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
The Sunnyside coal seam of the Cretaceous Blackhawk Formation in the Book Cliffs of
Eastern Utah is a 5m thick, laterally extensive coal formed in a topographically raised
mire along the western margin of the Western Interior Seaway. Detailed petrographic
analysis of over 300 outcrop and subsurface samples has enabled us to identify a complete
record of very high-resolution base-level changes throughout its formation, which spans at
least two fourth order sequences.
The seam also contains two laterally extensive splits formed by the inundation of the mire with marine derived material during base-level rise. Peaks in the inorganic content of the coal provide clear signatures of the flooding surfaces related to these splits at least 15km back up depositional dip into the unsplit coal. This enables us to constrain equivalent packages of coal and shallow-marine strata and to integrate sequence stratigraphic models based on the coal data with models based on the study of shallow-marine sediments. This integration is central to understanding sequence stratigraphic expressions in non-marine systems and enables coal data to be used to improve the resolution of sequence stratigraphic studies.
A combination of outcrop and subsurface measurements has been used to construct a 3-D model of the geometry of the Sunnyside coal using Roxar’s IRAP RMS reservoir modelling software. The model can be populated with a range of coal property data in order to show how coal composition changes vertically and laterally across the seam in relation to distance from the palaeoshoreline and splits.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.