RIVERA, MARK A.
Department of Geological Sciences, New Mexico State University, Las Cruces, New Mexico 88001

Abstract: Depositional Facies Analysis of Phylloid Algal Mound Complexes within the Upper Pennsylvanian Holder Formation, Sacramento Mountains, New Mexico

The Upper Pennsylvanian, Lower Holder Formation contains wellexposed phylloid algal mound complexes along the eastern margin of the Orogrande Basin, (NM). Detailed field and petrographic analyses indicate that these mound complexes consist of stacked, high frequency, carbonate cycles (sequences) that are bounded by subaerial exposure surfaces. Three facies assemblages were recognized: (1) mound core boundstones rich in encrusting tubular foraminifera, phylloid algae, and micrite mud, (2) mound flank wackestones and packstones containing encrusting tubular foraminifera, phylloid algae, skeletal debris, and peloids, and (3) intermound facies consisting of carbonate facies (oolitic packstones and grainstones, foraminiferal-peloidal wackestones and packstones, and oncoidal-blue green algal wackestones and packstones) and siliciclastic facies (chert pebble conglomerate, lithic wacke, intrabasinal arenite, and fossiliferous siltstone/shale). Stratal cyclicity within this system was controlled by high frequency, high-amplitude glacioeustasy. However, the internal character of individual cycles was largely controlled by the lateral position within the mound complex (i.e. mound core, mound flank, intermound/off-mound).

Three-dimensional correlation of mound complex facies reveals that mound progradation was parallel to the axial trend of the actively evolving, northwest-plunging La Luz anticline. Furthermore, the positions of greatest mound growth shifted laterally depending on the availability of accommodation space through time.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas