Date of Graduation

2009

Document Type

Dissertation

Abstract

Carboniferous plant fossils have been reported from the Appalachian Basin since the middle part of the nineteenth century. The lack of easy access to European literature and comparative specimens resulted in a body of work characterized by overly diagrammatic figures and confusing lists of junior synonyms with limited figures. This report provides 41 photographic plates of Carboniferous plant fossils from the Appalachian Basin. Comparative range charts are used to summarize the similarity of the fossil macrofloras of the Appalachian region with those of other parts of Euramerica, although each paleoregion has a small number of endemic species. First occurrences and extinctions of taxa are broadly similar across Euramerica, although there are regional differences due to the presence of temporally-brief geographic or climatic barriers that slow migration. Lithostratigraphies and chronostratigraphies are discussed and the Carboniferous macrofloral succession of the Appalachian Basin is correlated with other Euramerican regional stage boundaries, including various Westphalian stage boundaries, the Westphalian-Stephanian boundary and notably the mid-Carboniferous boundary. Late Mississippian (early Namurian; Serpukhovian) paleogeographic reconstructions place eastern Euramerica on the paleoequator while western regions were farther south. Correlation between lower Namurian rocks of the Central Appalachian Basin (CAB) and eastern Euramerica is demonstrated by the presence of a common paleoflora which is discussed and doicumented. Paleoflorules from the informal upper member of the Bluestone Formation, the youngest Mississippian strata in the CAB, contain Karinopteris renieri and Lyginopteris stangerii, correlated herein with Wagner’s (1984) Zone of Lyginopteris larischi and Purkynova’s (1996b) NA 3 macrofloral biozone. These Late Mississippian macrofloral biozones correlate, in order, with the lower and upper parts of the E2 ( Eumorphoceras) goniatite zone. A late Arnsbergian macrofloral-based age assignment for the uppermost Mississipppian in the CAB agrees with previous age estimates based on conodonts from the Bramwell Member (Bluestone Fm.). Bramwell conodonts have been assigned to the Adetognathus unicornis conodont zone, a position slightly below the mid-Carboniferous boundary GSSP at Arrow Canyon, Nevada. An east-west paleomoisture gradient developed across Euramerica due to the periodic contraction and expansion of southern hemisphere glacial ice. Early Namurian paleoclimate proxies indicate that eastern Euramerica enjoyed a tropical-wet climate. In contrast, the upper Hinton and Bluestone formations (CAB) contain numerous paleovertisols, common calcareous glaebules (caliche), rare salt crystal casts, possible gypsum films coating vertic structures and gypsiferous nodules within at least one calcic paleovertisol. Coal beds are areally discontinuous, low in quality and thin, suggesting ground water control on peat accumulation. These proxies suggest the CAB paleoclimate varied between semi-arid and subhumid. Reasons for the climatic gradient are discussed and a model that suggests that periodically varying polar ice volumes altered the position of the tropical monsoon which controlled, in part, the distribution of equatorial moisture across Euramerica. The Bluestone is overlain by the Lower Pennsylvanian Pocahontas Formation. A sub-Pocahontas (Lashmeet) paleovalley has been identified in southern West Virginia. The Lashmeet paleovalley was incised over 35 m into the Upper Mississippian Bluestone Formation strata during the mid-Carboniferous eustatic event. This major glacio-eustatic sea-level fall formed a prominent unconformity across the shallow shelf areas of Euramerica that is used to demark the boundary between the Mississippian and Pennsylvanian subsystems. The Green Valley paleosol complex (GVPC) has been identified at the contact between the Bluestone and Pocahontas formations on associated interfluves. Together, the Lashmeet paleovalley and the GVPC demonstrate a substantial period of subaerial exposure in the CAB and argue strongly in favor of a Mississippian-Pennsylvanian unconformity. Paleontological data from the Upper Mississippian Bluestone Formation (discussed above) support a late, but not latest Arnsbergian age assignment. Marine fossils are not known from the Pocahontas Formation, but macrofloral and palynomorph taxa support a Langsettian age for most of the Pocahontas suggesting the absence of the middle and upper Namurian in the CAB.

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