ABSTRACT Data from 33 locations were utilized in a stratigraphic study of the Early Mississippian Grainger Formation and related units in northeast Tennessee. Isopach maps, stratigraphic cross sections, and lithologic trends indicate the Grainger Formation was deposited in four deltaic lobes: Monroe, Rock Haven, Hancock, and Grainger-Borden. Each is in a separate outcrop belt: Chilhowie Mountain, Clinch Mountain, Newman Ridge, and Cumberland Mountain. The Monroe lobe is the eastern and southernmost of the lobes. Within it, the Grainger Formation is thicker and coarser than in the other locales. It is underlain by gray and black shale; the gray shale is a probable nearshore gray version of the usually greenish Maury Formation. The Greasy Cove Formation, a heterogeneous unit of sandstone, shale, red beds, and limestone, overlies the Grainger Formation and occupies the stratigraphic position of the Maccrady Formation and Newman Limestone in outcrop belts to the northwest. The Greasy Cove Formation is recognized only in the Monroe lobe. In the Rock Haven lobe, both the Grainger Formation and Chattanooga Shale are divisible into mappable members. The Chattanooga Shale consists of an upper Big Stone Gap Member, a middle Brallier Member, and a lower Millboro Member. The Chattanooga Shale locally is 600+ m thick. The Grainger Formation in the Rock Haven lobe is divisible into three newly named members: an upper Hayters Sandstone member, a middle Greendale member, and a basal Bean Station member. The Alumwell glauconite zone, within the upper part of the Greendale member, is also new. The center of the zone approximates a time line and is a key stratigraphic horizon. All Grainger members and the Alumwell glauconite are traceable into the Price Formation of southwest Virginia. In the Rock Haven lobe, the Chattanooga Shale, Grainger Formation, and Maccrady Formation were deposited in a subsiding trough; subsidence began in the Givetian and perhaps in the Eifelian, caused by a migrating peripheral bulge generated by Neoacadian deformation in the Carolina Piedmont. Highlands created by the deformation were the eastern sediment source for the Chattanooga, Grainger, and Maccrady formations in this lobe. Sediment for the Hancock and Grainger-Borden lobes originated from northerly sources. In the Hancock lobe, the Chattanooga Shale and Grainger Formation are thinner, and the Grainger Formation has increased shale content to the south. Paleocurrent data indicate a north-south current flow. The Hancock lobe is likely a southern extension of the Price delta system in southwest Virginia. The Grainger-Borden lobe is the southern terminus of the Borden delta system of Kentucky. Both the Chattanooga Shale and Grainger Formation thin to the south and southeast. The Floyds Knob glauconite bed was deposited during a pause in sediment delivery and separates the Fort Payne Chert from the underlying Grainger Formation as a distinct sedimentary unit. The Fort Payne Chert overlaps the Grainger Formation from a deeper southern basin where the dolostone and chert have little or no interbedded shale. The overlap does not interfinger with the Grainger Formation. The Fort Payne Chert becomes thinner as it progresses northward, finally passing into the Muldraugh Formation in Kentucky. It also made a minor incursion eastward into the western margin of the Hancock lobe, where some chert(y) beds occur at the Maccrady position.

ABSTRACT During latest Devonian to Middle Mississippian parts of the Neoacadian and Ouachita orogenies, the Appalachian Basin and parts of the Illinois Basin were filled with clastic debris derived from the westward-prograding Borden-Grainger-Price-Pocono clastic wedge. This delta complex is overlain by the widespread shallow-water Newman–Greenbrier–Slade–St. Louis–Warsaw–Salem–Harrodsburg carbonate interval across sediment-starved surfaces, comprising the Floyds Knob bed or interval. The Middle Mississippian (late Osagean; early Viséan) Floyds Knob interval is less than a meter to several meters thick and is composed of multiple zones of pelletal glauconite, finely divided glauconitic shales, glauconitic carbonates, and locally derived carbonate mud mounds. The interval occurs across most of the Borden-Grainger delta platform, delta front, prodelta, and within the starved-basin area seaward of the delta complex, which was then filled with the Fort Payne Formation. This study reports herein the first occurrence of the Floyds Knob interval within the Fort Payne Formation. Glauconite deposition in this interval apparently occurred in mildly oxic to dysoxic, sediment-starved, shallow-marine settings and is believed to represent termination of major clastic influx in more proximal parts of the Neoacadian foreland basin during lowstand conditions. Moreover, these starved-basin conditions can be correlated with delta diversion following bulge migration during flexural loading–type relaxation. During these sediment-starved, lowstand conditions, glauconite was deposited across deltaic and basinal settings in central and distal parts of the Neoacadian foreland basin, as well as in eastern parts of the present-day Illinois intracratonic basin. The cessation of deltaic clastic sedimentation permitted development of carbonate mud mounds and associated glauconitic shales on and near reactivated structures in central parts of the Fort Payne starved basin and set the stage for the widespread deposition of thick, Meramecian–Chesterian carbonates throughout the basins during succeeding subtropical and lowstand conditions. Whether less-than-a-meter or tens-of-meters thick, the Floyds Knob interval is a widespread Middle Mississippian chronostratigraphic interval in the east-central United States that reflects a change in tectonic regime, which is recorded in the shift from predominantly clastic to carbonate sedimentation across a broad region. Aside from its correlative value, the unit demonstrates consequent sedimentary responses to the interplay among tectonism, paleoclimate, and paleogeography.

Abstract On this fieldtrip, we visit outcrops of Middle Mississippian siliciclastic mounds that have affinities with the famous European Waulsortian mud mounds and younger submarine channels incised into the lower part of the Fort Payne Formation. The purpose of this fieldtrip is to stimulate discussion of these unique geometries in a mixed carbonate-clastic system. It is now generally conceded that these stratigraphic features were built in a basin plain setting, but their origin is poorly understood. Further, we will see other geologic strata (Chattanooga Shale and Maury Shale) whose origins have been, and continue to be, intensely debated in the geologic literature. The mounds at the base of the Fort Payne are about the same age as the classic European Waulsortian mounds and have a similar fauna. The largest Tennessee mounds are as large as some in Europe, but differ in having a matrix of terrigenous clay rather than carbonate mud. Channels in the Fort Payne are filled with a mix of alternating carbonates and fine-grained clastics. Deposition in the channels was likely due to carbonate-rich sediment gravity flows on the slope, evidenced by grainstones that exhibit grading and imbrication of crinoid skeletal fragments. Siliciclastic mudstones interbedded with carbonate facies suggest that event-driven flows punctuated periods of slope quiescence and hemipelagic deposition during the Mississippian.