Abstract This chapter is concerned with the main faults and folds within the Southeastern Oman Mountains based on available literature. The main, best and most widely exposed thrusts are those related to the SW-directed late Cretaceous obduction of the allochthonous nappes onto the Arabian platform and margin. These thrusts are related to obduction of rocks, which had formed hundreds of kilometres offshore Oman. The thrusts were active from the Cenomanian to the Campanian. Obduction-related thrusts and folds are spectacularly exposed within the rocks of the Arabian platform in the eastern part of the Saih Hatat Dome, including large-scale recumbent cylindrical folds and sheath folds. At least six fold sets can be studied in the Southeastern Oman Mountains. At least two of them had formed prior to obduction and are exposed in the Pre-Permian formations of the Jabal Akhdar Dome. At least three fold sets formed in the course of obduction, while at least one fold set is postobductional in age. Besides the compressional structures, the Oman Mountains expose major post-obductional extensional faults, mostly at the margins of the Jabal Akhdar and Saih Hatat domes. The throw of these faults amounts to a few to several kilometres. Finally, this chapter provides an overview of the enigmatic Batinah Mélange which consists of slivers of Hawasina rocks, resting (unusually) structurally above the Semail Ophiolite.

ABSTRACT The geology of Great Smoky Mountains National Park (GRSM) in Tennessee and North Carolina is dominated by siliciclastics and metamorphic strata. However, in the western portion of GRSM, a series of carbonate fensters (windows) expose the Lower Ordovician–age section of the Knox Group, a series of dolomite and limestone units that are partially marbleized as a result of contact metamorphism from the Great Smoky fault. The fensters create opportunities for allogenic recharge to occur at points along the contact of the surrounding insoluble strata with the underlying soluble carbonates. The combination of chemically aggressive surface recharge and vertical relief has resulted in the formation of deep caves, many of which have active streams and water resources. Though the karst is limited in extent and the number of caves is fairly small, the significance of the resources is substantial, with several of the caves in the area over 150 m in depth and at least two being major bat hibernacula. In 2017, the U.S. Geological Survey (USGS) began a study to better understand the hydrologic behavior of these karst systems through hydrologic and geochemical monitoring, groundwater tracing using fluorescent dyes, and seepage runs. Stage and water-quality instrumentation was installed in two caves in GRSM, the main stream of Bull Cave, and in a sump pool in Whiteoak Blowhole, at 173 m and 70 m below land surface, respectively. Following setup of the cave sites, dye injections were conducted to determine discharge points for four of the deep cave systems on Rich Mountain and Turkeypen ridge. Results show water in these systems has an extremely rapid travel time, with tracers detected from caves to springs in less than 24 h for each of the systems. This field guide describes the complex geology, regional hydrogeology, and unique landscape characterized by high-gradient subterranean streams, carbonate fensters, and deep caves of the GRSM karst.

Abstract Little is known about the effect of thrusting on lithological and petrophysical properties of reservoir sandstone. Here we use field observations, probe permeability measurements and thin-section analysis along ten transects from the Muddy Mountain thrust contact downwards into the underlying Jurassic Aztec Sandstone to evaluate the nature and extent of petrophysical and microstructural changes caused by the thrusting. The results reveal a decimetre- to metre-thick low-permeable (≤50 mD) and indurated (0–3% porosity) zone immediately beneath the thrust contact in which dominant microscale processes, in decreasing order of importance, are (1) cataclasis with local fault gouge formation; (2) pressure solution; and (3) very limited cementation. From this narrow zone the petrophysical and microstructural effect of the thrusting decreases gradually downwards into a friable, highly porous ( c. 25%) and permeable (≤2 D) sandstone some 50–150 m below the thrust, in which strain is localized into deformation band populations. In general, the petrophysical properties of the sandstone as a result of overthrusting reveal little impact in overall primary reservoir quality below some tens of metres into the footwall, except for the relatively minor baffling effect of deformation bands.

Abstract Recent field and associated studies in eight 7.5-minute quadrangles near Mount Rogers in Virginia, North Carolina, and Tennessee provide important stratigraphic and structural relationships for the Neoproterozoic Mount Rogers and Konnarock formations, the northeast end of the Mountain City window, the Blue Ridge–Piedmont thrust sheet, and regional faults. Rocks in the northeast end of the Mountain City window constitute an antiformal syncline. Overturned Konnarock and Unicoi formations in the window require a ramp-flat geometry in the hanging wall of the Blue Ridge thrust sheet or stratigraphic pinch-out of the Konnarock Formation. Undulose and ribbon quartz, fractured feldspars, and mylonitic foliations from the Stone Mountain and Catface faults indicate top-to-NW motion, and ductile deformation above ∼300 °C along the base of the Blue Ridge thrust sheet on the southeast side of the window. The Stone Mountain fault was not recognized northeast of Troutdale, Virginia. The Shady Valley thrust sheet is continuous with the Blue Ridge thrust sheet. The ∼750 Ma Mount Rogers Formation occurs in three volcanic centers in the Blue Ridge thrust sheet. Basal clastic rocks of the lower Mount Rogers Formation nonconformably overlie Mesoproterozoic basement in the northeasternmost Razor Ridge volcanic center, but the basal contact in parts of the Mount Rogers and Pond Mountain volcanic centers is strongly tectonized and consistent with a NW-directed, greenschist-facies high-strain zone. The contact between the Mount Rogers Formation and Konnarock Formation is nonconformable, locally faulted. Metarhyolite interbedded with lacustrine and fluvial rocks suggests that volcanism and glaciation were locally coeval, establishing an age of ∼750 Ma for the Konnarock Formation, a pre-Sturtian glaciation. Multiple greenschist-facies, high-strain zones crosscut the Blue Ridge thrust sheet including the Fries high-strain zone (2–11 km wide). Foliations across the Fries and Gossan Lead faults have similar orientations and top-to-NW contractional deformation.