The Pennsylvanian System in New Mexico— overview with suggestions for revision of stratigraphic nomenclature Barry S. Kues, Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico 87131

Abstract tions, including the widely exposed and rec- Mountains); 6) reevaluate the lithostrati- ognizable units still called “lower gray lime- graphic (formation and group) names of Understanding of Pennsylvanian lithostra- stone” and “upper arkosic limestone” mem- Thompson (1942), which remain valid and of tigraphy in New Mexico has developed at an bers; 4) apply the earliest valid formal names potential use as members of more broadly uneven pace, and the nomenclature current- for the latter two units (Gray Mesa and defined Pennsylvanian formations; and 7) ly applied to Pennsylvanian strata is in some Atrasado, originally defined in the Lucero use New Mexico lithostratigraphic names for cases antiquated, inconsistent, redundant, or uplift) widely throughout the Madera Group subsurface Pennsylvanian strata within the inappropriate. The main Pennsylvanian rock outcrop area; in some cases replace other for- state, rather than names applied to sequences in New Mexico are reviewed, and mation names that have been proposed, and Pennsylvanian rocks in central Texas. several recommendations for revision of the recognize that locally a third upper Madera lithostratigraphic nomenclature are pro- unit (Bursum Formation and equivalents) posed. In some cases these recommendations may also be present; 5) recognize Madera Introduction build upon or broaden changes that have Group strata and terminology more widely Pennsylvanian strata were among the first been implemented by other workers in (e.g., into the Caballo and Robledo to be observed in detail by geologists restricted areas. These recommendations Mountains), yet retain current non-Madera entering New Mexico during and immedi- include: 1) abandon use of Magdalena terminology where appropriate, especially Group in New Mexico; 2) raise Madera for sequences associated with rapidly sub- ately after the American occupation, and Formation to Group rank; 3) treat previously siding basins (e.g., San Andres Mountains, Pennsylvanian fossils were among the first used members within the Madera as forma- Sacramento Mountains, Sangre de Cristo to be described from New Mexico Territory

FIGURE 1—Currently used Pennsylvanian stratigraphic nomencla- ern Sangre de Cristo Mountains, with the upper part recognized as the ture in New Mexico (reproduced from Armstrong et al., 1979). The Alamitos Formation and Madera raised to Group rank (Baltz and only significant addition since 1979 has been establishment of the Myers, 1984, 1999). Porvenir Formation for the lower part of the Madera in the southeast-

November 2001 NEW MEXICO GEOLOGY 103 FIGURE 2—Main exposures of Pennsylvanian strata discussed in text tains; 12) Sierra Oscura; 13) Fra Cristobal Range; 14) Sierra Cuchillo area; (reproduced from Armstrong et al., 1979). Numbers refer to mountain 15) Mud Springs Mountains; 16) Caballo Mountains; 17) Derry Hills area; ranges and other locations as follows: 1) northern Sangre de Cristo Moun- 18) Kingston area; 19) Santa Rita–Silver City area; 20) Big Hatchet tains; 2) southern Sangre de Cristo Mountains; 3) southeastern Sangre de Mountains; 21) Peloncillo Mountains; 22) Robledo Mountains; 23) San Cristo Mountains; 4) Nacimiento and Jemez Mountains; 5) Sandia Moun- Andres Mountains; 24) northern Organ Mountains; 25) northern Franklin tains; 6) Manzanita–Manzano Mountains; 7) Los Pinos Mountains; 8) Mountains and Bishop Cap Hills; 26) northern Hueco Mountains; 27) Socorro area; 9) Lucero uplift; 10) Sierra Ladrones; 11) Magdalena Moun- Sacramento Mountains.

(e.g., Hall, 1856; Marcou, 1858). Later 19th real attempt to recognize, correlate, and Although Pennsylvanian strata are not century geologists (e.g., Stevenson, 1881) name lithostratigraphic units throughout as widely exposed in New Mexico as added information on Pennsylvanian New Mexico; Kottlowski (1960a) summa- Permian, Triassic, Cretaceous, and Paleo- stratigraphy of the territory, but subdivi- rized in detail Pennsylvanian stratigraphic gene strata, they include a greater diversi- sion and naming of Pennsylvanian strata sequences and nomenclature for much of ty of depositional environments and a began in the early 1900s (e.g., Herrick, the state; and Armstrong et al. (1979) pro- greater variety of reported fossil species 1900; Gordon, 1907) and has continued vided a general summary of New Mexico (more than 1,250) than any system except ever since. Thompson (1942) made the first Pennsylvanian strata (Fig. 1). the Cretaceous (Kues, 1982, table 2). Thick

104 NEW MEXICO GEOLOGY November 2001 (500+ m [1,640+ ft]) Pennsylvanian sec- summary of the major recommendations chronostratigraphic units, particularly tions are exposed in many parts of north- was presented earlier (Kues, 2000). A cor- with respect to their boundaries, rather ern and southern New Mexico (Fig. 2) relation chart of major exposed Pennsyl- than defining groups and formations chiefly in fault-block mountain ranges vanian sequences in New Mexico incorpo- entirely on a lithologic basis, as is required along the Rio Grande rift and adjacent rates proposed revisions in lithostrati- by the North American Code of regions, and Pennsylvanian strata are graphic nomenclature that are discussed in Stratigraphic Nomenclature. It is a miscon- widely present in the subsurface in most this paper (Fig. 3). ception, however, that Thompson’s litho- parts of the state, where some units are In proposing revisions of currently used stratigraphic units were nothing more than reservoirs for oil and gas (e.g., Broadhead, stratigraphic nomenclature, the desirabili- faunal zones, as claimed by some workers 1999), and others are hydrogeologic ty of maintaining stability of nomenclature (e.g., Kelley and Silver, 1952, p. 89). His aquifers producing water. by preserving familiar and long-used lithostratigraphic units were defined pre- Development of our understanding of names is recognized, even if in retrospect cisely, described in detail, and type sec- Pennsylvanian stratigraphy in New they may not have been the most logical or tions for each of them were designated. Mexico has proceeded at an uneven pace. appropriate names to apply to a particular A second difficulty with Thompson’s Pennsylvanian sequences in a few areas stratigraphic unit. Separate formation units, however, was that they were based have been intensively studied, whereas, names are appropriate for distinctive litho- almost entirely on the stratigraphy of two more commonly, sequences in other areas logical units that are mappable at a scale of restricted areas. His Atokan and Des- have been examined in only moderate 1:24,000; however, the same lithostrati- moinesian units were based on exposures detail, typically in the context of struc- graphic names should be used for similar in the Derry Hills–Mud Springs Mountains tural/stratigraphic studies of individual lithologic units that may be exposed wide- area, and his Missourian and Virgilian mountain ranges. The Pennsylvanian of ly in a region, cropping out, for example, in units were based on strata in the northern some ranges is known only at the level of several isolated mountain ranges. New Sierra Oscura, with the exception of one reconnaissance mapping done several and existing names should reflect signifi- group having a type section in the north- decades ago. Similarly, the stratigraphic cant lithological differences from equiva- ern Sacramento Mountains. Although nomenclature applied to Pennsylvanian lent units in a region, but not be estab- Thompson stated that many of his units sequences in New Mexico has developed lished simply as a convenient way to des- could be recognized in areas far distant in a piecemeal fashion, producing a large ignate local successions of strata with little from their type sections, he provided little number of currently used group, forma- reference to equivalent successions else- information to aid such correlations. Later tion, and member names, some of which where in the region. In this paper, little field geologists found that many of his are inappropriate, redundant, informal, or attention is devoted to the nomenclature of units could not be recognized easily very applied only to unnecessarily restricted the transitional Pennsylvanian–Permian far from their type areas. areas, and some of which have been wide- units noted above. Recent proposals to Thirdly, Thompson’s groups and forma- ly used for decades without designation of raise the Pennsylvanian–Permian bound- tions largely represented restricted strati- type sections or adequate formal defini- ary to a position within the Wolfcampian graphic intervals that in some cases were tion. stage in North America (e.g., Baars et al., not easily distinguishable lithologically Lateral facies changes may frustrate 1994; Lucas et al., 2000) are likewise not from underlying or overlying units, and in recognition of stratigraphic units very far addressed. These are the focus of ongoing many cases were not mappable at the from their type sections. This has con- studies by the author and others, and con- scales required by the present Code of tributed, on the one hand, to the establish- clusions will be presented in a future Stratigraphic Nomenclature. ment of unique successions of formation paper. Although the focus here is on Thompson’s work is noted here in part names in individual, closely spaced moun- exposed parts of the Pennsylvanian because the rejection of his stratigraphic tain ranges, and, on the other hand, to sequence, some observations are included terminology was premature and done with approaches that deemphasize the lithostra- on terminology of subsurface units as well. little discussion of its merits. While it is tigraphic subdivision of thick Pennsyl- true that Thompson’s unit names general- vanian sequences in favor of relying on Nomenclature of Thompson (1942) ly cannot be applied very widely, some fusulinid biostratigraphy to recognize units can be recognized more than 160 km chronostratigraphic units, such as the five Thompson (1942), in a publication titled (100 mi) away from their type localities Pennsylvanian series—Morrowan, Ato- Pennsylvanian System in New Mexico, (e.g., Kottlowski, 1960a, p. 21). Other units, kan, Desmoinesian, Missourian, and Vir- sought to classify the strata of the entire such as Thompson’s Bruton Formation, gilian—as the only subdivisions of the Pennsylvanian using eight group names, were well defined lithologically and recog- Pennsylvanian (Kottlowski, 1960a). In two each for the “Derryan” (Atokan), nizable regionally, to the extent that U.S. addition, in many parts of the state, Upper Desmoinesian, Missourian, and Virgilian Geological Survey geologists adopted and Pennsylvanian strata grade upward Series; 15 formation names; and one mem- mapped it, although renaming it the through a transitional sequence with pro- ber name, all of which were new. His Bursum Formation (see Wilpolt and gressively less marine influence, into non- names were not used by the U.S. Wanek, 1951). Thompson’s Armendaris marine, clastic, red-bed units near the Geological Survey in its large-scale recon- and Bolander Groups (Desmoinesian) are Pennsylvanian–Permian boundary. The naissance mapping projects in the 1940s, together lithologically similar to the wide- position of this boundary within some of and ultimately none of Thompson’s names spread “lower gray limestone” member of these transitional sequences and the termi- were used by other workers in later strati- the Madera of many previous workers, a nology for them deserve more study. graphic studies in New Mexico, although unit now considered a formation with for- A century after the first Pennsylvanian Kottlowski (1960a) continued to apply mal names in some areas of the state. formation was named in New Mexico Thompson’s Missourian and Virgilian unit Thompson’s group and formation names (Sandia Formation, Herrick, 1900), this names in the Sierra Oscura. in the Mud Springs Mountains, Derry paper 1) provides an overview of Penn- Thompson’s nomenclature was rejected Hills, and Sierra Oscura areas remain sylvanian stratigraphy around the state, 2) by later workers for essentially three rea- available (most appropriately as member reviews current lithostratigraphic nomen- sons. First, he initially divided the names, because the current Code of clature, 3) proposes some revisions of this Pennsylvanian using fusulinid biostratig- Stratigraphic Nomenclature [NACSN, nomenclature in some areas, and 4) indi- raphy into the four series (chronostrati- 1983, p. 858] does not require that mem- cates locations where additional study of graphic units) noted above, and then fit the bers be mappable) for units in those areas, the Pennsylvanian would be useful. A brief lithostratigraphic units he defined to the should future workers studying the

November 2001 NEW MEXICO GEOLOGY 105 FIGURE 3—Stratigraphic nomenclature for major Pennsylvanian exposures in New Mexico, as pro- posed in this paper. Note that in some areas, formation-rank units within the Madera Group have yet to be established. Pennsylvanian stratigraphy in detail Magdalena Group essentially all Pennsylvanian sequences in require member names. New Mexico, and in later decades the U.S. In his 1942 study, Thompson (p. 26) pro- Gordon (1907) proposed the name Mag- Geological Survey and others continued to posed the term Derry Series for “all rocks dalena Group to include the Sandia For- use the term Magdalena throughout the in the central to the extreme south central mation (of Herrick, 1900; Herrick and state, from the Sangre de Cristo to Franklin areas of New Mexico between the base of Bendrat, 1900) and overlying Madera Mountains. Rock units of Late Missis- the Pennsylvanian system and the basal Limestone (of Keyes, 1903). The name was sippian age (e.g., the “lower limestone part of the…Des Moines series,” and this taken from the Magdalena Mountains west member” of the Sandia Formation of Wood name has persisted in the more recent lit- of Socorro, and the group was recognized and Northrop, 1946, now the Arroyo erature as a New Mexico equivalent to the by Gordon in Socorro, Bernalillo, and Peñasco Group) and of Early Permian age Atoka Series of the midcontinent. It is now Sierra Counties, although he noted that it (e.g., Bursum Formation, Wilpolt et al., known that Thompson’s type Derry sec- could not be subdivided in Sierra County. 1946) were also included in the Magdalena tion (Derry Hills, south of Truth or When proposed, the Magdalena Group Group. P. B. King (1942, pp. 675–677) Consequences) includes strata of late was believed to represent the lower part of believed that the upper part of the Morrowan and Atokan age (e.g., Clopine the Pennsylvanian, the upper part being Magdalena Group in New Mexico includ- et al., 1991), and that thick sequences of represented by the Manzano Group (of ed much Wolfcampian strata and could be Morrowan strata occur at the base of the Herrick, 1900) and consisting of the Abo, traced southward into the Early Permian Pennsylvanian in both northern and south- Yeso, and San Andres Formations (Lee and Hueco Limestone. ern New Mexico. Recognition of the Girty, 1909). The Permian age of the forma- Objections to use of the term Magdalena Morrowan and Atokan Series in New tions of the Manzano Group was soon rec- Group, registered in the literature for more Mexico is straightforward, and it is there- ognized (e.g., Lee, 1917, 1921), and the than 50 yrs, fall generally into three cate- fore preferable to use these series names term Manzano Group passed out of usage gories. First, as commonly used in most (which are used widely across much of the in the 1930s, leaving the Magdalena Group regions, the name is synonymous with U.S.) rather than the superfluous and local essentially synonymous with the Pennsylvanian System and thus is super- term Derry Series. Pennsylvanian System. Indeed, Darton fluous. Second, over the years, the name (1928) and Needham (1940) applied the Magdalena Group has been applied in so term Magdalena Group or Formation to many different ways and to such different

