Sequence Stratigraphic Interrelationship of Lower Cretaceous Dakota and Purgatoire Formations in Northeast New Mexico/Southeast Colorado and Correlative Strata (Muddy, Skull Creek, Plainview) of the Denver Basin

HOLBROOK, JOHN M., Indiana University, Bloomington, IN

The Albian Glencairn Member (Purgatoire Formation) and underlying Dakota Sandstone of southeastern Colorado and northeastern New Mexico are related depositionally to the Tucumcari, Mesa Rica, and Pajarito formations of east-central New Mexico and to the Plainview, Skull Creek, and Muddy formations of central Colorado. Depositional interrelationships of these strata are best understood when placed in a sequence-stratigraphic framework.

The Plainview Formation, Long Canyon sandstone bed (basal Glencairn) and Campana sandstone bed (basal Tucumcari) overlie a correlative lowstand surface of erosion (LSE) and represent backfilling of valleys during Kiowa-Skull Creek transgression. These strata are separated from overlying marine transgressive shale deposits of the lower Skull Creek, Glencairn, or Tucumcari, respectively, by a correlative transgressive surface of erosion. Lowermost Muddy and upper Skull Creek deposits represent progradation of highstand deposits over a marine flooding surface (Weimer, 1989) and are correlative to upper Glencairn sandstones that are also representative of highstand deposition.

Fluvial incision during maximum Kiowa-Skull Creek regression is manifest as an LSE atop Skull Creek and Glencairn marine deposits. Southward-flowing streams debouched into the maximum regressive sea forming a lowstand wedge, the remnants of which are represented by the Mesa Rica, Pajarito, and uppermost Tucumcari formations. Stable base level conditions developed near the maximum regressive shoreline resulting in widening of paleovalleys and deposition of a fluvial lowstand sheet sandstone (basal Dakota sandstone member) in southeastern Colorado and northeastern New Mexico. Transgression followed lowstand deposition and resulted in backfilling of paleovalleys represented by portions of the Muddy and Dakota sandstones.

AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)