5: Depositional Cyclicity Within the Mayes Group (Meramecian–Chesterian) Along the Western Edge of the Mississippian Outcrop Belt in Northeastern Oklahoma
Published:January 01, 2019
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Cory J. Godwin, James O. Puckette, 2019. "Depositional Cyclicity Within the Mayes Group (Meramecian–Chesterian) Along the Western Edge of the Mississippian Outcrop Belt in Northeastern Oklahoma", Mississippian Reservoirs of the Midcontinent, G. Michael Grammer, Jay M. Gregg, James Puckette, Priyank Jaiswal, S. J. Mazzullo, Matthew J. Pranter, Robert H. Goldstein
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Multiple orders of depositional cyclicity in the Mayes Group of northeastern Oklahoma are delineated by refined depositional facies associations and stratigraphic surfaces. Facies associations include deep subtidal facies, shallow subtidal facies (including distal and proximal subfacies), carbonate shoal facies, and shoal crest facies. The Mayes Group records a primary transgressive–regressive depositional cycle bounded below by a major unconformity (sub-Mayes unconformity) and above by an important provincial conodont biostratigraphic boundary and widespread flooding surface at the base of the Fayetteville Shale. Within the Mayes Group, two secondary transgressive–regressive depositional cycles are separated by an interpreted unconformity. The lower Mayes cycle comprises the Bayou Manard and Lindsey Bridge members of the Pryor Creek Formation, whereas the Ordnance Plant Member is grouped with the Hindsville Formation in the upper Mayes cycle. Present in both the lower and upper Mayes cycles are high-frequency shallowing-upward cycles bounded by flooding surfaces. Evaluating the distribution of facies and stratigraphic surfaces within a framework of multiple orders of depositional cyclicity is essential to interpreting the geologic evolution of the southern mid-continent during the Meramecian and Chesterian, and impacts oil and gas production by improving our understanding of reservoir compartmentalization.
The Mayes Group, consisting of the Pryor Creek Formation (a new name formally proposed by Godwin et al., 2019) and overlying Hindsville Formation, is exposed in outcrops and was penetrated in shallow subsurface cores in northeastern Oklahoma, including the Mayes Group type area in central Mayes County, where a collection of complete or nearly stratigraphic sections is easily accessible (Figure 1). Because of their position along the western edge of the Mississippian outcrop belt, these sections are relevant to potential studies concerning hydrocarbon-bearing time-equivalent strata in the subsurface of Oklahoma. Additional surface localities and subsurface core were examined in Missouri, Kansas, and Arkansas because they represent reference points for understanding the Hindsville Formation, which is more widely distributed that is the Pryor Creek Formation.
During the Mississippian, northeastern Oklahoma was located approximately 15° south of the equator along a broad carbonate platform, interpreted as a shelf (Lane and De Keyser, 1980; Gutschick and Sandberg, 1983) and ramp to distally steepened ramp (Handford, 1986, 1995; Mazzullo et al., 2013) that extended across the midcontinent and into the southwestern United States. Within this setting, Mayes Group facies distribution and depositional cyclicity were influenced by eustatic sea-level changes associated with the onset of late Paleozoic glaciation (Mii et al., 1999; Smith and Read, 2000) and early phases of Ouachita tectonism (Huffman, 1958; Bradley and Leach, 2002; Houseknecht et al., 2014; Mazzullo et al., 2019).
The clear majority of previous work concerning or referencing the Mayes Group focused on lithostratigraphic nomenclature, surface mapping, and subsurface correlation (e.g., Snider, 1915; Buchanan, 1927; Brant, 1934, 1941; Selk, 1949; Bollman, 1950; Huffman and Barker, 1950; Douglass, 1952; DeGraffernreid, 1953; Slocum, 1955; Huffman, 1958; Starke, 1961; Krueger, 1965; Huffman et al., 1966; Selk, 1973; Turmelle, 1982). Although as many as two transgressive–regressive depositional cycles have been interpreted in the Mayes Group, internal variations in lithology were simply attributed to facies interfingering with minimal discussion concerning organization of facies beyond that of an overall shallowing-upward succession (Huffman, 1958; Turmelle, 1982). Recognition of depositional cycles in the type Mayes Group serves as the foundation upon which more comprehensive sequence stratigraphic models can be constructed. These models are critical to future evaluation of the Mississippian petroleum system, including predicting potential reservoir compartmentalization. Identification of Mayes Group depositional cycles relies on an improved understanding of the distribution of, and relationships between, an expanded suite of depositional facies and revised stratigraphic surfaces of local to regional extent.
The purpose of this report is to describe stratigraphic surfaces and facies assemblages, which provide the basis for recognizing a hierarchy of depositional facies in the Mayes Group. Additionally, the proposed depositional cycles and facies relationships, described herein, explain in a predictable manner the lithostratigraphic variations evident in the Mayes Group.
A total of 27 surface and shallow subsurface sections were examined in northeastern Oklahoma, with an emphasis placed on central Mayes County where the Mayes Group type area contains nine closely spaced and nearly complete to complete stratigraphic sections (locations 11–19; Figure 1). Surface locations within the outcrop belt, away from the type area, are typically less complete and more widely separated. To the west-southwest of the type area, three additional subsurface cores were examined, two in Mayes County and one in Okmulgee County (Figure 1). These cores supplement the sections within the type area and strengthen surface-to-subsurface correlations.
