2019 AAPG Annual Convention and Exhibition:

Datapages, Inc.Print this page

Paleodrainage Reconstruction of the Cretaceous Gallup Sandstone Formation, New Mexico: Insights From U-Pb Detrital Zircon Geochronology


Detrital zircon data supplemented with paleocurrent, petrographic and facies distribution data has been integrated to reconstruct the paleodrainage of the Late Cretaceous Gallup Sandstone Formation. High-resolution sequence stratigraphic correlations have recently been conducted along depositional dip of this fluvio-deltaic formation, however, an 81km gap in outcrop exposure has caused uncertainties for correlations and sequence stratigraphic interpretations. Representative sandstone samples were collected from distinguishable cut and fill episodes from two incised valleys (IV1 and IV2) located 81km apart on either side of the outcrop exposure gap. IV1 is situated more proximally and was interpreted as being sourced from the Mogollon Highlands to the SSW. The oldest terrace in this valley has a more diverse range of zircon ages which is characteristic of sediment sourced from the Sevier Fold-and-Thrust Belt whereas the youngest terrace is dominated by Mogollon Highlands (1.6-1.8Ga) sourced zircons. Petrographic analysis of this incised valley has exhibited a more arkosic and subangular texture likely caused by a primary source of sediment. IV2 is located more distally along depositional dip and was interpreted as being sourced from both the Mogollon Highlands and the Sevier Fold-and-Thrust Belt to the WSW. IV2 has a more subrounded, moderate to well sorted texture likely caused by the influx of secondary sourced sediment from the Sevier Fold-and-Thrust Belt as well as downstream maturation of sediment. Detrital zircon data from the youngest terrace of this valley possesses a similar spike of Mogollon aged zircons to the youngest terrace in IV1. This data leads to the conclusion that sediment provenance changed through time from a mixed source to a lone source of sediment. Previously the Gallup Sandstone Formation has been interpreted as being a single incised valley system with its sediment provenance sourced from the Mogollon Highlands. This study provides evidence for a multiple valley and multiple source fluvial system feeding the Gallup Sandstone Formation and changing to a sole source of sediment through time. This sediment provenance research has implications for reservoir heterogeneity applications in that, mature, well rounded quartz-rich sandstones are typically superior reservoirs compared to immature, angular feldspathic sandstones.