of  the  performance  of  acetic
acid  and  EDTA  protocols  was  based  on  the  analysis  of
infrared spectra performed pre and post treatment.
Although  based  on  a  limited  dataset,  the  results  obtained
showed  that  for  an  EDTA  (0.5M –  2h  treatment)  based
protocol crystallinity values were closer to those observed in
fresh  bone  than  those  of  an  acetic  acid  (0.1M  –  4h
treatment)  based  protocol.  These  first  promising  results
warrant  further  investigation  to  include  a  larger  dataset,
testing of protocols with varying solution concentrations and
treatment  times,  and  the  use  of  other  methods  (e.g.
radiocarbon dating) to compare protocol performance.

This paper describes an experiment set up in 1987 to investigate the decomposition of animal bones, mainly from smaller species, within an accumulating dump of organic refuse. The project forms part of a wider comparative study by the author into the degradation of mainly smaller animal bones with the aim of modelling taphonomic processes and providing data to enhance our understanding of bone preservation on archaeological sites. Following 7 years of burial within an accumulating domestic compost heap, a suite of mammal, bird and fish skeletons was excavated and examined for evidence of morphological, histological and chemical modification. By comparison with similar suites of bones buried and excavated at around the same time, most of the bones from the compost heap were very well preserved. It is argued that this may be a consequence of the cross-linking of collagen with humics from the soil, resulting in a structure resistant to enzymatic attack.

Dolomite cement is a significant and widespread component of Phanerozoic sucrosic dolomites. Cements in dolomites that were never deeply buried are limpid, have planar faces (non-saddle forms), often distinct zonation in cathodoluminescence and form syntaxial overgrowths on crystals facing pores. Five samples of sucrosic dolomites, interpreted as having had mostly limemudstone or wackestone precursors in four carbonate aquifers, provide insights into the abundance of planar cements in sucrosic dolomites. Such cement comprises 11% to 45% (32% mean) of peritidal to sub-tidal dolomites on an outcrop in the Edwards aquifer (Early Cretaceous) of central Texas; 19% to 33% (25% mean) of ramp dolomites in the Hawthorn Group (Oligo-Miocene) and 50% to 70% in shelf dolomites of the Avon Park Formation (Eocene) in the Upper Floridan aquifer of sub-surface peninsular Florida; 18% to 45% (32+% mean) of sub-tidal shelf dolomites in quarry sections of the Burlington-Keokuk Formation (Early Mississippian) in south-eastern Iowa; and 18% to 76% (50% mean) in shallow cores and outcrops of outer-shelf dolomites from the Gambier Limestone (Oligo-Miocene) of South Australia. Backstripping the cement phases revealed by cathodoluminescence colour photomicrographs documents the effects of cements on textural coarsening, pore-space reduction, induration and general 'maturation' of these dolomites. Most pre-Holocene dolomites are multiphase crystalline rocks composed of: (i) seed crystals or 'cores'; (ii) crystal cortices that concentrically enlarged the cores; and (iii) free-space, syntaxial precipitates of limpid cement around the crystals. Remaining CaCO 3 grains and micrite can be replaced by dolomite, but typically they are dissolved between stages (ii) and (iii), creating systems of intercrystal and mouldic pores typical of sucrosic dolomites. Networks of cement overgrowths, aided by water-filled pore systems under hydrostatic to lithostatic pressure, are judged to slow or prevent compaction in sucrosic dolomites. It can be argued that cortex growth involves both replacement of CaCO 3 particles and microcementation of their interparticle pores. This interpretation, and the abundance of cements in so many dolomites, would obviate the controversy over the volumetrics of 'replacement dolomitization'. Limpid, planar and syntaxial dolomite cements of early diagenetic origin are interpreted to have precipitated from clear pore waters, at low temperatures (<30 to 35°C) and shallow burial depths (<100 m), in water-saturated networks of dolomite 'silt' and 'sand'. Cements in many dolomites in island and continental-aquifer systems appear to result from event-driven processes related to sea-level highstands. Cementation events can follow 'replacement 1

