Shortercontributions lo New Mexico Geotogy ZuniSandstone and Acoma Tongue defined by 0rin J. AndersonNewMexico Bureau of Minesand Mineral Resources, Socono, NM 87801 Seldom in the history of our sciencehas Entrada Sandstone into New Mexico and Section c, North American Stratigraphic a stratigraphic name 6een so badly mis- advocated the Wingate-to-Entrada name Code, 1983). treated and misunderstood as the Zuni change (Baker et al., 1947) also recognized In deference to Harshbarger et al. (1957), Sandstone. Ironically, it is a valid strati- the lower san Rafael Gqoup at Fort win- they did provide insight oi regional coi- graphic name and represents valid strat- gate and near Zuni Pueblo. relations. From their work otheri were able igraphic concepts. It lacks only a clear The significance of this last point will to ascertain that the Zuni Sandstone cor- definition. Fortunately pro- this can be be examined, but first the use of Cow relates with the Cow Springs Sandstone vided with historical perspective, prop", Springs Sandstone must be explained. at Black Mesa, Arizona, and they did rec- appllcatlon ot the requirements stated in Owing to the lack of interest in the barren ognize the Entrada Sandstone below their the North American Stratigraphic Code Jurassic rocks of the Zuni Indian Reser- "Cow Springs" atZuni Pueblo. Thus, they (1983), and an understanding-of the re- vation the name Zuni Sandstone had lan- acknowledged the presence of two for- gional correlationsof MiddleJurassic rocks. guished for years as a vague stratigraphic mations in this 500-ft-thick sandstone in- The excellent exposures of light-colored concept. Perhaps this is why Harshbarger terval, consistent with what is stated earlier eolian sandstones near Zuni-pueblo in et al. (1951, 1957) felt at liberty to intro, in this paper. However, their (Harshbar- west-central New Mexico were desig- duce their Arizona name, Cow Springs ger et al., 1957) failure to recognize Zuni nated the "Zuni sandstones" bv Dutto'n Sandstone, to designate the rocks that as a local stratigraphic name was the sec- (1885). Dutton also had introduced the Dutton had named the "Zuni sand- ond time in a decade that U.S. Geological name Wingate sandstone for the under- stones." The authors offered no expla- Survey authors had, for relatively trivial lying strata, which are well exposed near nation for how their name (or unit) related reasons, sought to abandon valid nomen- Fort Wingate, but when correlating be- to the Zuni Sandstone, which added to clature and install their own. And what tween the two areashe inadvertently mis- the confusion. One of their colleagues at two names more readily summon up the placed the Zuni-Wingate contact in the the U.S. Geological Survey, the venerable New Mexico landscap-e than Zuni and Zuni Pueblo section. He dropped this Carle H. Dane, protested the use of Cow Wingate? The abandonment of the orig- contact to the level that is cunently rec- Springs Sandstone in New Mexico in a inal concept of a Wingate Sandstone is ognized as the top of the Rock point Mem- 1956 memo to the Geologic Names Com- accepted. Not so for the Zuni; it remains ber of the Chinle, and thus by error mittee. ln this memo Dan-econtended that a valid name in New Mexico. The name (probably based on color) he included in use of the name Cow Springs Sandstone Cow Springs was invalid and superfluous the "Zuni sandstones" strata that were in New Mexico "curdles my gizzard." the day it was introduced to New Mexico, recognized as Wingate 30 mi to the north. While it may be true that language can and it is not recognized by the New Mex- The actual contaci is now known to be produce unusual reactions and maladies, ico Bureau of Mines and Mineral Re- some 280 ft above the original placement, perhaps the more pertinent point to be sources. at an interval that has been designated by made here is that the rule of nomencla- The significance of the lower San Rafael some authors as the "Todilto nolch.,, Oni tural priority was not followed (Article 7, Group is that it is a sequence that repre- problem is, as Anderson (1983)discussed in a preliminary pdper, that the ,,notch,, ls not recognizable everywhere; conse- quently, there are localities where the contact is problematic. (ssw) (NNE) As is now well known, the southern U.S. Geo- SanJuan logical Survey (Bakeret a|.,7947) changed Basin the name from Wingate to Entrada Said- stone. This tells us a number of things. First, we see that a perfectly valid aid propelly defined straiigraphic name can be willfully abandoned-in the interest of regional correlations. This process is not necessarily bad because gieater knowl- edge leads to progressive refinement of stratigraphic concepts, which in turn may expose excessive or superfluous nomen- clature. Second, it tells us that the Entrada Sandstone is