Revised Stratigraphic Relationships of the Dakota Group in the Tucumcari Basin, San Miguel County, New Mexico, USA
— Anna E. Van Yperen, Lina H. Line, John M. Holbrook, Miquel Poyatos-Moré, and Ivar Midtkandal

Recent stratigraphic studies in Colorado and northeastern New Mexico have provided a new detailed understanding of large-scale transgressive-regressive cycles in the Dakota Group, and their spatio-temporal impact on sediment distribution. In this region, the Dakota Group consists of the Mesa Rica Sandstone, Pajarito Formation, and Romeroville Sandstone, and the latest published stratigraphic framework has provided a further subdivision of the Mesa Rica Sandstone. Early studies established stratigraphic relationships of Jurassic to Lower Cretaceous strata at the northwestern rim of the Tucumcari Basin, in northeastern New Mexico (San Miguel County, USA). In order to apply the most recent stratigraphic framework, this area has been revisited. Six sedimentary logs and aerial imagery allow for analyses of facies association distribution, depositional architecture, and spatial extent of stratigraphic surfaces. These were then correlated to previously published log data to establish an integrated correlation panel, which stretches ~16 km along depositional dip and contains two main sandstone successions. The lower succession (6–10 m thick) is continuous throughout the study area and changes from fluvial to shallow-marine strata in a depositional down-dip direction. The upper succession (up to 6 m thick) is characterized by a discontinuous distribution of fluvial strata. Key stratal surfaces are correlated to the latest sequence stratigraphic framework and the two sandstone successions are identified as the lower and upper Mesa Rica Sandstone. This provides an update to previous interpretations, in which the Mesa Rica Sandstone was not subdivided and locally identified as the Pajarito Formation. Petrographic results reveal a high kaolin content, which is attributed to meteoric water diagenesis related to restricted accommodation at time of deposition. The Mesa Rica Sandstone may contain recycled detritus from the underlying Jurassic Morrison Formation, based on similar XRD analysis results for both sandstone units.