The preservation of bone or bioapatite over geologic time has presented paleobiologists with 11 long-standing and formidable questions. Namely, to elucidate the mechanisms, processes, rates, 12 and depositional conditions responsible for the formation of a fossil from a once living tissue. 13 Approaches integrating geochemistry, mineralogy, physics, hydrology, sedimentology, and 14 taphonomy have all furthered insights into fossilization, but several fundamental gaps still 15 remain. Notably, our understanding of: (1) the timing of processes during diagenesis (e.g., early 16 and/or late), (2) the rate of bioapatite transformation into thermodynamically more stable phases, 17 (3) the controls imparted by depositional environment, and (4) the role of (micro)biology in 18 determining the fate of bone bioapatite (dissolution or preservation) are limited. The versatility 19 of fossil bioapatite to provide information on the biology of extinct vertebrates rests on our 20 ability to identify and characterize the changes that occurred to bioapatite during diagenesis. This 21 review will evaluate our current understanding of bioapatite diagenesis and fossilization, 22 focusing on the biogeochemical transformations that occur during diagenesis to the mineral and 23

Compressional and shear-wave velocities ( V p and V s) of 210 minicores of carbonates from different areas and ages were measured under variable confining and pore-fluid pressures. The lithologies of the samples range from unconsolidated carbonate mud to completely lithified limestones. The velocity measurements enable us to relate velocity variations in carbonates to factors such as mineralogy, porosity, pore types and density and to quantify the velocity effects of compaction and other diagenetic alterations. Pure carbonate rocks show, unlike siliciclastic or shaly sediments, little direct correlation between acoustic properties ( V p and V s) with age or burial depth of the sediments so that velocity inversions with increasing depth are common. Rather, sonic velocity in carbonates is controlled by the combined effect of depositional lithology and several post-depositional processes, such as cementation or dissolution, which results in fabrics specific to carbonates. These diagenetic fabrics can be directly correlated to the sonic velocity of the rocks. At 8 MPa effective pressure V p ranges from 1700 to 6500 m/s, and V s ranges from 800 to 3400 m/s. This range is mainly caused by variations in the amount and type of porosity and not by variations in mineralogy. In general, the measured velocities show a positive correlation with density and an inverse correlation with porosity, but departures from the general trends of correlation can be as high as 2500 m/s. These deviations can be explained by the occurrence of different pore types that form during specific diagenetic phases. Our data set further suggests that commonly used correlations like ``Gardner's Law'' ( V p-density) or the ``time-average-equation'' ( V p-porosity) should be significantly modified towards higher velocities before being applied to carbonates. The velocity measurements of unconsolidated carbonate mud at different stages of experimental compaction show that the velocity increase due to compaction is lower than the observed velocity increase at decreasing porosities in natural rocks. This discrepancy shows that diagenetic changes that accompany compaction influence velocity more than solely compaction at increasing overburden pressure. The susceptibility of carbonates to diagenetic changes, that occur far more quickly than compaction, causes a special velocity distribution in carbonates and complicates velocity estimations. By assigning characteristic velocity patterns to the observed diagenetic processes, we are able to link sonic velocity to the diagenetic stage of the rock.

The factors affecting the amounts and types of organic matter in lacustrine sediments are summarized in this review, and synthesis, of published studies. Biota living in the lake and in its watershed are the sources of the organic compounds initially contributed to the lake system. Microbial reworking of these materials during sinking and early sedimentation markedly diminishes the total amount of organic matter while replacing many of the primary compounds with secondary ones. Much of the organic matter content of sediments is the product of this microbial reprocessing. Various organic matter components of lake sediments nonetheless retain source information and thereby contribute to the paleolimnological record. Carbon/nitrogen ratios of total organic matter reflect original proportions of algal and land-derived material. Carbon isotopic compositions indicate the history of lake productivity and carbon recycling. Biomarker compounds provide important information about contributions from different biota. Sterol compositions and chainlength distributions of n-alkanes, n-alkanoic acids, and n-alkanols help distinguish different algal and watershed sources and also record diagenetic alterations.Stabilization of functional-group-containing biomarkers by conversion into saturated or aromatic hydrocarbons or by incorporation into bound forms improves their preservation and hence record of source information. Lignin components provide important evidence of watershed plant cover, and pigments reflect algal assemblages. The interplay of the factors influencing the organic matter content of lake sediments is illustrated by overviews of sedimentary records of four lake systems—Lake Biwa (Japan), Lake Greifen (Switzerland), Lake Washington (Pacific Northwest), and the Great Lakes (American Midwest).

