Devonian Stratigraphy and Correlations in Southeastern Arizona Dietmar Schumacher, 1978, Pp
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New Mexico Geological Society Downloaded from: http://nmgs.nmt.edu/publications/guidebooks/29 Devonian stratigraphy and correlations in southeastern Arizona Dietmar Schumacher, 1978, pp. 175-181 in: Land of Cochise (Southeastern Arizona), Callender, J. F.; Wilt, J.; Clemons, R. E.; James, H. L.; [eds.], New Mexico Geological Society 29th Annual Fall Field Conference Guidebook, 348 p. This is one of many related papers that were included in the 1978 NMGS Fall Field Conference Guidebook. Annual NMGS Fall Field Conference Guidebooks Every fall since 1950, the New Mexico Geological Society (NMGS) has held an annual Fall Field Conference that explores some region of New Mexico (or surrounding states). Always well attended, these conferences provide a guidebook to participants. Besides detailed road logs, the guidebooks contain many well written, edited, and peer-reviewed geoscience papers. 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Guidebook, 29th Field Conf., Land of Cochise, 1978 175 DEVONIAN STRATIGRAPHY AND CORRELATIONS IN SOUTHEASTERN ARIZONA DIETMAR SCHUMACHER Phillips Petroleum Company Bartlesville, Oklahoma INTRODUCTION STRATIGRAPHY AND CORRELATION Devonian strata in southeastern Arizona comprise a com- Martin Formation plex mosaic of interbedded dolomite, limestone, sandstone Upper Devonian rocks throughout most of southern Ari- and shale which is widely exposed in the many mountain zona are assigned to the Martin Formation. Ransome (1904) ranges of the area. Over the years, numerous names have been proposed the name Martin Limestone for a predominantly car- proposed for the Devonian rocks in central and southeastern bonate sequence between the Cambrian Abrigo Formation and Arizona based on lithologic and paleontologic characteristics the Mississippian Escabrosa Limestone in the Bisbee area. Sub- and geographic distribution. Most of these names seem to sequently the name Martin Formation has been applied to apply to local faunal or facies zones and have not been recog- equivalent strata in southern and central Arizona by Ransome nized by subsequent workers, but five formation names have (1916), Stoyanow (1936) and Huddle and Dobrovolny (1952). been widely adopted and remain in current usage. These are Teichert (1965) subdivided the Martin Formation of central the Martin, Swisshelm, Portal, Morenci and Percha forma- Arizona into the Beckers Butte Sandstone Member and the tions. The nomenclatural history of these formations has been overlying Jerome Member. The Jerome was further subdivided, reviewed by Pye (1959), Wright (1964), Teichert (1965) and in ascending stratigraphic order, into the fetid dolomite unit, Pine (1968). All these formations are of Late Devonian age, the aphanitic dolomite unit and a lithologically heterogeneous but their exact placement within the Upper Devonian has been upper unit. Pine (1968) extended Teichert's subdivisions into uncertain because diagnostic macrofossils frequently are rare south-central Arizona. Schumacher and others (1976) demon- or absent. The age and correlation of the Martin and Percha strated that part of Teichert's upper unit is considerably formations in southern Arizona was discussed by Schumacher younger than the remainder of the Martin Formation and in and others (1976); however the most complete regional fact disconformably overlies typical Martin strata in much of synthesis is that of Poole and others (1967). The most current southeastern Arizona, locally resting directly on Cambrian or and comprehensive stratigraphic synthesis of Upper Devonian Ordovician strata. Schumacher and others (1976) recom- depositional complexes in the western United States by Sand- mended these strata be removed from the Martin Formation berg and Poole (1977) unfortunately does not include central and assigned to the Percha Formation. This recommendation is and southern Arizona within its study area; however, their followed here since the Martin Formation, thus restricted, detailed maps and discussions are critical for anyone interested forms a more natural stratigraphic unit and can be recognized in the Devonian or Mississippian of Arizona. throughout the study area. Based on the invertebrate macro- The purpose of this paper is to summarize the nomencla- fossils and conodonts, the Martin Formation is assignable to ture, dating and correlation of the Devonian formations of the lower Upper Devonian (Frasnian), although the basal beds southern Arizona. Most of the data and new interpretations may locally be slightly older (Stoyanow, 1936; Ethington, presented here are based on the results of recent stratigraphic 1965; Witter, 1976; Schumacher and others, 1975; N. Meader, and biostratigraphic investigations of the Devonian System in 1977). southern Arizona by Witter (1976), S. Meader (1976), Schumacher and others (1976), N. Meader (1977), Boyd (1978) and Schumacher and Witter (in preparation). The data Percha Formation (Arizona) summarized here are based on 54 principal stratigraphic sec- Schumacher and others (1976) proposed the name Percha tions (fig. 1 and Table 1) distributed across an area of more Formation for a sequence of slope-forming shales and silt- than 82,000 km2 (36,000 mil) that extends from the Mexican stones with overlying ledgy carbonates that occurs above the border north to the Salt River, and from the New Mexico Martin Formation and is well developed in the Mescal, Drip- border west to the Vekol Mountains. ping Spring and Galiuro mountains. Sandstone replaces all or Conodonts have played a vital role in interpreting Devonian part of the shale unit of the Percha Formation in the Whet- stratigraphy. This has been made possible by significant ad- stone, Rincon, Santa Catalina, Slate and Vekol mountains. vances in refining the Upper Devonian conodont zonation pro- Stoyanow (1936) first recognized the distinctive nature of posed and emended by Zeigler (1962, 1971) (see Sandberg and these strata and proposed they be assigned to a separate forma- Poole, 1977, p. 148) and recent developments concerning our tion, the Lower Ouray Formation, because of the presence of understanding of conodant biofacies and paleoecology the brachiopod Paurorhyncha endlichi, which is common in (Seddon and Sweet, 1971; Sandberg, 1976; Schumacher, the lower Ouray Limestone of southwestern Colorado. Be- 1976; Klapper and Barrick, 1978). The standard Upper Devo- cause Stoyanow's Lower Ouray Formation was defined by its nian conodant zonation now consists of 28 zones, some of faunal characteristics rather than by its lithologic and strati- which can be subdivided laterally into 3-5 biofacies. The appli- graphic characteristics, the name was never accepted and sub- cation of this highly refined zonation in southern Arizona has sequent workers included these strata within the Martin greatly clarified age relations and correlations within the Formation. Because Stoyanow's name was invalid, Schu- Upper Devonian. macher and others (1976) proposed the name Percha Forma- 176 SCHUMACHER tion for this unit because of its lithologic similarity to the tion most closely resembles the Martin Formation, differing Percha Shale (Box Member) of New Mexico with which it only in the predominance of sandstone and siltstone over car- correlates. The present study confirms that these strata do bonate rocks and shale. The upper one-third of the formation indeed form a lithologically distinct, mappable unit which can is largely impure limestone and shale, whereas quartz sand- be recognized over most of southern Arizona. Conodonts and stone, siltstone and minor dolomitic limestone predominate in rhynchonellid brachiopods independently suggest an upper the lower two-thirds. Both conodonts and macrofossils indi- Upper Devonian (Famennian) stratigraphic assignment for the cate that the lower two-thirds of the formation is assignable to Percha Formation (Stoyanow, 1936; Stainbrook, 1947; the uppermost Middle Devonian to lower Upper Devonian Ethington, 1965; Witter, 1976; S. Meader, 1976; Schumacher (upper Givetian to Frasnian). The upper third of the formation and others, 1976;