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.

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.

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]

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.

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.

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.

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.