From the sections examined, more than 300 slabbed and polished hand samples and 200 standard thin sections were prepared to complement field and core descriptions. Hand samples and thin sections from outcrops and cores were described using the carbonate classification of Dunham (1962) and Embry and Klovan (1971). Observations from outcrops and subsurface cores were augmented with descriptions of sections reported in Slocum (1955), Huffman (1958), and Turmelle (1982).
Conodonts recovered from bulk samples taken from outcrops and some shallow subsurface core are used in this study to define the relative age constraints of the Mayes Group, as well as to ascertain any correlation between depositional cyclicity and faunal trends (see Godwin et al., 2019).
The Mayes Group includes the Pryor Creek Formation and overlying Hindsville Formation (Figure 2; Godwin et al., 2019). In ascending order, the Pryor Creek Formation is divided into the argillaceous limestone of the Bayou Manard Member, fine to coarse bioclastic limestone of the Lindsey Bridge Member, and calcareous siltstone and shale of the Ordnance Plant Member. The Bayou Manard Member is latest Meramecian in age, whereas the Lindsey Bridge Member, Ordnance Plant Member, and overlying Hindsville Formation are early to middle Chesterian (Thompson, 1972; Lane and Brenckle, 2005; Godwin et al., 2019). The Hindsville Formation generally consists of fine to coarse-grained bioclastic and oolitic limestone, but also includes lime mudstone, calcareous siltstone-sandstone, and shale.
The base of the Mayes Group is recognized as a regionally extensive unconformity (Cline, 1934; Laudon, 1948; Huffman, 1958). Where the Pryor Creek Formation is present, this unconformity coincides with the base of the Bayou Manard Member and separates it from underlying strata ranging in age from Ordovician through early Meramecian (Figure 3; Godwin et al., 2019). Where the Pryor Creek Formation is absent, the Hindsville Formation rests unconformably on sub-Mayes strata, typically units of the Boone Group (Osagean–Meramecian). Possibly correlative unconformities occur below the Caney Shale and Sycamore Limestone of southern Oklahoma, the Moorefield Formation or Hindsville Formation of northern Arkansas, and the Barnett Shale of Texas (Singh, 2007; Boardman et al., 2012; Godwin et al., 2019). The unconformity surface is characterized by small- to large-scale paleotopographic relief (Figure 3) that influenced Mayes Group deposition. Within the study area, the Bayou Manard and Lindsey Bridge members were most affected by paleotopographic relief along the unconformity and display greater variations in thickness and facies distribution. In contrast, the Ordnance Plant Member and the Hindsville Formation display more consistent thickness and predictable facies trends.
The contact separating the Bayou Manard and Lindsey Bridge members is commonly sharp and characterized by unlined burrows in the uppermost bed of the Bayou Manard Member that were passively filled by sediment of the basal Lindsey Bridge Member (Figure 4). Huffman (1958) noted these features, separately interpreting them as load structures in one instance and as worm borings in another, and described the contact as conformable. Evidence from outcrops at locations 13–15 indicate a period of nondeposition and submarine erosion along the contact, including truncation of the uppermost beds of the Bayou Manard Member and inclusion of subrounded to rounded clasts of Bayou Manard lime mudstone in the basal Lindsey Bridge Member.
The contact between the Lindsey Bridge Member and the Ordnance Plant Member shows evidence of erosional truncation of the Lindsey Bridge in outcrop at locations 13 and 15, as well as in the cores from locations 16–18. Elsewhere in central Mayes County, the contact is characterized by an irregular and mineralized (phosphate, iron-oxide) surface (Figure 5A, B) with clasts of the Lindsey Bridge Member incorporated in the basal beds of the Ordnance Plant Member (Figure 5C). At location 13, large (>2.5 cm [1 in.]) clasts of Osagean Boone Group strata, including apparent clasts of cherty limestone of the Bentonville Formation and oolitic limestone of the Short Creek Oolite Member, occur at the base of the Ordnance Plant Member, where an unconformity separates the Lindsey Bridge and Ordnance Plant members. Away from the central Mayes County, an unconformity was also interpreted between these two members at location 4 in Adair County, Oklahoma.
The boundary between the Ordnance Plant Member and overlying Hindsville Formation appears conformable and is commonly marked by the contact between silty shale or shaly siltstone of the upper Ordnance Plant with dark gray–black shale or silty coarse-grained bioclastic packstone–wackestone to floatstone–rudstone of the Hindsville Formation (Figure 6). The contact between the Hindsville Formation and the Fayetteville Shale is a widespread flooding surface, which coincides with the boundary between the Gnathodus bilineatus–Cavusgnathus altus and overlying Gnathodus bilineatus–Kladognathus mehli conodont zones of Collinson et al. (1971; Thompson, 1972). In northern Arkansas, the contact was interpreted as diachronous based on ammonoid fauna (Saunders et al., 1977; Handford, 1995).