106 NEW MEXICO GEOLOGY November 2001 successions of formations that it is essen- this…term by merely restricting the name System, of which the term Magdalena is a tially meaningless in any precise strati- in any sense to a small portion of the somewhat unnecessary duplication.” graphic sense. Third, the highly faulted, Pennsylvanian in New Mexico.” R. E. King Inclusion of Mississippian strata is no intruded, metamorphosed, and incom- (1945, p. 21) echoed Thompson’s recom- longer an issue, as these have been sepa- plete Pennsylvanian section in the Mag- mendation and added his own: “…the rated out and named (e.g., Kelly Lime- dalena Mountains makes this area unsuit- unfortunate name Magdalena has become stone, Arroyo Peñasco Group). And, as able for a type section, as Kottlowski (1959, more deeply entrenched in recent geologic Kottlowski undoubtedly realized, if use of p. 59) aptly noted: “Even with deliberate literature published by the U.S. Geological the name Magdalena Group is an unneces- care a more unsuitable type section proba- Survey…and it is recommended that the sary duplication of “Pennsylvanian,” it is bly could not be found.” In reality, no type term Magdalena, a relic of an antiquated even more nebulous a term when applied section for the Magdalena Group has ever type of stratigraphic nomenclature, be per- to Pennsylvanian plus Lower Permian been established, nor could an adequate manently abandoned.” Pray (1961, p. 72), strata. type section be established in the future in rejecting use of Magdalena Group in the In recent decades, use of the term Mag- because of the anomalous nature of the Sacramento Mountains, stated that the dalena Group has been discontinued in Pennsylvanian section in the Magdalena “term is so broad…and the sections to many areas of New Mexico where it for- Mountains, including the absence of which it has been applied are so varied in merly had been applied. These areas Upper Pennsylvanian beds owing to fault- New Mexico, that it serves little practical include the San Andres Mountains ing or erosion, and the lack of a strati- purpose.” Kottlowski (1960a, p. 21) specu- (Kottlowski et al., 1956), Sacramento graphic contact with the overlying Abo lated that the main reason for continuing Mountains (Pray, 1961), Sangre de Cristo Formation (Kottlowski, 1960a). to use Magdalena Group rather than sim- Mountains (Sutherland, 1963; Baltz and As early as 1942, Thompson (p. 22) aban- ply Pennsylvanian might be to “indicate Myers, 1984, 1999), northern San Andres doned use of the term Magdalena Group inclusion of more than only Pennsylvanian and Oscura Mountains (Bachman, 1968; as a stratigraphic unit in New Mexico, stat- strata within the group,” and noted Bachman and Harbour, 1970), Joyita Hills ing that the term “Magdalena…seems to (Kottlowski, 1962, p. 343) that “if pre and (Kottlowski and Stewart, 1970), Manzano be essentially synonymous with the sys- post-Pennsylvanian units were eliminated and Manzanita Mountains (Myers, 1973), temic term Pennsylvanian…” and “…it from the Magdalena Group…the remain- Los Pinos Mountains (Myers et al., 1986), seems inadvisable to attempt to preserve der is the equivalent of the Pennsylvanian Nacimiento Mountains (Woodward, 1987),

November 2001 NEW MEXICO GEOLOGY 107 and generally in central and south-central recognized the formation as the upper part mations, in place of the lower “gray lime- New Mexico (Bachman and Myers, 1975). of his Magdalena Group in Bernalillo and stone” and upper “arkosic limestone” The term Magdalena Group does not Socorro Counties. No formal type section members, respectively. These revisions of appear anywhere in the statewide for the Madera has ever been established, Madera terminology reflect more detailed Pennsylvanian stratigraphic correlation but a reasonable reference section was pre- stratigraphic study and illustrate chart of Armstrong et al. (1979, fig. 8). sented by Kelley and Northrop (1975, p. approaches that are applicable to other There is clearly an ongoing, progressive 125) at Montezuma Ridge, east of Placitas ranges as well. These approaches, which recognition that application of the name and a few kilometers north of the site of La are used below, include: 1) raising the Magdalena Group or Formation serves no Madera village. Madera Formation to Group, a more useful purpose. Further use of the name Although Thompson (1942) argued appropriate rank, given its great thickness should cease in all parts of New Mexico against using the name Madera because (typically 300–700+ m [1,000–2,300 ft]), where it is currently still used. These areas Keyes’ (1903) definition was so poor and widespread distribution, and long dura- include the Hueco Mountains (e.g., he was inconsistent in his usage, the term tion (Desmoinesian to Virgilian or early Williams, 1963; Stoklosa et al., 1998); has proven useful for the thick, predomi- Wolfcampian); 2) formally naming forma- Franklin Mountains (e.g., Harbour, 1972; nantly limestone unit between the Sandia tions to replace informal subdivisions such LeMone, 1982, 1992; Kelley and Matheny, Formation and the Wolfcampian Abo red as lower "gray limestone" and upper 1983); Bishop Cap Hills (Seager, 1973); beds. By 1950 the Madera Formation was "arkosic limestone" members; and 3) where Silver City–Santa Rita area (e.g., Jones et recognized in the Sandia, Manzano, appropriate, formally naming members to al., 1967, 1970; Pratt, 1967); Caballo Nacimiento, Sangre de Cristo, Los Pinos, designate localized but distinctive litho- Mountains and Derry Hills (e.g., Kelley Oscura, and Magdalena ranges, the Lucero logic units within formations. The Madera and Silver, 1952; Seager and Mack, 1991, uplift, the Joyita Hills, and elsewhere in Group encompasses two or three forma- 1998; Mack et al., 1998); Mud Springs Socorro County. Detailed stratigraphic sec- tion-rank units that are readily mappable Mountains (Maxwell and Oakman, 1990); tions were published for the Madera in at a scale of 1:24,000. Fra Cristobal Mountains (Nelson, 1986); many of these areas, leaving no doubt as to The Madera Group generally reflects Socorro County (e.g., Siemers, 1983; its lithologic composition and stratigraph- two major depositional sequences. During McLemore and Bowie, 1987); Lucero uplift ic position. In the 1940s (see Read and Desmoinesian time marine deposition (Kelley and Wood, 1946); and Sandia Wood, 1947) the U.S. Geological Survey across widespread carbonate shelf envi- Mountains (Kelley and Northrop, 1975, (USGS) adopted the convention in recon- ronments (e.g., Ye et al., 1996) produced although Lucas et al., 1999a, b, extended naissance mapping of recognizing infor- massive, gray, cliff-forming limestone into the Sandias Myers’ [1973] terminology mally a lower “gray limestone member” of units, typically cherty, with little interbed- for the Manzano–Manzanita Mountains, Desmoinesian age and an upper “arkosic ded clastic sediments. This was followed which specifically rejects usage of the term limestone member,” typically of Missour- by marine environments that were increas- Magdalena Group). The most recent North ian and Virgilian age. An exception was in ingly, although not everywhere evenly, American Code of Stratigraphic Nomen- the Lucero uplift area (see below), where affected by influx of siliciclastic sediments clature (NACSN, 1983, p. 855) states that Kelley and Wood (1946) applied formal derived from increased tectonic activity in “…the lack of need or useful purpose for a names to these subdivisions of the Madera. (principally) the Uncompahgre, Pedernal, unit, may be a basis for abandonment; so, In central New Mexico, from the south end and Zuni land masses associated with too, may widespread misuse in diverse of the Manzano Mountains southward, a Ancestral Rocky Mountains tectonism dur- ways which compound confusion.” Both separate Bursum Formation was also rec- ing Missourian, Virgilian, and locally into are true of the Magdalena Group. Perhaps ognized, incorporating Early Permian beds Wolfcampian time. Expansion of continen- the most obvious misuse of the name transitional between the mainly marine tal, transitional (e.g., delta, lagoon), coast- occurs in the Franklin Mountains, where a sediments of the Madera Formation and line, and marine, clastic shelf environ- sequence of three Morrowan to Des- the nonmarine red-bed clastics of the Abo ments at the expense of carbonate shelf moinesian formations, composed of mas- Formation. In southern New Mexico, environments occurred during this time sive limestone at the base, and becoming Madera terminology generally has not (Ye et al., 1996). In the upper part of the increasingly shaly upsection, are included been used. Strata correlative with the Madera Group, marine limestones typical- in the Magdalena Group, in complete con- Madera have received local formation ly still predominate, but generally in thin- trast to the Magdalena as used in central names, resulting in separate stratigraphic ner beds and with little to no chert. New Mexico, which is primarily clastics at nomenclatures applied to the Pennsylvan- Interbedded shales and siltstones the base and massive limestones in the ian sequences in the Caballo, San Andres, approach (in the Missourian and Virgilian) Desmoinesian portion. Discontinuing use Sacramento, and Franklin Mountains, and or may locally surpass (in the Virgilian and of the name Magdalena Group will not in the Silver City–Santa Rita area. early Wolfcampian) the thickness of the adversely affect stratigraphic understand- As studies progressed, the Madera limestones. Siliciclastic beds in the upper ing of the Pennsylvanian sequences any- Formation in two areas was raised to Madera Group are generally gray or where in New Mexico. group status, its members raised to forma- brown low in the upper unit, but become tions, formal formation names given to the gradually more colorful upsection, with Madera Formation/Group lower “gray limestone” and upper the addition of red, maroon, purple, and “arkosic limestone” members, and formal green lithologies, which ultimately domi- The name Madera Formation was first member names given to subdivisions of nate the uppermost part of the Madera applied to Upper Carboniferous blue to these units. For example, in the Manzano sequence. Finally, marine deposition and gray beds, “the superior part of the great and Manzanita Mountains (see below) the limestone lithologies cease, and continen- limestone formation” in the Sandia lower member was named the Los Moyos tal nonmarine red-bed clastics of the Abo Mountains by Keyes (1903). Herrick (1900) Limestone and the upper member the Wild Formation prevail. had recognized this interval between his Cow Formation by Myers (1973), within a The term Madera Group appropriately “Sandia series” and “Manzano series” but Madera Group that also included the encompasses this broad depositional pat- applied no name to it. Gordon (1907) Bursum Formation. Similarly, in the south- tern, which can be recognized across much adopted the name Madera Limestone for eastern Sangre de Cristo Mountains (see of New Mexico. Units of formation rank, as “the great limestone plate along the back below), Baltz and Myers (1984, 1999) characterized in the present Code of slope of the Sandia Mountains,” named for raised the Madera to group rank and rec- Stratigraphic Nomenclature (NACSN, the former village of La Madera, and he ognized the Porvenir and Alamitos For- 1983, p. 858), are suitable for the main