The book is a collection of 13 scientific articles presenting the problems of the weathering zone of anhydrite and gypsum rocks on the example of their exposures in western Ukraine, Poland, Spain, Canada and Russia. Most of the articles are devoted to unusual forms of relief and associated caves, rare in the world, that are formed today as a result of the local increase in volume of the weathered rocks. Such forms (described in this book) are domes and hydration caves currently developing within anhydrites at Pisky near Lviv (Ukraine), as well as at Dingwall in Canada, and the so-called gypsum tumuli – developing in gypsum, near Sorbas in Spain. The book deals with various geomorphological, hydrogeological, microclimatic, petrographic, and speleological issues, as well as those related to the threats of active karst development. The articles were written in Polish, Ukrainian and English by 17 scientists from Poland, Ukraine and Germany.

O principal propósito deste estudo é descrever a geometria e a mineralogia associada ao meio poroso bem como identificar possíveis mecanismos de dano a formação no Membro Carmópolis (Cretáceo Inferior) no campo de petróleo de Siririzinho, Bacia de Sergipe-Alagoas, nordeste do Brasil. Os reservat6rios situam-se entre as profundidades de 400 e 600m. Descrição de testemunhos, microscopia óptica convencional, MEV e analises petrofísicas e químicas das águas intersticiais foram utilizadas para interpretação do modelo deposicional e dos eventos diagenéticos, e para a reinterpretação de testes de laboratório de suscetibilidade a água doce previamente realizados em plugs de testemunhos e que conduziram a conclusões opostas: Monteiro (1980) identificou que as permeabilidades das amostras eram altamente sensíveis ao fluxo de água doce enquanto Branco (1986) concluiu que o fluxo de água doce não causava muitos danos à permeabilidade. Os reservatórios são conglomerados Iíticos e arenitos com estratificações cruzadas, com intercalações de folhelhos, siltitos e calcários laminados, capeados por gipsita e halita. Os Iitoclastos são fragmentos de rochas metamórficas. Um modelo deposicional de leques aluviais progradantes sobre um sistema lacustre parece explicar a deposição do Membro Carmópolis. A porosidade média é 18% com as melhores permeabilidades nas fácies mais grossas. A porosidade primária intergranular é dominante, mas contagens de pontos em lâminas delgadas indicam que pelo menos 29% da porosidade é secundaria, principalmente relacionada a dissolução de feldspatos. Outros tipos incluem intragranular ern fragmentos de rochas metamórficas, em graãs de quartzo corroídos, encolhimento de argilas, vugular e intergranular por dissolução de cimento carbonático. 0 revestimento de grãos detríticos por corrensita (um argilomineral interestratificado expansivo) e extensiva dolomitização são importantes eventos diagenéticos. A corrensita ocorre próximo ao topo do membro Carmópolis, refletindo sua associação bastante comum com evaporitos. A dolomitização parece ter ocorrido antes e depois da geração da porosidade secundaria, e cálculos termodinâmicos indicam que as águas intersticiais se encontram saturadas ou próximo ao equilíbrio com respeito a dolomita nas condições de reservat6rio (50°C). As diferenças nas conclusões dos testes de suscetibilidade a água doce previamente conduzidos são atribuídas a diferenças mineralógicas nas amostras coletadas para os testes: Monteiro (1980) realizou os testes em amostras de arenitos ricos em corrensita, ao passo que Branco (1986) utilizou amostras de arenitos livres de corrensita, Por este estudo, pode-se também estimar razoavelmente bem a magnitude do dano à permeabilidade causado por um fluxo de ágna doce em função do teor de corrensita na amostra, sugerindo adicionalmente que o alto teor de Fe+3 da corrensita pode constituir fonte de dano a formação durante tratamentos ácidos.

Salt beds and salt allochthons are transient features in most sedimentary basins, which through their dissolution can carry, focus and fix base metals. The mineralisation can be subsalt, intrasalt or suprasalt, and the salt body or its breccia can be bedded or halokinetic. In all these evaporite-associated low-temperature diagenetic ore deposits there are four common factors that can be used to recognise suitably prepared ground for mineralisation: (i) a dissolving evaporite bed acts either as a supplier of chloride-rich basinal brines capable of leaching metals, or as a supplier of sulfur and organics that can fix metals; (ii) where the dissolving bed is acting as a supplier of chloride-rich brines, there is a suitable nearby source of metals that can be leached by these  basinal brines (redbeds, thick shares, volcaniclastics, basalts): (iii) there is a stable redox interface where these metalliferous chloride-rich waters mix with anoxic waters within a pore-fluid environment that is rich in organics and sulfate/sulfide/H2S; and (iv) there is a salt-induced focusing mechanism that allows for a stable, long-term maintenance of the redox front, e.g. the underbelly of the salt bed or allochthon (subsalt deposits), dissolution or halokinetically maintained fault activity in the overburden  (suprasalt deposits), or a stratabound intrabed evaporite dissolution front (intrasalt deposits).

