INTRODUCTION

Coal Geology of the Paleocene-Eocene Calvert Bluff Formation (Wilcox Group) and the Eocene Manning Formation (Jackson Group) in east-central Texas: 1995 Field Trip for The Society for Organic Petrology

By Peter D. Warwick and Sharon S. Crowley

U.S. Geological Survey, MS 956, Reston, VA 22092

OVERVIEW

The Jackson and Wilcox Groups of eastern Texas (fig. 1) are the major lignite producing intervals in the Gulf Region. Within these groups, the major lignite-producing formations are the Paleocene-Eocene Calvert Bluff Formation (Wilcox) and the Eocene Manning Formation (Jackson). According to the Keystone Coal Industry Manual (Maclean Hunter Publishing Company, 1994), the Gulf Coast basin produces about 57 million short tons of lignite annually. The state of Texas ranks number 6 in coal production in the United States. Most of the lignite is used for electric power generation in mine-mouth power plant facilities. In recent years, particular interest has been given to lignite quality and the distribution and concentration of about a dozen trace elements that have been identified as potential hazardous air pollutants (HAPs) by the 1990 Clean Air Act Amendments. As pointed out by Oman and Finkelman (1994), Gulf Coast lignite deposits have elevated concentrations of many of the HAPs elements (Be, Cd, Co, Cr, Hg, Mn, Se, U) on a as-received gm/mmBtu basis when compared to other United States coal deposits used for fuel in thermo-electric power plants. Although regulations have not yet been established for acceptable emissions of the HAPs elements during coal burning, considerable research effort has been given to the characterization of these elements in coal feed stocks. The general purpose of the present field trip and of the accompanying collection of papers is to investigate how various aspects of east Texas lignite geology might collectively influence the quality of the lignite fuel. We hope that this collection of papers will help future researchers understand the complex, multifaceted interrelations of coal geology, petrology, palynology and coal quality, and that this introduction to the geology of the lignite deposits of east Texas might serve as a stimulus for new ideas to be applied to other coal basins in the U.S. and abroad.

There have been numerous organized field trips to investigate the geology of Gulf Coast lignite deposits (see Johnston and Jobling, 1977, 1979; Finkelman and Casagrande, 1986; Finkelman and others, 1987, Ayers and others, 1989; Breyer and others, 1993; Durham and Shannon, 1995), however, few trips have integrated the depositional setting with the palynologic, petrographic, and geochemical characteristics of the lignite deposits. During this field trip, two lignite-bearing intervals of east Texas will be studied: the Calvert Bluff Formation (Wilcox Group) and the Manning Formation (Jackson Group) (fig. 1). The following field guidebook contains 5 papers that address the geologic setting, depositional environments, palynology and paloecology, and lignite petrography and geochemistry of the two formations. The first and second stops of the field trip will concentrate on the Manning Formation. The paper by Yancey (chapter 1) reviews the stratigraphy, depositional setting, and sequence stratigraphy of the Manning Formation. The paper by Warwick and others (chapter 2) presents detailed stratigraphy, lignite geochemistry, and petrology for two lignite beds that are mined at the Gibbons Creek mine. Raymond and others (chapter 3) review detailed palynological studies they have made on Manning Formation strata exposed at the Lake Somerville spillway, our second stop on the trip. Finally, Middleton and Luppens (chapter 4), and Crowley and others (chapter 5) present the general geology, and lignite geochemistry and petrography of Calvert Bluff Formation lignite beds mined at the Calvert mine near Bremond. The Calvert mine is the final stop on our field trip. As we approach the Calvert mine area, watch for the power plant which employs fluidized bed combustion technology.

ACKNOWLEDGEMENTS

The authors wish to thank Thomas D, Demchuck and Amoco Production Company for their help in arranging logistics for the field trip and for the printing of the field guide.

ITINERARY - 1995 TSOP FIELD TRIP, AUGUST 30, 1995

Because of the travel routes taken by the field trip, the first stratigraphic interval to be studied will be exposures of the Manning Formation at the Gibbons Creek Lignite Mine. We then travel to the Lake Somerville spillway exposures that are at approximately the same stratigraphic interval as that exposed in the Gibbons Creek mine. The end of the trip will be at the exposures of the Paleocene-Eocene Calvert Bluff Formation. A generalized map showing geology, place names, and roads is shown on figure 2. The locations of each stop on the field trip is also shown: Stop 1 - the Gibbons Creek mine; Stop 2 - Lake Somerville spillway; and Stop 3 - the Calvert mine. Below is an approximate itinerary for the field trip.

