Kansas Geological Survey, Current Research in Earth Sciences, Bulletin 258, part 4
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Kansas Geological Survey, Current Research in Earth Sciences, Bulletin 258, part 4
Prev Page--Introduction, Boundary ||
Next Page--Systematic Paleontology
Thompson (1954) described the fusulinids of the Admire, Council Grove, and Chase Groups in Kansas when all three units were considered early Permian (Wolfcampian) in age. As described above, with the recent conodont-based correlation of the new global Carboniferous (Pennsylvanian)-Permian boundary from the Eurasian stratotype to the North American midcontinent, the Admire and lower part of the Council Grove Groups (below the Glenrock Limestone- Member-Bennett Shale Member contact) are now considered to be latest Pennsylvanian (Virgilian, Gzhelian) (fig. 2). As shown by Thompson (1954), the Admire and lower part of the Council Grove fusulinids are characterized by large species of Triticites, several species of Leptotriticites (which Thompson called Dunbarinella), and the earliest primitive species of Schwagerina. Ross and Ross (1994, 1998) suggested the orphaned interval from the base of the Admire to the new systemic boundary be designated a new stage, the Bursumian. However, that proposal has not been widely accepted, and most authors have placed the orphaned interval into the uppermost Pennsylvanian Virgilian Stage. The arguments against the Bursumian concept are 1) the lack of definitive supporting conodont data for the lower boundary; 2) the finding that the fusulinid genus Leptotriticites, once considered a typical "Bursumian" genus, actually appears lower in the section, within the middle and upper parts of the Wabaunsee Group (Virgilian) of Kansas (Douglass, 1962; Sanderson and Verville, 2000; Sanderson et al., 2001); and 3) the facies of the Bursum Formation that crop out in New Mexico do not contain faunas sufficient to define a new chronostratigraphic unit.
Fusulinids in the Glenrock Limestone Member of the Red Eagle Limestone, which directly underlies the new Carboniferous (Pennsylvanian)-Permian boundary at its contact with the Bennett Shale Member, are Leptotriticites glenensis (Thompson, 1954), Schwagerina campa (Thompson, 1954), and Triticites rockensis (Thompson, 1954) (fig. 2). Leptotriticites glenensis is slightly larger than most earlier species of Leptotriticites from the Wabaunsee, Admire, and lower part of the Council Grove Groups (Thompson, 1954; Sanderson et al., 2001), and is slightly smaller than the stratigraphically higher species of the genus in the Neva Limestone Member (Grenola Limestone). Schwagerina campa is a relatively small, elongate, primitive species of that genus. Triticites rockensis is a rather small species relative to other Admire-Council Grove Triticites (e.g., T. ventricosus), and it has some morphological characteristics that are more similar to earlier Triticites in the late Virgilian Wabaunsee Group (Thompson, 1954).
O'Connor and Jewett (1952) illustrated a few fusulinids in photomicrographs of the Bennett Shale and Howe Limestone Members of the Red Eagle Limestone, but did not identify or describe the specimens.
Thompson (1954, fig. 2) did not describe any fusulinids in the interval between the Glenrock Limestone Member-Bennett Shale Member contact and the base of the Neva Limestone Member of the Grenola Limestone, where the first inflated schwagerinid Paraschwagerina kansasensis (Beede and Kniker) appears. The Neva fauna also contains Schwagerina longissimoidea (Beede, 1916), a large, elongate, and primitive species of the genus whose range straddles the new systemic boundary (fig. 2), and the stratigraphically highest and largest species of Leptotriticites, i.e., L. tumida (Skinner, 1931), L. obesa (Beede, 1916), and L. koschmanni (Skinner, 1931). Thompson's (1954, fig. 2) chart showed another thin interval lacking fusulinids above the Neva Limestone Member. The next higher fusulinid assemblage in the section is from the Cottonwood and Morrill Limestone Members of the Beattie Limestone, which contain typical early Wolfcampian morphotypes of Schwagerina (S. vervillei Thompson, 1954, and S. jewetti Thompson, 1954), and Schwagerina emaciata (Beede, 1916), which is also known from the Waldrip Shale Member of north-central Texas and therefore straddles the new Carboniferous (Pennsylvanian)-Permian boundary. Thompson's (1954, fig. 2) chart then showed a thick stratigraphic interval (approximately 230 ft) above the Beattie Limestone that lacks fusulinids, and the first inflated Pseudoschwagerina (P. texana Dunbar and Skinner, 1937) appears in the Florence Limestone Member of the Barneston Limestone (Chase Group), which is late Wolfcampian. It is noteworthy that although the Wolfcampian is commonly referred to as the Zone of Pseudoschwagerina, that genus does not appear until high above the (Carboniferous) Pennsylvanian-Permian boundary in the midcontinent, probably because of unsuitable offshore normal marine environments through the upper part of the Council Grove and lower part of the Chase Groups (fig. 2).