The diagenetic evaporite-basemetal association includes world-class Cu deposits, such as the Kupferschiefer-style Lubin deposits of Poland and the large accumulations in the Dzhezkazgan region of Kazakhstan. The Lubin deposits are subsalt and occur where long-term dissolution of salt, in conjunction with upwelling metalliferous basin brines, created a stable redox front, now indicated by the facies of the Rote Faule. The Dzhezkazgan deposits las well as smaller scale Lisbon Valley style deposits) are suprasalt halokinetic features and formed where a dissolving halite-dominated salt dome maintained a structural focus to a regional redox interface. Halokinesis and dissolution of the salt bed also drove the subsalt circulation system whereby metalliferous saline brines convectively leached underlying sediments. In both scenarios, the resulting redox-precipitated sulfides are zoned and arranged in the order Cu, Pb, Zn as one moves away from the zone of salt-solution supplied brines. This redox zonation can be used as a regional pointer to both mineralisation and, more academically, to the position of a former salt bed. In the fault-fed suprasalt accumulations the feeder faults were typically created and maintained by the jiggling of  brittle overburden blocks atop a moving and dissolving salt unit. A similar mechanism localises many of the caprock replacement haloes seen in the diapiric provinces of the Gulf of Mexico and Northern Africa.
 
Evaporite-associated Pb-Zn deposits, like Cu deposits, are focused by brine flows associated with both bedded and halokinetic salt units or their residues. Stratabound deposits, such as Gays River and Cadjebut, have formed immediately adjacent to or within the bedded salt body, with the bedded sulfate acting as a sulfur source. In allochthon/diapir deposits the Pb-Zn mineralisation can occur both within a caprock or adjacent to the salt structure as replacements of peridiapiric organic-rich pyritic sediments. In the latter case the conditions of bottom anoxia that allowed the preservation of pyrite were created by the presence of brine springs and seeps fed from the dissolution of nearby salt sheets and diapirs. The deposits in the peridiapiric group tend to be widespread, but individual deposits tend to be relatively small and many are subeconomic.

However, their occurrence indicates an active metal-cycling mechanism in the basin. Given the right association of salt allochthon, tectonics, source substrate and brine pending, the system can form much less common but world-class deposits where base-metal sulfides replaced pyritic laminites at burial depths ranging from centimetres to kilometres. This set of diagenetic brine-focusing mechanisms are active today beneath the floor of the Atlantis II Deep and are thought to have their ancient counterparts in some Proterozoic sedex deposits. The position of the allochthon, its lateral continuity, and the type of sediment it overlies controls the size of the accumulation and whether it is Cu or Pb-Zn dominated. [References: 122]

The reservoir potential of hydrocarbon sandstone reservoirs may be significantly reduced by compartmentation as a result of the development of stylolites. A petrographic and fluid inclusion microthermometric study was performed on sandstones containing abundant stylolites from the Buchan, Galley and Scott Fields in the Outer Moray Firth, offshore Scotland, and from a palaeo-oil bearing sequence in East Greenland. The main objective of this study was to further constrain the temperatures and burial depths at which stylolitization occurs in sandstone reservoirs. The sandstones containing abundant stylolites are also characterized by their highly cemented nature. Numerous occurrences of quartz overgrowths clearly truncated by sutured stylolites are evident in all of the samples. Fluid inclusion microthermometry reveals that quartz cementation, which is interpreted to be coeval with stylolitization, occurred at minimum temperatures of between 86 and 136°C. Basin modelling of the Scott and Galley Fields indicates that quartz cementation and stylolite development formed at depths greater than 2.5 km which were attained during rapid Tertiary burial. The occurrence of hydrocarbon fluid inclusions within healed microfractures orientated at high angles to the stylolites suggests that these microfractures provided pathways for hydrocarbon migration in the highly cemented, low permeability zones associated with highly stylolitized sandstones.