Thickness and Distribution of the Mayes Group
In outcrop, the Pryor Creek Formation is limited to northeastern Oklahoma, excluding the Tri-State Mining District in the far northeastern corner, and is thickest in central Mayes County where it reaches 95.8 feet (29 m) at location 14 (Figure 7). From there, the Pryor Creek Formation thins rapidly to the north and east, eventually pinching out in Craig and Delaware counties (Huffman, 1958). In the southeastern part of the outcrop area, in Cherokee and Adair counties, the Pryor Creek Formation also thins and pinches-out across a regional paleotopographic high, herein termed the Adair–Cherokee high (Figure 7). Where the Pryor Creek Formation is absent, the Hindsville Formation rests on sub-Mayes strata. To the west of the outcrop area, the Mayes Group dips into the subsurface and the Pryor Creek Formation continues thickening. It is 127 feet (39 m) thick in core M-207 (location 11), 229 feet (70 m) in core M-211 (location 10), and 213 feet (65 m) in the Baker Hughes BH-1 core (location 27). In the subsurface of Oklahoma, the Mayes Group and more specifically the Pryor Creek Formation has been historically known by several informal names including, but not limited to, the “subsurface Mayes,” “Seminole Mayes,” and “Mississippi black limestone.” The correlation of the Mayes Group with the “subsurface Mayes” has a long and somewhat contentious history. Cram (1930), Brant (1934, 1941, 1957), and Selk (1949) considered the “subsurface Mayes” to be a downdip facies equivalent of Osagean or Kinderhookian strata to the north and east. In contrast, Aurin et al. (1921), Buchanan (1927), Cline (1934), Huffman and Barker (1950), and Huffman (1958) considered these subsurface strata Meramecian–Chesterian and equivalent to the Mayes Group of the outcrop area.
The Hindsville Formation is between 25 and 45 feet (7.5 and 14.5 m) thick and present throughout northeastern Oklahoma, including the Tri-State Mining District, southwestern Missouri, and northern Arkansas. In northeastern Oklahoma, it thins in the southern part of the study area within Muskogee and Okmulgee counties. Where the Hindsville Formation is absent, the Fayetteville Shale rest on the Pryor Creek Formation.
Depositional Facies Associations
The type Mayes Group consists of four broadly defined depositional facies associations: deep or restricted subtidal, shallow subtidal, carbonate shoal, and shoal crest. Boundaries between these facies associations are commonly gradational and their distribution is interpreted within an inferred carbonate ramp setting following the model of Burchette and Wright (1992; Figure 8). Additional depositional facies associations are recognized, but they are volumetrically insignificant. Although the precise lithologic expression of each depositional facies, when present, varies between lithostratigraphic units, the defining character of each facies is consistent in terms of their overall depositional energy and inferred bathymetric position. The most notable difference between lithofacies within a defined facies association is the ratio between the carbonate (lime mud and allochems) and siliciclastic (terrigenous silt and clay) components. Representative lithofacies in the Bayou Manard Member, Lindsey Bridge Member, and Hindsville Formation tend to be carbonate-dominated, with lesser amounts of terrigenous quartz silt and terrigenous clay. Lithofacies of the Ordnance Plant Member are rich in terrigenous silt and clay.
Deep or Restricted Subtidal Facies Association
Lithofacies included in this association are typically dark in color, terrigenous clay or lime mud-rich, and very thin to medium-bedded. Deep subtidal facies are often horizontally laminated (occasional low-angle cross-laminations) with distinct burrows including Planolites, Chondrites, and Zoophycos. Some lime mudstone–wackestone beds are pervasively bioturbated (fabric-destructive) and therefore appear massive, although faint remnant laminations and distinct horizontal burrows and bedding-plane traces were observed. Quartz silt, silt-size bioclasts and peloids (microbioclasts), and larger disarticulated open marine fauna are rare to common and may represent down-dip storm transport (Handford, 1986). These lithofacies are interpreted as the deep or restricted subtidal facies association. This facies association occurs throughout the Mayes Group and represents deposition in low-energy, open marine to partially restricted conditions below storm wave base in an outer ramp position (Burchette and Wright, 1992; Figure 9).
Shallow Subtidal Facies Association
Lithofacies in this facies association are storm-influenced and represent a wide spectrum of depositional conditions from low energy in more distal positions through moderate to high energy in more proximal positions (Burchette and Wright, 1992). Distally, just above storm wave base, shallow subtidal facies transition to deep subtidal facies. These facies are characteristically very thin to medium-bedded, brownish-gray to dark brownish-gray, lime mud or terrigenous clay-rich, and burrowed to pervasively (fabric-destructive) bioturbated. Internal horizontal to low-angle cross-laminations occur, but are rare. In more proximal positions, closer to fair-weather wave base, shallow subtidal facies are gradational with carbonate shoal facies, and are thus marked by an increase in the percentage of fine- to coarse-grained bioclasts, and decrease in bioturbation, quartz silt, lime mud, and terrigenous clay. Discrete burrows in the shallow subtidal facies association include Skolithos and Planolites. Although symmetrical ripples are present locally in the Ordnance Plant Member, no evidence of periodic subaerial exposure is apparent. Interpreted as shallow subtidal facies association, these lithofacies represent deposition between storm wave base and fair-weather wave base in what is considered the middle ramp (Burchette and Wright, 1992; Figure 10).
Carbonate Shoal Facies Association
Carbonate shoal facies are quite diverse, but generally consist of bioclastic–lithoclastic packstone–grainstone and crinoidal–bryozoan packstone–grainstone (Figure 11). Allochems include typical open-marine fauna, (often with micritic coatings), ooids, and peloids. Allochtonous lithoclasts are common in the Lindsey Bridge Member (Figure 11A, C), and include sand- to cobble-size chert clasts derived from erosion of the Boone Group and locally abundant pebble-size lime mudstone clasts derived from the top of the Bayou Manard Member. Chert clasts are also common in carbonate shoal facies at the base of the Hindsville Formation where it rests on the Boone Group, including location 21 in Craig County, Oklahoma, location 22 in Ottawa County, Oklahoma, and location 25 in Barry County, Missouri. Interpreted as the carbonate shoal facies association and is characterized by high-energy deposition in open-marine waters above fair-weather wave base where sediments are well-washed, grain-supported, and cross-stratified.
