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_Journal of Structural Geology 32 (2010) 1923-1932_ _Cathodoluminescence imaging reveals that sandstones of the middle Pennsylvanian Lee Formation and Breathitt Group along the Pine Mountain Overthrust (PMO) contain interand intra-granular authigenic quartz in proportions that differ markedly between samples of contrasting deformational state. Fracture surfaces generated during fault movement provided nucleation substrates favorable for the emplacement of substantial amounts of intragranular quartz (up to 11 volume percent in the Lee Formation). Relatively undeformed sandstones contain cement that is dominantly intergranular whereas sandstones from highly deformed cataclasites along the trace of the PMO contain cement that is dominantly localized within intragranular fractures. Therefore, the chemical diagenetic histories of different samples of Breathitt and Lee sandstones diverged markedly as a consequence of differing deformational histories and the cementation history thus constitutes a record that is relevant to deciphering the timing of deformation._ _The small quantities of early-formed, intergranular cement within the cataclasites (average 3.7 volume percent), show evidence of breakage and accordingly, must have largely pre-dated the deformation. Quartz cementation modeling suggests that emplacement of this pre-deformational intergranular cement within these deformed rocks can be bracketed within a period from approximately 280 to 260 Ma. An interpretation of fault movement that shortly post-dates this initial period of quartz cementation is consistent with other estimates for the timing of the Alleghanian orogeny. Because of their protracted period of burial, rocks in the vicinity of the PMO remained at temperatures amenable to continued quartz cementation until the middle Cenozoic, and thus, most of the quartz cementation in the cataclasites and also in the surrounding undeformed sandstones post-dates movement on the fault._ _1. Introduction_ _Deciphering the way in which chemical and mechanical processes operate in concert is vital for understanding the evolution of rock properties (both chemical and mechanical). For example, brittle processes such as compactional grain crushing and through-going fracturing impact chemical processes such as cementation by dramatically changing the availability of essential nucleation substrates (Chuhan et al., 2002; Makowitz and Milliken, 2003; Laubach et al., 2004; Makowitz, 2004; Milliken et al., 2005), thus affecting the ultimate volume and spatial distribution of cement (Bloch et al., 2002; Makowitz and Milliken, 2003; Milliken et al., 2005; Eichhubl et al., in press) and even the rates of cement emplacement (Lander et al., 2008). In turn, emplacement of cement induces lithification that profoundly impacts the mechanical properties of granular aggregates (Dvorkin et al., 1991, 1994; Bernabé and Brace, 1992; Zang and Wong, 1995; Elata and Dvorkin, 1996; Dewhurst and Jones, 2003; Laubach and Ward, 2006; Olson et al., 2007)._ _Several authigenic minerals display precipitation-rate behavior that can be described using empirically-determined Arrhenius kinetics (Walderhaug, 1994b, 1996; Lander and Walderhaug, 1999; Perez and Boles, 2005; Lander et al., 2008). Thus, the observed volumes of these cements can provide an estimate of the timing and conditions of cement precipitation when such kinetic models are used in concert with reconstructed thermal histories (Makowitz et al., 2006). If the paragenesis of such cements can be placed in the context of a deformational event or process (e.g., Laubach and Diaz1924, Tushman, 2009; Becker et al., 2010), the quantitative estimates of timing that arise from the modeling of cement emplacement can then be applied to the deformation as well._ _This study uses empirical-kinetic modeling of quartz cement precipitation in middle Pennsylvanian sandstones and associated fault rocks to obtain constraints on the timing of the Pine Mountain Overthrust (PMO), a classic and well-documented example of thrust-faulting along the eastern side of the Southern Appalachian foreland basin._ _2. Geologic setting_ _The complex history of the Appalachian Basin foreland basin involves a multi-stage history that includes Taconic (450 Ma, Ordovician), Acadian (410-380 Ma, Devonian), and Alleghenian (320-260 Ma, Carboniferous) thrusting episodes (Quinlan and Beaumont, 1984; Tankard, 1986; Beaumont et al., 1987). The Alleghanian Orogeny is the most important deformation event in terms of its strong overprint on the depositional style and structure of the region._ _The PMO is the western-most Alleghenian-age structure in the southern Appalachians, crossing Virginia, Tennessee, and Kentucky (Fig. 1) and is considered to be a classic example of the structural style in fold and thrust belts adjacent to foreland basins (Wilson and Stearns, 1958; Miller, 1962; Zafar and Wilson, 1978; Mitra, 1988). The fault disrupts the orogenically-derived clastic sediments of the Lee Formation and Breathitt Group, and thus must post-date the middle-Pennsylvanian. The structural geometry consists of an east-northeast striking major thrust that climbs from a detachment in the Cambrian Rome Formation through successively younger units and flattens into a detachment localized in the Devonian Chattanooga Formation wherein it reaches the surface (Zafar and Wilson, 1978; Mitra, 1988). The surface exposure of the thrust sheet consists of a rectangular block about 200 km long and 40 km wide, bounded on the northwest by the Pine Mountain Fault, to the southeast by the Wallen Valley and Hunter Valley faults (Mitra, 1988). The thrust sheet terminates to the southwest and northeast at two primary tear faults, the Jacksboro and Russell Fork Faults, respectively. Total displacement associated with the PMO system decreases from about 21.3 km at the southwestern end to less than 3 km on the northeastern end (Mitra, 1988)._ _Fig. 1. 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