108 NEW MEXICO GEOLOGY November 2001 lithologic units, including the lower cherty lithostratigraphic units in the Madera names were the first formal names to be limestone sequence and the upper Group typically reflect local, gradational applied to the three subdivisions of the interbedded limestone/siliciclastics se- lateral or vertical facies changes, and there- Madera that can be recognized widely in quence. As previous workers have done in fore are restricted in extent, perhaps limit- central and south-central New Mexico. some areas, this upper sequence can be ed to individual mountain ranges. Fine- Kelley and Wood's descriptions of the divided into two formation-rank units, the scale sequence-stratigraphic studies, such three formations, though brief, adequately lower of which is dominated by marine as have been undertaken in restricted parts characterize them, and subsequent work- limestone with no or few red, maroon, or of the Madera Group in the Sandia ers (Martin, 1971, for the Gray Mesa and green beds, and the upper of which is typ- Mountains (e.g., Wiberg and Smith, 1993; Atrasado, and Kues and Kietzke, 1976, for ically thinner and dominated by colored Smith, 1999), will help to refine under- the Red Tanks) have studied the stratigra- clastic beds, typically of nonmarine origin, standing of the cyclic sedimentary process- phy of these units in detail, providing the with subsidiary marine limestones. es responsible for Madera lithologic units basis for comparing them with equivalent The Madera Group reflects deposition and ultimately, the nomenclature that is units elsewhere in New Mexico. on shelf and basin margin, and in slowly applied to them. As defined by Kelley and Wood (1946), subsiding basin conditions that were dom- Recommendations for revision of strati- the Gray Mesa Limestone consists of pre- inated by marine environments until near- graphic nomenclature for units within the dominantly massive, gray, markedly cher- ly the end of Madera deposition. Madera Group follow the philosophy dis- ty, cliff-forming limestones, as well as Sequences of similar age deposited in cussed above. The earliest formal names minor amounts of gray shale and sand- rapidly subsiding basins (e.g., Orogrande applied to the lower "gray limestone" and stone, and a conspicuous tan-weathering Basin, Taos trough) are lithologically con- upper "arkosic limestone" members of the limestone at the top. Thin-bedded and siderably different and generally much Madera Formation were established by locally noncherty limestones are also pre- thicker than Madera Group sequences. Kelley and Wood (1946) in the Lucero sent, though not abundant. Martin (1971), Thus, although Baltz and Myers (1984, uplift–Sierra Ladrones region of western on the basis of stratigraphic sections mea- 1999) included the Porvenir and Alamitos Valencia and northwestern Socorro sured on Gray Mesa (= Mesa Aparejo on Formations within the Madera Group in Counties (see below). These members, USGS topographic maps) and Carrizo north-central New Mexico, these Taos Gray Mesa and Atrasado, respectively, in Mesa, Monte de Belen (= Mesa Sarca), and trough formations differ so greatly from this paper are considered formations with- in the northern and southern Sierra typical Madera lithologies that application in the Madera Group, and are recognized Ladrones, determined the thickness of the of the term Madera Group to them is not widely in central New Mexico, from the Gray Mesa Limestone to range from recommended. The Desmoinesian Porve- Nacimiento and Jemez Mountains on the approximately 215 m to 250 m (700–820 ft), nir Formation (see below) consists of dom- north, to the Caballo and Robledo and its composition to be between 70% and inantly clastic facies (even in the most car- Mountains on the south, along the western 88% marine limestones, 4–23% shale/silt- bonate-rich sections, limestones—general- platform margin of the Orogrande Basin. stone, and 4–7% sandstone/conglomerate. ly noncherty—are less than 50% of the total The transitional Pennsylvanian–Permian The highest proportion of fine to coarse thickness), in contrast to the uniform, mas- strata at the top of the Madera Group, siliciclastics (30%) is in the southernmost sive, cherty limestone beds of the lower including the Bursum Formation and section (southern Sierra Ladrones). The part of the Madera Group. The late Bursum-equivalent strata, whether named age of the Gray Mesa Limestone, based on Desmoinesian to Virgilian Alamitos For- or not, are not covered in detail here; a detailed fusulinid biostratigraphy (Martin, mation consists predominantly of nonma- future paper will describe and correlate 1971), ranges from at or just above the rine arkosic sandstones and conglomer- these strata and consider their nomencla- Atokan–Desmoinesian boundary to the ates, shale, and minor marine limestones, ture. end of the Desmoinesian. The Desmoi- quite different from the alternating marine nesian–Missourian boundary corresponds limestones and shales, with minimal Lucero uplift–Sierra Ladrones in all sections to an abrupt change in lithol- coarse clastics, that characterize the upper ogy from massive limestone beds to a thick part of typical Madera sequences. Kelley and Wood (1946) recognized the shale sequence at the base of the overlying Similarly, rapid subsidence and filling of Sandia and Madera Formations within the Atrasado Formation. the central Orogrande Basin in the Magdalena Group in the Lucero uplift– Kelley and Wood (1946) characterized Missourian and Virgilian produced an Sierra Ladrones region and named (in the Atrasado Formation as consisting of abnormally thick (1,000 m; 3,280 ft) ascending order) the Gray Mesa, Atrasado, thin- to thick-bedded, gray limestone, gray Panther Seep sequence that consists main- and Red Tanks Members within the and reddish shales, and red to light red- ly (74%) of coarse to fine siliciclastics Madera. Thickness of the Madera ranges dish-brown and gray conglomeratic sand- (Schoderbek, 1994) with minor marine from approximately 525 m to 700 m (1,725– stone. The limestones in the Atrasado have limestone and some evaporite beds that 2,300 ft) from north to south along the far less chert than those of the Gray Mesa reflect mainly nonmarine deposition— Lucero uplift to the Sierra Ladrones, and Limestone. Martin's (1971) study indicated again, so different in lithology and thick- each member is lithologically distinctive, thicknesses ranging from approximately ness from typical upper Madera units that more than 100 m (325 ft) thick, and can be 225 m (740 ft) on the north to possibly as Madera Group terminology is clearly inap- mapped at a scale of 1:63,000 (Kelley and much as 450 m (1,475 ft) in the southern propriate. Wood, 1946). These members meet all the Sierra Ladrones. Martin (1971), using Within the general succession of typical requirements of formation-rank units. The series divisions within the Madera, did not Madera strata defined above, lateral varia- term Magdalena Group is herein aban- indicate the division between the Atrasado tions in deposition reflect different envi- doned in the Lucero uplift area, for reasons and Red Tanks Formations in his strati- ronments, distance from land masses, and noted above, and the Madera is raised to graphic analysis, and in the southern short-term transgressive and regressive group status, with its constituent members Sierra Ladrones the boundary is not clear. sequences owing to fluctuations in tecton- as formations, as has been done in the Kottlowski (1960a) reported a similar ic and eustatic activity. Where warranted neighboring Manzano–Manzanita and Los thickness of approximately 420 m (1,375 ft) by considerable differences in lithology, Pinos Mountains (Myers, 1973; Myers et for the Atrasado-equivalent (Missourian– these units may also be recognized as local al., 1986). Virgilian) sequence, and Siemers (1983) formations, but normally recognition as The formations of the Madera Group in reported 455 m (approximately 1,500 ft) for members of more broadly defined forma- the Lucero uplift area are important, as this sequence in the Sierra Ladrones. The tions is recommended. Member-level they are each well exposed and their Atrasado consists of a cyclic sequence of

November 2001 NEW MEXICO GEOLOGY 109 from 15 to more than 20 thin-to-thick lime- along the east slope of Gray (= Aparejo) most places the top of the Sandia stone units separated by shale intervals of and Carrizo Mesas, as measured by Martin Formation is easily placed at the base of equal or greater thickness. Age ranges (1971) in sec. 14 T5N R3W and sec. 7 T6N the first massive limestone of the lower from earliest Missourian to well into, and R2W southwestward to sec. 35 T6N R3W. Madera. In the Sandia Mountains, the possibly near the end of, the Virgilian The type section for the Red Tanks thickness of the Sandia Formation ranges (Martin, 1971). The northernmost section Formation is the locality where Kelley and from approximately 15 m (50 ft) to possibly of the Atrasado (Mesa Aparejo–Mesa Wood (1946) indicated the most complete as much as 90 m (300 ft), and its age, Carrizo) includes approximately 63% of section of this unit is exposed, and where though poorly constrained, is Atokan to fine- to coarse-grained siliciclastic beds Kues and Kietzke (1976) measured a com- possibly early Desmoinesian (Kelley and and approximately 37% limestones; the plete stratigraphic section, along Carrizo Northrop, 1975). The Sandia Formation proportion of limestone increases to nearly Arroyo near the northeast end of Mesa has been recognized widely in central New 50% to the south, in the Sierra Ladrones. Carrizo (= South Mesa of Kelley and Mexico, from the southeastern Sangre de 1 Sandstone and conglomerate beds are very Wood), around the center of SW ⁄4 sec. 6 Cristo Mountains (Baltz and Myers, 1984, minor (typically approximately 2–3% in all T6N R2W. All of these localities are in 1999) on the north to the Mud Springs sections), and shale units, mostly gray to Valencia County. Mountains (Maxwell and Oakman, 1986) greenish gray in the Missourian part of the To complete this summary of Pennsyl- on the south. formation, display more varied coloration vanian strata in the Lucero uplift area, the In the Sandia Mountains, Kelley and (yellow, purple, red) in the Virgilian por- Sandia Formation is conformably present Northrop (1975) treated the Madera, which tion. below the Madera Group, resting uncon- is 400+ m (1,300+ ft) thick, as a formation The Red Tanks Formation, as thick as formably on Mississippian limestones. It is in the Magdalena Group, using the infor- approximately 135 m (440 ft; Kues and composed of mainly shale and sandstone, mal lower “gray limestone” and upper Kietzke, 1976) consists mainly of green, and thickens southward from approxi- “arkosic limestone” member names. Lucas red, reddish-brown, and gray shales (the mately 46 m (150 ft) at Mesa Aparejo to et al. (1999a, b) provisionally extended the latter locally carbonaceous with a thin coal approximately 150 m (500 ft) in the south- names Los Moyos Limestone and Wild seam), and subordinate gray marine lime- ern Sierra Ladrones. Sandstones and con- Cow Formation from the Manzano stone beds and sandstones, both essential- glomerate, primarily quartz arenites, rep- Mountains into the Sandias, implicitly ly restricted to the lower 60% of the forma- resent approximately 72% of the total abandoning the Magdalena Group and tion. Kelley and Wood (1946) and Sandia Formation to the north but dwindle raising Madera to group rank. As suggest- Armstrong et al. (1979) believed the Red to 12% in the south. In contrast, dark, often ed elsewhere in this paper, the Lucero Tanks to be of Late Pennsylvanian age, but carbonaceous shales represent 11% of the uplift names Gray Mesa, instead of Los later work on its prolific and varied fauna total thickness to the north but increase to Moyos, and Atrasado, instead of Wild and flora (e.g., Tidwell et al., 1999, and ref- 83% in the south. Marine limestones are Cow, may be more appropriate names for erences therein) suggest that most of the limited to between one and a few thin beds these units, based on similarity of lithology formation is Wolfcampian. The Red Tanks and total no more than 17% of the forma- and priority, in the Manzano as well as the is therefore coeval with, although litholog- tion thickness at any locality. Fusulinid Sandia Mountains. A retreat to the old ically distinct from, the upper unit of the biostratigraphy (Martin, 1971) indicates an informal members of a Madera Formation Madera Group (Bursum Formation) to the Atokan to earliest Desmoinesian age for in recent mapping in the Sandia and east. the Sandia Formation at most localities in Manzano Mountains (e.g., Ferguson et al., Kelley and Wood (1946) did not desig- the Lucero uplift area. 1996; Read et al., 1998, 1999) is based nate type sections for the three members of apparently on the perception that formal the Madera they defined, and the names Sandia Mountains lithostratigraphic units cannot be recog- Gray Mesa and Atrasado (from Atrasado nized if the boundaries between them are Arroyo) were based on geographic fea- The first two formation names (Sandia, gradational, and that the named lithostra- tures indicated on their map, which were Madera) in current usage that were tigraphic units in the Manzano Mountains later replaced by the names Mesa Aparejo applied to Pennsylvanian strata in New are based on fusulinid biostratigraphy. and Arroyo Alamitos on U.S. Geological Mexico were based on rocks in the Sandia Both are erroneous misconceptions, and Survey topographic maps. A name change, Mountains. Herrick (1900) and Herrick the informal Pennsylvanian stratigraphic or even the disappearance of a geographic and Bendrat (1900) established the “Sandia divisions of these workers are rejected. feature, is not a basis for abandoning a series” for a 46-m-thick (250-ft-thick) Further work is needed in order to estab- lithostratigraphic name that was based on sequence of shales, sandstones, and con- lish the boundaries between the Los the feature (see NACSN, 1983, pp. glomerate above Proterozoic granite in the Moyos (or Gray Mesa) and Wild Cow (or 852–853), so Gray Mesa and Atrasado, Sandia Mountains, and Gordon (1907) Atrasado) Formations in the Sandia which have been used in the Lucero uplift adopted Herrick’s name for the lower part Mountains. Read et al. (1944) for example, area for more than a half century, are con- of his Magdalena Group. Kelley and assigned only the lower 39% and 34% of sidered valid names. Later workers (e.g., Northrop (1975) summarized the subse- two measured Madera sections (Monte Bates, 1947; Jicha and Lochman-Balk, 1958) quent development of the concept of the Largo and Tejano Canyon) to the lower indicated Gray Mesa (Mesa Aparejo) as the Sandia Formation in the Sandia and neigh- “gray limestone” member, whereas Kelley type section for the Gray Mesa Member, boring ranges, including eventual recogni- and Northrop (1975, p. 125), in their indicated tributaries of Red Tanks Arroyo tion of a basal, intermittent, thin lower car- Montezuma Ridge reference section, as the type locality for the Red Tanks bonate sequence as Mississippian in age. included 239 m (783 ft) of the total 386 m Member, and stated that no type section In the Sandia Mountains, the Sandia (1,267 ft; = 62%) thickness of the Madera in for the Atrasado had been designated. Formation consists of (in order of abun- the lower member, despite their assertion However, this information was apparently dance) sandstone, shale, limestone, con- (p. 34) that the lower member constitutes based on the assumption that type sections glomerate, and siltstone. Although lateral only 40–45% of the total Madera thickness. must be at the localities that were the facies changes are pronounced, clastics In addition, their probable boundary sources of the names for particular units, always dominate, and in some sections between the lower and upper members which, of course, is not necessarily true. limestone beds are very sparse. The shale was placed at the base of a 38-m-thick (126- Here, the type section for the Gray Mesa is black, gray, or olive and has local coal ft-thick) sequence of blue-gray, cherty Limestone and Atrasado Formations is seams and plant fossils. Contact with the limestones, which would appear lithologi- considered to be the sequence exposed overlying Madera is gradational, but in cally to be better placed in the lower mem-