Shoal Crest Facies Association
Although closely associated with the carbonate shoal facies association, the shoal crest facies association occurs only within the Hindsville Formation and is characterized by a predominance of fine- to coarse-grained ooids and micrite-coated bioclasts (immature ooids) and internal cross-stratification (Figure 11F).
Backshoal Intertidal Facies Association
Backshoal intertidal facies represent low-energy deposition landward of an active carbonate shoal and are only recognized in the Hindsville Formation in the Tri-State Mining District during this investigation. At location 22 in Ottawa County, Oklahoma, the Hindsville Formation contains features indicative of an intertidal setting, including mudcracks, symmetrical ripples, and mud rip-ups. At location 23 in Ottawa County, the Hindsville Formation consists of thin-bedded, silty to sandy, very fine- to fine-grained oolitic–bioclastic packstone–grainstone with mudcracks in more mud-rich rocks.
Important regionally extensive stratigraphic surfaces used to interpret Mayes Group depositional cyclicity include the sub-Mayes unconformity, Bayou Manard–Lindsey Bridge contact, sub-Ordnance Plant unconformity, Ordnance Plant–Hindsville contact, and the Hindsville–Fayetteville contact. Important secondary stratigraphic surfaces include flooding surfaces (Figure 6B) and burrowed surfaces (Figure 4). Flooding surfaces separate relatively deeper water facies from underlying shallower water facies and are characterized by one or more of the following: glauconite, phosphate, and skeletal lags. Facies variation across the flooding surface can be subtle and identification predicated on the occurrence of grain-rich lags. Some flooding surfaces also coincide with unconformities. Burrowed surfaces are likewise important to the interpretation of depositional cyclicity because they are often well-developed at the transition between transgressive and regressive deposition. These surfaces contrast with more commonly occurring smaller, but distinct burrows, trace fossils, and texture-destructive bioturbation in that burrowed surfaces occur along bed boundaries separating relatively deeper water facies below from shallower water facies above. The Bayou Manard–Lindsey Bridge contact is an example of one such burrowed surface, but unlike others it is regionally extensive. Burrowed surfaces also occur in the Ordnance Plant Member and Hindsville Formation.
Interpreted Depositional Cycles
Based on the distribution of depositional facies associations and stratigraphic surfaces, multiple orders of depositional cyclicity are recognized within the Mayes Group (Figure 12). These cycles are traced with variable confidence in central Mayes County (Figure 13) and into the shallow subsurface (Figure 14). As a whole, the Mayes Group succession records overall shallowing-upward, herein referred to as the primary transgressive–regressive depositional cycle. This succession is easily traceable across the type area, as well as throughout much of northeastern Oklahoma and into the shallow subsurface. This primary cycle contains two prominent secondary transgressive–regressive depositional cycles, herein termed the lower Mayes cycle and upper Mayes cycle (Figure 12). Each of these secondary cycles contains higher frequency depositional cycles, which are interpreted and correlated with less confidence than the secondary transgressive–regressive depositional cycles.
Where both the Pryor Creek and Hindsville formations are present, the overall shallowing-upward succession that characterizes the primary transgressive–regressive cycle is easily recognizable throughout central Mayes County and much of northeastern Oklahoma in general, regardless of overall thickness of the Mayes Group. Where the Pryor Creek Formation is present, both the lower and upper Mayes cycles, separated by the sub-Ordnance Plant unconformity, are also recognizable and traceable in central Mayes County and much of northeastern Oklahoma where lithostratigraphic divisions are well defined.
Lower Mayes Cycle
The lower Mayes cycle consists of the Bayou Manard and Lindsey Bridge members of the Pryor Creek Formation and is bounded below by the sub-Mayes unconformity and above by the sub-Ordnance Plant unconformity. The Bayou Manard Member represents initial transgression across the sub-Mayes unconformity within accommodation formed by the apparent removal of Boone Group and older strata. Basal beds of the Bayou Manard Member are siltier than overlying beds and contain abundant glauconite, phosphate, quartz-silt, and silt-size skeletal debris. In some instances, thin (centimeter-scale) variably cross-laminated, calcareous siltstone beds (shallow subtidal facies) are present at the base of the Bayou Manard Member. These beds represent the initial transgression across the unconformity surface. Overlying Bayou Manard Member strata are typically dominated by lime mudstone–wackestone of the deep subtidal to distal shallow subtidal facies, although proximal shallow subtidal facies are present in northern Mayes County and along the flank of the “Adair–Cherokee high” (Figure 7), both of which are associated with overall thinning (and inferred shallowing) of the Pryor Creek Formation. Transition between the transgressive and regressive depositional stages of the lower Mayes cycle coincides with the lithostratigraphic boundary between the Bayou Manard and Lindsey Bridge members. This contact is a burrowed surface interpreted as a marine firmground discontinuity or omission surface characterized by low-diversity Glossifungites ichnofacies (MacEachern et al., 1992). The thickness of the lower Mayes cycle (i.e., Bayou Manard and Lindsey Bridge members) varies across the study area. Thus, characteristics of both the transgressive and regressive stages vary, as does the several interpreted higher frequency cycles. Where the lower Mayes cycle is less than 30 feet (9 m) thick, the regressive stage consists only of carbonate shoal facies. However, where the lower Mayes cycle is thicker, the regressive stage above the marine firmground discontinuity includes deep subtidal and shallow subtidal facies that grade upward into an upper carbonate shoal facies. In the southern part of the study area and in the subsurface of southwestern Mayes County and Okmulgee County, proximal shallow subtidal and carbonate shoal deposits of the regressive stage Lindsey Bridge Member are thin or absent and replaced by distal shallow subtidal to deep subtidal facies. These more distal facies are lithostratigraphically assigned to either the Bayou Manard Member or Ordnance Plant Member, or simply grouped with them as the undifferentiated Pryor Creek Formation, such as in southern Muskogee County (Huffman, 1958) or in the subsurface cores from locations 10 and 27. In such instances, definitive shallowing-upward character is not recognized.
