VOLUME 75 FALL 2016 STRATIGRAPHIC NOMENCLATURE OF THE OUACHITA MOUNTAINS IN OKLAHOMA: FORMAL, INFORMAL, OBSOLETE, AND INCORRECT or THE GOOD, THE BAD, AND THE UGLY INSIDE ON PAGE 5 OKLAHOMA GEOLOGICAL SURVEY OKLAHOMA GEOLOGICAL SURVEY DR. JEREMY BOAK, Director OGS Geologist Neil Suneson Editor delves into the Good, the Bad, and Ted Satterfield the Ugly of the topic of stratigraphic nomenclature in the Ouachita Mountains. Cartography Manager James Anderson GIS Specialist Russell Standridge Copy Center Manager Richard Murray This publication, printed by the Oklahoma Geological Survey, Norman, Oklahoma, is issued by the Oklahoma Geological Survey as authorized by Title 70, Oklahoma Statutes 1981, Section 3310, and Title 74, Oklahoma Statutes 1981, Sections 231—238 The Oklahoma Geological Survey is a state agency for research and public service, mandated in the State Constitution to study Oklahoma’s land, water, mineral and energy resources and to promote wise Cover: Outcrop of the Wapanucka Limestone use and sound environmental practices. east of Hartshorne, Oklahoma. (Photo by TED SATTERFIELD). 2 FALL 2016 Grateful to be back As the Director of the Oklahoma Geological Survey (OGS), I am very glad to see the revival of the Oklahoma Geology Notes, which had been a feature of the Oklahoma geology scene since the early 40s, but was last published in 2014. This issue, marking the return, introduces a new format, becoming less of a newsletter and more of a scientific publication. From there we proceed, as many geological investigations do, from the surface downward. We start up the Notes again with Neil Sune- son’s take on stratigraphic nomenclature in the Ouachita Mountains. Just the word “nomen- clature” tends to produce yawns among many scientists, but making sure that we are talking about the same rock units can be a challenge when different regional names don’t necessarily meet in the middle due to the lateral variations Jeremy Boak of rock units. OGS Director As geologists, we are tasked with character- izing the crust of the earth in three spatial di- Providing clear rationale, and straightforward mensions, through time. But, as OGS geophysi- description of any revision of rock names — cist Kevin Crain pointed out to me recently, the what names are being changed, and how do the problem is really n-dimensional, as we must new names relate to existing stratigraphic terms identify and measure critical properties, each — is needed to ensure that the value of older of which covers its own natural range, varying literature will not be lost. through time as well. In the realm of sedimen- Our hope is that the new Oklahoma Geology tary rocks, we can count in general on greater Notes will channel the best of the previous long variation in the vertical than the horizontal series and bring some new scenes, new takes on dimension (or we would not be able to iden- old locations, current developments, interesting tify strata to begin with). But the recognition ideas, and show that, no matter how old, there that lithostratigraphic units are not the same as is always something new to be learned about chronostratigraphic units can lead to confusion. Oklahoma geology. 3 OKLAHOMA GEOLOGICAL SURVEY 4 FALL 2016 STRATIGRAPHIC NOMENCLATURE OF THE OUACHITA MOUNTAINS IN OKLAHOMA: FORMAL, INFORMAL, OBSOLETE, AND INCORRECT or The Good, the Bad, and the Ugly By Neil H. Suneson INTRODUCTION units that are exposed or are in the subsurface in the Oklahoma Ouachita Mountains and that are present The nomenclature of the stratigraphic units in the subsurface near the Choctaw Fault. The units (groups, formations, members) in the Ouachita Moun- in the subsurface in the southern part of the Arkoma tains in Oklahoma has changed since the first geologic Basin are typically folded and faulted and are part of map of part of the mountain range was published in the Ouachita tectonic belt. The names are limited to 1902 (Taff, 1902). Proposed revisions to the formation those of units that are older than the Desmoinesian names were typically based on a number of factors: Hartshorne Formation. Whereas the Hartshorne and 1) more detailed mapping than was previously avail- younger formations are folded and faulted, they are not able; 2) more and better paleontological data; 3) bet- present at the surface south of the trace of the Choctaw ter stratigraphic correlations with units exposed in the Fault and are therefore beyond the scope of this paper. Oklahoma and Arkansas Ouachita Mountains and the Arkoma Basin; and 4) more and better subsurface data. BACKGROUND In addition, changes in the “rules” for naming geologic units as prescribed in the 1933, 1961, 1970, 1983, and The basis for this paper is the Code of Stratigraphic 2005 “Codes of Stratigraphic Nomenclature” forced Nomenclature. As discussed below, many names were Ouachita stratigraphers and geologists to reexamine assigned before any code existed. Ashley et al. (1933) formerly