ABSTRACT: Stacking Patterns, Scales of Cyclicity, and Eolian Facies Distribution in Carbonate-Clastic Cycles of Upper Pennsylvanian Rocks in Canyonlands National Park and Cataract Canyon, Southeastern Utah

Mark R. Williams

The Honaker Trail Formation and its temporal equivalents in the northern Paradox basin contain several time-bounded, progradational units that exhibit a hierarchy characterized by systematic changes in total unit thickness, bed thickness, facies distribution, and lateral facies offset relative to underlying units. Progradational units are typically floored by a thin skeletal grainstone above a transgressive, frequently erosional surface indicating an abrupt landward shift of facies. This lag is overlain by a shoaling-upward succession of marine carbonates, coastal dune, interdune, and fluvial strata. This succession may be abruptly truncated at various positions by the transgressive surface of the overlying progradational unit.

The stacking pattern of twenty-two progradational units defines two depositional sequence scale cycles. The lowest progradational units within each of these cycles are thin (5-15 m) and stack in a landward stepping pattern. Successive units become vertically stacked and increase in thickness up to 40 m. These units comprise the transgressive and highstand systems tracts, respectively, of Exxon terminology. Changes that occur between these progradational units include a shift from thinly bedded subtidal to intertidal grainstones and packstones to thicker beds of subtidal mudstones. The clastic fraction of successively deposited units becomes dominated by eolian sandflow and grainfall

strata that exhibit high angles of bedform climb and evidence of marine modification.

Upper progradational units within each depositional sequence gradually decrease in total thickness and lateral continuity. These units contain a large variety of eolian, interdune, and fluvial deposits. Eolian strata exhibit an increase in internal complexity with a greater concentration of first- and second-order bounding surfaces, lower foreset dips, and lower angles of bedform climb. Carbonates, if present, are typically silty, oolitic wackestones or dolomites.

Thick, steeply climbing bedforms of eolian strata were deposited as relative sea level approached a maximum at the scale of the depositional sequence. Their preservation within progradational units of the upper transgressive to highstand systems tracts is attributed to the landward shift of sediment accommodation space during this sealevel rise.

AAPG Search and Discovery Article #91002©1990 AAPG Rocky Mountain Section Meeting, Denver, Colorado, September 16-19, 1990