Higher frequency cycles were not identified with a high level of confidence in surface exposures in which the lower Mayes cycle was less than 30 feet (9 m) thick (Figure 13 and location 13 in Figure 14). Higher frequency cycles are, however, interpreted and correlated with more confidence in thicker Bayou Manard Member sections where flooding surfaces are characterized by subtle lithologic variations (between distal shallow subtidal and deep subtidal facies associations) and thin lag deposits consisting of skeletal debris and phosphate grains (Figure 14). That said, the overall vertical succession in these thicker shallow subsurface sections of the lower Mayes cycle appear to be aggradational in nature following the initial deepening apparent in the basal Bayou Manard Member above the sub-Mayes unconformity. Potential cycle boundaries are also tentatively interpreted in sections of the Bayou Manard Member where the cycle boundary is associated with burrow-nucleated black vitreous chert. At location 14, 5.5 feet (1.7 m) of abundant burrow-nucleated nodules of black vitreous chert is located 12–15 feet (3.6–4.6 m) above the base of the Bayou Manard Member and separates sections of the deep or restricted subtidal facies association. A similar zone of black vitreous chert was observed in the subsurface core at location 17. The cross-section illustrated in Figure 14 depicts a decrease in the several identifiable higher frequency cycles between the expanded sections in the subsurface cores (locations 10 and 11) and thinner sections in surface exposures (locations 13 and 14). In sections in which the lower Mayes cycle is greater than 30 feet (9 m) thick, including locations 14, 15, 17, and 18, the regressive stage (Lindsey Bridge Member) of the lower Mayes cycle is a single high-frequency cycle that shallows upward from deep subtidal facies through carbonate shoal facies (Figure 14). In thinner sections, the Lindsey Bridge Member consists predominantly of carbonate shoal facies. At both locations 14 and 15, however, the shallowing-upward succession of the regressive stage Lindsey Bridge Member consists of northeastward dipping strata interpreted as prograding foresets associated with paleotopographic highs (Swinchatt, 1967).
Upper Mayes Cycle
The upper Mayes cycle includes the Ordnance Plant Member and overlying Hindsville Formation. This secondary transgressive–regressive cycle is bounded below by the sub-Ordnance Plant unconformity and above by the contact between the Hindsville Formation and Fayetteville Shale (Huffman, 1958; Ogren, 1968). The siltstone- and shale-dominated Ordnance Plant Member represents the transgressive stage and the carbonate sand-dominated Hindsville Formation represents the regressive stage.
Two characteristics set the upper Mayes cycle apart from the lower Mayes cycle. First, the upper Mayes cycle displays a greater consistency in overall thickness across the study area, whereas the thickness of lower Mayes cycle is more variable and increases into the subsurface. Second, the upper Mayes cycle consists of conspicuous higher frequency cycles that are interpreted and correlated with more confidence than those of the lower Mayes cycle. The Ordnance Plant Member consists of higher frequency cycles (Figure 15) characterized by silty shallow subtidal and shaly deep subtidal facies, with scarce carbonate shoal facies. Higher frequency cycles in the Ordnance Plant Member are bounded by flooding surfaces with abundant phosphate and skeletal-lag deposits (Figure 16). Stacking of cycles in the Ordnance Plant Member appears to be retrogradational. To the south and west of central Mayes County, deep subtidal facies in the Ordnance Plant Member become more predominant during the transition from proximal to distal ramp settings (Huffman, 1958). The Hindsville Formation contains higher frequency cycles (Figure 17) dominated by carbonate shoal, shoal crest, and proximal shallow subtidal facies, but locally includes deeper subtidal and distal shallow subtidal facies in parts of central Mayes County and at locations to the south and west. Higher frequency cycles in the Hindsville Formation are bounded by glauconitic flooding surfaces overlain by silt-rich beds. Contrasting those in the Ordnance Plant Member, stacking of higher frequency cycles within the Hindsville Formation appears to be progradational. As such, the Hindsville Formation is interpreted as the regressive stage of the upper Mayes cycles. To the south and west of the outcrop area, the lithostratigraphically defined Hindsville Formation is thin to absent and the Fayetteville Shale appears to rest on shaly deep subtidal facies of the Ordnance Plant Member. In both Ordnance Plant and Hindsville higher frequency cycles, relatively deeper water facies (transgressive stage) are separated from relatively shallower water facies (regressive stage) by a distinct burrowed surface. For the upper Mayes cycle, the transition between the transgressive stage (Ordnance Plant Member) and regressive stage (Hindsville Formation) is placed at the base of the interpreted deepest water facies. This facies is represented locally by either a 2- to 6-inch (5–15 cm) section of dark gray to black calcareous to noncalcareous shale (deep subtidal facies) or coarse bioclastic wackestone–packstone to floatstone–rudstone (shallow subtidal facies) at the base of the Hindsville Formation. The interpreted deepest water facies is overlain, and in some cases removed, by the first definitive carbonate shoal facies of the Hindsville Formation. Burrowed surfaces are present throughout the Hindsville Formation. They occur within higher frequency cycles separating transgressive stage deposition (relatively lower energy facies) from overlying regressive stage deposition (relatively higher energy facies). An intensely burrowed surface is also common near the base of the Hindsville Formation and marks the transition between the transgressive stage deposition (Ordnance Plant Member) and regressive stage deposition (Hindsville Formation) within the upper Mayes cycle.