The Howe Limestone Member of the Red Eagle Limestone was named by Condra (1927, p. 86) for a 4-ft (1.22-m)-thick, gray, massive, and dense, poorly fossiliferous, vuggy limestone that weathers buff to yellowish and crops out south of Howe, Nebraska. Moore et al. (1951) described the Howe Limestone Member as consisting of variable facies and ranging from less than 1 ft to 15 ft (0.3-4.57 m) in thickness. O'Connor and Jewett (1952) pointed out north-to-south lithologic changes in the Howe Limestone Member, being composed of vuggy dolomites in Nebraska and northern Kansas, to granular and fossiliferous limestones in central Kansas, and then to massive fine-grained limestone in southern Kansas and Oklahoma. Zeller (1968) described the Howe Limestone Member as a fine-grained algal limestone containing tiny pelecypods and gastropods, ostracodes, and foraminifers. McCrone (1963) described the Howe Lime-stone Member in southern Nebraska and northern Kansas as a characteristically fine-grained, massive, sparsely fossiliferous limestone that is deeply weathered and has a very vuggy nature. McCrone further described that the Howe Limestone Member changed southward through central and southern Kansas to pseudo-oolitic, pelletoid, and osagiid limestones, and that in southern Kansas and adjacent northern Oklahoma the upper part of the Howe Limestone Member was characterized by large stromatolitic and osagiid masses.
The Howe Limestone Member is the upper regressive highstand limestone of the Red Eagle Limestone cyclothem. Boardman and Nestell (2000) and Boardman et al. (2009) defined the Red Eagle cyclothem as a composite 4th order depositional sequence, composed of, in ascending order, the upper part of the Johnson Shale, the Red Eagle Limestone (Glenrock Limestone, Bennett Shale, and Howe Limestone Members), and the Roca Shale (fig. 2). Within the Red Eagle 4th order depositional sequence, those authors recognized six 5th order sequences (A-F), with the bottom three (A-C) being subtidal cycles and the upper three (D-F) being more marginal-marine to nonmarine exposure cycles. The basal 5th order sequence A is developed entirely within the upper part of the Johnson Shale. The 5th order sequence B is composed of the Glenrock Limestone and lower part of the Bennett Shale Members of the Red Eagle Limestone, with transgression throughout Glenrock deposition to a maximum flooding surface in the basal part of the Bennett shale. The 5th order sequence C is entirely within the upper part of the Bennett shale. The 5th order sequence D is composed of the Howe Limestone Member and the paleosols of the overlying lower part of the Roca Shale. The 5th order sequences E and F are nonmarine to marginal-marine cycles in the middle and upper parts of the Roca Shale, respectively.
The Glenrock Limestone Member is the transgressive limestone of the Red Eagle 4th order cyclothemic depositional sequence (fig. 2). Transgression continued into the overlying Bennett Shale Member where two condensed maximum flooding horizons occur in the basal 0.3 m and contain the basal Permian conodont index fossil Streptognathodus isolatus, along with orbiculoid brachiopods, ammonoids, and fish debris (Boardman et al., 1995). The upper part of the Bennett Shale Member generally contains deeper-water to offshore shelf fossil biotas. The Howe Limestone Member is the highstand marine regressive facies of the Red Eagle 4th order cyclothemic depositional sequence and is overlain by the thick, mostly nonmarine, lower part of the Roca Shale, which is composed of stacked paleosols (Miller et al., 1996). The Howe Limestone Member represents widespread shallow-water, normal to restricted marine conditions. The northern mud-rich sparsely fossiliferous carbonate facies represent shallow subtidal, normal to restricted marine shelf paleoenvironments, and the more southern grain-rich and algal-rich facies represent higher-energy, very shallow subtidal to peritidal, restricted marine paleoenvironments.