Depositional processes control initial porosity and permeability relationships in basinfilling sedimentary successions. These initial conditions then determine how diagenesis modifies the hydraulic properties of sediments as they undergo burial and lithification. Therefore, combining sedimentology, stratigraphy and diagenesis to understand the paleohydrologic evolution of sedimentary rocks throughout the evolution of basins is a necessary part of "basin analysis". Understanding the timing of fluid flow through sedimentary rocks is pre-requisite for the development of hydrologic models. Delineating temporal relationships requires integration of sedimentology and diagenesis through paragenetic relationships to constrain fluid flow associated with specific events, including those related to petroleum migration and formation of mineral deposits.

Portable X-ray Fluorescence Spectroscopy (XRFS) was applied to the skeletal remains of 13 bog bodies and their bog burial environments. The objective was to create a better understanding of Northern European bog environmental chemistry and its diagenetic effects on interred bog bodies, determine bog body geographic disparity and/or origin, and identify if post-discovery preservation procedures were applied to the bog body remains. This article summarizes the portable XRFS findings for the “Girl from the Uchter Moor”. The elements analyzed include Bromine, Copper, Iron, Manganese, Molybdenum,
Lead, Rubidium, Strontium, Zinc, and Zirconium.

Keywords “Girl from the Uchter Moor”, bog bodies, portable XRF spectroscopy, elemental analysis, diagenesis, post-discovery
preservation procedures

Aspek mikrofasies dan diagenesis batuan karbonat Anggota Batugamping Formasi Pamutuan telah dipelajari guna mengetahui mekanisme pengendapan batuan dan sejarah proses geologi paska pengendapan batuan. Sampel-sampel batugamping yang telah diambil secara sistematis berdasarkan pada runtunan stratirafi hasil pengukuran penampang stratigrafi rinci pada formasi batuan yang berumur Miosen Tengah tersebut dan telah dipakai untuk bahan pengujian petrografi di laboratorium. Analisis petrografi telah dilakukan terhadap empat belas sampel batugamping yang memperlihatkan bahwa jenisnya adalah wackestone, packstone, grainstone, floatstone, rudstone, dan framestone. Lingkungan pengendapan batuan karbonat Anggota Batugamping Formasi Pamutuan tersebut meliputi fasies landaian laut dalam, tepian cekungan, lerengan terumbu depan, dan terumbu organik di tepi paparan. Beragam proses diagenesis yang terjadi pasca pengendapan batuan yang meliputi : penyemenan, pemikritan, pemampatan, neomorfisme, dan pelarutan.

The Poza Rica trend of the Tampico embayment, Mexico, will ultimately produce more than 2.3 x lo9 barrels of oil from Mid-Cretaceous (Albian-Cenomanian) basin-margin deposits. Bioclastic grainstone, packstone, and wackestone are interbedded with polymictic lime breccia and dolomitized debris; all were deposited by sediment gravity flow. Indigenous sediment was pelagic lime mud. Typical reservoir porosities are about 10%; permeabilities average 2 md and rarely exceed 100 md. Porosity is largely the result of selective dissolution of rudist fragments, which were originally aragonite.

Lower Cretaceous deltaic sandstones of the Scotian Basin, offshore eastern Canada, are important gas reservoirs. The influence of several factors on diagenesis has been investigated: depositional lithofacies, sea level changes, chemistry of basinal sediments and basinal fluid flux during burial. The distribution and chemistry of diagenetic minerals was determined from nine wells located along a dip section of the Sable Subbasin. Mineral type and paragenesis were characterized using a combination of optical petrography, back-scattered electron images, and electron microprobe analyses. Siderite is unusually abundant in marine sediments of the Scotian Basin and has thus been studied in detail. Siderite occurs in several generations. Early and late siderites are similar in chemical composition, suggesting buffering by pre-existing siderite, but rare low-Mg siderite is related to a greater contribution of meteoric water. Siderite has locally dissolved to create microporosity and has suppressed quartz overgrowths. Siderite is most common in those muddy prodeltaic lithofacies where there is the highest availability of detrital ilmenite. Reactive Fe released by breakdown of this ilmenite is responsible for the unusual presence of early siderite in marine sediments, with the Ca and Mg content of the siderite indicating fully marine waters. Lithofacies have a strong influence on early diagenetic mineral assemblages. Lithofacies deposited in the transgressive system tract have abundant early Fe-calcite and siderite. Early kaolinite occurs principally in proximal (fluvial and river mouth) lithofacies, where meteoric water was most likely available during the deposition. Contrary to other studies, we find little impact of sequence stratigraphy on diagenetic minerals except in the transgressive system tract. Mesogenetic minerals are related to flux of formation water and maturing hydrocarbon products, resulting first in pyrite and siderite and later in ankerite and ferroan calcite. The principal controls are interpreted to be high Fe 2+ and low Ca 2+ of formation waters and vertical movement of the waters along faults. Overall, the bulk chemical composition of terrigenous sediments and the depositional lithofacies are the most important factors controlling diagenetic minerals in the Lower Cretaceous of the Scotian Basin.