110 NEW MEXICO GEOLOGY November 2001 ber. Such great variation in the thickness of to black calcareous shale, and thin- to the “upper arkosic limestone member” of the two Madera units is less likely a result thick-bedded calcarenite that is locally the Madera Formation. of lateral depositional variation over short cherty” (Myers, 1982, p. 236). The three The relationship between the late distances than due to inconsistent defini- members of the Wild Cow defined by Virgilian–early Wolfcampian La Casa tion of the two units. The Red Tanks and Myers (1973) are of similar thickness, and Member of the Wild Cow Formation plus Bursum Formations have not been rec- each includes sandstone, conglomerate, Bursum Formation in the Manzano ognized in the Sandia Mountains, but a shale, and limestone beds that vary lateral- Mountains and the Red Tanks Formation transitional sequence of predominantly ly lithologically from north to south to a in the Lucero uplift is less certain and cur- nonmarine siliciclastic sediments (noted considerable degree. There do not appear rently under study. by Kelley and Northrop, 1975, p. 30), of to be any consistent lithologic characteris- varying thickness, is present at the top of tics of any of these members that distin- Socorro County the Madera Group, immediately below the guish them from each other. In the Abo Formation. This transitional sequence Manzanita Mountains, the Pine Shadow Siemers (1983) studied the Pennsylvanian is thin in the Placitas area (Lucas et al., Member includes a deltaic sequence, strata of uplifts in Socorro County, includ- 1999b) but is much thicker to the southeast, exposed in Kinney quarry, which contains ing the Magdalena, Lemitar, southeast San where it is currently under study. a remarkable mainly nonmarine fauna and Mateo, and northern Oscura Mountains, The member names of the Wild Cow flora that is documented in a book-length Sierra Ladrones, Joyita Hills, Little San Formation established by Myers (1973) in volume (Zidek, 1992). Pasqual Mountain, and the Cerros de the Manzano and Manzanita Mountains The Madera section in the Man- Amado. He used the lithostratigraphic are explicitly not extended to the Sandias zano–Manzanita Mountains is quite simi- units of earlier workers—Sandia Forma- at the present time, as more detailed strati- lar to that in the Lucero uplift, only 60–70 tion and Madera Limestone within the graphic study is required to evaluate their km (37–43 mi) to the west, and it is unfor- Magdalena Group, with lower “gray lime- presence or absence there. tunate that Myers coined new names for stone” and upper “arkosic limestone” the formation-rank units in the Manzanos members in the Madera—but analyzed Manzano–Manzanita Mountains without detailed comparison with the pre- characteristics of the strata for the Atokan viously named equivalent units in the through Virgilian Series within the Read and Wood (1947) continued Gordon’s Lucero uplift. With little doubt, the Los Pennsylvanian sequence. (1907) division of the Pennsylvanian in the Moyos Limestone in the Manzano In this region, the Sandia Formation Manzano Mountains into the Sandia and Mountains is the same formation as the (Atokan) is predominantly gray, green, Madera Formations of the Magdalena Gray Mesa in the Lucero uplift. The and brown, fine-grained, terrigenous sedi- Group, and they divided the Madera into descriptions of the overlying Missourian– ments. Sandstones increase in amount to lower “gray limestone” and upper Virgilian Atrasado Formation provided by the east, and carbonates increase to the “arkosic limestone” members. Myers Kelley and Wood (1946) and Martin (1971) south. The Sandia attains a greater thick- (1973), based on extensive mapping in the suggest that it is the same unit described ness in this area than elsewhere, typically range, raised the Madera to group rank, by Myers (1973) as the Wild Cow Forma- more than 100 m (325 ft) and as much as named the lower member the Los Moyos tion in the Manzano–Manzanita Moun- 211 m (692 ft) in the Cerros de Amado, east Limestone, and named the upper member tains. Detailed comparison between the of Socorro. the Wild Cow Formation, and he included Atrasado and Wild Cow Formations, in The lower “gray limestone” member of the Bursum Formation as the upper unit of terms of fine-scale vertical and lateral dis- the Madera is Desmoinesian in age, the Madera Group. Three named members tribution of lithologies and facies, would although beginning in the late Atokan and of the Wild Cow Formation, in ascending be worthwhile. It is clear that the Wild extending into the earliest Missourian in order, Sol se Mete, Pine Shadow, and La Cow Formation is characterized by signifi- some places; thickness ranges from Casa Members, were also established and cant lithologic heterogeneity as a sequence approximately 115 m to 250 m (approxi- mapped. The ages of all of these units are of interbedded limestone, sandstone, silt- mately 375–825 ft). The upper “arkosic well constrained by fusulinid biostratigra- stone, shale, and conglomerate, the relative limestone” member, essentially the Mis- phy (Myers, 1988a, b). proportions of these lithologies varying sourian–Virgilian part of the Madera, is In the Manzanos, the Sandia Formation laterally and vertically. The Atrasado typically approximately 180 m (600 ft) or ranges from 15 m to 92 m (50–300 ft) in Formation has a similar heterogeneous less in thickness but reaches 455 m (1,500 thickness; is Atokan in age; and consists of lithology, although local facies differences ft) in the Sierra Ladrones. As is the case in a basal conglomeratic sandstone overlain are present. Both formations occupy the other regions, Desmoinesian strata are pre- by gray to brown sandstones, dark-gray to same position in the Pennsylvanian strati- dominantly gray, thick-bedded, cherty brownish-gray, locally carbonaceous and graphic succession, both are of Mis- limestone units. Missourian and Virgilian plant-bearing shales, and thin, gray marine sourian–Virgilian age, are geographically strata are also chiefly limestones (averag- limestones, which are more common near closely spaced, and possess extreme litho- ing 59% and 67% of total thickness, respec- the top (Myers, 1982). Within the Madera logic heterogeneity of the same general tively; Siemers, 1983, table 2). They become Group, the Los Moyos Limestone is 180 m kind, “which in itself may constitute a progressively more thinly bedded upsec- (approximately 600 ft) thick; is early form of unity when compared to the adja- tion, and the proportion of shale and sand- Desmoinesian to earliest Missourian in cent rock units” (North American Code of stone beds in the upper Madera is about age; gradationally overlies the Sandia Stratigraphic Nomenclature, 1983, p. 858). twice that in the Desmoinesian sequence. Formation; and is predominantly gray, The latter point is emphasized by the code Siemers (1983) noted that in the Mis- highly cherty limestone, calcarenitic in as one of the bases on which formations sourian–Virgilian, limestones increase in parts of the sequence, with much thinner may be recognized. It is difficult to escape abundance and terrigenous grains become interbeds of sandstone, siltstone, shale, the conclusion that strata very similar to finer from east to west across the Socorro and conglomerate. The overlying Wild the unit named the Atrasado Formation in area, indicating derivation of siliciclastic Cow Formation is 225–275 m (approxi- the Lucero uplift are present in the material mainly from the Pedernal uplift, mately 750–900 ft) thick; is early Manzano Mountains (where they have the local Joyita uplift being a minor source Missourian to earliest Wolfcampian in age; been called the Wild Cow Formation), as of sediments. and “consists of alternating sequences of well as in the Sandia Mountains, the uplifts The Pennsylvanian strata of Socorro arkosic sandstone, sandstone, conglomer- of Socorro County, and elsewhere where County fit into the revised lithostrati- ate, gray to yellow siltstone and shale, gray they have been recognized informally as graphic nomenclature advocated in this

November 2001 NEW MEXICO GEOLOGY 111 paper—Sandia Formation overlain by the onlap relationships upon earlier sedimen- Mesa and Atrasado Formations, and those Madera, raised to group rank, and the tary and Precambrian rocks. The most names are here extended to the Madera Magdalena Group abandoned. Kelley and complete and well-exposed Madera sec- sequence in the Nacimiento/Jemez Wood (1946) mapped their Gray Mesa and tion in the Nacimiento Mountains is in Mountains. Equivalence of the uppermost Atrasado Members into the Sierra Guadalupe Box, where it totals 232 m (760 part of the Madera Group in this area to Ladrones of north-central Socorro County, ft) in thickness (DuChene, 1974; Wood- the transitional Madera/Abo formations and their names, as formations within the ward, 1987). Here, as in other sections, the recognized farther south (Red Tanks and Madera Group, are appropriate for the lower “gray limestone” member is much Bursum Formations) remains to be demon- lower “gray limestone” and upper thinner (38 m [125 ft]) than the upper strated; if present, this interval is both thin- “arkosic limestone” members used by “arkosic limestone” member. Ages of the ner and older (middle Virgilian) than is the Siemers (1983) and earlier workers. two Madera units are not well constrained, case with these units farther south, closer Tidwell et al. (2000) and Lucas and Estep but the lower member appears to be late to their type areas. (2000) have extended Gray Mesa–Atrasado Atokan to middle Desmoinesian (Read terminology eastward across the Rio and Wood, 1947), and the upper member Sangre de Cristo Mountains Grande into the Cerros de Amado area. It middle Desmoinesian to middle Virgilian is also of interest that Rejas (1965) used (Woodward, 1987). The Pennsylvanian of the Sangre de Cristo Thompson’s (1942) stratigraphic terminol- The lithology of the lower member of Mountains was observed and described by ogy in the Cerros de Amado area, and the Madera is predominantly dense, gray, early workers on New Mexico geology Kottlowski (written comm., 2000) noted cherty limestones intercalated with thinner (e.g., Marcou, 1858; Stevenson, 1881). that Thompson’s Missourian and Virgilian intervals of arkosic sandstone and gray Reconnaissance mapping (e.g., Read et al., formations are traceable from the Sierra shale, although in some localities (Wood 1944; Northrop et al., 1946) led to extension Oscura to the Cerros de Amado, Sierra and Northrop, 1946) chert is nearly absent. of the Sandia and Madera Formation Ladrones, and Mesa Sarca. Thompson’s The upper “arkosic limestone” member is names (and Magdalena Group), and of the formation names might well be used in a cyclic sequence (Yancey et al., 1991; “lower gray limestone” and “upper these areas as members of the Atrasado Swenson, 1996) of arkosic limestone, arkosic limestone” members of the Madera Formation. Although not discussed by arkose, and shale, with siliciclastics becom- (Read and Wood, 1947; Brill, 1952) into the Siemers (1983), the type section of the early ing more abundant and variably colored, Sangre de Cristos. Sutherland (1963), how- Wolfcampian Bursum Formation is also in and limestones less abundant near the top ever, did not recognize a distinct lithologic Socorro County (Lucas et al., 2000), and (Woodward, 1987). break between rocks equivalent to the here it is considered the uppermost forma- Sutherland and Harlow (1967) defined Sandia and Madera Formations along the tion of the Madera Group in areas where it in San Diego Canyon a thin (9–12 m [30–40 west side of the range; instead, the only can be differentiated from the Red Tanks ft]), red shale unit near the top of the major lithologic break he observed was Formation of the Lucero uplift region. Madera as the Jemez Springs Shale between the “lower” and “upper” mem- Member, although not including in it an bers of the Madera. Accordingly, the terms Nacimiento and Jemez Mountains overlying marine limestone (1–2 m [3–7 ft] Magdalena, Sandia, and Madera were not thick) at the top of the Madera sequence in used by Sutherland in this area. He named Wood and Northrop (1946), who mapped this area. The interval called the Jemez a Morrowan–Desmoinesian unit (La Pasa- this area, recognized the Sandia Forma- Springs Shale is part of a Missourian– da Formation, type section at Dalton Bluff, tion, consisting of a “lower limestone” and Virgilian sequence at least 80 m (260 ft) north of Pecos) that is equivalent to the “upper clastic” members, and the Madera thick (Kues, 1996), in which marine lime- strata of the Sandia and “lower gray lime- Formation, composed of lower “gray lime- stones predominate over marine shales in stone” member of the Madera of previous stone” and upper “arkosic limestone” the Missourian part but nonmarine to workers, and he named the “upper arkosic members within the Magdalena Group. marine, gray, red, brown, and purple limestone” member the Alamitos For- Subsequent work revealed the “lower shales are collectively thicker than marine mation (type section north of Pecos). limestone” member of the Sandia For- limestone ledges in the Virgilian. Good The La Pasada Formation ( 297 m [973 ft] mation to be Mississippian (it is now the fusulinid and macroinvertebrate data thick at its type section) is primarily clastic Arroyo Peñasco Group, e.g., Armstrong place the age of the top of the Madera as in its lower (Morrowan) part (limestone = and Mamet, 1974). The lower part of the middle Virgilian, with Abo red beds con- 27%, shale/siltstone = 50%, sandstone/ “upper clastic” member was separated as formably overlying the Madera. Although conglomerate = 23%), but carbonates the 20-m-thick (66-ft-thick) Osha Canyon the Madera is relatively thin in the increase upsection, so that in the Des- Formation (DuChene et al., 1977), which Nacimiento and Jemez Mountains com- moinesian part, the (upper 178 m [584 ft] of consists of bioclastic limestones and gray pared with other areas, Woodward (1987, the La Pasada), the ratio of major rock to tan shales of Morrowan age, and may be fig. 5) noted thicknesses as great as 540 m types is: limestone = 67%, shale/siltstone = an erosional western remnant of the La (1,775 ft) along the north side of San Pedro 24%, sandstone/conglomerate = 9%. Very Pasada Formation of the southwestern Mountain, just north of the Nacimientos. little chert is present in the limestones, Sangre de Cristo Mountains. The remain- In the Nacimiento–Jemez Mountains which thus differ from Desmoinesian lime- ing upper strata of the Sandia Formation area, the term Magdalena Group is aban- stone units farther south. The late Des- are Atokan in age, as much as 70 m (230 ft) doned here, and the Madera is considered moinesian–Virgilian Alamitos Formation, thick, and consist mainly of a basal, brown a group consisting of two formations. approximately 390 m (1,275 ft) thick at its quartz sandstone unit, overlain by slope- Madera sedimentation and lithologies type locality, is a heterogeneous assem- forming, green, gray, and yellow shales were influenced by local uplift of the blage of complexly interbedded fine to and sandstones, and ledges of subordinate Peñasco axis, an elongate island that exist- coarse clastics with subsidiary limestones. gray marine limestones (Woodward, 1987). ed during the Pennsylvanian at the Northward from the type section, the La Woodward (1987) used the terminology approximate location of the present Pasada thickens and changes laterally into of Wood and Northrop (1946) in describing Nacimiento Mountains (Woodward, 1987). an almost entirely marine and nonmarine the Madera in the Nacimiento Mountains. Lithologies, thickness, and durations of the clastics-dominated unit, which Sutherland Although widely exposed in the Naci- two Madera formations therefore differ to named the Flechado Formation (type local- miento and Jemez Mountains, the thick- a modest degree from that of the Madera ity northwest of Tres Ritos; thickness 762 m ness of the Madera varies considerably Group to the south, but overall their gen- [2,500 ft]). The Alamitos also thickens to because of faulting and locally differing eral features broadly resemble the Gray the north of its type locality, to 1,220 m

