Shallow Gas Studies of the Gulf of Lions, Including the Rhone Delta and Cap de Creus Canyon Head

摘要

To enhance and expand our understanding of the inter-relationship of shallow gas, seafloor morphology, and seafloor/shallow sub-surface acoustic properties. To continue our successful collaboration with our EuroSTRATAFORM colleagues through Gulf of Lions (GoL) post-cruises analysis, interpretation, and integration with geophysical data sets. The main Institutions we have collaborated with are: CEREGE, France; U.S. Geological Survey, USA; ISMAR-CNR, Italy; Fugro Surveys Ltd., UK; and Univ. Laval, Canada. To compare the Gulf of Lion (GoL) system with other areas worldwide and augment including an industry data set from the eastern Mediterranean. Our two main topics of interest are the distribution and effects of shallow gas on both the seafloor and the shallow sub-surface, and the origin and evolution of 'crenulated seafloor' (wavy bedforms, slope failure features, or a combination of the two) and seafloor rills. To understand how shallow gas and flood events are inter- related in the GoL system through the integration of mapping and coring. Previous ONR work in the Adriatic (2003-2004) showed that the Po flood deposits resulted in a localized region of high organic matter deposition, and that the rapid accumulation of flood deposits removed the organic matter from the reach of physical and biological re-working, leading to high concentrations or shallow gas. Our goal in the GoL was to determine if this model also holds for the Rhone system, which experienced a large flood in December, 2003. Specific detailed sites of interest in the GoL include the Grand Rhone prodelta (inferred to be the main source for organic matter and therefore potential gas), along the western coast of the GoL (the circulation patterns, satellite and shuttle images as well as models indicate that this is the main pathway for flood-derived material) and in the Cap de Creus canyon, where flood sediments may be transported off the shelf (see Figure 1).