Conodont faunal abundance and diversity trends correspond to interpreted higher frequency depositional cycles in Hindsville Formation, with the highest diversity and abundance occurring at the base of the regressive stage of each higher frequency cycle (Figure 18). In contrast, recoveries from the Ordnance Plant Member, as well as from the lower Mayes cycle, were too poor to establish correspondence to interpreted higher frequency depositional cycles (Godwin et al., 2019). Also of note in Figure 18, the highest overall conodont abundance and diversity within the Hindsville Formation occurs in the regressive stage of the lowermost higher frequency cycle, which also represents the base of the regressive stage of the upper Mayes cycle.
Inclusion of the Ordnance Plant Member within the Upper Mayes Cycle
Huffman (1958) interpreted two transgressive–regressive depositional cycles within the Mayes Group, but placed the boundary between them at the contact between his “Moorefield Formation” (Pryor Creek Formation of this study) and the overlying Hindsville Formation. This placement was based on the interpretation of the contact as an unconformity, which Huffman (1958) supported with two lines of evidence. First was the apparent northward truncation of the Ordnance Plant Member below the Hindsville Formation in northern Mayes County, Oklahoma. This interpretation was based on apparent juxtaposition of the Hindsville Formation on increasingly older sections of the Ordnance Plant Member as the contact is traced northward. In central Mayes County, the Ordnance Plant Member typically consists of a lower shaly siltstone section, middle siltstone section, and upper shaly siltstone section. As Huffman (1958) noted, the middle siltstone transitions to a shaly siltstone and silty shale southward from central Mayes County, representing proximal to distal facies change. Huffman (1958) did not, however, interpret reciprocal facies changes in the lower and upper shaly sections northward from central Mayes County and attributed the absence of the upper shaly siltstone to removal by erosion. An alternative explanation is that the apparent superposition of the Hindsville Formation on the middle siltstone of the Ordnance Plant Member is the result of facies change of the upper shaly siltstone to siltstone in the more proximal position. Thinning of the Ordnance Plant Member northward from central Mayes County also seems to support the truncation interpretation of Huffman (1958), but coincident thinning of the entire Pryor Creek Formation implies possible depositional control. The second line of evidence cited by Huffman (1958) was the reported occurrence of clasts of Ordnance Plant Member in the basal Hindsville Formation outcropping southeast of location 3 of this study in Cherokee County, Oklahoma. This has not been confirmed, as we were unable to locate that referenced location, nor have similar occurrences been observed elsewhere within the study area. Where observed, the boundary between the Hindsville Formation and underlying Ordnance Plant Member appears conformable. It is possible, however, that local erosion of the uppermost Ordnance Plant Member occurred during the transition to higher energy regressive deposition of the Hindsville Formation.
Both Huffman (1958) and Turmelle (1982) reported interfingering of lithofacies or lithologies typically assigned to different lithostratigraphic units within the Mayes Group. Although similar lithologic variation was observed during this investigation, such instances of “interfingering” appear predictable and ordered, and are therefore interpreted as higher frequency shallowing-upward depositional cycles within both the lower Mayes cycle and upper Mayes cycle. Correlation of higher frequency cycles, however, is less reliable in the lower Mayes cycle than the upper Mayes cycle (Figure 14). Observed differences between upper Mayes higher frequency cycles between study sections are attributed to lateral facies variation.
