The Jurassic Tilje Formation located on the Norwegian continental shelf contains many thick (>10 mm) and macroscopically homogenous mudstone layers. These mudstone layers are interpreted to have accumulated rapidly from “fluid-mud,” a highly concentrated aqueous suspension of fine-grained sediment. Fluid muds in the Tilje are recognized in tidal-fluvial channel, mouth-bar and distal delta-front environments. From detailed thin-section work it is clear that these mudstone layers are not homogenous. Three facies are observed: unstratified mudstone (UM), some of which contain “floating” coarse grains, planar-laminated mudstone (PLM) and cross-laminated mudstone (CLM). Each facies represents deposition at differing suspended-sediment concentrations (SSC) (UM−high SSC, PLM−low-moderate SSC and CLM−low SSC). The thickest mudstone layers are always associated with underlying dune-scale cross-bedding, which has led to a proposed model where fluid mud can accumulate and is protected from the over-riding flow in the troughs of large dunes. This model is most relevant to tidal-fluvial channels where large dunes occur in the deepest water and in terminal distributary channels in mouth bars. The vertical stacking of facies within a single mudstone layer allows reconstruction of changes of the near-bed SSC values and current velocities that reflect deceleration and acceleration of the tidal currents over the tidal cycle or waning wave energy following a storm. Based on repeating patters termed “vertical successions” and “succession combinations,” individual tidal cycles can be observed within single mudstone layers and the relative strength of subordinate and dominant currents can be ii inferred. To aide in the understanding of how mud can accumulate over the complete range of SSCs, current velocities and grain sizes, a preliminary three-dimensional bedform phase diagram has been constructed for fine-grained sediment based on recent flumes studies. The phase diagram can be applied to mudrocks beyond the Tilje Formation. / Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2013-09-15 17:14:19.827

Within the middle McMurray exposures along the Steepbank River (Steepbank River Outcrops 3 and 4), nine recognized facies can be divided into three genetically related groups: sand-dominated facies, inclined heterolithic stratification (IHS) facies and mixed heterolithic facies. Together, these facies are interpreted to represent a fluvially dominated, tidally influenced point bar that experienced strong seasonal variation in river discharge. Annual fluctuations between river-flood stage and low-flow stage are responsible for the deposition of fluvially dominated sand beds alternating with brackish, tidally influenced mud beds that cover the point-bar surface as members of the various IHS facies. The dichotomy of fluvially dominated sand deposition and brackish-water ichnology of the mud beds represents the annual migration in position of the tidal and salinity nodes caused by fluctuations in fluvial discharge. Recognition of metre-scale cycles (MSCs) of alternating sandier and muddier intervals within the IHS facies imply that decadal climate cycles, likely caused by fluctuations in ocean and/or solar dynamics, influenced point-bar deposition. These MSC packages are defined by an upward decrease in sand-bed thickness, an upward increase in mud-bed frequency, and an upward increase in bioturbation intensity, all occurring on a metre scale. MSCs are an important architectural element of these large-scale tidal-fluvial point bars because they are predictable, repeatable and continuous around the point bar. Analysis of paleocurrents relative to inclined-heterolithic-stratification bedding planes indicates that bend-flow modifications (BFMs) were effective in redistributing flow around the point bar. Furthermore, this suggests that Outcrop 3 is representative of an upstream-to-bend-apex transition within a large-scale point-bar planform. Recognition of multiple channels at Outcrop 4 was based on large-scale erosional truncation, IHS bed-orientation changes, large cumulative thicknesses of the middle McMurray, thick sand-package thicknesses, changes in relative scale of sedimentary structures, and the occurrence of large mud clasts. Similarities in depositional expression between channels suggest autogenic channel stacking (within-valley stacking), rather than the stacking of separate valleys. Finally, discordant paleocurrents within the basal sand-dominated facies are likely representative of amalgamated channel-bottom facies from several generations of channel. This suggests that only the upper intervals of basal sand-dominated facies are genetically linked to the overlying IHS facies. / Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2012-01-30 13:25:32.53

Understanding modern features allows for their use as analogues for understanding the environments of the past and even environments on other planetary bodies. This study uses Ground-Penetrating Radar (GPR) to image the near surface sedimentary structures on a large linear dune in the northern Namib Sand Sea and image the sedimentary structure of an auxiliary dune. GPR data was collected using a 200 MHz antenna with a continuous scan method and was processed by removing direct arrival, gain balancing, migration and more which produced the highest resolution imagery from this region to date. Large dune data was analyzed to determine depositional process for different sedimentary patterns observed. Auxiliary dune data was analyzed to determine dune type and migration direction. Our results indicate five sedimentary process zones in the near surface of the large primary dune. These processes include motion of the dune crest as well as different phases of superimposed dune deposition. It is evident from our interpretation that there have been at least two phases of superimposed dune deposition separated by an erosional process boundary. These phases of deposition have produced a reversed succession of strata on opposing sides of the dune with deposits of 3D superimposed dunes beneath 2D superimposed dune deposits on the west and deposits of 2D superimposed dunes beneath 3D superimposed dune deposits on the east. This suggests a reversal of wind environment in the region in the recent past and could provide insight into the building and stability of linear dunes on Earth. Our results also indicate that the auxiliary study dune is oblique in nature with migration to the north-northeast and that it and other similar dunes in the vicinity are formed because of their proximity to Tsondab Vlei. The apparent dependence of these smaller scale features on interruptions in the dunefield like Tsondab Vlei suggest that the normal wind patterns within the dunefield are a combination of the regional wind patterns with significant influence from the large linear dunes themselves.