New Mexico Geological Society Downloaded from: http://nmgs.nmt.edu/publications/guidebooks/4 Paleozoic sedimentary rocks of southwestern New Mexico Rousseau H. Flower, 1953, pp. 106-112 in: Southwestern New Mexico, Kottlowski, F. E.; [ed.], New Mexico Geological Society 4th Annual Fall Field Conference Guidebook, 153 p. This is one of many related papers that were included in the 1953 NMGS Fall Field Conference Guidebook. Annual NMGS Fall Field Conference Guidebooks Every fall since 1950, the New Mexico Geological Society (NMGS) has held an annual Fall Field Conference that explores some region of New Mexico (or surrounding states). Always well attended, these conferences provide a guidebook to participants. Besides detailed road logs, the guidebooks contain many well written, edited, and peer-reviewed geoscience papers. These books have set the national standard for geologic guidebooks and are an essential geologic reference for anyone working in or around New Mexico. 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One printed copy of any materials from the NMGS website or our print and electronic publications may be made for individual use without our permission. Teachers and students may make unlimited copies for educational use. Any other use of these materials requires explicit permission. This page is intentionally left blank to maintain order of facing pages. NEW MEXICO GEOLOGICAL SOCIETY * FOURTH FIELD CONFERENCE* SOUTHWESTERNNEW MEXICO PALEOZOIC SEDIMENTARY ROCKS were deposited the sands and silts which contain the OF SOUTHWESTERN NEW MEXICO most prolific successionaf trilobites in North America. by If the Bad Axe beds were consolidated and subjected Rousseau H. Flower to the weathering conditions of an arid, instead of a moist climate, they would look very muchlike the Bliss sandstone Bliss sandstone. The Bliss may be considered a "Bad Axe facies" laid downin the center of a basin. The Bliss sandstone(type section in the southern The marginal sediments to the west, in southern Franklin Mountains,near Ft. Bliss, whereit is 250 Arizona, contain a succession of Upper Cambrian feet thick) forms characteristic dark, often black faunas, beginning, as a matter of fact, in the Dres- weathering ledges which contrast strongly with the bachian which precedes the Franconian. Any red weathering Precambriangranites beneath, and marginal sediments to the north were removedby the overlying grey-brown weathering EI Paso lime- erosion and to the east were deeply covered. stone. The Bliss is dominantly a sandstone, with abundantglauconite and hematite, but also with a El Paso limestone considerable amountof dolornitic material in certain layers. The Bliss was originally considered Cambrian The El Paso formation consists of a group of on the basis of Lingulepis, which unfortunately is a limestones, with minor amountsof dolomite in New long ranging type and is not necessarily diagnostic. Mexico, with more abundant dolomite and somede- The discovery of Ordovician (Gasconade)fossils finitely sandy beds in the sections in western Texas. the northern end of BeachMountain in Texas raised Deposition extended throughout Canadiantime (often a controversy, someinsisting that the wholeBliss called Beekmantawnexcept by those who have seen was Ordovician, others that the lower part was Cam- the type section at Beekmantown,which is miserable). brian in Texas, and that the entire unit was Cambrian At the southern end of the Franklin Mountainsthe in NewMexico. Until recently, the fossils known lowest sediments are of Gasconadeage, lower from the Bliss sandstone in NewMexico were not Canadian0and the highest are equivalent to the Black diagnostic types, but did suggest an age of either Rock formation of Missouri and the Odenville lime- late Trempealeauor earliest Ordovician. stone of Alabama. In New Mexico the El Paso is generally considerably thinner than the 1590 feet Three recent discoveries indicate three different measuredat El Paso by Cloud and Barnes (1946), ages. Thefirst, of Ptychaspis striata and Chario- and post-Canadian erosion has removed variable cephalus, indicates middle Franconia age. The second, amountsof the upper limestones in different places. of Briscoia and Prosaukia, indicates late Franconia age. The third, the discovery of Bellefontia in association