The Geology of Texas - Vol. 1

NAVARRO GROUP⁵⁹

 Nomenclature.— The existence of Ripley strata in Texas was announced by Shumard (1475, p. 152) in 1861 (printed in 1863), and the name "Navarro beds" was first used by him in 1861 (1469, p. 189). Shumard's type area was Navarro County, but he had in mind no specific type locality, except that Chatfield Point and Corsicana are frequently mentioned as fossil localities in his text.  Other synonyms of Navarro in the literature are: Glauconitic or Greensand division; Ripley group; Exogyra costata clays; Webberville formation (Hill and Vaughan, 795, p. 241; Hill and Vaughan, 808); Pulliam formation (Vaughan, 1686, p. 2).

 Equivalents of the Navarro in Arkansas were early named Saratoga, Nacatoch, and Arkadelphia, and there the Navarro is by implication treated as a group, as it should be also in Texas. The formations of the Navarro have not all been named in Texas. Hill in 1901 (803, pp. 342-343) gave the name "Corsicana⁶⁰ beds" to a basal, more sandy portion, apparently including the Nacatoch sand, in Navarro County; and the upper Navarro he called the "Kemp beds." The medial Navarro sand is now generally correlated with the Nacatoch of Veatch, 1906 (1691, p. 27). Stephenson (391, 1534, 1536, 1539) treats the Navarro in the central Texas outcrop as consisting of the following units in ascending order: (1) Exogyra cancellata marls; (2) Nacatoch sand; (3) unnamed chalky marl; and (4) unnamed clay. He states that south of about the latitude of Cameron the two basal units are absent and the chalky marl rests on Taylor. For formations of Navarro, see p. 516.

Stratigraphy and contacts.—The Navarro is the uppermost group of the Upper Cretaceous in the Texas-Arkansas-Louisiana region, and is unconformably overlain by various overlapping Tertiary formations of Midway or Wilcox age. The amount of hiatus between the uppermost known Navarro or Escondido and the overlying Tertiary has been much discussed, but is unknown because (a) the intervening zonation is unknown, and (b) the missing strata are nowhere filled in, so far as yet discovered, in the region. The question is further discussed under "Midway group." The upper Navarro unconformity is widely reported (803; 1193, p. 414; 969, p. 327).

 In southern Arkansas the lower Navarro contact (Marlbrook-Saratoga) is lithologically sharp but is unconformable, and shows an irregularity of a few inches vertically in the base of the Saratoga. The basalmost Saratoga is marked by glauconite, phosphatic nodules and fossil casts, and small borings filled with this Saratoga material extend down into the underlying Marlbrook (392, p. 99). Stephenson (1539, p. 13) indicates a questionable unconformity at the base of the Navarro as far south as Cameron, and he states that from Cameron southwards the basal Navarro (Exogyra cancellata clays, and Nacatoch equivalent) is absent, only the upper Navarro being left. In Maverick County the non-marine Olmos beds are supposed to represent a break in sedimentation in the lower Navarro. In the Big Bend the basal Navarro contact has not been precisely located, but lies probably somewhere within the Aguja formation.^60a

^60a Taliaferro (Jour. Geol., 41: 12—37, 1933) records sediments which indicate the nearness of Upper Cretaceous shore lines in northeastern Sonora (Cabullona district, southwest of Douglas, Ariz.).

⁶¹ Thomas and Rice (1601b) state that the Saratoga fauna is more closely similar to the underlying Taylor than to the overlying faunas.

^61a Vanderpool considers that the San Miguel foraminifera ally the formation more closely with the Navarro than with the Taylor.