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Distribution and generalized thickness (maximum reported) trend of the Hell for Certain tonstein. Type area for the tonstein is shown. A portion of the Hyden West 7.5-minute Quadrangle showing Hell for Certain Creek and the Daniel Boone Parkway (in red).

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hell for certain a carboniferous volcanic ash in the eastern u s

Distribution and generalized thickness (maximum reported) trend of the Hell for Certain tonstein. Type area for the tonstein is shown.

A portion of the Hyden West 7.5-minute Quadrangle showing Hell for Certain Creek and the Daniel Boone Parkway (in red).

Hand sample of the Hell for Certain tonstein or flint clay. Note the conchoidal fracture in this fresh sample. Color may vary from beige to black. Upon weathering, the flint clay decrepitates or breaks up into smaller pieces, unlike other clays.

Don Triplehorn and an outcrop of the Fire Clay coal and the Hell for Certain flint clay, eastern Kentucky. In some places, the flint clay is underlain by other, thin clastic rocks between the upper and lower benches of the coal. These clastic interbeds are not widespread.

Abstract ID#: 69125

Copyright by Don Chesnut, 2004

Hell For Certain—A Carboniferous Volcanic Ash in the Eastern U.S.

Chesnut, Donald R., Jr., Emeritus, Kentucky Geological Survey, 228 MMRB, University of Kentucky, Lexington, KY 40506-0107, chesnut@kgs.mm.uky.edu

The Hell For Certain flint clay bed or tonstein is a new name for the flint clay parting of the Fire Clay coal and the coal's lateral equivalents in the central Appalachian basin. The bed has been mapped in Tennessee, Kentucky, Virginia and West Virginia where it was known as "the flint clay parting" or the "jackrock parting" of the coal. The coal name changes from valley-to-valley or county-to-county, but the names are widely recognized to represent the same coal bed and the flint clay, the same flint clay bed. In practice, the bed is a key stratigraphic horizon used in all these states.

The tonstein and coal bed are part of the Hyden Formation of the Breathitt Group in eastern Kentucky. The Hyden Fm. consists of shales, siltstones, sandstones, underclays and several important coal beds. The tonstein is Duckmantian in age (Middle Pennsylvanian) based on palynology (C. Eble, personal communication)

The extensive distribution of this volcanogenic tonstein in the Fire Clay coal (and its lateral equivalents) is strong evidence for the idea that this major coal was formed as a peat deposit that covered a large area of eastern North America. In turn, it is likely that other extensively-mapped major coal beds represent equally widespread peat deposit.

The repeated alternation between extensive coastal peat deposits with marine and overlying terrestrial sediments has been noted by many workers. Chronologic analyses supports glacioeustatic changes as a mechanism for these cycles. The concept that these “cyclothems” are eustatic and, thus, worldwide, implies that cyclothems can eventually be correlated around the world. If this cyclothem containing the Hell for Certain tonstein can be correlated to other strata around the world, then the radiometric date for this tonstein can be applied to the correlative cyclothems as well.

The isochronous nature of the Hell for Certain has also been important in studies involving areal and chronologic variations in the mire environments and the floral communities that made the Fire Clay peat. For more information about these studies, see papers on the Fire Clay coal by Eble, Greb and Hower (not listed here).

"Jackrock" is a mining term and refers to the suitability of the hard rock (in this case, flint clay) as a floor for mining jacks and other roof support systems. Because of its utility in mining, the mining industry has independently noted the flint clay’s extensive distribution across the region.

  • Reported volcanic minerals
  • euhedral sanidine
  • beta-form quartz
  • other volcanic quartz: embayed, splinted, magmatically resorbed
  • euhedral rutile
  • euhedral ilmenite
  • euhedral zircon (high length-to-width ratio)
  • euhedral apatite
  • anatase with negative crystals

The Hell For Certain flint clay or tonstein takes its name from Hell For Certain Creek in northern Leslie County, Kentucky. The Fire Clay (Hazard No. 4) coal was extensively mined in this area. The creek is located in the northern part of the Hyden West 7.5-minute Quadrangle. Outcrops have now been overgrown and access is limited, the creek being the only road in many places. A nearby reference section is a roadcut at mile-marker 40 on the Daniel Boone Parkway reported in Cobb et al, 1981 (see reference). Additional sections (e.g. Thousands Sticks) on this Parkway are also noted in this publication.

Note: the Daniel Boone Parkway has just been renamed the Hal Rogers Parkway after Senator Hal Rogers. Publications prior to 2004 will have the Parkway listed with the old name.

The name Hell For Certain is appropriate because conditions must have been very difficult during the heavy ash fall.

Numerous researchers in the last two decades have reached the consensus that this widespread bed is an altered volcanic ash, most of the ash altering to kaolinite in the mire environment (see references). The suite of included volcanic minerals and the lack of common resistant sedimentary minerals (e.g. tourmaline) has been used, among other observations, to support a volcanic origin (as opposed to a solely pedogenic origin). Pedogenic underclays are a common feature in the coal fields.

Sanidine in the tonstein has been dated by several laboratories and all provide an Ar/Ar date of 311-312 ma, the only confirmed radiometric date for Carboniferous strata in the basin.

Suggested References and References Cited

Chesnut, D.R., 1985, Source of the volcanic ash deposit (flint clay) in the Fire Clay coal of the Appalachian Basin: Dixieme Congres International de Stratigraphie et de Geologie du Carbonifere, Madrid, Spain, 1983, Compte Rendu, v. 1, p. 145‑154. [See references listed here for important papers published before 1983.]

Cobb, J.C., Chesnut, D.R., Hester, N.C., and Hower, J.C., 1981, Coal and coal‑bearing rocks of eastern Kentucky: Guidebook and roadlog for Coal Division of Geological Society of America, Field Trip No. 14: Kentucky Geological Survey, ser. 11, 169 p. [This guidebook contains locations for the tonstein along the Daniel Boone Parkway, now called Hal Rogers Parkway.]

Kunk, M.J. and Rice C.L., 1994, High-precision 40Ar/39Ar age spectrum dating of sanidine from the Middle Pennsylvanian Fire Clay tonstein of the Appalachian basin. Geological Society of America Special Paper 294, p. 105-113.

Rice, C.L., Belkin, H.E., Henry, T.W., Zartman, R.E., and Kunk, M.J., 1994, The Pennsylvanian Fire Clay tonstein of the Appalachian basin--Its distribution, biostratigraphy, and mineralogy. Geological Society of America Special Paper 294, p. 87-104. [These last two papers also contain useful references.]

For Fire Clay coal correlations in the Appalachians, see http://www.uky.edu/KGS/coal/webcoal/pages/formhyden.html

Stratigraphic nomenclature for Pennsylvanian rocks in Kentucky. This nomenclature has been formalized in Kentucky. Dates for formation boundaries are estimates only.

Hypothetical distribution and volcanic source area based on upper convection-cell wind patterns (Hadley cell) and continental reconstructions for Middle Pennsylvanian times. For more detailed discussion, see Chesnut (1985).