New Mexico Geological Society Annual Spring Meeting — Abstracts

Upper Cretaceous strata exposed in the Hagan basin in Sandoval County, north-central New Mexico, contain ammonites and other marine molluscan fossils that span middle Cenomanian to early Campanian time. The fossiliferous formations and members (ascending order) are: Cubero Member of Dakota Formation; Greenhorn Limestone, Carlile and Semilla Sandstone, Juana Lopez, D-Cross, El Vado and Satan members of Mancos Formation; Hosta-Dalton Sandstone and Point Lookout Sandstone. Previously, the mollusks from these units in the Hagan basin have been little studied. Ten ammonite and/or inoceramid zones are indicated by moderately to well preserved marine invertebrate fossils recovered from these strata.

The Acanthoceras amphibolum Zone in the Cubero Member of the Dakota Formation establishes a middle Cenomanian age. The inoceramid zonal taxon Mytiloides mytiloides (Mantell) in the Greenhorn Limestone indicates the ammonite zone of Mammites nodosoides, and thus a latest early Turonian age. The Prionocyclus hyatti Zone in the Carlile and Semilla members establishes a latest middle Turonian age. The upper Turonian Scaphites ferronensis Zone in the Juana Lopez Member is established by that eponymous taxon. The occurrence of Prionocyclus novimexicanus (Marcou) and Scaphites (Scaphites) cf. S. whitfieldi Cobban in the approximate top of the Juana Lopez Member identifies the middle upper Turonian S. whitfieldi Zone. Forresteria (Forresteria) sp. and cf. Prionocyclus sp. from the D-Cross Member indicate a late Turonian age. Inoceramus undabundus Meek and Hayden high in the El Vado Member indicates a late Coniacian age and may further identify the lower upper Coniacian Magadiceramus subquadratus inoceramid zone. The Clioscaphites choteauensis Zone in the lower Hosta-Dalton establishes an earliest late Santonian age. The associated ammonites Placenticeras syrtale (Morton) and Baculites codyensis Reeside, also present in the Hosta-Dalton, further indicate a Santonian age. Desmoscaphites cf. D. erdmanni Cobban together with Scaphites leei I Reeside identify the upper Santonian D. erdmanni Zone in the Satan Member. The Scaphites leei III Zone near the base of the Point Lookout Sandstone establishes an earliest Campanian age. Haresiceras (Haresiceras) montanaense (Reeside) and Baculites aquilaensis Reeside indicate the lower Campanian Scaphites hippocrepis I Zone and also establish an early Campanian age for the Point Lookout Sandstone.

Very few Cretaceous ammonites or inoceramids have previously been documented from the Hagan basin. Lee (1912) listed fossils from measured sections in the Hagan coal field. They included the ammonites Placenticeras sancarlosense Hyatt, P. whitfieldi Hyatt, P. intercalare Meek and Hayden, P. planum Hyatt and Scaphites sp. related to S. hippocrepis Dekay and the nautiloid Nautilus dekayi Morton and other mollusks from the “Mesaverde Formation”; Prionocyclus wyomingensis Meek, inoceramids and gastropods from the Mancos; Prionotropis [Collignoniceras woollgari] and Placenticeras sp. from the “Cephalopod Zone” and Inoceramus labiatus Schlotheim from the Greenhorn Limestone. Placenticeras whitfieldi (a junior synonym of P. meeki Böhm) is too young of a species to occur in the reported unit. Reeside (1927) illustrated a specimen of P. sancarlosense from the lower part of the “Mesaverde Formation” at the Hagan Coal Mine. He also illustrated a specimen of Scaphites leei var. parvus Reeside [S. leei III] from near the base of the “Mesaverde” at the same location (Reeside, 1927; Cobban, 1969). Harrison (1949), in an unpublished master’s thesis on the geology of the Hagan coal basin, mentioned fossils in his measured sections of the Mancos and “Mesaverde” formations. He also stated that a 6-ft-thick calcareous zone 487 ft above the Mancos base contained a well-preserved ammonite fauna. Black (1979) mentioned fossiliferous marine limestones in the Hosta-Dalton and fossiliferous, crossbedded and lenticular marine-bar sandstones of the Semilla Sandstone in the Hagan basin. Ingersoll and Kelley (1979) mentioned common marine fossils in the Mancos Formation similar to those of the “Mesaverde” that included Bivalvia, Gastropoda, Cephalopoda and the trace fossil Ophiomorpha. Fleming (1989) proposed a reference section for the Semilla Sandstone in the Hagan basin and stated he collected the index fossil Prionocyclus hyatti (Stanton) from that unit. Lucas et al. (1998) briefly described the Hagan basin Cretaceous section and illustrated two fossils, including a Prionocyclus. Cather et al. (2002) published a geologic map of the Hagan quadrangle listing localities and mollusks from mostly the Mancos and Dakota formations. Most of the ammonite and inoceramid taxa and zones reported here have not previously been reported from the Hagan basin.

References:

1. Black, B. A., 1979, Structure and stratigraphy of the Hagan embayment: A new look: New Mexico Geological Society, Guidebook 30, p. 101-105.
2. Cather, S. M., Connell, S. D., Lucas, S. G., Picha, M. G. and Black, B. A., 2002, Geologic map of the Hagan quadrangle, Santa Fe County, New Mexico: New Mexico Bureau of Geology and Mineral Resources Open-file Digital Geologic Map OF-GM 050, scale 1:24,000.
3. Cobban, W. A., 1969, The Late Cretaceous ammonites Scaphites leei Reeside and Scaphites hippocrepis (DeKay) in the Western Interior of the United States: U. S. Geological Survey, Professional Paper 619, 47 p.
4. Fleming, T. F., 1989, New reference sections for the Semilla Sandstone Member of the Mancos Shale and their genetic implications: New Mexico Geology, v. 11, no. 1, p. 1-7.
5. Harrison, E. P., 1949, Geology of the Hagan coal basin, New Mexico (M.S. thesis): University of New Mexico, Albuquerque, 177 p.
6. Ingersoll, R. V. and Kelley, V. C., 1979, Stratigraphy and paleoenvironments of the Hagan basin, north-central New Mexico: New Mexico Geological Society Guidebook, 30th Field Conference, p. 197-200.
7. Lee, W. T., 1912, Stratigraphy of the coal fields of northern central New Mexico: Geological Society of America Bulletin, v. 23, p. 571-686.
8. Lucas, S. G., Anderson, O. J., and Estep, J. W., 1998, Stratigraphy and correlation of middle Cretaceous rocks (Albian-Cenomanian) from the Colorado Plateau to the southern high plains, north-central New Mexico: New Mexico Museum of Natural History and Science, Bulletin 14, p. 57-66.
9. Reeside, J. B., Jr., 1927, The cephalopods of the Eagle Sandstone and related formations in the Western Interior of the United States: U. S. Geological Survey, Professional Paper 151, 87 p.