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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 65 (1981)

Issue: 5. (May)

First Page: 984

Last Page: 984

Title: Eustatic Control of Distribution of Lower Upper Cretaceous Coal Beds in Utah: Application in Coal Exploration: ABSTRACT

Author(s): Thomas A. Ryer

Article Type: Meeting abstract


Upper Cretaceous rocks in the Western Interior of North America record a series of transgressions and regressions that reflect shifts in the balance between rates of tectonic subsidence and sediment input and rates of eustatic sea level fluctuation. One of the transgressive-regressive cycles spans latest Albian through middle Turonian time and appears to have been primarily controlled by the rise and fall of worldwide sea level. The distribution of coal-bearing strata in this part of the Upper Cretaceous section in Utah reflects, and is probably a direct function of, this eustatic cycle. Rocks deposited during the transgressive phase of the cycle generally contain only thin beds of high-ash and high-sulfur coal that are of little or no economic value. Likewise, rocks of t e regressive phase contain little coal. The accumulation of thick deposits of peat was restricted to the transgressive and regressive maxima of the eustatic cycle. These peats formed the coals of the Alton, Harmony and Kolob, and the Emery and Vernal coalfields, respectively. The delicate balance between subsidence, sediment input, and eustatic sea level change that existed at times of maximum transgression and maximum regression allowed for the stacking of deltaic sequences, which then resulted in the accumulation of thick bodies of peat. This situation invites the development of a predictive model relating the distribution of economic deposits of coal to the various phases of the eustatic cycle. This model is applied to predict the areas most likely to contain thick beds of coal in the deep subsurface between the northern limit of the Emery coalfield and the southern edge of the Uinta basin in central Utah.

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