Table of Contents - SPE285: Tonsteins: Altered Volcanic Ash Layers in Coal-Bearing Sequences


Abstract

Nomenclature and Classification

Geographical Occurrence of Tonsteins

Volcanic Characteristics of Tonsteins

Methods of Study

Disaggregation
Dispersion
Ultrasonic Treatment
Mechanical Disaggregation
Chemical Disaggregation
Digestion in Hydrofluoric Acid
Fractured Surfaces
Size Separation and Panning
Polished Specimens

Mineralogy

Primary Minerals
Quartz
Feldspars
Biotite
Apatite
Ilmenite and Magnetite
Zircon
Rutile and Sphene (Titanite)
Other Primary Components
Glass
Secondary Minerals
Kaolinite
Smectite
Illite
Phosphates
Pyrite
Diatoms
Weathering Products

Gross Texture of Tonsteins

Vermicules, Plates, and Microspherules
Accretionary Lapilli
Graupen
Breccia
Flint Clay
Clay-Free Partings
Glass Shards and Lapilli
Rooting and Burrowing
Stumps, Twigs, and Other Plant Materials
Reworking

Alteration of Volcanic Ash to Tonstein

Time of Alteration
Influence of Bed Thickness
Ash Composition
Alteration Sequence

Environmental Effects of Thick Ash Falls

Plants, Hydrology, and Coal Chemistry
Secondary Minerals

Stratigraphic Uses of Tonsteins

Radiometric Dating of Primary Minerals
Calibration of Fossil Zones
Isochron Horizons
Correlation of Individual Units Lithologic Succession
Field Appearance (e.g., Thickness, Color, and Texture)
Bulk Clay Mineralogy
Bulk and Trace-Element Chemistry
Relative Abundance of Nonclay Minerals
Elemental Composition of Mineral Species
Morphology of Mineral Species
Recording Eruptive Histories
Intercontinental Correlations

Summary and Conclusions

Acknowledgments

References Cited