Large-scale sandstone injectite complexes located in California and in Tunisia have exposures of external geometries and sedimentary structures. Substantial macroscale erosion occurred along the margins between the injected sandstones and host mudstones that include scalloped upper margins that cut up to 5 m into the overlying host mudstones. Sedimentary structures preserved in the sandstone injectite complexes record fluid-flow, sedimentation and post-sedimentation processes. Bedload layers moving in traction along fluid-sediment interfaces is identified as a significant transport mechanism of grains in sills, low-angle dykes, and irregular injectites, as evidenced by laminae defined by differences grain size, grain composition, and grain packing. High-angle sandstone dykes are characterised by a distinct suite of sedimentary structures that include horizontal bands and pipes. Horizontal bands record the movement of fluidised sand as bands during the waning phase of sand injection. Pipes are interpreted to have formed due to post-sand-injection consolidation and fluid-escape. The distinct sedimentary structures and microtextures that characterise each intrusive element reflect the coupled relationships between the fluid-flow and sedimentation processes and the element type. Sedimentation, post-sedimentation, and diagenetic processes thereafter, resulted in the formation of heterogeneous permeabilities; values vary three-orders-of-magnitude. The heterogeneity is predictable and correlates with the type of intrusive element and its primary and secondary microfabrics. This link demonstrates the influence of primary sedimentation processes and secondary diagenetic processes on the injected sandstone permeability. By constraining the permeability heterogeneity of injected sandstones, it is possible to accurately quantify and thereby anticipate their impact on fluid flow in sedimentary basins.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:521234 |
| Date | January 2009 |
| Creators | Scott, Anthony Stephen John |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=92505 |
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