Davies, Roy C.1, John A Howell2, Stephen Flint1, Claus
Diessel3, Ron Boyd3
(1) University of Liverpool, Liverpool, United Kingdom
(2) University of Bergen, Bergen, Norway
(3) University of Newcastle, Callaghan, Australia
ABSTRACT: An Integrated Study of the Sedimentology, Stratigraphy and Coal Petrography of the Sunnyside Member of the Blackhawk Formation, Book Cliffs, Eastern Utah
Coal seams are highly sensitive indicators of changes in accommodation and organic
productivity, yet detailed coal petrographic analysis is rarely integrated with
sedimentological and stratigraphic studies of coal bearing strata. This study combines
these disciplines in order to provide an integrated model for the development of both the
marine and non-marine components of the Sunnyside Member of the Cretaceous Blackhawk
Formation, in the Book Cliffs of Eastern Utah.
The Sunnyside Member is comprised of three marine shoreface parasequences, marginal to non-marine coastal plain strata, a 5 metre thick, laterally extensive coal seam and fluvial/tidal successions interpreted as incised valley fills. The Sunnyside coal contains two laterally extensive splits which open out basinward into packages of shallow-marine sediments. Peaks in the inorganic content of the coal provide clear signatures of the flooding surfaces related to these splits at least 15 kilometres back up depositional dip into the unsplit coal, thus constraining time-equivalent packages of coal and shallow-marine strata.
Furthermore changes in coal composition and vitrinite reflectance enable us to identify a complete record of high-resolution base-level changes throughout the formation of the seam and equivalent shallow-marine strata, and to demonstrate that the seam spans at least two 4th order depositional sequences (approx 60 Ka). This study has also improved our understanding of the relative timings of coal formation, parasequence development and valley incision for the Sunnyside Member, the non-marine expressions of base-level change and the use of coal data to improve the resolution of sequence stratigraphic studies.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.