accepted names. In many cases, however, published the first “code” (although the term “code” geologists ignored the existing code and introduced was not included in the title), and two of its co-authors new terms without emphasizing their informal nature. – Charles Gould and Hugh Miser – were very familiar Petroleum geologists exacerbated the confusion, par- with the stratigraphy of the Ouachita Mountains. The ticularly in the northern frontal belt (Figure 1) of the authors used the word “rules” in their paper, but ad- Ouachitas, by using new names that applied to strata mitted that the “rules” were really “guidelines.” The encountered only in the subsurface. American Commission on Stratigraphic Nomenclature This report briefly describes the history of the (ACSN) published a revised code in 1961 (ACSN, stratigraphic nomenclature of the Ouachita Moun- 1961) and an only slightly revised code again in 1970 tains in Oklahoma. It describes the currently accepted (ACSN, 1970). The code was largely rewritten in 1983 group, formation (Figure 2), and member names and by the North American Commission on Stratigraphic distinguishes between those that are generally con- Nomenclature (NACSN) (NACSN, 1983) who also sidered “formal” by geologists and those that, while published a revised version in 2005 (NACSN, 2005). widely used, are informal. This report also comments Like the 1933 “code,” the 2005 version is more a set on some problems with the accepted formal and in- of guidelines than rules as evidenced by the common formal nomenclature and proposes some solutions to use of the word “should” instead of “must.” For exam- those problems. The subsurface nomenclature used ple, when naming a subsurface unit, “the hole or mine in the northern frontal belt is discussed and clarified. should be (instead of “must be”) located precisely” More importantly, perhaps, this paper recommends that (NACSN, 2005, p. 1564) (author’s italics and paren- some commonly used but informal names be viewed theses). as formal and that formal, but little-used or poorly jus- Many of the units in the Oklahoma Ouachita tified, names or those of local units be changed. Mountains were named before the 1933 “code” was The names reviewed in this report are of those published and have been widely used for almost 100 5 OKLAHOMA GEOLOGICAL SURVEY Figure 1. Generalized geologic map of the Ouachita Mountains, Oklahoma. Modified from Arbenz (2008, plate 2). years. Although their names do not fulfil many of the logic Names Lexicon (“Geolex”) (http://ngmdb.usgs. criteria now necessary for a name to be recognized, gov/Geolex/search). Geolex is a searchable database they are considered formal because they have been based on lexicons published as hard-copy bulletins by used for many years and are well-established in the the USGS. This database lists names used by the USGS geologic literature. Article 7 (c) of the modern strati- and the different state surveys and claims to identify graphic code (NACSN, 2005) recognizes the need with a slash (see website) those that do not conform to preserve commonly used, but perhaps imprecisely with the stratigraphic code(s) cited above; in fact, defined, names of stratigraphic units. One unit – the Geolex does not do this (e.g., see discussion on Lynn Spiro Sandstone at the base of the Atoka Formation – Mountain Formation, below). Geolex also does not al- is widely used in the petroleum industry and is easily ways restrict the name of a unit to a specific rank; for recognized and mapped on the surface and subsurface. example, the USGS and OGS recognize the Springer Although it has not met the rigorous requirements for as a group and a formation. In addition, the OGS rec- being considered formal, this paper recognizes it as ognizes Springer Shale as a formal unit. Table 1 shows such. the names of the units in the Oklahoma Ouachita An important source for stratigraphic nomencla- Mountains as recognized by the USGS and Oklahoma ture is the U.S. Geological Survey’s (USGS) U.S. Geo- Geological Survey (OGS) (source: Geolex database at 6 STRATIGRAPHIC COLUMN OF OUACHITA MOUNTAINS FALL 2016 Platform Stratigraphy Ouachita Stratigraphy n a i Atoka Formation Atoka Formation n Atokan a v l y s Wapanucka Limestone Johns Valley Shale n n e Jackfork Group P Morrowan Springer Formation Chest- n erian a i Stanley Group p Mera- p i mecian s s Caney Shale i s Osagean s i M Kinder- hookian Arkansas Novaculite Upper Middle Devonian Lower Upper Missouri Mountain Shale Lower Blaylock Sandstone Silurian Polk Creek Shale Upper Bigfork Chert Middle Womble Shale Blakely Sandstone Ordovician Mazarn Shale Lower Crystal Mountain Sandstone Upper Collier Shale Cambrian Figure 2. Generalized stratigraphic column of the Ouachita Mountains, Oklahoma. Subdivisions of groups and formations discussed in text. Modified from Arbenz (2008, plate 2). 7 OKLAHOMA GEOLOGICAL SURVEY ngmdb.usgs.gov/Geolex/search; accessed June 28, 2016).