present near Zuni pueblo, despite the locilly problematic rpp", .orr- tact, and that two formations (Enirida an<l Zuni) occupy the =500-ft-thick sandstone interval that lies between the Chinle For_ mation and the Dakota Sandstone. Last. FIGURE l-Diagrammatic stratigraphic it tells us crosssection from Zuni Pueblo to southern San Basin that the authors who correlated showing relatioiship Juan of TodiltolSurnmerville-Bluff to Zuni Sandstoneand strati6;raphicposition of the Acoma Tongueof the Zuni. May 1993 New Mexico Ceology sents a transgression and highstand dur- choice for the umbrella formation. ButZuni sary, to acknowledge the facies contrast ing Middle furassic (Callovian) time, a time was not chosen; nor is any modification with the Acoma Tongue. of rather extfeme aridity in western North in nomenclature necessarv. Considerably upsection in the Zuni America. The highstand is recorded by Sandstone at Thoreau and at Haystack the Todilto Formation (limestone and Mountain some coarse-grained sand- gypsum) deposited in a paralic salina as- Acoma Tongue of the Zuni Sandstone stones are present that might represent sociated with, and at the southern end of, A change in the bedform at the toP of facies transitional to the overlying Morri- the Curtis-Sundance seaway. The south- the Bluff Sandstone can be recognized son Formation. The base of the Morrison Ba- ern margin of the basin of Todilto depo- across the southern San fuan Basin. The Formation in the southern San |uan sition-precipitation was just north of Zuni change is relatively abrupt and includes sin is herein considered to be the region- Pueblo (the area central to this discussion; crossbed type, scale and magnitude of ally traceable scoured surface at the base Fig. 1). However, the local stratigraphic crossbeds, crossbed-dip direction, and a of what has been called the Westwater relationships are clear; thicknesses and li- slight increase in grain size. This contrast Canyon-et Member of the Morrison. Ander- thologies db not vary significantly south- with the underlying facies of the Bluff can son al. (1993)assert that the Westwater ward to Zuni, and the "Todilto notch" helps be recognized at Mesa Gigante, Mesita, Canyon Member cannot be correlated define the highstand. Thus, the "notch" Seama Mesa, Acoma, Haystack Mountain from the type area in Utah into the San not only represents the break between north of Grants, Church Rock where there Juan Basin, and thus the Prewitt Member lower and upper San Rafael Group but is a definite change in lithology at the break, (from Smith, 1954) may be a more appro- also the attendant change from a trans- and near Zuni Pueblo. At the Seama Mesa- priate name for the basal Morrison unit. gressive facies tract to a regressive facies Acoma localities, Maxwell (1976,7979) re- References ferred the upper, boldly crossbedded tract. to Anderson,O. J., 1983,Preliminary report on redefi' The regressive sequence comprising the unit as the Zuni Sandstone. With the rec- nition of Zuni Sandstone, west-central New Mex- upper San Rafael Group has been well ognition of this unit at the toP of the "main ico: New Mexico Geology, v. 5, no. 3, pp. 56-59. Middle defined in Utah where for the most part body" of the Zuni Sandstone near Zuni Anderson, O. J., and Lucas, S. G.,1992, The Formation, northern New to regard Jurassic Summeruille it overlies the Curtis Formation. The base Pueblo, it has become necessary Mexico: New Mexico Geology, v. 14, no. 4, pp.79- of the regressive sequence consists of thinly Maxwell's Zuni as merely a tongue of the 92. bedded, gypsiferous sandstone, siltstone, larger unit, and thus Anderson and Lucas Anderson, O. J-, Lucas, S. C., and Maxwell, C. H, subdivisions, northwest and mudstone and represents deposition (1992)proposed the name Acoma Tongue 1993, Morrison Formation New Mexico (abs.): New Mexico Geological Society, on an arid coastal plain-sabkha having of the Zuni. This bedform change and the Proceedings volume 1993 Annual Spring MeeiinS, short-lived, broad, shallow lakes and pe- recognition of its regional extent have o.9. riodic influx of fine-grained eolian sand. permitted reconciliation and proper cor- Baker, A. A., Dane, C. H., and Reeside, l. B.' Jr.' of These strata were designated the Sum- relation of Maxwell's (7976) Zuni Sand- 1947, Revised correlation of Jurassic Formations parts Arizona, New Mexico, and Colorado: at of Utah, merville Formation by Gilluly and Ree- stone with the original Zuni Sandstone American Association of Petrolbum Geologists, side (1928) and in part overlap the Curtis Zuni Pueblo. This uncertainty admittedly Bulletin, v. 31, no. 9, pp. 1664-"1668 in age. Summerville strata thin consid- had been a hindrance to the use of the Condon, S. M., and Peterson, F., 1986, Stratigraphy erably southeastward through the Four name Zuni.