Mollusk shells excavated from archeological sites have been used to reconstruct paleoenvironment, human foraging , and migratory patterns. To retrieve information on past environment or human behavior, chemical signatures such as oxygen stable isotopes (δ 18 O shell) are analyzed. Shell archeological remains usually represent food waste. Thermal treatments such as boiling and roasting may influence shell structure and biochemical composition. However, little is known about the relationship between changes at macro-, microstructural and chemical levels. This work is a calibration study on modern Phorcus (Osilinus) turbinatus shells. A simulation of two different cooking methods (boiling and roasting) was carried out at four temperatures (100 °C, 300 °C, 500 °C and 700 °C) for two durations (20 min and 60 min). The structure and biochemistry of shells boiled at 100 °C did not significantly change. However, treatments at higher temperatures strongly affected both the structure and the biochemistry of the shells. At 300 °C the external coloration, as well as nacre iridescence, were altered. Raman spectroscopy revealed that, at this temperature, the aragonite-calcite polymorphic transformation starts. Scanning electron microscope (SEM) analysis showed drastic changes in the microstructural organization also beginning at 300 °C. Furthermore, the isotopic δ 18 O shell values were significantly affected. Increasing cooking temperatures resulted in an enhancement of the above-mentioned alterations. These results provide a set of temperature-related morphological, structural and biochemical characteristics for investigating the thermal behavior of biocarbonates and for estimating different cooking treatments in archeological record.

Understanding paleohydrologic systems in terms of basin evolution requires the integration of information derived from the sedimentology, stratigraphy, diagenesis and geology of basin-filling successions. Combination of these is prerequisite for realistic basin analysis and to guide any hydrologic or geochemical modeling. Ancient basins, in particular, represent systems that can record protracted burial histories, thereby constraining the composition of specific fluid events that normally affected vast areas.

The results on the elemental and mineralogical compositions of clays from Central Uganda differed from those from the volcanic sediments of the Mt. Elgon in Eastern Uganda. Utilisation of the two types of clays should be strict after understanding their structural differences. Whereas elemental, mineralogical, DTA, IR, XRD and pH data on selected clays from Kumi, Nakawa, Seeta, Kajansi, Kawuku, Lwanda, Chodah and Umatengah indicated that they were kaolinites. Similar data on clays from Mutufu, Budadiri, Chelel and Siron indicated that they were largely smectites. The IR data accumulated on Kawuku, Kajansi, Lwada, Seeta, Chodah, Umatengah, Kumi and Nakawa clays revealed they were largely kaolinites yet that on Mutufu, Chelel, Budadiri and Siron clays indicated they were smectite-rich.

This study examines the various diagenetic controls of the Miocene Surma Group sandstones encountered in petroleum exploration wells from the Surma Basin, which is situated in the northeastern part of the Bengal Basin, Bangladesh. The principal diagenetic minerals/cements in the Surma Group sandstones are Fe-carbonates (with Fe-calcite dominating), quartz overgrowths and authigenic clays (predominantly chlorite, illite-smectite and minor kaolin). The isotopic composition of the carbonate cement revealed a narrow range of d 18 O values (À10.3‰ to À12.4‰) and a wide range of d 13 C value (+1.4‰ to À23.1‰). The d 13 C VPDB and d 18 O VPDB values of the carbonate cements reveal that carbon was most likely derived from the thermal maturation of organic matter during burial, as well as from the dissolution of isolated carbonate clasts and precipitated from mixed marine-meteoric pore waters. The relationship between the intergranular volume (IGV) versus cement volume indicates that compaction played a more significant role than cementation in destroying the primary porosity. However, cementation also played a major role in drastically reducing porosity and permeability in sandstones with poikilotopic, pore-filling blocky cements formed in early to intermediate and deep burial areas. In addition to Fe-carbonate cements, various clay minerals including illite-smectite and chlorite occur as pore-filling and pore-lining authigenic phases. Significant secondary porosity has been generated at depths from 2500 m to 4728 m. The best reservoir rocks found at depths of 2500-3300 m are well sorted, relatively coarse grained; more loosely packed and better rounded sandstones having good porosities (20-30%) and high permeabilities (12-6000 mD). These good quality reservoir rocks are, however, not uniformly distributed and can be considered to be compartmentalized as a result of interbedding with sandstone layers of low to moderate porosities, low permeabilities owing to poor sorting and extensive compaction and cementation.