112 NEW MEXICO GEOLOGY November 2001 (4,000 ft), but its age is constricted to the Sangre de Cristo Formation, and Baltz and Series”) is of latest Morrowan age; that the middle–late Desmoinesian, owing to earli- Myers (1999, p. 96) noted some marine Red House extends through the Atokan; er onset of influx of red continental clastics limestones a little above the top of the that the Nakaye is of early to late Des- of the Sangre de Cristo Formation from the Alamitos as defined by Sutherland (1963) moinesian age; and that the Bar B is of late nearby Uncompahgre uplift as the Taos in its type area. Desmoinesian, Missourian, and possibly trough became filled with sediments. Although there might be a tendency to earliest Wolfcampian age, with the Vir- In the southeastern part of the Sangre de expect a unified nomenclature for Pennsyl- gilian missing because of an unconformity Cristos, detailed mapping and stratigraph- vanian strata in the Sangre de Cristos, the (Seager and Mack, 1991; Mack et al., 1998). ic work by Baltz and Myers (1984, 1999) nomenclatures of both Sutherland (1963) Lithologically, the Red House consists led to a different classification of the and Baltz and Myers (1984, 1999) are based predominantly of thin-bedded, gray lime- Pennsylvanian sequence. They recognized on detailed stratigraphic studies, and each stone beds (64% of total thickness in the a clastic-dominated Sandia Formation that set of formational stratigraphic names is Derry Hills; Seager and Mack, 1991), spanned Morrowan and Atokan time and appropriate to studies of the lithologic interbedded with thin, gray shale units thickened northward from approximately sequences in the areas in which they have and brown to green siltstone. The Nakaye 10 m (33 ft) near Bernal to more than 1,525 been applied. As noted earlier, it is recom- is mainly thick, massive, gray, cherty lime- m (5,000 ft) east of Mora, paralleling the mended that the term Madera Group not stone, becoming somewhat thinner bed- northward thickening of the Morrowan– be used in the Sangre de Cristo Mountains. ded toward the top, and having minor Atokan lower part of the La Pasada/Fle- The nature of the Pennsylvanian sequence amounts of gray shale. The Bar B consists chado Formations to the west, but contain- in the Sangre de Cristos, strongly influ- chiefly of thin-bedded limestone separated ing fewer carbonates than the equivalent enced as it is by proximity to the by thicker intervals of gray shale (shale is part of the La Pasada Formation. The Uncompahgre land mass and rapidly sub- approximately 80% of the total thickness). Madera, above the Sandia Formation, was siding Taos trough and other local basins, The uppermost 15 m (50 ft) of the Bar B is raised to group status, containing the is unlike that of any other part of New composed of reddish-brown siltstone, Porvenir Formation, a new name for strata Mexico, and the formational nomencla- limestone conglomerate, and sandstone formerly mapped as “lower gray lime- ture, with the exception of use of the beds beneath the overlying Abo red beds, stone” member, overlain by the Alamitos Sandia Formation, is likewise restricted to and appears to be Bursum-equivalent stra- Formation. The Porvenir Formation this part of north-central New Mexico. ta. Curiously, although Kelley and Silver (Desmoinesian) is 325 m (1,065 ft) thick at Even the Sandia Formation, recognized by (1952, p. 89) strongly criticized Thomp- its type locality west of Gallinas and Baltz and Myers (1984, 1999) in the south- son’s (1942) units in this area as being, increases in thickness northward to a max- eastern Sangre de Cristos on lithologic among other things, “scarcely mappable,” imum of almost 500 m (1,640 ft). It is repre- grounds, differs from Sandia deposits to they did not map the three formations they sented by a carbonate facies (with signifi- the south in attaining a much greater thick- recognized either; nor did Seager and cant shale) through most of its distribution ness and spanning Morrowan and Atokan Mack (1991, 1998) in the Derry Hills and in the southeastern Sangre de Cristos, by a time. The study by Baltz and Myers (1999) Nakaye and Red House Mountain areas. sandstone-shale-limestone facies to the represents the most detailed and compre- Doubt has been expressed as to the validi- north, and by a shaly facies to the north- hensive examination and synthesis of ty of Kelley and Silver’s formations as car- west (Baltz and Myers, 1999). All three Pennsylvanian stratigraphy yet completed tographic units (Gehrig, 1958, p. 6; facies contain considerable shale, sand- in any part of New Mexico, and stands as a Bachman and Myers, 1975, p. 108). stone, and conglomerate beds; limestone model for future studies in other parts of The Red House Formation, although represents less than 50% of the total the state. temporally closely correlative with the Porvenir stratigraphic thickness even in Sandia Formation, is lithologically distinct the carbonate facies of the type section. Caballo Mountains in its high abundance of limestone beds. The carbonate facies of the Porvenir is lat- The Nakaye Formation is not significantly erally equivalent to the carbonate-rich Current nomenclature for the Pennsyl- different lithologically from the wide- Desmoinesian upper part of the La Pasada vanian of the Caballo Mountains and spread, massive, cherty, cliff-forming lime- Formation to the west, and the shaly facies neighboring small uplifts such as the stone unit of Desmoinesian age that crops of the Porvenir in the northwest part of its Derry Hills is that of Kelley and Silver out throughout central New Mexico, and outcrop belt grades westward into the (1952). They assigned the Pennsylvanian which should be designated with a single upper part of Sutherland’s Flechado section to the Magdalena Group, divided name, which here is recommended to be Formation. into, in ascending order: the Red House Gray Mesa Limestone. Although proposed The Alamitos Formation in the south- (110 m [362 ft] thick at the type section), by the same worker (V. C. Kelley) who eastern Sangre de Cristos is similar in its Nakaye (128 m [419 ft] thick), and Bar B coined the name Gray Mesa in the Lucero lithologic heterogeneity and dominance of (103 m [339 ft] thick) Formations. Although uplift, Nakaye Formation is a good exam- clastic strata to the formation in the west- no age data were provided for these for- ple of a redundant, unnecessary strati- ern Sangre de Cristos; in both areas are fos- mations, Kelley and Silver (1952, fig. 11) graphic name. siliferous limestones near the top and bot- correlated the Red House with the Sandia The Bar B Formation generally resem- tom that allow accurate dating of its upper and lower part of the “lower gray lime- bles that unit earlier called “arkosic lime- and lower boundaries. To the west, the stone” member of the Madera in central stone” member of the Madera in central Alamitos ranges from late Desmoinesian New Mexico; the Nakaye with most of the New Mexico, albeit with more shale and a to Virgilian in the southern part of its out- “lower gray limestone” member and basal smaller proportion of limestone than typi- crop, but is restricted to middle and late “arkosic limestone” member; and the Bar B cally is present in that unit in some other Desmoinesian to the north (Sutherland with most of the “arkosic limestone” mem- areas. Tentatively, the name Bar B is 1963; Sutherland and Harlow, 1973). In the ber and the Bursum Formation. Later stud- retained, but further work may demon- southeastern Sangre de Cristos, the forma- ies of these units in the Derry Hills, includ- strate that Atrasado and Bursum are more tion ranges from late Desmoinesian to ear- ing data based on fusulinids, conodonts, appropriate terms for this unit. Use of the liest Wolfcampian, based on fusulinids and brachiopods (Clopine, 1991, 1992; term Magdalena Group is unnecessary for (Baltz and Myers, 1999). In both areas, red, Clopine et al., 1991; Sutherland, 1991; this sequence of Pennsylvanian strata in green, and purple clastic units and thin Kaiser and Manger, 1991), indicate that the the Caballo Mountains. The upper two of marine limestones are present within a base of the Red House Formation (and the Kelley and Silver’s (1952) formations transition zone into the basal nonmarine base of Thompson’s, 1942, “Derryan accord well with the concept of the Madera

November 2001 NEW MEXICO GEOLOGY 113 Group farther north, and it is recommend- Oakman, 1986) stating that it had not been Mountains to the south, recognizing the ed that this term be applied in the reviewed for conformity with U.S. Geo- Red House, Nakaye, and Bar B Formations Caballos. As noted below, Madera termi- logical Survey stratigraphic nomenclature within the Magdalena Group, which nology has been employed in the Cuchillo perhaps explains the changes in nomencla- encompasses the entire Pennsylvanian sec- and Mud Springs Mountains a short dis- ture introduced on the final map. tion. Unfortunately, too little detailed tance to the northwest. The contrasting nomenclature used by stratigraphic information on these units is Maxwell and Oakman (1986, 1990) illus- provided to allow comparison with other Mud Springs Mountains trates the similarities of the central New Pennsylvanian sequences in the region. An Mexico Madera sequence to that of the earlier study (Cserna, 1956), summarized Kelley and Silver (1952) simply mapped Caballos, with its local stratigraphic termi- by Kottlowski (1960a), described three the Pennsylvanian of the southern Mud nology, and the application of different Pennsylvanian units: 1) a lower shaly Springs Mountains as Magdalena Group, nomenclatural philosophies to the Mud member (81 m [266 ft] thick), 2) a medial and Kottlowski (1960a) gave brief litholog- Springs Mountains Pennsylvanian cherty limestone member (331 m [1,087 ft] ic and thickness information for the sequence. As in the Caballo Mountains, it thick), and 3) an upper shaly member (81 Atokan through Virgilian divisions of the seems clear to me that the unit called m [266 ft] thick) having a thin (6-m [20-ft]) sequence. Earlier (see above), Thompson Nakaye is the Gray Mesa, and that the transition zone of purplish limestone and (1942) used the excellent section in Gray Mesa–Bar B–Bursum sequence of the shale grading into the overlying Abo Whiskey Canyon as type and reference Mud Springs Mountains represents the Formation. The lithology of these units sections for his Atokan and Desmoinesian Madera Group. Similarly, use of the term suggests the presence of the Sandia groups and formations, and Gehrig (1958) Magdalena Group should be discontinued Formation at the base, overlain by the provided a detailed stratigraphic section of in this range, as Maxwell and Oakman “lower gray limestone” (= Gray Mesa Thompson’s Desmoinesian units (Armen- (1986) implicitly suggested. Possibly some Limestone) and “upper arkosic limestone” daris and overlying Bolander Groups, with of Thompson's (1942) lithostratigraphic (probably the Atrasado Formation) of the included formations), totaling 216 m (709 names might be useful as member names Madera Group. ft) in Whiskey Canyon. Strata of Mis- in the Mud Springs Mountains. Fusulinid biostratigraphy (Verville et al., sourian and Virgilian age in the Mud 1986) in a section south of Cserna’s more Springs Mountains attain thicknesses of 98 Cuchillo Mountains complete section records only 10 m (33 ft) m (320 ft) and 140 m (460 ft), respectively of Atokan strata; 260 m (853 ft) of (Kottlowski 1960a), and these are overlain In the Cuchillo Mountains of northwestern Desmoinesian strata, equivalent to by approximately 19 m (62 ft) of possibly Sierra County, the Pennsylvanian sequence Cserna’s medial cherty limestone unit; 60 Wolfcampian Bursum-equivalent beds. is relatively poorly exposed and has been m (197 ft) of Missourian strata, mainly Maxwell and Oakman (1986), in a pre- little studied. It was divided into the gray, medium- to thick-bedded limestones liminary map of the Mud Springs Sandia and Madera Formations (of the with less chert than the Desmoinesian Mountains, recognized a thin Sandia Magdalena Group) and as much as 67 m limestones; and 50 m (164 ft) of Virgilian Formation (46 m [150 ft] thick) only in the (220 ft) of “Magdalena transition beds” strata that grade upward into the red beds southern part of the range, overlain by a below the overlying Abo Formation by of the Abo. The stratigraphically highest thick Madera Formation (457 m [1,500 ft]), Jahns (1955) and Jahns et al. (1978). The fusulinids, a few meters below the base of consisting of three units: 1) a lower part Sandia Formation, as much as 53 m (173 ft) the Abo, are no younger than middle consisting of thin-bedded, locally cherty thick, consists principally of shale and Virgilian. limestones and considerable gray to green greenish-gray to red-brown siltstones and shale beds; 2) a middle part of mainly mas- sandstones interbedded with gray, locally Robledo Mountains sive cherty limestone; and 3) an upper part cherty, limestone ledges. Strata assigned to of thin-bedded limestones alternating with the Madera Limestone attain a thickness of The Pennsylvanian sequence exposed in gray shale and greenish to reddish shale 275–300 m (900–985 ft) and are predomi- the Robledo Mountains was deposited on and siltstone. The upper part of the nantly gray, thin-bedded to massive, often the Robledo shelf along the west side of the Madera was said to grade into the overly- cherty limestones separated by minor beds Orogrande Basin. It is unusually thin, ing, 50-m-thick (160-ft-thick) Bursum of shale and sandstone. Stratigraphic infor- especially compared with the basinal Formation, composed mainly of red, green, mation is currently insufficient to allow sequences to the east, and unusually rich and purple shales and minor sandstone subdivision of the Madera or to compare it in carbonates. Not much clastic material and limestone. in detail with Madera sections elsewhere. reached the Robledos during the In the final version of their map The “transition beds” are greenish, brown, Pennsylvanian from the Pedernal and (Maxwell and Oakman, 1990), the term or maroon clastics, interbedded with lime- Florida land masses (Kottlowski, 1960b). Madera was not used, the Pennsylvanian stone beds and some sandstone, limestone, Kottlowski (1960a, b) published a relative- units were assigned names derived from and quartzose conglomerates, similar to ly detailed stratigraphic section of Penn- the Caballo Mountains, and these units, the uppermost Madera regionally and sylvanian and early Wolfcampian strata together with the overlying Bursum For- probably in part equivalent to the lower that included Atokan (30 m [100 ft] thick), mation, were included in the Magdalena Bursum Formation to the northeast. Desmoinesian (69 m [225 ft]), Missourian Group. Specifically, the middle part of the More detailed information on this (52 m [170 ft]), and Virgilian (73 m [240 ft]) Madera of the earlier map was termed Pennsylvanian sequence would be desir- strata totaling approximately 225 m (735 ft) Nakaye Formation, the upper Madera was able. For now, the term Magdalena Group thick (Kottlowski and Seager, 1998), over- called Bar B (although the uppermost part should be abandoned, and Madera should lain by a 55-m-thick (180-ft-thick) Bursum of this unit was included in the Bursum be raised to group rank, though with for- interval. Atokan strata, thinned by partial Formation on the later map, as the thick- mations yet to be defined. assimilation in an Oligocene sill, consist of ness of the Bursum increased from 50 to 90 blackish, silty limestone and greenish-gray m [160 to 300 ft] from the earlier to later Fra Cristobal Range shale; the Desmoinesian predominantly of map), and the Sandia Formation (plus massive, cherty limestones interbedded apparently the lower part of the Madera) The most recent geological study of the Fra with minor limy shale and calcareous of the earlier map was included in the Red Cristobal Range (Nelson, 1986) uses the sandstone; the Missourian of slope-form- House Formation on the final map. A note Pennsylvanian terminology introduced by ing limestones and limy shales with sever- on the preliminary map (Maxwell and Kelley and Silver (1952) in the Caballo al ledge-forming limestones; and the

