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Capturing key attributes of fine-grained sedimentary rocks in outcrops, cores, and thin sections; nomenclature and description guidelines

O. Remus Lazar, Kevin M. Bohacs, Joe H. S. Macquaker, Juergen Schieber and Timothy M. Demko
Capturing key attributes of fine-grained sedimentary rocks in outcrops, cores, and thin sections; nomenclature and description guidelines
Journal of Sedimentary Research (March 2015) 85 (3): 230-246

Abstract

An integrated nomenclature scheme is proposed to capture the inherent heterogeneity of fine-grained sedimentary rocks at the 10 (super 2) to 10 (super -3) mm scale and to assist the evaluation of these rocks as sinks of organic carbon, barriers to fluid flows, and reservoirs of oil and gas. This scheme incorporates previous knowledge and the latest field, petrographic, and laboratory observations. We propose to name fine-grained sedimentary rocks using a root term based on their texture (grain size), which is modified by description of bedding, composition, and grain origin. Regarding texture, we suggest the use of "mudstone" as a class name for the entire spectrum of fine-grained sedimentary rocks. We define mudstone as a rock in which more than fifty percent of its grains are mud (clay and silt) size (<62.5 mu m). Similar to the approach used for the description of sandstone texture, mudstone texture can be refined by a "coarse", "medium", or "fine" size-range term. Regarding bedding, we follow Campbell's (1967) genetic approach to define laminae, laminasets, and beds, and describe lamina geometry, continuity, and shape. Regarding composition, we propose terms such as "siliceous", "calcareous", "argillaceous", and "carbonaceous" to capture differences in rock composition. The name of a mudstone can be further modified by additional attributes that detail the form and origin of the rock components. Application of this approach to the Cretaceous Eagle Ford Shale illustrates the variability typically present in mudstone successions and demonstrates how our detailed characterization can be used to decipher and predict rock properties of economic interest.


ISSN: 1527-1404
EISSN: 1938-3681
Serial Title: Journal of Sedimentary Research
Serial Volume: 85
Serial Issue: 3
Title: Capturing key attributes of fine-grained sedimentary rocks in outcrops, cores, and thin sections; nomenclature and description guidelines
Affiliation: ExxonMobil Upstream Research Company, Houston, TX, United States
Pages: 230-246
Published: 201503
Text Language: English
Publisher: Society for Sedimentary Geology, Tulsa, OK, United States
References: 115
Accession Number: 2015-032318
Categories: Sedimentary petrology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Includes appendices
Illustration Description: illus.
N25°45'00" - N36°30'00", W106°30'00" - W93°30'00"
Secondary Affiliation: Indiana University, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by SEPM (Society for Sedimentary Geology), Tulsa, OK, United States
Update Code: 201515
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