Septarian concretions are abundant in many Phanerozoic marine and marginalmarine shales and mudstones. They range from a few centimetres to several metres in size and are spherical or ellipsoidal in morphology. In general, formation by localized calcite or siderite cementation in argillaceous sediments began under less than a few metres of burial. Septarian cracks vary widely in shape and con®guration: included are networks of wide, vertically, radially and sometimes concentrically oriented, lenticular shrinkage cracks; and narrower, parallel-sided, straight to irregular tension cracks locally accompanied by brecciation, and plumose and en eÂchelon sigmoidal cracks indicative of shear stresses. Crack types are intergradational; many concretions exhibit multiple cracking events. Enclosed macrofossils and isopachous ®brous calcite cement that lines earlier formed cracks are commonly broken and displaced. In some cases, cracks contain injected lime mud and silt. These features, taken together, testify that cracking involved a spectrum of responses in concretion interiors, from loss of shear strength, dewatering and shrinkage to brittle failure, demonstrating variations in, and contrasts between, the rheological properties of the matrix and enclosed objects. Localization to interiors and outward tapering of lenticular cracks make a case for fracture partitioning and indicate that interiors were softer than exteriors at the time of shrinkage. Parallel-sided cracks point to greater stiffness, and evolving crack shape in multiply cracked concretions shows that rigidity increased with time. Crack orientations indicate highly variable tensile and shear stress directions within individual concretions. Rupture, brecciation, displacement of fragments, loss of shear strength, liquefaction and injection of unconsolidated granular sediment suggest that deformation events were rapid, if not virtually instantaneous. Previous explanations for the internal cracking, such as gas generation, spontaneous chemical dehydration or localized overpressuring due to compaction, seem either untenable or fail to account for the spectrum of observed features. However, syndepositional earthquake-induced shaking of cementing bodies of varying rigidity at shallow burial depths seems to be a plausible source for the requisite short-lived, variable to anisotropic, high-stress regime inside the concretions. Septarian concretions may thus preserve a signature of basin seismicity as it relates to their cementation history.

A series of isothermal hydrous pyrolysis experiments was performed on immature sedimentary rocks and peats of different lithology and organic source input to explore the generation of diamondoids during the thermal maturation of sediments. Oil generation curves indicate that peak oil yields occur between 340 and 360°C, followed by intense oil cracking in different samples. The biomarker maturity parameters appear to be insensitive to thermal maturation as most of the isomerization ratios of molecular biomarkers in the pyrolysates have reached their equilibrium values. Diamondoids are absent from immature peat extracts, but exist in immature sedimentary rocks in various amounts. This implies that they are not products of biosynthesis and that they may be generated during diagenesis, not just catagenesis and cracking. Most importantly, the concentrations of diamondoids are observed to increase with thermal stress, suggesting that they can be used as a molecular proxy for thermal maturity of source rocks and crude oils. Their abundance is most sensitive to thermal exposure above temperatures of 360-370°C (R 0 = 1.3-1.5%) for the studied samples, which corresponds to the onset of intense cracking of other less stable components. Below these temperatures, diamondoids increase gradually due to competing processes of generation and dilution. Calibrations were developed between their concentrations and measured vitrinite reflectance through hydrous pyrolysis maturation of different types of rocks and peats. The geochemical models obtained from these methods may provide an alterative approach for determining thermal maturity of source rocks and crude oils, particularly in mature to highly mature Paleozoic carbonates. In addition, the extent of oil cracking was quantified using the concentrations of diamondoids in hydrous pyrolysates of rocks and peats, verifying that these hydrocarbons are valuable indicators of oil cracking in nature.

