The Silurian rocks in Delaware County, Indiana, include, in ascending order, the Salamonie Dolomite, Limberlost Dolomite, Waldron Formation, and Louisville Limestone, and Mississinewa Shale Member of the Wabash Formation, all of the Niagaran Series (middle Silurian).The oldest exposed Silurian rocks are the Salamonie and the overlying Limberlost Formation (lower Niagaran) are exposed in Irving and Eaton quarries. The Salamonie is 25 feet of apparently reefflank rocks within the Salamonie, with primary dips to 20 degrees, are exposed in Eaton Quarry. The Limberlost, averages six feet and is generally brown, vuggy, dolostone.The Waldron and Louisville formations (middle Niagaran), are exposed in Hoyt, Irving, and Eaton quarries. The Waldron averages six feet and is interbedded grey shale and argillaceous dolostone, and is fossiliferous. It is conformably overlain by about 60 feet of Louisville Formation, predominately argillaceous dolostone with nodular chert and fossils.At Buchanan Quarry, 10 feet of grey dolomitic siltstone and shale of the Mississinewa Member, Wabash Formation, comprise the youngest Silurian strata exposed.Correlation of distinct units within the Louisville between Hoyt, Irving, and Eaton quarries shows considerable lateral continuity and general thinning toward the north.

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This dissertation represents an investigation of the mid-Paleozoic tectono-thermal and kinematic evolution of the crust in eastern coastal Maine as recorded by the plutonic rocks of this region. The first chapter describes the plutonic rocks of the Coastal Maine Magmatic Province. A tectonic model is developed in which late Ordovician-Silurian bimodal magmatism is interpreted to reflect crustal melting as a result of intraplating of mantle melts at high crustal levels during a period of tension. Large scale melting of lower crustal source regions, represented by voluminous intrusion of Devonian granites, reflects a period of transpression during which upwelling mantle melts were confined to the base of the crust. The diversity of granitic plutons reflects changes in the mineral assemblages present during partial melting, and in some instances, modification as a result of mixing/mingling with mantle melts. The second chapter examines the effect of accessory minerals on the initial Pb isotopic signature of anatectic granites. Their initial Pb isotopic composition reflects (a) the age, type, modal distribution, and heterogeneity in the initial U and Th content of the accessory phase(s) present in the source, (b) variation in melt composition and temperature during partial melting, (c) the fraction of the source melted, and (d) the extent to which the melt is homogenized prior to crystallization. It is shown that granitic plutons derived by crustal anatexis of a common source material are not required to have similar initial lead isotopic compositions. The third chapter presents the results of a Pb isotopic investigation of selected plutonic rocks from the Coastal Maine MagmaticProvince. This study was designed to test and refine petrogenetic models presented in Chapter 1. The Pb isotopic signature of the granitic plutons reveals the presence of two lithologically heterogeneous source regions beneath the Avalon Composite Terrane. The upper crustal source region has an mean V-Pb age of -2.0 Ga and the high 207Pb/204Pb-206Pb/204Pb characteristic of Avalonian crust. The lower crustal source region has an average U-Pb age of -1.3 Ga and lower 207Pb/204Pb. This source region may represent either the autochthonous basement to the Avalon platform or the eastern extension of the basement to the Gander Terrane of central Maine. / Ph. D.

Sedimentary dikes at the Pipe Creek Junior Quarry were found to fill fractures formed by compaction and rotation of the reef flank beds and by regional stresses of less certain origin. A sequence of fracturing events has been established as well as a sequence for the emplacement of dike materials. Most of the carbonate dikes are found to be of Cayugan (Silurian) age, although some of the las carbonates are shown to be of Devonian age due to the presence of rounded detrital quartz grains within them. All of the quartz arenite dikes are found to be of Devonian age and are divided into two major groups: older white arenites and younger brown arenites. The two types of arenties have different characteristics and were deposited under different conditions.The arenites of Pipe Creek Junior Quarry were found to be similar to the arenites of the Bluffton Quarry which are also fracture fillings in Silurian reef rock. Other Devonian sand bodies are compared to the fracture filling and, although they are not identical, they show a similarity in materials and a pattern of environment and deposition that point to a northwestern source for all of the rounded quartz studied in this work. Environmental analysis of the quartz grains indicates a litoral mode of transport and sorting for most of the samples with an ecolian mode present in the sands outside the reef area and as a minor component for some of the younger sands within the reef area.A map of the glaciated quarry surface has been prepared for the purposes of this work and to preserve relationships that are constantly being removed by quarrying of the reef flank beds.

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