Abstract The Namurian and Westphalian sequences from the onshore well Scaftworth-B2, located in the Gainsborough Trough, central England, have been analysed for whole-rock inorganic geochemical data via inductively coupled plasma optical emission spectrometry (ICP-OES) and mass spectrometry (MS). The changes within key elements, and elemental ratios, results in a chemostratigraphic zonation scheme consisting of eight chemostratigraphic sequences and 13 chemostratigraphic packages, providing the type zonation for the Bowland Shale and overlying formations. Mineralogical data are provided by whole rock X-ray diffraction (XRD) and are used to calibrate the mineral modelling in order to generate a modelled mineral log for the study well. Furthermore, the modelled mineralogy is then used to calculate a relative brittleness for the samples, which can then be collaborated with traditional rock properties data at a later date. Elemental data can also be used to model the relative abundance of detrital quartz and biogenic silica; while total silicon is detected by ICP, biogenic silica is not detected by XRD owing to its amorphous nature. Enrichment factors calculated from the inorganic elemental data suggest that the sediment was deposited in an unrestricted marine setting, which experienced periods of anoxia.

Abstract: High-resolution, time-significant correlations are integral to meaningful stratigraphic frameworks in depositional systems but may be difficult to achieve using traditional sequence stratigraphic or biostratigraphic approaches alone, particularly in geologically complex settings. In steep, reefal carbonate margin-to-slope systems, such correlations are essential to unravel shelf-to-basin transitions, characterize strike variability, and develop predictive sequence stratigraphic models—concepts that are currently poorly understood in these heterogeneous settings. The Canning Basin Chronostratigraphy Project integrates multiple independent data sets (including biostratigraphy, magnetostratigraphy, stable isotope chemostratigraphy, and sequence stratigraphy) extracted from Upper Devonian (Frasnian and Famennian) reefal platform exposures along the Lennard Shelf, Canning Basin, Western Australia. These were used to generate a well-constrained stratigraphic framework and shelf-to-basin composite reconstruction of the carbonate system. The resultant integrated framework allows for unprecedented analysis of carbonate margin-to-slope heterogeneity, depositional architecture, and sequence stratigraphy along the Lennard Shelf. Systems tract architecture, facies partitioning, and stacking patterns of margin to lower-slope environments were assessed for six composite-scale sequences that form part of a transgressive-to-regressive supersequence and span the Frasnian–Famennian (F–F) biotic crisis. Variations are apparent in margin styles, foreslope facies proportions, dominant resedimentation processes, downslope contributing sediment factories, and vertical rock successions, related to hierarchical accommodation signals and ecological changes associated with the F–F boundary. We present these results in the form of carbonate margin-to-basin sequence stratigraphic models and associations that link seismic-scale architecture to fine-scale facies heterogeneity. These models provide a predictive foundation for characterization of steep-sided flanks of reefal carbonate platform systems that is useful for both industry and academia. This study emphasizes the utility of an integrated stratigraphic approach and the insights gained from better-constrained facies and stratal architecture analysis, insights that were not achievable with traditional sequence stratigraphic or biostratigraphic techniques alone.

Abstract Laterally extensive, thin, eustatically controlled, transgressive marine shale beds that occur within paralic sequences are generally regarded as reliable correlative markers. Such shale beds in the Carboniferous of NW Europe are referred to as marine bands and have been used extensively for stratigraphic correlations, particularly in the petroleum industry, where they are used to construct interwell correlations. True marine bands are represented by black anoxic shales (characterized by high U levels and high gamma API responses) that contain definitive ammonoid assemblages, i.e., demonstrably were deposited in a marine environment. However, not all black shales in the Carboniferous of NW Europe are the product of marine deposition, despite which they are still colloquially referred to as “marine bands” and are used for stratigraphic correlations. The problem of “marine band” recognition and correlation is exacerbated when dealing with well bores, where only wireline-log data and cuttings are available. This study demonstrates how inorganic geochemical data are used as a means to refine the identification of true marine bands and how these data can be used for enhanced stratigraphic correlations. “Marine-band chemostratigraphy” is established using core sections from the onshore Carboniferous Coal Measures sequences encountered in the West Midlands of England. Using variations in U, Mo, Zn, Cu, V, P 2 O 5 , Al 2 O 3 , Th, and Zr concentrations, a geochemically based facies classification scheme is erected, which allows the differentiation of mudstones deposited in marine, freshwater lacustrine, and floodplain environments, and which has been validated by palynological and sedimentological facies data. This scheme is successfully extended to a nearby well from which only cuttings are available. The general concept of marine-band chemostratigraphy can be applied to the sedimentary rocks deposited in any coastal-plain to marginal-marine setting. The methodology provides a robust technique for the identification and correlation of “marine bands” and also demonstrates the importance of inorganic geochemical data in the context of sequence stratigraphy. Application of Modern Stratigraphic Techniques: Theory and Case Histories SEPM Special Publication No. 94, Copyright © 2010 SEPM (Society for Sedimentary Geology), ISBN 978-1-56576-199-5, p. 221–238.