Sandstone Diagenesis in Interbedded Carbonate-Siliciclastic Sequence, Virgilian Holder Formation, New Mexico

Mark W. Bowman, Robert H. Goldstein

The Pennsylvanian (Virgilian) Holder Formation, New Mexico, consists of shales and sandstones interbedded with paleosol-capped limestones. Approximately 10 of these cycles were described in 13 stratigraphic sections. Analyses of paleosols on limestone surfaces and sedimentary structures in overlying sandstones indicate an upward transition from nonmarine to marine conditions.

Diagenesis of sandstones was compared to diagenesis of previously studied limestones using transmitted-light, cathodoluminescence, and back-scattered electron microscopy, energy dispersive analysis, and electron microprobe analysis for Ca, Mg, Fe, Mn, and Sr. Results suggest that sandstones underwent three temporally distinct stages of diagenesis.

First, nonferroan calcite cement precipitated before compaction in sandstones underlying paleosol-capped limestone. Elemental composition, comparison to cathodoluminescence in limestones, and precompactional nature suggest that these cements precipitated from low-temperature, near-surface meteoric waters introduced during intraformational subaerial exposure. Clay coats and hematite precipitated in sandstones less proximal to these subaerial surfaces.

Second, ubiquitous precipitation of quartz overgrowths postdated compaction. Later, minor kaolinite and chlorite precipitated in pores and replaced feldspar and argillaceous rock fragments. Coeval cements apparently did not precipitate in limestones during this deeper burial stage.

Finally, ferroan-calcite cement and minor ferroan-dolomite cement precipitated during and after fracturing. Ferroan calcites in limestone and sandstone are identical in composition and display similar cathodoluminescent patterns. These observations indicate contemporaneous near-total occlusion of porosity in both lithologies during deep burial. Secondary petroleum-filled fluid inclusions in later fracture-fill cements indicate petroleum migrated after most porosity was occluded.

AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.