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A whole-rock geochemical approach to the recognition and correlation of "marine bands"

A whole-rock geochemical approach to the recognition and correlation of "marine bands"

Pearce, T. J., McLean, D., Martin, J. H., Ratcliffe, K. T. and Wray, D. ORCID: 0000-0002-0799-2730 (2010) A whole-rock geochemical approach to the recognition and correlation of "marine bands". In: Ratcliffe, Kenneth T. and Zaitlin, Brian A., (eds.) Application of Modern Stratigraphic Techniques: Theory and Case Histories. SEPM Special Publication (94). SEPM (Society for Sedimentary Geology), pp. 221-238. ISBN 978-1-56576-199-5

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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, P2O5, Al2O3, 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.

Item Type: Book Section
Additional Information: [1] This item appears in the section entitled Miscellaneous Stratigraphy Methodologies
Uncontrolled Keywords: chemostratigraphy, palynology, marine bands, Carboniferous
Subjects: Q Science > QD Chemistry
Q Science > QE Geology
Faculty / Department / Research Group: Faculty of Engineering & Science > Department of Pharmaceutical, Chemical & Environmental Sciences
Related URLs:
Last Modified: 08 Dec 2016 12:22
Selected for GREAT 2016: None
Selected for GREAT 2017: None
Selected for GREAT 2018: None
URI: http://gala.gre.ac.uk/id/eprint/4120

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