Significantly, according to Sawin et al. (2006), the condensed horizons in the lower part of the Bennett Shale Member represent the maximum flooding events for the entire Admire-Council Grove interval in the midcontinent. Those authors cited evidence that the amplitude of sea-level fluctuations and the sedimentary characteristics of cyclothem sequences changed after Red Eagle deposition. Geochemical evidence from paleosols through the stratigraphic section indicates that the more humid paleoclimatic conditions of the Late Pennsylvanian changed after Red Eagle deposition to distinctly more arid paleoclimatic conditions in the overlying section (Miller et al., 1996).
In 2007, Ron West (Kansas State University, Manhattan) and Robert Sawin (Kansas Geological Survey) collected two fusulinid-bearing samples from the Howe Limestone Member at the Tuttle Creek Lake Spillway section in northeast Kansas (Locality 1, fig. 1), which Sawin et al. (2006) proposed as the Carboniferous (Pennsylvanian)-Permian boundary reference section in Kansas. Those samples were sent to the senior author for analysis of the fusulinids. The samples were brownish-yellow skeletal limestone (wackestone and packstone) that were severely recrystallized and somewhat leached, with numerous large fusulinid skelmolds on the surface; however, after slabbing the samples it was found that they also contained some preserved fusulinids. The fusulinid skelmolds all have a similar size and fusiform shape to the preserved specimens, and none of the skelmolds appeared to represent inflated fusulinid shell forms. Fusulinids in the recrystallized, leached limestone are not very well-preserved, and the soft nature of the limestone made it rather difficult to thin-section the fusulinids without losing parts of the specimens. Nevertheless, 16 oriented fusulinid thin sections were made from the two samples (Plate 1). Associated fossils in the samples are bryozoan and brachiopod fragments, echinoderm ossicles, and smaller foraminifers (e.g., Globivalvulina, palaeotextulariids), an assemblage that represents a normal marine-shelf paleoenvironment.
In 2009, Ron West collected fusulinids from a second Howe Limestone Member locality (Locality 2, fig. 1), from an outcrop along South Seth Child Road (Hwy 113), about 1,400 ft (426.72 m) south-southeast of the intersection with Amherst Avenue in Manhattan, Kansas, which is located about 5.5 mi (8.85 km) south-southwest of the Locality 1 exposure at the Tuttle Creek Lake Spillway. The occurrence of the fusulinids in this sample corresponds with unit 34 of West (1994), occurring 1.3 ft (40 cm) above the base of the Howe Limestone Member. O'Connor and Jewett (1952) noted that the lithofacies of the Bennett shale are quite variable from north to south. The Bennett Shale Member-Howe Limestone Member contact is rather transitional in the Locality 2 area, and the sampled interval could be considered the lowermost part of the Howe Limestone Member or the uppermost part of the Bennett Shale Member (see O'Connor and Jewett, 1952; McCrone, 1963; Clark, 1989). The locality 2 sample comes from a relatively light-colored brownish-gray calcareous mudrock interval between the base of the massive Howe Limestone Member and the top of the dark (black) mudrocks/shales of the Bennett Shale Member. The light-colored mudrock facies was assigned to the basal part of the Howe limestone in this study mainly because it contains a relatively shallow-water fossil assemblage that is characteristic of the Howe Limestone Member, including articulate brachiopods, bryozoans, and fusulinids. Fusulinids have not been reported from the Bennett Shale Member in the area. As noted by O'Connor and Jewett (1952, p. 340-341) and McCrone (1963), the fossil assemblage in the Bennett Shale Member is composed of mostly orbiculoid and lingulid brachiopods, conodonts, fish teeth, ostracods, and agglutinated foraminifers. That distinct difference in fossil assemblages allows differentiating the two units where the Bennett Shale Member becomes predominantly limestone, as in the southern part of Kansas. As the Bennett Shale Member and Howe Limestone Member are part of the same depositional cycle, from a biostratigraphic viewpoint, the lithostratigraphic assignment of the unit is not important. The sample from Locality 2 consists of free fusulinid specimens in washed residue from the mudrock unit (fig. 2). Those free specimens vary in size and preservation, but all have elongate fusiform tests, and no inflated (i.e., Wolfcampian-like) shell forms were present. Many specimens were too weathered for thin-sectioning, but nine specimens were oriented and thin-sectioned (Plate 2).
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