Expedition 362: Site U1480

Abstract

Site U1480 (proposed Site SUMA-11C) is located on the Indian oceanic plate, east of the Ninetyeast Ridge and west of the North Sumatran subduction margin. The primary drilling objective at Site U1480 was to recover a complete section of the oceanic-plate sedimentary section and the uppermost basaltic basement. Specific objectives for this site include the following: (1) To identify the principal lithologies that may be involved in development of the broad prism and the plate boundary fault; (2) To establish how the mechanical/strength properties of the different lithologies change with depth to determine the trends and effects of burial rate and burial time; (3) To identify potential discontinuities that may be candidates for décollement positions; (4) To identify any thermal history indicators and any effects of early diagenesis and to establish the present-day thermal structure of the section; (5) To identify fluid sources and changes with depth; and (6) To determine the primary sources of sediment delivered to the site (in particular sediment above seismic Horizon C) and changes in source with time. Potential sources include the Himalaya and Ganges Brahmaputra floodplain through the Bengal Fan system, the Indo-Burman range and Irrawaddy River, the Sunda forearc, the Sumatran mainland (including volcanic arc), and the Ninetyeast Ridge.