Kelley and Silver (1952) have treated the El Paso with l inguloids, ribbed brachiopods,and the graptolite as a group and separated it into two formations: Dictyonema,indicates earliest Ordovician, and is possibly the correlative of zone I of Rossin the Sierrite limestone - Generally thin-bedded lime- GardenCity formation of Utah (Flower, 1953, p. 2055). stones, sometimesslightly dolomitic0 and extensively dolomitized in the Hatchet Mountains. Bedding planes The Bliss represents~plainly, very slow and fre- are undulant or crinkled, and often highly styolitic. quently intermittent deposition which began, from our There are beds of limestone pebbles, and of.small present evidence, in the middle of the UpperCambrian, algal masseswsome spherical, sometubular and and continued into early Ordovician time. The diag- branched, but massive stromatolite beds are wanting. nostic fossils, all from zonesof 6 inches or less in The fauna indicates a correlation with the Gasconade, thickness, represent infrequent periods of morerapid though the top of the formation mayextend slightly deposition, higher than the Gasconadeand its equivalents in the east. The fauna is sparse. Clarkeaceras, Ophileta, The Bad Axe "formation" of Wisconsin and Symphysurina,and Histricurus have been collected, Minnesotawhich consists of glauconitic and ferruginous and a zone in the HatchetMountains has yielded sands, has been interpreted as representing an environ- Kainella and Leiostegium. ment of very slow deposition. Along the edgeof the basin, deposition was too slow for the preservation The Sierrite limestone ranges between100 to 175 of fossils in general, but in the center of the basin feet in thickness. About 100 feet of the basal dolo- 106 IIiI I I NEW MEXICO GEOLOGICAL SOCIETY * FOURTH FIELD CONFERENCE* SOUTHWESTERNNEW MEXICO LOWER PALEOZOIC STRATIGRAPHY OF SOUTHERNNEW MEXICO Standardsectign f~9~M~ic 9 ~9~tign Percho Connewongoon Choutoquon UPPER z Contodro ’~ Senecon Sly Gap O \\\\\\\\\\\ > Onote uJ Erieon o M I DDLE ~.~"~~’~ Ulsterion Oriskonian LOWER Helderbergion Woterlirne CAYUGAN Solino Guelph N IAGARAN Racine Clinton ALEXANDRIAN Medina ~~ ? Cutter "’ Richmond Alemon CINCINNATIAN Moysville ~\\~\~ Covington .... ~ Montoyo ~: Eden ~~ I Z Uphom Cable ~, Con. <~ Trenton MOHAWKIAN ~ > Block River O o C H AZYAN Chozy n- ~~ O Block Rock Smithville U. lowell Cotter _~ o CANADIAN Jefferson City o Bat Cove M. Roubidoux uJ Gosconode Sier rite Von Buren Trempeoleou BI i s s CR 0 I X I A N DFronconiores och A,.ERA W AUCOBIAN ~,,~~’~ mite at El Pasois the equivalentof this formation. Rockequivalents. The successionof the El Paso in NewMexico and western Texas is providing a Bat Cave formation - The Bat Cave contains more link betweenthe eastern sectionsin whichthe faunal massiveI~ds~ and is morepmminentlycliff-forming succession is based primarily upon the molluscs, thanthe Sierrite limestone.It is characterizedby a and the Utah sections in whichthe successionis widevariety of sedimentary typese but chiefly by based primarily uponthe trilobites. thick layers of stromatoliticlimestone, and, often in associationwith the sh’omatolite reefs, layers of The faunas of the Bat Cave limestones are largely coarsedetrital limestone.Many of the bedsare thin undescribed.The most conspicuouselements are the layers of lime mud, containing algal pellets and small siphuncles of endocemid and piloceroid cephalo~ds, gastropods,The Bat Caveformation contains a suc- whichare often silicified and weatherred on expos- cessionof faunas ranging in age from the Middle ures; them are abundant sponges, and a considerable Canadian(Gorman and Roubidouxequivalents) variety of gastropods,brachiopods, and trilobites. beds of Powell or possibly your~er age. At El Paso The New Mexico-succession in the Bat Cave interval the highest bedsinclude the Smithville and Black is briefly as follows: 107 NEW MEXICO GEOLOGICAL SOCIETY * FOURTH FIELD CONFERENCE* SOUTHWESTERNNEW MEXICO 1. A fauna in stromatolitic and detrital limestones Kelley and Silver(1952) divided the Montoyainto abovethe Sierrite limestone, characterized by the four formations; the Cable Canyonsandstone, the first (lowest) encloceroids, someprimitive pliomerid Uphamdolomite, the Alemanformation, and the Cutter trilobites, and abundant gastropods¯ The most common