The textural evidence in septarian concretions shows that the septa formed as tensile fractures during burial and compaction of the host shale. Comparison of the combinations of vertical and horizontal stresses and pore-fluid pressure required for tensile fracture of cemented concretions and those likely to occur during shale burial indicates that septarian fracturing will be favoured by overpressuring and low horizontal stress, most likely to occur during times of rapid burial. Burial histories of septarian concretions from the Eocene London Clay and the Jurassic Kimmeridge Clay show that fracturing can form under as little as 50 m of sediment. By relating episodes of septarian fracturing to times of rapid burial, the timing of diagenetic cement formation can be constrained.

The Upper Cretaceous of the Umbria-Marche Basin (Italy) consists of an alternation of calcareous and siliceous fine-grained sedimentary rocks in which the calcareous lithologies are predominant. The Cenomanian succession is dominated by white, micritic limestones and contains a black shale horizon (Bonarelli Level) in its uppermost part which is the regional expression of oceanic anoxic event 2. In the Turonian, the rocks gradually become red upwards and are referred to as Cretaceous oceanic red beds. The lithological variability in the succession reflects the local response of sedimentary systems to varying local and global environmental conditions. In this study, local processes behind the transition from black shale to red bed deposition and, in particular, behind lithological oscillations within the lowermost Turonian are studied and placed in their global context. Sediment colour, composition, geochemistry and nannofossil content were studied using samples of the Scaglia Formation at Moria (Umbria-Marche Basin). The results show that, following the Cenomanian/Turonian boundary, terrigenous input decreased and its composition was different in calcareous and siliceous oozes. Organic productivity was high during the deposition of siliceous ooze due to upwelling and varied on orbital timescales. The alternation between the siliceous and calcareous ooze was further controlled by carbonate dissolution. Small fluctuations in the calcite compensation depth (CCD) had a significant impact on sediment composition because depositional depth was between the lysocline and the CCD. Diagenesis resulted in the segregation of carbonate and silica, in the concentration of terrigenous material in smarl interbeds and in the enhancement of bedding. After the earliest Turonian, ocean circulation patterns changed, seawater temperatures declined slowly and seawater became better oxygenated. Productivity and terrigenous input also declined and the resulting combination of oxygen demand in the sediments and sedimentation rates favoured the formation of authigenic haematite in the sediments which led to their reddening.

We have measured a suite of ''diagenetic parameters'' for several populations of archaeological bones buried in a number of northwest European sites since the last Ice Age. These are: the structural damage due to microbes; changes in bone micro-and macro-porosity; protein content; a measure of the crystallinity of hydroxyapatite as reflected in the phosphate infra-red spectrum peak splitting; and a measure of the carbonate content as given by the ratio of carbonate to phosphate infra-red absorption peaks. The results provide a database that clearly characterises the patterns, which are often site-dependent, of diagenetic change in buried bone. Our main conclusions are that individual site hydrology appears to have a strong influence on the outcome of bone preservation and that porosity is the most effective single diagenetic parameter which both determines and reflects the preservation of bone in the burial environment.

In a case study of two wells from the Namur synclinorium, the black shale-dominated Chokier Formation was analyzed for petrography, mineralogy and organic geochemistry. Thin section petrography revealed a different facies assemblage for each well and a total of six microfacies types. Whole rock mineralogical data largely confirms a facies-dependent mineral composition. All different microfacies types of locality 1 (MFT-1, laminated silty mudstone; MFT-2, laminated mud-clast-rich mudstone; MFT-3, calcareous bioclast-rich mudstone) and locality 2 (MFT-4, lenticular mudstone; MFT-5, burrow-mottled mudstone; MFT-6, burrowed silty laminated mudstone) show ample evidence of a distal shelf environment that is sourced by currents, which may be linked to seasonal (monsoonal) transport of sediment from land to sea. Erosive bedload transport is an important mechanism of sedimentation whereas accumulation by settling from the water column can be excluded for the majority of investigated strata. Frequently, endobenthic activity and other processes after deposition, e.g. winnowing and reworking, caused strong fabric modifications. Various, but simple ichnofabrics prove at least temporary dysoxic conditions as confirmed by relatively low TS/TOC ratios. With regard to sedimentary features, organic geochemistry data hints to organic matter preservation due to rapid burial rather than intense anoxity. Silicification is a widespread diagenetic feature independent from facies and locality. It is most likely linked to a high supply rate of terrestrially dissolved silica as indicated by sEM observations, paleogeographic constraints and sedimentary features.