114 NEW MEXICO GEOLOGY November 2001 Virgilian chiefly of several thick, noncherty Middle Pennsylvanian strata in southern The total thickness of the Horquilla is limestone cliffs interbedded with thin-bed- New Mexico (e.g., Lead Camp Limestone approximately 1,000 m (3,280 ft), of which ded limestone and shale. The interval con- of the San Andres Mountains), and the approximately 765 m (2,500 ft) is of taining early Wolfcampian “Bursum” Syrena reflects increased siliciclastics in the Pennsylvanian age. Zeller (1965) and fusulinids (Thompson, 1954) is predomi- Upper Pennsylvanian, comparable to the Thompson and Jacka (1981) informally nantly limestone and is not similar to the Atrasado and equivalent units to the north divided the Horquilla into lower (420 m lithostratigraphic unit called Bursum and east. The unneeded term Magdalena [1,380 ft] thick; Morrowan to upper Formation to the north; Jordan (1975) did Group is abandoned here, but the names Desmoinesian) and upper (570 m [1,870 ft] not recognize the Bursum Formation in the Oswaldo and Syrena are retained as useful thick; upper Desmoinesian to Wolf- Robledos, nor have more recent workers local divisions of an incomplete Pennsyl- campian) members. The lower member is such as Krainer et al. (2000) and Wahlman vanian sequence. 90+% gray limestones with moderate chert and King (in press). To the east, near Kingston, Kuellmer beds, and the upper member is 70% lime- To date there has been little published (1954) described in detail three incomplete stone and 30% dolostone with little chert. detailed information on the Pennsylvanian sections of Pennsylvanian strata, indicat- In the Big Hatchet Mountains, these car- in the Robledo Mountains, and no litho- ing a composite thickness of approximate- bonates were deposited primarily in shal- stratigraphic names have been applied to ly 200 m (655 ft) or more, assigned to the low marine shelf environments. The shal- this sequence. The Atokan section litholog- Magdalena Limestone but not further sub- low carbonates of the upper member ically resembles the Sandia Formation, and divided. Faulting and quartz monzonite change laterally to the southwest into basi- the Desmoinesian interval is closely com- intrusions complicate interpretation of nal deposits of dark mudstones and lime- parable in lithology, if not in thickness, to these outcrops. In two sections, 15–23 m stones, reflecting onset of subsidence of the the lower Madera Group formation farther (50–75 ft) of basal, Sandia Formation-like, Pedregosa (or Alamo Hueco) Basin at a north for which the name Gray Mesa dark shales and sandstones rest uncon- faster rate than deposition occurred (e.g., Limestone is recommended. The Mis- formably on Mississippian limestone, and Greenwood et al., 1977; Thompson and sourian and Virgilian units are tentatively are overlain by as much as 20 m (65 ft) of Jacka, 1981; Wilson, 1989). Large, mainly regarded as a southern, thinner expression massive, cherty limestones similar to Late Pennsylvanian and Wolfcampian of the Atrasado Formation, although with Desmoinesian units deposited widely phylloid algal bioherms are conspicuous a higher proportion of carbonates in the across the state. The thickest section (III, of on outcrop and mark the shelf margins Virgilian part. Kuellmer, 1954) rests on a quartz mon- adjacent to the subsiding basin (e.g., Zeller, zonite intrusion and consists mainly of 1965). Deposition of the Horquilla For- Silver City, Santa Rita, and Kingston massive, gray, cherty limestones (130 m mation was very cyclic, and its cyclic stra- [425 ft]) overlain by approximately 60 m tigraphy can be correlated with midconti- areas (200 ft) of gray and brown shaly limestone, nent Pennsylvanian cyclothems (Connolly yellow shale, thin-bedded and nodular and Stanton, 1992). The incomplete, faulted, and generally limestone, and limestone-pebble conglom- Deposition and thickness of the poorly exposed Pennsylvanian sequence erate. At the base is approximately 10 m Horquilla were strongly influenced by sub- in the Silver City–Santa Rita area was ini- (33 ft) of interbedded dark shale and lime- sidence of the Pedregosa (or Alamo tially included with Mississippian and stone. The isolation of these sections from Hueco) Basin and represent an unusually Permian strata within the Fierro Formation others and the fact that fusulinid ages of long span of nearly completely carbonate (Paige, 1916). Spencer and Paige (1935) dis- these strata have not been reported com- deposition that is unlike that of the carded the term Fierro and divided the plicate correlation, but the thickest section, Pennsylvanian–Early Permian of any other Pennsylvanian section into the lower although thinner than is typical of the part of the state. It is a well-defined, litho- Oswaldo Formation (130 m [425 ft] thick) Madera, lithologically resembles the logically homogeneous, lithostratigraphic and overlying Syrena Formation (120 m Madera Group in its lower cherty lime- unit, appropriately considered to be of for- [395 ft] thick) of the Magdalena Group, stone formation and upper interbedded mation rank. The Horquilla has been because the sequence appeared lithologi- limestone and siliciclastic formation. More traced northward in New Mexico to the cally different from the Sandia and Madera detailed study and comparison with the Peloncillo Mountains, where a highly Formations used elsewhere. These forma- nearest Pennsylvanian sequences to the faulted and intruded section approximate- tions were summarized by Kottlowski east (Caballo Mountains), north (Cuchillo ly 450 m (1,475 ft) thick apparently extends (1960a) and discussed by Jones et al. (1967, Mountains), and west (Santa Rita–Silver from Atokan to Wolfcampian time 1970), Pratt (1967), and LeMone et al. City area) would increase our understand- (Gillerman, 1958; Kottlowski, 1960a). (1974), among others. The Oswaldo ing of all of these sequences. Deposition of carbonate shelf sediments Formation consists almost entirely of lime- extended continuously northeastward stone, locally cherty, with shale interbeds Southwestern New Mexico from the area of the Pedregosa Basin to the near the top and locally a shale unit at its Silver City and perhaps Robledo shelf base. The Syrena Formation includes a Pennsylvanian strata in southwestern New areas, but in those regions the Penn- basal, thick (as much as 40 m [131 ft]), dark Mexico, best exposed in the Big Hatchet sylvanian sequence is both much thinner shale or limestone unit and an upper Mountains, are assigned to the Horquilla and contains considerably more siliciclas- sequence of interbedded gray limestones Formation, which also includes units of tic beds than the Horquilla. and nodular limestones and brown, yel- Wolfcampian age (Zeller, 1965; Ross, 1979; low, and red shale. Thompson and Jacka, 1981; Drewes, 1991). San Andres Mountains LeMone et al. (1974) reported a The time represented by Horquilla deposi- Morrowan–earliest Missourian age for the tion has been reliably determined by The San Andres Mountains extend for Oswaldo, an early Missourian to Virgilian fusulinid biostratigraphy as Morrowan to nearly 140 km (85 mi) from near the Sierra age for the Syrena, and suggested that Wolfcampian, with the following series Oscura on the north to the Organ these strata were deposited on open- thicknesses reported by Thompson and Mountains on the south. Pennsylvanian marine shelf environments between those Jacka (1981) for the Big Hatchet Peak sec- strata crop out along the entire length of of extreme southwestern New Mexico and tion: Morrowan, 75 m (247 ft); Atokan, 115 the range but are most accessible in a series the Robledo shelf to the east. Lithologically m (378 ft); Desmoinesian, 305 m (1,001 ft); of canyons, which from north to south are: the Oswaldo Formation reflects the pre- Missourian, 142 m (466 ft); Virgilian, 128 m Mockingbird Gap, separating the San vailingly carbonate character of Lower and (419 ft); and Wolfcampian, 219 m (719 ft). Andres from the Oscura range, and

November 2001 NEW MEXICO GEOLOGY 115 Rhodes, Hembrillo, San Andres, Ash, and total Panther Seep thickness (Schoderbek, Franklin Mountains, New Bear Canyons. The San Andres Mountains 1994, p. 92). The age of the Panther Seep Mexico–west Texas also occupy the western side of the ranges from middle or late Missourian to Pennsylvanian–Early Permian Orogrande early Wolfcampian (Bachman and Myers, The Pennsylvanian sequence in the Frank- Basin, resulting in a thick Pennsylvanian 1969, 1975), and its lithology is quite differ- lin Mountains was first studied in detail by sequence that differs markedly, especially ent from that of any other Late Pennsyl- Nelson (1940), who assigned it to the in the Missourian and Virgilian, from that vanian sequence in the state. Rapid subsi- Magdalena Formation and divided it into of the broad, stable Robledo shelf to the dence of the Orogrande Basin during this (in ascending order) the La Tuna, Berino, west (Robledo, Caballo, Mud Springs time was matched by enormous amounts and Bishop Cap Members. Harbour (1972), Mountains and Sierra Cuchillo), and from of sediment shed from the Pedernal land in mapping the range, added an unnamed the Pennsylvanian sequence deposited mass, keeping the basin filled nearly to or upper member between the Bishop Cap along the steep, fault-bounded eastern above sea level, while glacioeustatic fluctu- and the overlying Permian Hueco margin of the basin in the Sacramento ations of sea level imprinted cyclicity on Limestone, which was later found to be the Mountains. the depositional sequences (Schoderbek, Panther Seep Formation, described initial- The definitive work on the stratigraphy 1994). ly (Kottlowski et al., 1956) in the San of the San Andres Mountains is by Kottlowski et al. (1956) recognized from Andres Mountains. Current nomenclature Kottlowski et al. (1956), with subsequent 23 m (76 ft) of Bursum Formation in (LeMone, 1982, 1992) recognizes the summaries and updates by Kottlowski Hembrillo Canyon to 81 m (287 ft) of Magdalena Group as comprising the La (1960a, 1975) and Kottlowski and LeMone Bursum in Rhodes Canyon unconformably Tuna (as much as 156 m [511 ft] thick), (1994), among others. As described by overlying the Panther Seep and underly- Berino (as much as 157 m [514 ft] thick), these authors, Atokan strata (34–105 m ing the Hueco Formation in the north part and Bishop Cap (180 m [590 ft] thick) [107–345 ft] thick) are mainly siliciclastic to of the range. Bachman and Harbour (1970) Formations, overlain by the Panther Seep the north and carbonates to the south; apparently included both Bursum and Formation (213 to possibly 376 m Desmoinesian beds (56–190 m [183–622 ft] Hueco strata in the upper part of the [700–1,235 ft] thick). These formations thinning to the south) are chiefly massive Panther Seep north of Rhodes Canyon. have been accurately dated using fusulin- to medium-bedded cherty limestones with Similarly, Kottlowski et al. (1956) reported ids and conodonts (e.g., Wilson, 1989; some clastic and calcarenitic units; and the Panther Seep in Mockingbird Gap, but Clopine et al., 1991; Clopine, 1992). Missourian strata (44–83 m [145–271 ft] Bachman (1968) referred these strata to the The La Tuna Formation (Morrowan– thinning to the south) consist of interbed- upper member of the Madera Formation. early Atokan) is predominantly cliff-form- ded argillaceous limestone and calcareous Although Madera Group terminology is ing, gray, cherty limestones with algal shale, with local massive cherty lime- not appropriate for the Lead Camp and mounds and thin lenses of shale near the stones. Bachman and Myers (1969, 1975) Panther Seep Formations through most of top. The Berino (middle Atokan–middle combined this predominantly carbonate the San Andres Mountains, these forma- Desmoinesian) consists of alternating gray sequence into the Lead Camp Limestone, tions, and the Sandia Formation below the cherty limestone and gray shale beds in which is 262 m (861 ft) thick at the type Lead Camp in the northern part of the about a 70:30 ratio. The Bishop Cap locality in San Andres Canyon in the range, grade laterally into the familiar Formation (middle Desmoinesian–early southern part of the range. They recog- Sandia/Madera Group units to the north Missourian) comprises mainly gray to nized possible Morrowan fusulinids at the and west, where deposition occurred on brown shale (65–75%) alternating with base and early Missourian fusulinids at the the more stable shelf areas along the mar- thin ledges of gray limestone. As noted top. The lower, mainly siliciclastic beds in gins of the Orogrande Basin. Similarly, the previously, this sequence differs greatly in the Atokan part of the section to the north units of the predominantly basinal Penn- its lithology from the sequences in central were assigned to the Sandia Formation, sylvanian sequence exposed in the San New Mexico to which the term Magdalena which thus grade southward into the Andres Mountains can be traced in detail Group was first applied, and therefore use mostly cherty limestones of the lower Lead through individual cycles within facies of the name Magdalena is both confusing Camp Limestone. The upper part of the and thickness changes to the narrow, tec- and inappropriate; I strongly recommend Lead Camp Limestone is lithologically tonically active shelf to the east, in the that this group name be abandoned in the similar to units named Gray Mesa and Los Sacramento Mountains (e.g., Wilson, 1967; Franklin Mountains. Moyos Formations to the west and north. Algeo et al., 1991). The Panther Seep Formation in the Above the Lead Camp Limestone is an Franklin Mountains is a poorly fossilifer- abnormally thick sequence, named the Organ Mountains ous yellow-gray shale and siltstone Panther Seep Formation by Kottlowski et sequence, with minor carbonates, several al. (1956), which thickens progressively In the northern Organ Mountains, immedi- gypsum beds near the top, and a basal, 6- southward from approximately 250 m (820 ately south of the San Andres range, the m-thick (20-ft-thick), chert-pebble con- ft) near Mockingbird Gap (Kottlowski et Lead Camp Limestone (200–265 m glomerate, marking an unconformable al., 1956) to 865 m (2,885 ft) in the Ash [650–870 ft] thick) intertongues with the contact with the underlying Bishop Cap Canyon area and 975+ m (3,200 ft) in the overlying Panther Seep Formation Formation (LeMone, 1982). Its age is mid- subsurface of the central Orogrande Basin (approximately 600 m [1,970 ft] thick). The dle Missourian to possibly earliest (Schoderbek, 1994). The Panther Seep con- lithologies of the two formations in the Wolfcampian, as it conformably underlies sists of cyclic (Schoderbek, 1994; Soreghan, Organ Mountains are not greatly different the basal limestones of the Hueco Group, 1994), brackish-water, deltaic, stream chan- from their lithologies in the San Andres which are known to be of early (but not nel and marginal marine, brown to dark- Mountains, except for several thick gyp- earliest) Wolfcampian age (Williams, 1966). gray carbonaceous shales and coarse to sum beds near the base and near the top of In the Bishop Cap Hills, approximately fine-grained sandstones, argillaceous and the Panther Seep (Seager, 1981). The upper 10 km (6 mi) north of the Franklin calcarenitic limestones, calcareous sand- 120 m (400 ft) of the Panther Seep is transi- Mountains, only the La Tuna and Berino stones, phylloid algal bioherms (near tional into the overlying lower unit of the Formations are exposed (Harbour, 1972), Rhodes and Hembrillo Canyons, see Early Permian Hueco Formation. with thicknesses of approximately 80 m Toomey, 1991; Soreghan and Giles, 1999a, (260 ft) and 150 m (500 ft), respectively b), and several gypsum beds near the top (Seager, 1973, 1981). near Ash Canyon and southward. Terrigenous clastics represent about 74% of

