Alan M. Bailey

Organic chemical and petrographic changes induced by early-stage artificial coalification of peats

Abstract In order to investigate the changes that can occur during the earliest stages of coalification, a series of peat samples representing different depositional and vegetational settings were subjected to increasing temperatures and pressures in an open experimental system designed to simulate an approximate depth of burial of 1–1.5 km. Petrographic and chemical techniques (pyrolysis GC/FT-IR/FID and pyrolysis GC/MS) were utilized to analyze samples before and after coalification. Petrographic changes consisted not only of purely physical changes, such as compaction and creation of distinct microbands, but also, changes in color, obliteration of distinct cell walls in certain tissues, and the formation of new macerals. Chemical changes supported the destruction of the cellulosic components in the absence of microbial activity.

Petrographic changes induced by artificial coalification of peat: comparison of two planar facies (Rhizophora and Cladium) from the Everglades-mangrove complex of Florida and a domed facies (Cyrilla) from the Okefenokee Swamp of Georgia

Abstract Petrographic changes during coalification of three peat samples were investigated by artificial coalification experiments using a semi-open reactor system. Compressions of from 83 to 88% produced dark brown to black, shiny, flattened pellets exhibiting microscopic banding. Overall amounts of compression inversely correlated with the framework to matrix ratios ( F M ); although, certain tissue fragments remained relatively uncompressed due to the presence of tanniniferous cell fillings and also, hypothetically, to the presence of colorless plant secretions or gelified wall materials that were present in the cells but only recognizable after a change in color during coalification. The most distinct microscopic banding (longest and widest bands) developed in samples of the dome-formed peat facies, which had the highest framework to matrix ratios of any type and the greatest contents of surface litter composing the framework (i.e. highest S N ratio). The planar, root-dominated, Rhizophora facies showed the greatest change in microbanding character during coalification; in that, the numerous lens-like bands produced by the compressed roots were very distinct at the 60°/2100 psi (121.4 kg/cm 2 ) stage but nearly disappeared at the 175°/5000 psi (289.1 kg/cm 2 )) stage. This is explained as a result of differences in rates of coalification of the different telinitic precursors in the roots (multilinear vitrinization) and could explain why roots are significant components of many modern peats (and ancient coal ball concretions) but are difficult to recognize in bituminous coals. Similarly, separation of cuticles from leaves in modern peat-forming environments, due to irreversible shriveling and subsequent enhanced microbiological decay, partially explains why leaf remains are also difficult to recognize in most coals, even those with abundant cutinites. Microcracks developed in all pellets, with dominant orientations of cracks being either perpendicular to induced banding or horizontal to it. Minute, vertical microcracks (interpreted as ‘dewatering’ features) were observed primarily in gelinitic bands, especially in the most fire-prone, Cladium coal facies; but, these rarely extended into juxtaposed microlithotypes as did most of the larger vertical cracks. Horizontal cracks tended to form at microband boundaries. Almost all humotelinitic and humocollinitic precursors showed some changes in color during artificial coalification, with humotelinites exhibiting less or slower changes than humocolinites or humodetrinites (finer-grained matrix material). Additionally, nearly all dark brown, degraded tissues in the peats became dark orange or red during coalification; but, many of these tissue masses were observed to contain significant amounts of minute inertinite derived from microorganisms (‘pseudomicrinite’) that only became prominent after coalification and subsequent change in color of surrounding macerals. Fusinite precursors were only found in the fire-prone Cladium facies; and, although, the coalified, doming-generated, Cyrilla facies exhibited evidence of significant drying events (i.e. occasional bands or parts of bands containing significant pseudomicrinites, macrinites and sclerotinites), it was dominated by huminitic (vitrinitic) components. Liptinites were most common in the coalified, dome-formed, Cyrilla facies and displayed a slight qualitative increase in red/green fluorescence during coalification and some possible flow of components into nearby cracks. Changes in mean random reflectance of huminitic macerals, although still requiring more data and only measured to the 60°C/2100 psi (121.4 kg/cm 2 ) level, indicated increasing directions of change during artificial coalification, with humocollinitic macerals progressing from an average of about 0.21% to 0.32% and humotelinitic macerals (which consistently had lower inherent reflectances in the peats) progressing from 0.15 to 0.25%. The above petrographic results, along with previously reported chemical results, all suggest that the methods that we have used in these experiments have produced changes that might reasonably be expected to occur during natural coalification (despite the fact that we have speeded up the process). Although more work needs to be done to verify and refine these results and to establish a correlation between these artificial ‘coalification steps’ and true coalification, the new observations and conclusions from these studies might still be helpful in constructing models to predict or interpret coal seam characteristics and to establish the timing and release-potential of gaseous or liquid hydrocarbons from coals.

Report on the Acadiana Research Laboratory nuclear microprobe system

The Acadiana Research Laboratory of the University of Louisiana at Lafayette provides high energy ion beams for materials research. Major components of the ion beam systems include a National Electrostatics Corporation (NEC) 1.7 MV tandem Pelletron accelerator system with both SNICS and RF ion sources and a Varian CF-4 200 kV implanter. The NEC Pelletron has three operational beamlines that provide a wide range of capabilities for materials modification and analysis, including such techniques as PIXE, PIGE, RBS, RFS, TOF-ERDA and ion implantation. An Oxford Microbeams Ltd. microprobe system was recently declared operational with the attainment of a 1.5 μm×2.0 μm beam spot size. Microprobe techniques presently available include μPIXE, μRBS and scanning transmission ion microscopy (STIM).

