Browsing by Subject "Scotland"
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Item Deformation mechanisms in the Lewisian Gneiss and Cambro-Ordovician sediments at Heilam, Scotland(1982-12) Smoot, Kelley; Mosher, SharonHeilam, a 10 km2 area on the east coast of Loch Eriboll near the Moine Thrust in NW Scotland, is composed of three structural areas: 1) the Arnaboll Nappe, 2) the coastal schuppen zone and 3) the intermediate imbricate zone. Samples of each lithology taken from the zones show a progressive sequence of deformation. The least deformed rocks in the Arnaboll Nappe and in the intermediate imbricate zone have strain shadowed quartz grains and feldspars with deformation lamallae. Near the thrusts of the imbricate zone and in the schuppen zone, micas exhibit a strong preferred orientation, quartz grains show discontinuous undulatory extinction and recrystallization about the margins. Pressure shadows in the quartzites and styolites in the dolomites post-date earlier recrystallization in these areas. Mylonites, notably those along the Arnaboll Thrust, contain micas and quartz with a strong preferred orientation. All minerals show reduction in grain size by either recrystallization or brittle fracture. A sequence of deformation mechanisms affecting the lithologies is 1) initial recrystallization, 2) pressure solution, and 3) minor recrystallization. This sequence is best observed in the mylonites and schuppen zone.Item Fault-related fracture systems in the Cambrian Eriboll Formation, Northwest Scotland : a field and petrographic study of a tight gas sandstone analog(2010-12) Hargrove, Peter Gregory; Laubach, Steven E. (Stephen Ernest), 1955-Lower Cambrian Eriboll Formation sandstones of the Ardvreck Group that crop out in the Hebridean foreland west of the Paleozoic Moine Thrust Zone (MTZ) in the Northwest Highlands of Scotland contain five sets of opening-mode fractures with varying degrees of quartz deposits (cement) and topographically prominent but small displacement (mostly less than 10 m) northeast-striking faults. The faults crosscut and in some places displace the MTZ. I interpret these faults to post-date the MTZ and consider them to be late structures (kinematically unrelated to MTZ emplacement). Sparse slip lineations on fault surfaces and offset patterns are evidence for strike-slip to oblique slip. Using geologic mapping I show that relative to their lateral and vertical extents, the faults display small amounts of offset (less than 5 to 10 m). My research documented the patterns and petrology of fractures in a well exposed section of the foreland, documented for the first time fracture patterns adjacent to and within the post-MTZ fault zones, and proposes an account of how fault and fracture patterns developed and their probable effects on fluid flow. Fractures are barren (joints), partially filled (quartz lined), or completely filled (veins). Older fracture sets are typically completely filled, whereas younger sets may be lined with a thin veneer of quartz cement or are barren. Listed in order from oldest to youngest fractures containing quartz strike north, NW to WNW, NE, west, and north (sets A through E respectively). Previously proposed relative ages of the sets were confirmed using crosscutting relationships and preferred orientations of macro- and microfractures (Laubach and Diaz-Tushman, 2009). This study focuses on late northeast-striking fractures (set C) which I interpret to be related to the formation of the small-offset faults. Many of the attributes of late fractures and faults in the Eriboll Formation resemble those found in core from highly quartz cemented sandstone natural gas reservoirs ("tight gas sandstones"). I demonstrate that the well exposed fracture patterns I documented are good analogs for tight gas sandstones, by investigating fracture characteristics such as network configurations and connectivity, fracture intensity (abundance), fracture scaling, fracture length and spacing, and the degree of quartz cement deposits in fractures and cataclastic fault rock. Many of the narrow macroscopic fractures and microfractures I documented using CL methods contain varying amounts of quartz deposits. The excellent preservation of Eriboll outcrops is probably a manifestation of little or no fracture pore space preservation in many of the numerous fractures that are apparent in outcrop. Set C fracture abundance is not distributed in a uniform envelope (or "halo") around the late faults. Using scanlines, I show that set C fracture distribution is heterogeneous and highly variable over short lateral distances (tens of centimeters to meters). I also investigate wing crack assemblages (secondary opening-mode fractures) that are locally associated with set C fractures. The assemblages accommodate small amounts of the distributed displacement (a few millimeters) adjacent to fault zones and are locally responsible for increased amounts of fracture connectivity by linking neighboring fractures. Variations in fracture pattern complexity appears to be related to the presence (or absence) of wing crack assemblages. Localized wing crack development on closely spaced, en echelon set C fractures also leads to precursory development of fragmented lozenges of highly deformed volumes of rock (damage zones) that resemble geometries similar to those seen in preserved Eriboll fault cores. Fault-related deformation in the Eriboll Formation is markedly different than that in the underlying Late Proterozoic Torridonian Applecross Formation (subarkose fluvial sandstone), which is characterized by simple halos fault-related fracture arrays surrounding the same late (post-MTZ) faults. In addition to composition, the Eriboll and Applecross differ in mechanical layer thickness (centimeters versus > tens of meters), mechanical properties (high versus low brittleness), and greater propensity for fractures to be filled with quartz cement in Eriboll sandstones owing to quartz cement growth being impaired by the abundance of non-quartz substrate (feldspar and clay minerals) along fracture walls in the Applecross Formation. Although the Eriboll sandstones are more highly fractured than the older Applecross sandstones, Eriboll fractures are more prone to be filled by quartz cement. In this thesis I also report previously unrecognized early (set A; pre-MTZ) minor normal faults, sandstone petrography and rock mechanical properties of selected Eriboll sandstone samples, and the influence of fractures on the glacial geomorphology of the area. I also describe a previously unmapped igneous dyke. I describe previously unrecognized vugs that are partly strata bound and partly localized along fractures. The attributes of these vugs and a review of the literature suggests that these features could represent evidence of pre-glacial silici-karst in Eriboll quartzites.Item Flora of Forfarshire(London : Longman, Brown, Green and Longman, 1848) Gardiner, WilliamItem Flora of Forfarshire - Supplementary volume - Page 1(1848) Gardiner, William;Item Flora of Forfarshire - Supplementary volume - Page 10(1848) Gardiner, WilliamItem Flora of Forfarshire - Supplementary volume - Page 11(1848) Gardiner, WilliamItem Flora of Forfarshire - Supplementary volume - Page 12(1848) Gardiner, WilliamItem Flora of Forfarshire - Supplementary volume - Page 13(1848) Gardiner, WilliamItem Flora of Forfarshire - Supplementary volume - Page 14(1848) Gardiner, WilliamItem Flora of Forfarshire - Supplementary volume - Page 15(1848) Gardiner, WilliamItem Flora of Forfarshire - Supplementary volume - Page 16(1848) Gardiner, WilliamItem Flora of Forfarshire - Supplementary volume - Page 17(1848) Gardiner, WilliamItem Flora of Forfarshire - Supplementary volume - Page 18(1848) Gardiner, WilliamItem Flora of Forfarshire - Supplementary volume - Page 19(1848) Gardiner, WilliamItem Flora of Forfarshire - Supplementary volume - Page 2(1848) Gardiner, WilliamItem Flora of Forfarshire - Supplementary volume - Page 20(1848) Gardiner, WilliamItem Flora of Forfarshire - Supplementary volume - Page 21(1848) Gardiner, WilliamItem Flora of Forfarshire - Supplementary volume - Page 22(1848) Gardiner, WilliamItem Flora of Forfarshire - Supplementary volume - Page 23(1848) Gardiner, WilliamItem Flora of Forfarshire - Supplementary volume - Page 24(1848) Gardiner, William
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