Description of Research Opportunity
Subaqueous mudflows are known to be ubiquitous across the Mississippi River Delta Front (MRDF) and are identified as a hazard to offshore oil and gas infrastructure. Hurricanes and major winter cold fronts have been the primary triggers for catastrophic delta-front failure, but the underlying preconditioning factors that drive these events remain poorly constrained. Further, recent research on the MRDF has shown that these mudflows may move on a annually or semi-annually basis, without a passing hurricane or large winter storm, and these smaller-scale, but more frequent movements are capable of moving hydrocarbon pipelines and moving shipwrecks of national importance (potentially placing them and the infrastructure in their path at high risk). These unassessed risks also restrict future development of existing but untapped petroleum resources as comprehensive hazard assessments cannot be completed using the existing antiquated mapping and seismic reflection datasets, limited geologic, geotechnical, and geochronological sampling, and large gaps in knowledge about the underlying geologic processes.
Rapid flow decelerations at the mouths of the delta distributary channels, primarily Southwest Pass, South Pass, and Pass A Loutre, results in deposition of bed-load sand and coarser suspended sediment and progradation of channel levees and mouth bars. The fine fraction of the suspended sediment is distributed offshore and are rapidly deposited with rates varying from > 1 m/yr proximal to the distributary channel mouths to 1 cm/yr beyond water depths of 100 m. The fine-grain size, rapid sedimentation, high-water content and large quantities of in-situ gases generated by the breakdown of organic material, result in low-strength subaqueous deltaic deposits highly susceptible to failure.
Geophysical (seismic and mapping) and geological data necessary to enable hazard assessment in this critically vulnerable region are actively being collected with the primary goal of delivering a regional map of seafloor instability features, but also provide a unique opportunity to explore the short and long-term development of the Mississippi Delta region, explore relationships between deltaic and prodelta environments, biogenic gas distribution and source environments, changes in sediment transport with time, and other basic and applied science questions within the scope of the USGS mission.
Modern reassessment of mudflow processes and hazards to seafloor infrastructure and cultural heritage requires collection and interpretation of a comprehensive suite of mapping and geophysical data. This research opportunity (RO) will allow a postdoctoral fellow the opportunity to leverage ongoing research programs in marine geohazards and seafloor characterization projects, to enhance the understanding the role of antecedent and modern deltaic conditions in driving seafloor deformation over variable timescales. A key goal of the opportunity is to provide information on the subsurface framework of the MRDF that seamlessly links to ongoing interpretations of seafloor deformation patterns, plus geochronological, physical properties, and geotechnical analyses from planned physical sampling activities.
Potential research foci related to this opportunity:
- advanced processing techniques for improving data quality of chirp and/or multi-channel seismic reflection data in areas of complex water column (e.g., mixed salinity/density water column) and subsurface (e.g., gas saturated) imaging conditions
- development of subsurface geologic model of the Mississippi River Delta Front showing spatial and temporal transition from prodelta to modern mudflow-dominated processes
- explore new methods for identifying subsurface fluid/gas pathways and gas-saturated horizons and linking those to seafloor expressions of fluid/gas release (pockmarks)
Interested applicants are strongly encouraged to contact the Research Advisor(s) early in the application process to discuss project ideas.
Proposed Duty Station(s)
Woods Hole, Massachusetts
Areas of PhD
Geology, geophysics or related fields (candidates holding a Ph.D. in other disciplines, but with extensive knowledge and skills relevant to the Research Opportunity may be considered).
Qualifications
Applicants must meet one of the following qualifications: Research Geologist, Research Geophysicist
(This type of research is performed by those who have backgrounds for the occupations stated above. However, other titles may be applicable depending on the applicant's background, education, and research proposal. The final classification of the position will be made by the Human Resources specialist.)