Behavior of Inorganic Constituents During Early Diagenesis of Peats

ABSTRACT Extensive diagenetic changes occurring in peat during burial to approximately 1.5 km may result in the formation of lignite (or medium brown coal). Examination of available literature indicates very little research dealing specifically with the behavior of inorganic (non-carbon-based) compounds during this early postburial diagenesis. Because these inorganic constituents determine both the quantity and quality of ash in coals and may act as potential diagenetic agents in associated rocks, their behavior throughout the peat to lignite transformation is potentially important in several areas of study. Laboratory simulations of the early postburial diagenesis of peat offer a new approach for the study of such processes. In the present research, laboratory simulations have been used to study diagenesis of several well-characterized peats. During the experimental runs, approximately 80 g of peat were compressed and heated in a PTFE-lined reaction cell from atmospheric conditions to 2100 psi and 60°C, thus approximately simulating conditions necessary for the formation of lignite. Pressure and temperature were increased on a stepwise pattern, and prior to each increase, expelled solution from the previous interval was collected. Following completion of each experimental run, the residual solid plug was extracted from the cell intact. Extensive reorganization of organic compounds in the produced residual solids during laboratory simulations was documented by Rollins et al. (1991). In addition, extensive petrographic changes can be observed, including increases in gelatinous material, darkening of colors, and increases in reflectance. Concentrations of major inorganic constituents (Na, K, Ca, and Mg) released in solution are typically constant, or decrease, with increasing pressure and temperature for high-ash peats; whereas, minor inorganic concentrations (Fe, Cu, Zn, Mn, and Al) increase, occasionally reaching a maximum and then decreasing. With low-ash peats, concentrations generally are much lower than high-ash peats, and both major and minor inorganic concentrations typically increase throughout the experimental runs. For all peats, the ratio of major to minor inorganics decreases. The general behavior of inorganics during the diagenesis of these peats is strongly related to the composition of the original peat and to the stage of alteration. In addition, organic acids, including acetic and others, are present within the solutions. These organic acids may act as organic complexors and thus contribute to the mobilization of inorganic constituents.

Abstract: Geologic Framework, Processes and Rates of Subsidence in the Mississippi River Delta Plain

ABSTRACT Since the 1930s, Louisiana has lost an estimated 3,950 km2 of coastal wetlands and barrier islands. The loss of these coastal lands resulted primarily from subsidence and erosion rather than the draining and filling of wetlands. More than 40% of the coastal wetlands in the U. S. are found in Louisiana and 80% of our nations total wetland loss occurs here at alarming rates. Beach erosion rates exceed 10 m/yr and the rate of wetland loss is currently measured at 75 km2/yr The causes of Louisianas coastal land loss include delta switching, storm impacts, mans impacts on this deltaic system, and high rates of subsidence. Recent studies indicate that the highest subsidence and coastal land loss rates occur where the underlying Holocene sediments are the thickest. This relationship suggests that subsidence through the consolidation and settlement of these young deposits is of primary importance to the coastal land loss problem found in Louisiana. To understand the role of subsidence in Louisianas coastal land loss problem requires a knowledge of the Late Quaternary history of the lower Mississippi River, of the infilling of its incised valley during the Holocene transgression, and of the processes of delta switching. End_of_Record - Last_Page 644-------

Nuclear microprobe analysis of artificial coal

An artificially coalified Taxodium peat was used to examine the behavior of inorganic constituents in terrestrial organic matter during the early coalification process. The artificial coal is produced by subjecting the peat to incremental increases in temperature up to 60 °C and pressures to 14.48 MPa over a four-week period in a partially open reactor. A standard polished thin section 30 μm thick is then cut from the resulting disk and examined using light microscopy to select and mark areas to be cut from the polished thin section. The distribution of inorganic constituents in these areas of the solid produced during the coalification process is then studied using nuclear microscopy. Results suggest that concentrations of inorganic constituents, including silicon, are lower in the newly produced solids than in the initial material. Distributions of other inorganic elements, including aluminum, sulfur, chlorine, potassium, calcium, barium and iron are also investigated.

Paleoenvironmental Trends in Paleocene Wilcox Tew Lake Marker Beds, LaSalle Parish, LA

ABSTRACT The Tew Lake Marker (TLM) beds are recognized on electric logs throughout east-central Louisiana by an uncommon, resistive unit within the Wilcox delta complex. This study explores how the wide distribution of this marker sequence is linked to its paleoenvironmental history. Petrographic and foraminiferal data derived from continuous, conventional cores from two wells located one mile apart are used to identify paleoenvironments and to interpret paleoenvironmental trends recorded in the TLM beds. The main discoveries of this investigation are: The resistive TLM beds consist of a shale sequence interbedded with very thin, calcareous, fossiliferous layers. The TLM beds were deposited in bay/lagoon paleoenvironments having salinities that ranged from hyposaline to normal marine. The TLM beds are divisible into lower and upper depositional sequences that are related to paleoenvironmental changes in the region. The lower depositional sequence fines upward and records normal marine and hyposaline-normal marine bay/lagoon deposits. This lower depositional sequence rests unconformably upon freshwater lignite, documenting a marine transgression inland over a freshwater swamp of the Wilcox lower delta plain. The upper depositional sequence coarsens upward and contains hyposaline-normal marine bay/ lagoon deposits that grade upward into hyposaline bay/lagoon deposits, suggesting regression in the lower delta plain. Muddy, fresh waters from nearby delta-distributary streams and stream crevasses filled lakes, inner bays and inner lagoons with sediment and reduced the salinities of water bodies and wetlands of the lower delta plain. Lateral facies between the two wells indicate marine influence during TLM deposition was greater and more persistent toward the east.