A PEDOGENIC APPROACH TO THE CLASSIFICATION OF PALEOHISTOSOLS Mary E. Faw A Thesis Submitted to the Graduate College of Bowling Green State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE May 2012 Committee: James E. Evans, Advisor Margaret Yacobucci Jeff Snyder © 2012 Mary Faw All Rights Reserved iii ABSTRACT James E. Evans, Advisor This study assessed the transition between coals and the underlying siliciclastic sedimentary rocks, such as sandstones, siltstones, and mudstones. These underlying siliciclastic deposits are often referred to as underclays. These underclays often contain pedogenic features such as roots and slickensides. This study found that the underlying sedimentary deposits are cumulate paleosols profiles while the combination of the underlying sediments and the overlying coal forms a polygenetic soil profile. The use of the terms cumulate and polygenic soil profiles, a form of soil classification presented by Marriot and Wright (1993), is to emphasize the continuity of the soil transition from a mineral soil (typically a protosol or gleysol) to an organic soil (histosol) with intermediate phases and/or with partial overprinting of the underlying mineral soil. This study develops a field-based paleosol classification scheme for paleosols, by recognizing that there was an alteration in the hydrogeologic regime changing the soil from one that received clastic sediment to one that received little to no clastic sediment. In this study, application of the soil profile models presented by Marriott and Wright (1993), were modified to create four terms to describe soils: paleo-histosol, paleo- histogleysol, argillaceous paleo-histogleysol, and argilllaceous paleo-gleysol. This classification system was tested by describing three coal seams, from the Cretaceous Fruitland Formation and the Cretaceous Menefee Formation of the San Juan Basin, and the Pennsylvanian Pittsburgh Formation of the Appalachian Basin. It was iv possible to evaluate the success of this system by being able to reclassify the deposits as paleosols, by finding no evidence of unconformities between successive paleosols or diagenetic changes, and by finding the environmental implications consistent with other data and studies of the same units. In summary, this study determined that what has classically been described as “coal-underclay” sequences are better understood as polygenetic histosol-histogleysol sequences. The advantages in this method are: (1) a recognition that the similarities represent the continuity of soil-forming processes at a given locality, and (2) a recognition that the primary environmental change is the reduction in siliciclastic sediment input at this locality, due to hydrologic change. It also appears that the development of gleysols were hydrologically necessary for the histosols to establish themselves, develop and become preserved as a coal, unless the histosol formed from organic matter (peat) that had been transported from its place of development. v For Charles, who believed in me. vi ACKNOWLEDGMENTS I would like to thank my committee members at Bowling Green State University, Dr. J. Evans, Dr. J. Snyder, and Dr. P. Yacobucci, in their advisement and suggestions regarding this research. I would also like to thank Ohio’s Department of Natural Resources for access to Brown’s Lake Bog and allowing me to collect samples. And thanks to Carol Heckman at BGSU for allowing me use of the SEM laboratory. vi TABLE OF CONTENTS Page INTRODUCTION ................................................................................................................. 1 Soils and Paleosols…………………………………………………………………. 1 Coals Versus Paleohistosols………………………………………………………… 3 Potential Importance of Paleohistosols…………………………………………….. 3 Purpose of This Thesis……………………………………………………………… 4 GENERAL BACKGROUND ABOUT SOILS AND PALEOSOLS ................................... 6 Soil Properties ............................................................................................................ 6 . Soil Composition .......................................................................................... 6 Soil Textures .................................................................................................. 6 Soil Structures ............................................................................................... 6 Soil Horizons ................................................................................................. 9 Soil Classification .......................................................................................... 11 . Formation and Development of a Soil ........................................................... 12 Paleosols ............................................................................................................ 14 Recognition of Paleosols................................................................................ 14 Paleosol Classification ................................................................................... 15 HISTOSOLS, PALEOHISTOSOLS, AND COALS ............................................................. 16 Histosols ........................................................................................................ 16 Formation of Histosols ................................................................................... 16 Classification of Histosols ............................................................................. 19 Paleohistosols ......................................................................................................... 20 vii Recognition of Paleohistosols …………………………………………….. 20 Formation of Peat …………………………………………………………. 20 Classification of Peat ……………………………………………………… 21 Coal ……………………………………………………………………………….. 21 Formation of Coals ……………………………………………………….. 21 Classification of Coal …………………………………………………….. 22 UNDERCLAYS ........................................................................................................... 24 Description and Recognition of Underclays .............................................................. 24 Origin of Underclays...................................................................................... 25 Classification of Underclays .......................................................................... 27 Underclays as Parts of Soil Sequences…………………………………… 28 GEOLOGIC BACKGROUND .............................................................................................. 30 San Juan Basin of Colorado ....................................................................................... 30 Menefee Formation, Mesaverde Group………………………………… 31 Fruitland Formation ………………………………………………………. 32 Appalachian Basin of West Virginia ........................................................................ 33 Pittsburgh Formation, Monongahela Group .................................................. 35 METHODS ............................................................................................................ 36 Outcrop Studies …………………………………………………………………… 36 Lithofacies Analysis................................................................................................... 36 Pedofacies Analysis ................................................................................................... 36 SEM Analysis …………………………………………………………………… 37 FIELD RECOGNITION OF PALEOSOLS .......................................................................... 39 viii Brown’s Lake Bog ..................................................................................................... 38 Description of Cores ...................................................................................... 38 Menefee Formation .................................................................................................... 38 Descriptions of Coal and Underclays ............................................................ 38 SEM and Petrographic Analysis .................................................................... 41 Fruitland Formation ................................................................................................... 43 Descriptions of Coals and Underclays ........................................................... 43 SEM and Petrographic Analysis .................................................................... 46 Pittsburgh Formation ................................................................................................. 47 Descriptions of Coal and Underclays ............................................................ 47 SEM and Petrographic Analysis .................................................................... 48 DISCUSSION ............................................................................................................ 50 Paleosol Evaluation ................................................................................................... 50 Environment of Pedogenesis...................................................................................... 51 Menefee Formation ........................................................................................ 51 Fruitland Formation ....................................................................................... 52 Pittsburgh Formation ..................................................................................... 52 Summary of Field Relationships ................................................................................ 53 Evidence for Pedogenic Origins of Underclays