Although Huffman (1958) interpreted two transgressive–regressive cycles in the Mayes Group, he included the Ordnance Plant Member in his lower cycle with the Bayou Manard and Lindsey Bridge members, leaving the Hindsville Formation as the sole unit in his second cycle. In addition to the contrasting stacking patterns of high-frequency cycles described above, inclusion of the Ordnance Plant Member in the upper Mayes cycle was done for two reasons. First, the Ordnance Plant Member unconformably overlies the Lindsey Bridge Member, whereas it conformably underlies the Hindsville Formation. Therefore, the Ordnance Plant Member shares a closer genetic relationship with the Hindsville Formation. Although Huffman (1958) interpreted an unconformity between the Ordnance Plant Member and Hindsville Formation, no definitive evidence was observed during this investigation supporting that interpretation. Instead, the unconformity between the Ordnance Plant Member and Lindsey Bridge Member is clearly defined in central Mayes County and is also present to the southeast in Adair County. These observations agree with those of Swinchatt (1967) who noted an apparent truncation of the Lindsey Bridge Member along its contact with the overlying Ordnance Plant Member. Swinchatt (1967) described the contact as unconformable, which contradicts the conformable contact reported by Huffman (1958). Second, terrigenous quartz silt is common throughout the Mayes Group and tends to accumulate at or near the bases of cycles regardless of scale. Quartz silt is concentrated at the base of the Bayou Manard Member in central Mayes County. At location 12 in Mayes County and location 4 in Adair County, shallow-water (proximal shallow subtidal) ripple cross-laminated siltstone beds commonly occur at or near the base of high-frequency shallowing-upward cycles within the Hindsville Formation. At location 21 in Craig County, Oklahoma, the base of the Hindsville Formation includes a green–gray calcareous siltstone with ripple cross-laminations and vertical and horizontal burrows. Within the quarry walls, this siltstone bed thins and pinches out from north to south. Although lithostratigraphically included in the Hindsville Formation, this siltstone is similar to siltstones in the Ordnance Plant Member. It is possible that this green–gray siltstone represents the northern extent of the transgressive stage of the upper Mayes cycle and is equivalent to the Ordnance Plant Member farther south. Where the Hindsville Formation was observed in Ottawa County, it also includes a thin gray–green calcareous siltstone and silty calcareous shale near the base.
Sequence Stratigraphic Implications and Controls on Depositional Cyclicity
Sequence stratigraphic terminology was not applied to the Mayes Group earlier in this chapter because the interpretations discussed herein were predominantly based on observations made at locations in central Mayes County and subsequently applied on a limited basis to other areas of northeastern Oklahoma. Thus, interpretations of Mayes Group depositional cyclicity are essentially one- and two-dimensional. In this section, sequence stratigraphy of the Mayes Group in northeastern Oklahoma is addressed using conodont biostratigraphy-based time-averaging of the interpreted depositional cycles and comparisons with studies of time-equivalent strata in North America.
Based on conodont biostratigraphic data, the span of time represented by the Mayes Group is 5–6 m.y., with both the lower and upper Mayes cycles representing up to 3 m.y. (Menning et al., 2006; Godwin et al., 2019). The lower and upper Mayes cycles are therefore interpreted as third-order sequences, with the entire Mayes Group representing a second-order sequence relative to the order assigned to the lower and upper Mayes cycles. Higher frequency shallowing-upward cycles represent approximate time spans of between 300 and 550 k.y. and are therefore interpreted as fourth-order sequences.
Of specific interest is the comparison between observations of the Mayes Group in northeastern Oklahoma and the sequence stratigraphic model of Handford (1995) and Handford et al. (2014) for temporally equivalent strata in northern Arkansas. Handford (1995) proposed the “Marshall sequence” for Meramecian through Chesterian strata in northern Arkansas. The Marshall sequence sediment was deposited along following the development of a sequence-bounding unconformity (equivalent to the sub-Mayes unconformity of this study) and down-dip correlative conformity. Within the Marshall sequence, Handford (1995) interpreted the Moorefield Formation as the lowstand systems tract, the Hindsville Formation and Batesville Sandstone as the initial part of the transgressive systems tract, the Fayetteville Shale as the main part of the transgressive systems tract, and the Pitkin Limestone as the highstand systems tract. Although this interpretation does not address third-order and higher frequency depositional sequences similar to those interpreted in the Mayes Group, the overall geometry of the Mayes Group in northeastern Oklahoma compares favorably with that of the Moorefield Formation and Hindsville Formation of the Marshall sequence in northern Arkansas. Low-energy deep subtidal facies of the Pryor Creek Formation in Oklahoma and Moorefield Formation in northern Arkansas unconformably overlie the Boone Group and interpreted high-frequency shallowing-upward cycles appear to onlap the unconformity surface. In both instances, the lowstand systems tract thins and pinches out updip and high-energy carbonate shoal facies of the Hindsville Formation rest unconformably on sub-Mayes Group strata. At two locations in Boone County, Arkansas, where the Hindsville Formation rests unconformably on the Boone Group, the base of the formation includes brown-gray calcareous shale, greenish-gray calcareous siltstone, and thin lenses of calcareous sandstone. Here again, the initial transgressive phase of the Hindsville Formation is dominantly composed of terrigenous silt and clay and is possibly correlative to the Ordnance Plant Member of northeastern Oklahoma. It is likely that the Marshall sequence represents a supersequence of which the third-order sequences (lower and upper Mayes cycles) are a part.
Like the Mayes Group of northeastern Oklahoma and the Marshall sequence of Handford (1995), Lane (1974) identified a Meramecian–Chesterian basinward-thickening depositional wedge in southeastern New Mexico and west Texas consisting of the Rancheria and Helms formations, which was interpreted by Bachtel and Dorobek (1998) as a single depositional sequence. Interpreted third- and fourth-order depositional sequences in the Mayes Group appear to correspond to, or are similar to those reported in the Appalachian region in the eastern United States (Miller and Eriksson, 2000; Smith and Read, 2000; Al-Tawil and Read, 2003; Al-Tawil et al., 2003; Wynn and Read, 2007). Al-Tawil et al. (2003) interpreted the Appalachian Greenbrier Group, which is temporally correlative to the Mayes Group, as the transgressive stage of a larger supersequence that includes overlying strata equivalent to the Fayetteville Shale and younger strata.
