Cook, Timothy D. (2009-05). Facies Description and Interpretation of the Upper Lower Hickory Sandstone, Riley Formation, Central Texas. Master's Thesis. Thesis uri icon


  • Present models suggest that fluvial and marine depositional patterns were distinct
    from modern patterns prior to the appearance of land plants. Although these models are
    likely correct, problems exist when one attempts to distinguish between fluvial and
    shallow marine deposits in pre-Silurian strata, making it difficult to accurately determine
    depositional patterns. The lack of land plants and scarcity of body and trace fossils,
    especially in Precambrian and early Cambrian strata, make identification difficult.
    Based on core data and limited outcrops, the Lower Hickory Sandstone, a late Cambrian
    sandstone, has been interpreted to progress from fluvial to shallow marine. These data
    have allowed the development of an overall depositional model, but minimal detail of
    facies changes is available. Based on the limited data, both deltaic and estuarine models
    have been suggested for the Lower Hickory.
    Mining of the Lower Hickory for frac sand has created highwalls in the
    CarmeuseNA Mine, which provides an opportunity to study facies changes at this site.
    The CarmeuseNA Mine, located in McCulloch County, Texas, has exposed the
    formation along ~500 m long and 20 m-high faces, respectively. Because of limited exposure, only the south and west walls, as well as part of the east wall, could be
    examined. Digital photographs of the faces were mosaiced using standard
    photogrammetrical practices to produce visual representation of the highwalls. Bedding
    geometry was then mapped on the digital images to facilitate a detailed interpretation of
    the depositional process. Core and well data were used to map Hickory thickness to
    produce an isopach map.
    Four primary facies were observed in the quarry, dominated by small-scale and
    large-scale cross-bedding. Paleocurrents are generally unidirectional to the southsoutheast
    indicating a braided fluvial origin, but rarely opposing directions are seen.
    Bioturbation is rare low in the section, but increases upwards. Together with the rare
    herringbone cross-bedding, clay drapes, and bioturbation, a tidal influence is strongly
    suggested. The model suggested is a braided stream setting influenced and reworked by
    tides. A braided-delta fed by braided streams guided by a ridge and swale-dominated
    setting, which served as the sediment supply for the delta, is proposed.

publication date

  • May 2009