116 NEW MEXICO GEOLOGY November 2001 Hueco Mountains, New Mexico and stratigraphic nomenclature for the Penn- graben, the Alamo trough of Algeo et al. Texas sylvanian of the Hueco Mountains could (1991), which divided the Sacramento shelf be done with detailed stratigraphic study, into two independent tectonic blocks. The Beede (1920) first assigned the Pennsyl- dating, and correlation of units in the Gobbler sequence is very cyclic, and the vanian sequence in the Hueco Mountains northern and southern parts of the range, 20–25 independent cycles can be traced to the Magdalena Group, and King et al. and then correlation with Pennsylvanian laterally from shelf to slope to basinal (1945) divided what they called the sequences elsewhere in the region, espe- facies (Algeo et al., 1991; Algeo, 1996). Magdalena Limestone into three informal cially in the Franklin Mountains, approxi- The Beeman Formation consists mainly divisions—lower, middle, and upper. This mately 40 km (25 mi) to the west. Probably of interbedded calcareous shale and thin- nomenclature has persisted to the present the Hueco Mountains section could be bedded, locally argillaceous limestone. The (e.g., Williams, 1963; Seewald, 1968; accommodated by the formations defined lower third of the formation contains sig- Stoklosa et al., 1998). The upper part of the in the Franklin Mountains, as Wilson nificant sandstone bodies (Pray, 1961) that Magdalena sequence of these authors is (1989, p. 9, fig. 2B) suggested for the Mor- represent cyclically deposited shelf to basi- bounded by an unconformity at the base of rowan–Desmoinesian part of the sequence, nal environments (see Raatz and Simo, the Lower Permian unit (Powwow and Kottlowski (1960a) for the upper 1998, for detailed facies and sequence Conglomerate) of the overlying Hueco (“Panther Seep”) portion of the Penn- stratigraphic analysis). Basinal sequences Group, which rests on progressively older sylvanian–early Wolfcampian sequence in within the Beeman are considerably thick- beds from the north (Wolfcampian) to the the northern part of the range. Applying er and have many more parasequences south (Atokan in Powwow Canyon). the name Magdalena Limestone or Group than the shelf sequences. Thompson (1954) recognized a thin (6 m to this sequence in the Hueco Mountains is The Holder Formation consists of a wide [20 ft]) “Bursum” unit based on fusulinids inappropriate for the same reasons as in variety of sedimentary strata, primarily at the top of the Magdalena and below the the Franklin Mountains, and the name marine but increasingly brackish to non- unconformity, and Williams (1963) should be abandoned in future work. marine toward the top. Holder strata are described an additional 60-m (200-ft) of very cyclic, and the cycles can be traced Wolfcampian (“Pseudoschwagerina beds of Sacramento Mountains westward into the thicker basinal sequence the Magdalena Limestone”) along the west (Panther Seep Formation) of the Oro- side of the northern part of the range. Cys The Pennsylvanian sequence of the Sacra- grande Basin (Cline, 1959; Wilson, 1967). (1975), however, interpreted these beds as mento Mountains was divided into (in The basal Holder is characterized by large being part of the lower Hueco Group, with ascending order) the Gobbler, Beeman, and phylloid-algal bioherms as much as 23 m the Powwow Conglomerate being below, Holder Formations by Pray (1959, 1961), all (75 ft) high (e.g., Toomey et al., 1977; rather than above them. based on a continuous type section near Toomey, 1991), which grew along the shelf In the central and southern Hueco Long Ridge and Mule Canyon southeast of margin. Overlying the Holder conform- Mountains, according to Seewald (1968), Alamogordo. There, the Gobbler Forma- ably in the northern part of the Sacra- the “lower division” of the Magdalena (162 tion (?Morrowan or early Atokan–late Des- mentos is the 150-m-thick (500-ft-thick) m [530 ft] thick; Morrowan–early Atokan moinesian in age; Bachman and Myers, Laborcita Formation, initially considered in age) is composed mainly of massive, 1975; Wilson, 1989) is approximately 400 m latest Virgilian to early Wolfcampian in age gray, very cherty limestones, with abun- (1,300 ft) thick, and the Beeman (Missou- (Otte, 1959) but later determined on the dant oosparites (see also Connolly and rian–possibly early Virgilian in age; Bach- basis of fusulinid biostratigraphy to be Stanton, 1983). The “middle division” (90 man and Myers, 1975; Raatz and Simo, entirely Wolfcampian (Steiner and Willi- m [300 ft] thick; middle Atokan–middle 1998) is 120 m (400 ft) thick. The Holder ams, 1968). To the south, red beds of the Desmoinesian) is poorly exposed shale Formation (early–late Virgilian) attains a Abo Formation unconformably overlie and thin limestone beds with lithology and maximum thickness of approximately 275 each of the three Pennsylvanian forma- fauna “strikingly similar” to that of the m (900 ft) north of the type section. tions at various localities (Pray, 1961, fig. Berino Formation in the Franklin The basal 60–150 m (200–500 ft) of the 26). Mountains. The “upper division” (145 m Gobbler Formation consists of slope-form- Clearly, local paleogeography and the [480 ft] thick; late Desmoinesian–early ing quartz sandstone, gray to black shale, tectonic processes operating on it have Wolfcampian) is lithologically heteroge- and ledges of dark, cherty limestone. greatly influenced Pennsylvanian sedi- neous and characterized by cyclic sedi- Above this clastic interval, two facies of the mentary deposition in the Sacramento mentation, large algal mounds (Toomey, Gobbler are recognized: 1) a northern Mountains, resulting in a distinctive 1991), and a chiefly carbonate environ- detrital facies composed almost entirely of Pennsylvanian sedimentary sequence that ment, interrupted by thin shales and con- nonmarine to nearshore marine quartz has appropriately received unique forma- glomerates. Hardie (1958) pointed out that sandstone and shales with minor lime- tion and member names. These units have the lithology of the upper 365 m (1,200 ft) stone and 2) a cliff-forming, massive, local- become a focus for sequence stratigraphic of the Magdalena in the northern (New ly cherty marine limestone facies, named studies in the past decade, with the result Mexico) part of the Hueco Mountains is by Pray (1961) the Bug Scuffle Limestone that some of the cyclic sequences recog- considerably different from that in the Member, which is present in the northern nized here can be traced not only to the southern part of the range, consisting Sacramentos, dominates the central and west, into the axis of the Orogrande Basin, mainly of gray to grayish-red shale (50+%), southern parts of the range, and interfin- but also eastward to the midcontinent area massive gray limestone (35–40%), espe- gers with and grades into the detrital (e.g., Raatz and Simo, 1998). cially in the upper part, and lesser propor- facies. The Bug Scuffle Limestone repre- tions of limestone-pebble conglomerates, sents carbonate deposition widely across Subsurface stratigraphy and one gypsum bed as much as 23 m (75 the narrow Sacramento shelf and adjacent ft) thick near the top. Although precise slope along the east side of the Orogrande Although the emphasis in this paper is on ages for the northern sequence were not Basin. The detrital facies should be named exposed Pennsylvanian rocks, one com- available, Hardie believed most of the formally as a member of the Gobbler by ment on subsurface stratigraphic nomen- sequence to be of Virgilian and early those actively engaged in studying the for- clature in New Mexico is needed. Most Wolfcampian age, and Kottlowski (1960a) mation. It represents a wedge of terrige- reports have assigned intervals of the interpreted the sequence as “Panther Seep nous clastic sediments derived from the Pennsylvanian petroleum-bearing strata in formation” types of sediments. Pedernal land mass immediately to the eastern New Mexico to divisions such as Developing a formal, reasonable, litho- east and deposited within an intrashelf the Strawn, Canyon, and Cisco Series (e.g.,

