Shallow stratigraphy of the mid-atlantic bight: Constraints on siting of offshore wind projects.

摘要

Fluctuations in sea level during the Quaternary have resulted in pronounced three-dimensional variation of surficial and subsurface marine sediments along the Mid-Atlantic. This region presents possible development opportunities for emerging domestic energy production, specifically renewable wind energy. Infrastructure for offshore wind energy development is highly dependent on the nature of the site conditions including the type and distribution of sediments. Water depth, bathymetry, and the geotechnical properties of sediments are some of the factors that affect the design and dimensions of wind turbine foundations.;In this thesis, geological and geophysical investigations of the shallow stratigraphy within Delaware's Wind Energy Area (WEA), including multibeam bathymetry, echosounder sub-bottom profiles, acoustic Doppler current profiler measurements, and grab samples have been used to interpret bottom erosion and deposition patterns. I have identified variable surface sediments, including surficial, large, well-rounded cobbles, subsurface paleochannels, and complex subsurface bedding. These observations suggest that fluvial and near-shore coastal processes have had lasting influences on sedimentation patterns throughout periods of transgression. The most recent sea level rise associated with the early Holocene epoch in-filled fluvial channels with sediments progressing from fine muds, to estuarine sands and marine sands. These interpretations are confirmed through correlation with geophysical survey results in surrounding offshore areas within the Mid-Atlantic Bight. Probable sediment types and their associated engineering soil properties have been inferred from these studies. The data collected here support the fluvial and near-shore influence on the distribution of sediments and correlate with well studied transgressive facies patterns. Our interpretation provides valuable constraints on the development of offshore wind projects within the Mid-Atlantic Bight, in general, and, in particular, the type, design and location of turbine foundations within Delaware's WEA.