Late Paleozoic glaciation and early phases of Ouachita tectonism are herein considered in terms of their relative influence on the observed stratigraphic architecture and cyclicity of the Mayes Group. Glacioeustatic control on Mississippian deposition prior to and during the formation of the Mayes Group is documented in several studies (e.g., Isaacson et al., 2008; Kammer and Matchen, 2008; Bishop et al., 2009; Giles, 2009), and is herein interpreted as the primary control on the higher frequency cycles (fourth-order sequences) observed in both the lower and upper Mayes cycles. Third-order depositional sequences, represented by the lower and upper Mayes cycles, correspond to the sea-level curve published by Ross and Ross (1985) for the Upper Mississippi River Valley where a major unconformity occurs below the Meramecian upper St. Louis Limestone (Bayou Manard Member; see Godwin et al., 2019) and a second unconformity below the Chesterian Ste. Genevieve Limestone. The Lindsey Bridge Member and Ordnance Plant Member are considered Chesterian and probably equivalent to the Ste. Genevieve Limestone (Godwin et al., 2019). Consequently, the decline in relative sea-level between the St. Louis and Ste. Genevieve limestones (Ross and Ross, 1985) may correspond to the unconformity between the lower and upper Mayes cycles. Syndepositional tectonics during the Kinderhookian and Osagean is evidenced by post-Osagean uplift and erosion (i.e., sub-Mayes unconformity; Huffman, 1958). Syndepositional forebulge uplift and relaxation were invoked as mechanisms controlling the stratigraphic architecture of Kinderhookian through basal Meramecian strata in Oklahoma, Kansas, Arkansas, and Missouri by Mazzullo et al. (2016). Houseknecht et al. (2014) suggested that thinning of the Moorefield Formation in northern Arkansas resulted from syndepositional faulting. In both cases, structural movement was attributed to incipient Ouachita tectonism. Syndepositional tectonism continued into the Meramecian as evidenced by stratigraphic relationships within uppermost Boone Group strata in the Tri-State Mining District of northeastern Oklahoma (Godwin et al., 2019), but it is not clear, however, if structural movement continued during deposition of the Mayes Group. It is likely that many of the larger paleotopographic relief features along the sub-Mayes unconformity and resultant thickness and facies variations observed in the lower Mayes cycle resulted from a combination of the uplift and erosion, as interpreted by previous workers, and glacioeustasy. Such uplift is likely the cause of the informally named “Adair–Cherokee high,” an area across which the Pryor Creek Formation anomalously thins and pinches out, resulting in the Hindsville rests on sub-Mayes strata. More consistent thickness of units in the upper Mayes cycle suggests that the depositional surface was relatively stable and that post-Mayes Group flooding, represented by deposition of the Fayetteville Shale, was glacioeustatic in nature.
This investigation evaluated and re-interpreted the Mayes Group in light of modern stratigraphic concepts. As a result, five depositional facies associations and a hierarchy of cyclicity were defined. Recognizing facies stacking patterns and distribution, as well as identifying important stratigraphic surfaces in the Mayes Group provided evidence to support revising current lithostratigraphic boundaries and laid the foundation for more confident correlation of outcrop stratigraphy to the subsurface of Oklahoma.
The Mayes Group records a primary shallowing-upward or transgressive–regressive depositional cycle following subaerial exposure and erosion associated with the sub-Mayes unconformity. This primary depositional cycle appears equivalent to a second-order depositional sequence or the lowstand and transgressive systems tracts of a larger depositional sequence that includes the overlying Fayetteville Shale and Pitkin Limestone (e.g., Handford, 1995). The Mayes Group primary cycle consists of two secondary transgressive–regressive cycles, herein termed the lower Mayes cycle and upper Mayes cycle, each of which represents a third-order depositional sequence. Separating the lower and upper Mayes cycles is the previously unrecognized unconformity between the Lindsey Bridge and Ordnance Plant members of the Pryor Creek Formation. The lower Mayes cycle and upper Mayes cycle are both considered a third-order sequence of up to 3 m.y. in duration, each. Both cycles contain higher frequency depositional cycles bounded by flooding surfaces. These higher frequency cycles are believed to represent equivalent to fourth-order sequences, with temporal spans of 300–550 k.y.
The interpretations provided use depositional facies, stratigraphic surfaces, and lateral facies changes to clarify ambiguous lithostratigraphic relationships in the Mayes Group. We believe that this work provides a foundation for subsequent high-resolution stratigraphic studies seeking to construct a comprehensive regional sequence stratigraphic model for Meramecian and Chesterian ramp carbonates.
First and foremost, we would like to remember Darwin R. Boardman II, who passed away in January of 2015. We continue miss his enthusiasm for geology and life.
We would also like to thank the many quarry operators who allowed us access to their facilities, and exposures critical to advancing this project: BuzziUnicem U.S.A. (Pryor Quarry), Kemp Quarries (Pryor Quarry, Fairland Quarry, Neosho Quarry), Midwest Minerals (Quapaw Quarry), and APAC (Vinita Quarry). Parts of this study were supported by the Oklahoma State University Mississippian Carbonates Consortium. Access to the PM-21 core in Cherokee County, Kansas was provided by the Kansas Geological Survey in Lawrence, Kansas. Access to Oklahoma cores was provided by the Oklahoma Geological Survey’s Oklahoma Petroleum Information Center (OPIC) in Norman, Oklahoma.
We would also like to express our appreciation to S. J. Mazzullo and B. W. Wilhite for their critical reviews of earlier manuscript drafts. Both provided valuable input that helped to refine critical aspects of this manuscript.