--> Abstract: Coal Zone Stratigraphy -- A New Tool for High-Resolution Depositional Sequence Stratigraphy in Near-Marine to Non-Marine Fluvial-Deltaic Facies Associations: A Case Study from the Ferron Sandstone, East-Central Utah, by J. R. Garrison, Jr. and T. C. V (Coco) van Den Bergh; #90952 (1996).

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Abstract: Coal Zone Stratigraphy -- A New Tool for High-Resolution Depositional Sequence Stratigraphy in Near-Marine to Non-Marine Fluvial-Deltaic Facies Associations: A Case Study from the Ferron Sandstone, East-Central Utah

James R. Garrison Jr., T. C. V (Coco) van Den Bergh

A detailed 3 km strike cross-section in Willow Springs Wash and an intersecting 22 km dip cross-section from north of Last Chance Creek to north of Ivie Creek have delineated seven parasequence sets within the Ferron Sandstone near-marine to non-marine system. Nine near-marine parasequences have been identified within Parasequence Set 1 and three within Parasequence Set 2. In the study area, Parasequence Sets 3-7 are represented by delta plain facies associations.

Parasequence sets are capped by laterally extensive coal zones consisting of beds of coal and correlative carbonaceous shales, altered volcanic ash layers (tonsteins), rooted zones, organic-rich mudstones, siltstones, and crevasse deposits. The preservation of tonstein decreases with distance from the paleo-shoreline. These time transgressive coal zones are thickest near landward pinchouts of the older delta front sandstones within the set. They frequently split into multiple zones. Delta front sandstones of the more landward parasequences are frequently incised by distributary channels. With time, these channels are abandoned and filled with sandstones, thinly bedded heterolithics, or transgressive deposits; subsequently, peat accumulation begins. The seaward-stepping parasequence sets contain a large number of seaward-stepping parasequences, capped by a thin transgressive delta-plain facies association. The youngest parasequences may be embedded within splits in the coal zone, and may occur landward relative to older, underlying parasequences. Ferron Sandstone parasequence sets are punctuated by development of extensive peat accumulations and their correlative facies associations, which are preserved as coal zones.

AAPG Search and Discovery Article #90952©1996 AAPG Rocky Mountain Section Meeting, Billings, Montana