Fine grained sediments were common in epicontinental seas, with shallow slopes, such as the Cretaceous Western Interior Seaway. However, proposed mechanisms for offshore mud transport, such as turbidity currents, tempestites, and hyperpycnal flows, require significant slopes. A core from the Upper Mancos Shale, Mancos C, located in the San Juan Basin of New Mexico was analysed to determine the dominant transport processes bringing sediment offshore. A detailed facies analysis was conducted, over 54 m of slabbed core, using sedimentological data, such as grain size, type of sedimentary structures, bed thickness, lithology, clay content, fossils, ichnofacies, and degree of bioturbation. The facies observed in the core show that multiple processes, including ignitive turbidity currents, hypopycnal and hyperpycnal flows, and tempestites, were responsible for the deposition of the Mancos C core. The resuspension of mud on the inner shelf by storm waves also played a key role in moving mud further offshore. Tidal influence within the Mancos C was relatively small. / Thesis / Master of Science (MSc)

Populations residing on and near the world’s coasts have become increasingly dependent on coastal groundwater for their supply of freshwater. Under the conditions of predicted climate changes, the expected rise in global sea level can adversely affect the quality and quantity of freshwater resources in coastal areas as a result of saltwater intrusion. In this study, a suite of two- and three-dimensional variable-density groundwater flow models of major coastal landforms (e.g. deltas, estuaries and small islands) has been constructed to assess the effects of sea level rise (SLR), using different SLR rates of 0.5 m, 1m and 1.5 m over the next 90 years, from 2010-2100. The model results indicate that in natural coastal systems the extent of saltwater intrusion is significantly controlled by the stratigraphy of the depositional environments. Among deltaic aquifers, wave-dominated deltas are more prone to saltwater intrusion than river- and tide-dominated deltas. In case of a partially mixed, microtidal estuary, SLR can cause extensive porewater salinity increases, especially within estuarine sand deposits. Simulations of atoll and barrier islands reveal that carbonate atoll islands with high conductivity units, are severely affected by SLR, resulting in significant reduction of the volume of freshwater lens. In contrast, migrating sandy barrier islands could retain their freshwater resources with rising sea level under conditions of increased recharge, assuming the barriers can migrate in response to SLR. The freshwater lens of barrier island aquifers would reduce in size due to increased evapotranspiration caused by change in vegetation pattern. When examined for anthropogenic impacts of groundwater withdrawal through pumping, all the coastal aquifers show evidence of saltwater intrusion, with varying degrees of impact. Wave-dominated deltas are more affected by groundwater withdrawal than river- and tide-dominated deltaic aquifers. Saltwater intrusion in atoll islands is further enhanced by pumping withdrawal. It is evident from the results of the simulations that, the potential effects on coastal aquifers of groundwater withdrawals for potable water can easily exceed the adverse effects of SLR in terms of salinity increase.