November 2001 NEW MEXICO GEOLOGY 117 Broadhead and King, 1988). These units relation chart (Fig. 3) indicates the litho- implemented by some workers in areas are actually lithostratigraphic units stratigraphic terminology of New Mexico such as the Manzanita, Manzano, and Los (groups) composed of many formations Pennsylvanian strata advocated in this Pinos Mountains. with their type sections in north-central paper. In some areas, detailed studies of 3) Units previously regarded as mem- Texas and should not be used as chrono- the Pennsylvanian sequences are needed bers within the Madera Formation should stratigraphic units (series). According to to test the validity of the proposed nomen- be treated as formations, as they have all of Kier et al. (1979, p. S5) there was an clature. the attributes of formations as outlined in attempt in the 1940s to redefine these The paleogeography and tectonic histo- the present Code of Stratigraphic Nomen- groups as series to facilitate subsurface ry of New Mexico during the Pennsyl- clature. This especially applies to the infor- correlation between basins, but “…several vanian Period were complex. Although mal “lower gray limestone” and “upper attempts have been made to apply [this] deposition was mainly in shallow marine arkosic limestone” member names widely classification in the field” and “…such environments across much of the state dur- used beginning in the 1940s and continu- applications have proven difficult, if not ing all but the earliest (Morrowan) part of ing today in many parts of central New entirely inappropriate.” Present usage of the period, stable shelf environments were Mexico. These two units represent two the Strawn, Canyon, and Cisco names in interrupted, to varying degrees at different very different, widespread, easily recog- Texas is as groups (e.g., Kier et al., 1979; the times, by four major subsiding basins: Taos nized sedimentary sequences; the lower, Geologic Atlas of Texas maps), the stan- trough and Orogrande, Delaware, and an essentially Desmoinesian sequence of dard U.S. series names (e.g., Des- Pedregosa Basins. These basins accumulat- cherty, massive, cliff-forming, carbonate- moinesian, Missourian, Virgilian) as the ed unusually great thicknesses of sedi- shelf marine limestones and the upper, a major chronostratigraphic units. If these ment, although generally in shallow rather cyclic Missourian–Virgilian sequence of names are not used as series names in than deeper marine environments, from alternating, generally thinner and chertless Texas, there is no justification for using four large (Uncompahgre, Sierra Grande, marine limestones and siliciclastic units. these names as series names in the subsur- Zuni, and Pedernal) and several smaller Locally, a third unit at the top of the face of New Mexico. Nor is there any justi- island uplifts that provided fluctuating Madera may be recognized (e.g., Bursum fication for using them as group terms in volumes of siliciclastic sediments to and Red Tanks Formations), composed pri- New Mexico as these units do not extend marine and coastal environments (Fig. 2). marily of variably colored, nonmarine sili- laterally from north-central Texas into The interplay between paleogeography, ciclastic beds with subordinate marine New Mexico, and the lithologies of these tectonic activity, eustatic sea level changes, limestones, reflecting final regression of groups in north-central Texas do not and climate through the Pennsylvanian the Madera sea and replacement of marine resemble the lithologies of the subsurface produced depositional sequences of signif- strata with continental red beds near the units in New Mexico to which these names icant lithologic variability. Most Pennsyl- beginning of Permian time. have been applied. For example, the vanian sequences accessible for detailed 4) Formal formation names should be Strawn Group in Texas “consists predomi- study are within relatively recently (Ceno- applied to the “lower gray limestone” and nantly of cyclic terrigenous clastic facies zoic) uplifted, isolated, fault-block moun- “upper arkosic limestone” members. The deposited by…fluvial-deltaic systems” tain ranges, which have tended to empha- earliest valid, adequately defined, formal (Kier et al., 1979, p. S13), whereas size apparent differences between local names given to these widely distributed Desmoinesian strata in most of New sequences, rather than the broader deposi- and easily distinguished units within the Mexico are massive, cherty, marine lime- tional patterns that tie them together. Madera are Gray Mesa Limestone and stones. Use of these names in the New However, it is these broad patterns that are Atrasado Formation, respectively, in the Mexico subsurface should be abandoned, used here as the basis for lithostratigraph- Lucero uplift area (Kelley and Wood, and lithostratigraphic terms based on ic units such as formation and groups, 1946). These formations can be recognized exposed New Mexico strata (or if this is not with the view that for nomenclatural pur- widely in central New Mexico, and they, as possible, the standard series names) poses, most local lithologic variability is well as the Madera Group, are here extend- should be used for subsurface Pennsyl- properly accommodated within local ed southward into the Caballo and vanian stratigraphy. Permian lithostrati- member-rank units of rather broadly Robledo Mountains area. The Madera graphic units established on the basis of defined and geographically extensive for- sequence in the Lucero uplift area is an outcrops in and near New Mexico, such as mations. This approach is not new; it was important reference section for these Hueco, Abo, Yeso, and San Andres Forma- foreshadowed, albeit somewhat irregular- lithostratigraphic units. Only in cases tions, are routinely used as Permian sub- ly and informally, by the extensive recon- where the lithostratigraphy departs con- surface stratigraphic units in the state, and naissance mapping and stratigraphic stud- siderably from that of the type Gray Mesa there is no reason why the same cannot be ies undertaken by U.S. Geological Survey and Atrasado Formations need different done with Pennsylvanian units. geologists in the 1940s to 1960s. formation names be considered. The main recommendations for revision 5) Madera Group terminology reflects Summary and conclusions of current Pennsylvanian lithostratigraph- sedimentary sequences deposited on sta- ic nomenclature are as follows: ble platforms or along the margins of sub- This review of Pennsylvanian stratigraphy 1) Use of the term Magdalena Group in siding basins, as is the case with the Lucero in New Mexico is not intended to be com- those parts of the state (mainly southern uplift sequence. Broadly similar Madera prehensive, but rather to provide a broad New Mexico) where it is still being sequences, though variable locally, can be overview of the major Pennsylvanian employed should be abandoned. This recognized along the western and northern sequences across the state and the nomen- term, a relic of the earliest attempts to sub- margins of the Orogrande Basin, and clature that has been applied to them. The divide the Pennsylvanian in New Mexico, northward to the Peñasco uplift area. revisions suggested herein are designed to has been applied in so many confusing and Pennsylvanian sequences deposited more adapt the lithostratigraphic nomenclature contradictory ways as to render it mean- centrally in subsiding basins, such as in the to more appropriately and accurately ingless, and nearly a century of subse- San Andres Mountains or the Sangre de reflect the major features of the varied quent, more detailed stratigraphic work Cristo Mountains, or within unique tecton- Pennsylvanian successions exposed, and has deprived it of any utility it might once ic regimes, as along the eastern side of the to provide an integrated nomenclatural have possessed. Orogrande Basin in close proximity to the framework that can be consistently 2) The Madera Formation is most appro- Pedernal uplift (Sacramento Mountains) applied as studies of Pennsylvanian strati- priately regarded as a Group wherever it display strata that differ markedly from graphy around the state proceed. The cor- occurs in the state, an assessment already typical Madera Group sequences, and dif-

118 NEW MEXICO GEOLOGY November 2001 ferent sets of lithostratigraphic names, Guidebook 42, pp. 203–212. Mexico and adjacent areas of Texas and some including Morrowan and Atokan Armstrong, A. K., and Mamet, B. L., 1974, Colorado: New Mexico Bureau of Mines and strata not normally present in the Madera Biostratigraphy of the Arroyo Peñasco Group, Mineral Resources, Bulletin 137, pp. 181–186. Lower Carboniferous (Mississippian), north-cen- Clopine, W. W., 1992, Lower and Middle Group, have appropriately been applied tral New Mexico; in Siemers, C. T., Woodward, L. Pennsylvanian fusulinid biostratigraphy of by previous workers. A., and Callender, J. F. (eds.), Ghost Ranch: New southern New Mexico and westernmost Texas: 6) Pre-Madera (generally pre-Desmoin- Mexico Geological Society, Guidebook 25, pp. New Mexico Bureau of Mines and Mineral esian) strata are heterogeneous and have 145–158. Resources, Bulletin 143, 67 pp. received distinct formational names (e.g., Armstrong, A. K., Kottlowski, F. E., Stewart, W. J., Clopine, W. W., Manger, W. L., Sutherland, P. K., Mamet, B. L., Baltz, E. H., Jr., Siemers, W. T., and and Kaiser, D. A., 1991, Lower and Middle Sandia and Red House Formations), or are Thompson, S., III, 1979, The Mississippian and Pennsylvanian stratigraphic relations, type included in formations (such as the Lead Pennsylvanian (Carboniferous) Systems in the Derryan region, southern New Mexico and west- Camp Limestone in the southern San United States—New Mexico: U.S. Geological ernmost Texas; in Julian, B., and Zidek, J. (eds.), Andres Mountains) that show no signifi- Survey, Professional Paper 1110–W, 27 pp. Field guide to geologic excursions in New cant breaks in sedimentation from Early to Baars, D. L., Ross, C. A., Ritter, S. M., and Maples, Mexico and adjacent areas of Texas and Middle or even into Late Pennsylvanian C. G., 1994, Proposed repositioning of the Colorado: New Mexico Bureau of Mines and Pennsylvanian–Permian boundary in Kansas: Mineral Resources, Bulletin 137, pp. 173–181. time. The Atokan, predominantly clastic Kansas Geological Survey, Bulletin 230, pp. 5–10. Connolly, W. M., and Stanton, R. J., Jr., 1983, Sandia Formation is widely present Bachman, G. O., 1968, Geology of the Mockingbird Sedimentation and paleoenvironments of the beneath the Madera Group, but it becomes Gap quadrangle, Lincoln and Socorro Counties, Morrowan strata in the Hueco Mountains, west gradationally more carbonate-rich to the New Mexico: U.S. Geological Survey, Texas; in Geology of the Sierra Diablo and south- south, where other names have been Professional Paper 594–J, pp. J1–J43. ern Hueco Mountains, west Texas: Society of appropriately used for this interval. Bachman, G. O., and Harbour, R. L., 1970, Geologic Economic Paleontologists and Mineralogists, map of the northern part of the San Andres Permian Basin Section, Guidebook, pp. 36–64. 7) The lithostratigraphic formation and Mountains, central New Mexico: U.S. Geological Connolly, W. M., and Stanton, R. J., Jr., 1992, group names proposed by Thompson Survey, Miscellaneous Investigations Series Map Interbasinal cyclostratigraphic correlation of (1942), which were never widely used and I–600, scale 1:62,500. Milankovitch band transgressive-regressive are all but forgotten today, should be Bachman, G. O., and Myers, D. A., 1969, Geology of cycles—correlation of Desmoinesian–Missourian reevaluated. They designate legitimate, the Bear Peak area, Doña Ana County, New strata between southeastern Arizona and the Mexico: U.S. Geological Survey, Bulletin 1271–C, midcontinent of North America: Geology, v. 20, well-defined lithostratigraphic units, and pp. C1–C46. pp. 999–1002. some of them may be appropriate as mem- Bachman, G. O., and Myers, D. A., 1975, The Lead Cserna, E., 1956, Structural geology and stratigra- ber names locally within the more broadly Camp Limestone and its correlatives in south- phy of the Fra Cristobal quadrangle, Sierra conceived formations discussed above. central New Mexico; in Seager, R. E., Clemons, R. County, New Mexico: Unpublished Ph.D. disser- They also have priority over most other E., and Callender, J. F. (eds.), Las Cruces country: tation, Columbia University, New York, 105 pp. lithostratigraphic names used for parts of New Mexico Geological Society, Guidebook 26, Cys, J. M., 1975, New observations on the stratigra- pp. 105–108. phy of key Permian sections of west Texas; in the Pennsylvanian sequence in New Baltz, E. H., and Myers, D. A., 1984, Porvenir Permian exploration, boundaries, and stratigra- Mexico. Formation (new name)—and other revisions of phy: Society of Economic Paleontologists and 8) Lithostratigraphic names used for nomenclature of Mississippian, Pennsylvanian, Mineralogists, Permian Basin Section, and West Pennsylvanian strata in the subsurface of and Lower Permian rocks, southeastern Sangre Texas Geological Society, Publication no. 75–65, New Mexico should, as far as possible, be de Cristo Mountains, New Mexico: U.S. pp. 22–42. the same as those defined from exposed Geological Survey, Bulletin 1537–B, 39 pp. Darton, N. J., 1928, ”Red beds” and associated for- Baltz, E. H., and Myers, D. A., 1999, Stratigraphic mations in New Mexico with an outline of the strata in the state, rather than names based framework of upper Paleozoic rocks, southeast- geology of the state: U.S. Geological Survey, on surficial units in central Texas, which ern Sangre de Cristo Mountains, New Mexico, Bulletin 794, 356 pp. have no apparent relationships with New with a section on speculations and implications Drewes, H., 1991, Geologic map of the Big Hatchet Mexico strata. for regional interpretation of Ancestral Rocky Mountains, Hidalgo County, New Mexico: U.S. Acknowledgments. I thank Frank Kot- Mountains paleotectonics: New Mexico Bureau Geological Survey, Miscellaneous Investigations of Mines and Mineral Resources, Memoir 48, 269 Series Map I–2144, scale 1:24,000. tlowski, New Mexico Bureau of Mines and pp. DuChene, H. R., 1974, Pennsylvanian rocks of Mineral Resources, Spencer Lucas, New Bates, R. L., 1947, Developments in Arizona, west- north-central New Mexico; in Siemers, C. T., Mexico Museum of Natural History and ern New Mexico, and northern New Mexico in Woodward, L. A., and Callender, J. F. (eds.), Science, and Elmer Baltz for reviewing an 1946: American Association of Petroleum Ghost Ranch: New Mexico Geological Society, earlier version of this paper and offering Geologists, Bulletin, v. 31, pp. 1039–1044. Guidebook 25, pp. 159–162. suggestions that improved it. Thanks also Beede, J. W., 1920, Correlation of the upper DuChene, H. R., Kues, B. S., and Woodward, L. A., Paleozoic rocks of the Hueco Mountain region of 1977, Osha Canyon Formation (Pennsylvanian), to Mabel Chavez for word processing the Texas: Science, v. 51, p. 494. new Morrowan unit in north-central New manuscript. This paper is dedicated to Brill, K. 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A., 1999b, Facies char- some Pennsylvanian fusulinids from the Sandia Bureau of Mines and Mineral Resources, Open- acter and strata responses to accommodation in Formation and the Los Moyos Limestone, file Geologic Map Series, OF-GM–6, scale Pennsylvanian bioherms, western Orogrande Manzano Mountains, New Mexico: U.S. 1:24,000. Basin, New Mexico: Journal of Sedimentary Geological Survey, Professional Paper 1446–A, Read, C. B., and Wood, G. H., Jr., 1947, Distribution Petrology, v. 69, pp. 893–908. pp. A1–A20. and correlation of Pennsylvanian rocks in the late Spencer, A. C., and Paige, S., 1935, Geology of the Myers, D.A., 1988b, Stratigraphic distribution of Paleozoic sedimentary basins of northern New Santa Rita mining area: U.S. Geological Survey, some fusulinids from the Wild Cow and Bursum Mexico: Journal of Geology, v. 55, pp. 220–236. Bulletin 859, 78 pp. Formations, Manzano Mountains, New Mexico: Read, C. B., Wilpolt, R. H., Andrews, D. A., Steiner, M. B., and Williams, T. 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On October 15, 2001, the University of New Mexico Printing Services closed its doors after nearly 70 years of service. New Mexico Bureau of Geology and Mineral Resources was among many state-affiliated enti- ties that regularly did business with UNM Printing Services. They printed every issue of New Mexico Geology since its inception in February 1979. However, this association between the two organiza- tions goes back much farther. This long partnership owed its success to the dozens of dedicated and skilled employees who worked alongside bureau editors to make beautiful and accurate geologic publications and maps. We wish all of those employees well in their new endeavors.

122 NEW MEXICO GEOLOGY November 2001