• 7:30am - Depart from The Woodlands Conference Center. Route: from The Woodlands go north on I-45 to Conroe, west on SR 105 to Navasota, northwest on SR 6, northeast on SR 90 to Anderson, northwest on F&M 244 to the Gibbons Creek Mine. The distance from the Woodlands to the Gibbons Creek Mine about 85 miles.
• 9:00 - Arrive at the Gibbons Creek Mine, NW of College Station. Stop 1 - Mine Tour and discussions - Gibbons Creek Mine (Eocene, Manning Formation, Jackson Group).
• 11:00 - Depart from the Gibbons Creek Mine. Route: from Gibbons Creek Mine go northwest on SR 30, southwest on F&M 60 via College Station to Lyons, southeast on SR 36 to Somerville. The distance from the Gibbons Creek Mine to Somerville about 38 miles.
• 11:45 - Arrive at the Lake Somerville spillway outcrop. Stop 2 - Lunch and outcrop discussion on the exposures at Lake Somerville spillway (Eocene, Manning Formation, Jackson Group).
• 1:30pm - Leave the Lake Somerville spillway. Route: from Somerville go northwest on SR 36 to Milano, northeast on US 79 to Hearne, northwest on SR 6 to SR 14, northeast to Bremond and the Calvert Mine. The distance from Somerville to Bremond about 80 miles.
• 3:00 - Arrive at the Calvert Mine. Stop 3 - Mine Tour and discussions (Paleocene, Wilcox, Calvert Bluff Formation).
• 5:00 - Leave the Calvert Mine. Route: from the Calvert mine go south on SR 14, southeast on SR 6 to Navasota, east on SR 105 to Conroe, south on I-45 to The Woodlands. The distance from Bremond to The Woodlands is about 110 miles.
• 7:00pm - Arrive at The Woodlands Conference Center.

REFERENCES CITED

Ayers, W.B., Jr., Breyer, J.A., and Finkelman, R.B., 1989, eds., Depositional settings of Texas lignites: 28th International Geological Congress, Field Trip Guidebook T173, 37 p.

Breyer, J.A., 1991, Tertiary coals of the Gulf Coast, in Gluskoter, H.J., Rice, D.D., and Taylor, R.B., eds. Economic Geology, U.S., Boulder, Co., Geological Society of America, The Geology of North America, v. P-2, p. 573-582.

Breyer, J.A., Archer, A.W., and McCabe, P.J., 1993, Sequence stratigraphy of coal-bearing strata: field trip guidebook and short course supplement: American Association of Petroleum Geologists, Energy Minerals Division, Field Trip Guidebook, 48 p.

Durham, Clay, and Shannon, P.J., eds., 1995, Lignite mines and power plants and kaolinitic sandstone mining in east Texas: (with remote sensing applications): American Association of Petroleum Geologists, Energy Minerals Division, Field Trip Guidebook, unpaginated.

Finkelman, R.B., and Casagrande, D.J., eds., 1986, Geology of Gulf Coast lignites: Geological Society of America, Coal Division Field Trip, Houston, Environmental and Coal Associates, 224 p.

Finkelman, R.B., Casagrande, D.J., and Benson, S.A., eds., 1987, Gulf Coast lignite geology: The Fourteenth Biennial Lignite Symposium on the Technology and Utilization of Low-Rank Coals, Reston, Va., Environmental and Coal Associates, 224 p.

Johnston, J.E., III, and Jobling, J.L., 1977, Lignite resources in east-central Texas, in 27th annual meeting field trip guidebook: Austin, Texas, Gulf Coast Association of Geological Societies, approx. 16 p.

Johnston, J.E., III, and Jobling, J. L., 1979, Lignite resources in east-central Texas: AAPG-SEPM Guidebook, Houston Geological Society, 15 p.

Maclean Hunter Publishing Company, 1994, Keystone Coal industry manual. Chicago, Ill., Maclean Hunter Publishing Company, p. 527.

Oman, C.L., and Finkelman, R.B., 1994, Hazardous air pollutants in major U.S. coal-producing areas, in Shiao-Hung Chiang, ed., Eleventh Annual International Pittsburgh Coal Conference Proceedings, The University of Pittsburgh School of Engineering Center for Energy Research, p. 1096-1099.

Ruppert, L.F., Warwick, P.D., Crowley, S.S., and Pontolillo James, 1994, Tonsteins and clay-rich layers in coal-bearing intervals of the Eocene Manning Formation, east-central Texas. Gulf Coast Association of Geological Societies Transactions, v. 44, p. 649-656.

Contents

Chapter 1

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