The Miocene to Pliocene southern Bouse Formation preserves a record of depositional environments immediately prior to and during integration of the Colorado River to the Gulf of California. Uncertainty over Bouse paleoenvironments obscures our understanding of the timing and magnitude of regional uplift, as well as the conditions and processes that were active during integration and early evolution of the Colorado River. Prior studies over the past 20 years have concluded that the southern Bouse Formation accumulated in chain of lakes isolated from the ocean. Sedimentologic analyses presented here aid interpretation of depositional environments and provide evidence for a strong tidal influence on deposition, consistent with a marine interpretation of other prior studies. This interpretation places a critical constrain on the elevation of these deposits at ca. 5 Ma, and suggests post-Miocene uplift of the Lower Colorado River corridor. This thesis includes previously published coauthored material.

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

Master of Science / Department of Geology / Allen W. Archer / Turnagain Arm is the hypertidal (commonly exceeding 9 m) west-east trending extension of Cook Inlet in south-central Alaska. The inlet formed from a drowned glacial valley that was subsequently filled with tidal deposits of silt and fine sand. The tidal system is semidiurnal with a prominent diurnal inequality. There are also variations due to spring and neap tides. Turnagain Arm is home to a tidal bore generated during spring tides that can reach heights of up to 2 m and travel at speeds of up to 5 m/s. Current reversals can be dramatic with ebb tidal velocities of 6 m/s changing to flood velocities of 10 m/s over a period of a few minutes. During the initial flood tide, highly turbid water can rise as fast as 10 cm/min. This combination of elements results in a highly dynamic depositional setting. Measurements taken in the inner estuary during several neap-spring cycles in the summers of 2007-08 documented deposition upon mud bars of as much as 8.9 cm per tidal event. Conversely, erosion of up to 13.5 cm per tidal event has been measured. The highest rates of deposition and erosion occurred during the spring tides while much lower rates occur during the neap tides. Some portions of the inner estuary are only submerged during the extreme high tides. The magnitude of the high tide needed to cover each site increases with increasing distance into the upper estuary. Even if submerged, deposition does not always occur. Such a high percentage of non-depositional events has real implications when interpreting tidal cyclicity of the rhythmites found at these sites.

Syn-rift exposures are a prime source of knowledge on the structure and stratigraphy of rift basins and are vital for the petroleum industry as analogues for subsurface reservoirs. Focusing on superb exposures of the Oligo-Miocene rift initiation Nukhul half-graben in the Suez Rift, Egypt, this study investigates applications of 3D digital survey techniques, particularly terrestrial light detection and ranging (lidar), for (i) the analysis of syn-rift fault and facies architecture, and (ii) the building and testing of outcrop-based reservoir analogue models for early syn-rift settings. Lidar-based digital outcrop mapping of the Nukhul half-graben, combined with conventional fieldwork, facilitated quantification of thickness and facies relationships within syn-rift strata, and variations of throw along normal faults. The results provide new insights into the tectono-sedimentary evolution of the intra-block half-graben. At rift initiation, regional/eustatic sea-level and antecedent drainage are interpreted as the dominant controls on accommodation development and deposition, respectively. However, after just c. 2.5 myr of rifting, the structural template imposed by the propagation and linkage of four initially isolated pre-cursor segments of the Nukhul Fault became the dominant control on accommodation development and basin physiography. Progressive SE-NW back-stepping of facies strike-parallel to the Nukhul Fault suggests hangingwall subsidence was locally sufficient to outpace falls in regional sea-level, resulting in a dynamic transgressive system that progressed from a restricted tidal embayment to shallow marine seaway along fault strike. After c. 4.3 myr of rifting, regional drowning of the tidal system provides evidence for progressive localisation of displacement onto the present-day block-bounding structures and declining activity on the intra-block Nukhul Fault during the transition from rift initiation to rift climax. Development of digital outcrop techniques such as point cloud facies classification, 3D deterministic channel modelling and net-to-gross analysis provided reliable geostatistics on the geometry, distribution and heterogeneity of tide-influenced facies of the syn-rift Nukhul Formation. The high volume, reliability and spatial coverage of data reduced uncertainties related to stochastic facies modelling (in this case sequential indicator simulation and object-based techniques), facilitating building and testing of high-resolution analogue models for the complex facies and sequence architecture of early syn-rift tidal reservoirs. Visual analysis of static reservoir connectivity suggests some of the smallest-scale depositional elements, i.e. thin intercalations of mudstone and sandstone lamina in heterolithic facies, have the biggest impact on both reservoir volume and vertical connectivity in this syn-rift tidal system. Heterogeneities at the sequence stratigraphic scale also have significant impact on vertical reservoir compartmentalisation, whereas tidal channel lag deposits and tidal mud drapes have more localised effects. Use of lidar, when combined with conventional fieldwork, offers a powerful tool for quantitative spatial analysis of fault and facies architecture, tightly constraining 3D structural and stratigraphic interpretations and effectively increasing the statistical significance of outcrop analogues for reservoir characterisation. Future developments in survey technologies alongside geoscience-specific software for the integration and analysis of outcrop datasets will provide more diverse and quantitative information on geological heterogeneity, and promote wider-ranging applications in Earth sciences.

Tide-influenced point bars represent a significant proportion of shallow-marine deposits, commonly developed along meandering channels in most backbarrier and estuarine systems. However, sedimentological studies to characterize this type of deposit are still emerging. They often present very heterogeneous internal architectures which development is controlled by the complex flow patterns operating in tidal environments. The study of the sedimentological and morphological characteristics of these features provides better understanding of the hydrodynamic processes that shape coastal systems and control their evolution as well as it contributes to better reservoir potential prediction and production strategy optimization, as tidal point bars may represent hydrocarbon reservoirs in subsurface and their heterogeneous characteristics directly impact reservoir quality. In this study, we investigated six modern tidal point bars located along distinct estuarine tidal channels in Georgia. Using core data, 2D shallow seismic data and current measurements and flow velocity profiles, we discussed the main hydrodynamic controls on sediment transport and distribution, and determined how they affect the morphology, the internal architecture and the sediment distribution within these bars. We confirmed that the influence of fluvial input in tidal channels plays an important role on the development of the morphology and the heterogeneous architecture of point bars as it adds more complexity to the system hydrodynamics, promoting more asymmetric variations in water level fluctuations and huge variations of current velocities. We proved that point bars developed in distinct tide-influenced channels and estuaries, although present very different sedimentary facies distribution, may have sedimentary facies in common, which organization is analogous to surface processes operating at each environment. We demonstrated that differences in tidal asymmetries between the ebb and flood channels produce sedimentological differences between the different parts of the bar. This study showed that tidal point bars present distinct heterogeneous sediment distributions, morphologies and internal architectures that do not conform to the existing theoretical models of fluvial point bars and highlighted that, despite the differences in local hydrodynamic conditions, similarities identified between the different bars permitted us to distinguish the sedimentological responses to regional allogenic events, which can be mistakenly interpreted as sedimentological responses to local autogenic events.