HR: 1330h
AN: OS52A-0887    [PDF]
TI: Headspace Gas Analysis from the Po Delta and Adriatic Sea: Abundant Deltaic Gas and Associated Anomalous Sub-bottom Profiler Records
AU: * Garcia-Garcia, A
EM: agarcia@es.ucsc.edu
AF: UCSC, Department of Earth Sciences, 1156 High Street, Santa Cruz, CA 95064 United States
AU: Orange, D L
EM: Dan_Orange@AOAGeophysics.com
AF: UCSC, Department of Earth Sciences, 1156 High Street, Santa Cruz, CA 95064 United States
AU: Lorenson, T D
EM: tlorenson@usgs.gov
AF: USGS, 345 Middlefield Road MS-999, Menlo Park, CA 94025 United States
AU: Trincardi, F
EM: fabio.trincardi@bo.ismar.cnr.it
AF: ISMAR-CNR, via Gobetti 101, Bologna, 40129 Italy
AB: During a EuroSTRATAFORM cruise onboard the RV `Seaward Johnson II' the Adriatic Sea was sampled in order to evaluate the presence and distribution of shallow gas in the area, and its association with anomalous seafloor and sub-bottom acoustic data. The productivity of the Northern Adriatic is one of the highest in the Mediterranean Sea and high-resolution seismic data showed areas with anomalous sub-bottom profiler data suggestive of shallow gas. As part of a multi-PI program, we sampled 61 cores from the western Adriatic coast by capturing the basal portion of slow cores, gravity cores, kasten cores and box cores (the cores were, in a large part, collected to address other questions in the EuroSTRATAFORM program). Samples were preserved at sea, and analyzed in the lab for C1-C6, CO2, H2S, and H2. Preliminary results show that the highest values of CH4 and CO2 are associated with anomalous sub-bottom profiler data (suggestive of shallow gas) and the shallow, high sediment accumulation rate sediments of the Po delta. 14 sites had more than 70 uL/L of CH4 and of those, 5 sites had more than 20000 uL/L. The highest gas values were found in the kasten and gravity cores, whilst the box cores gave high results only where the gas was very shallow, like in front of the Po discharge area. Due to the high methane content in 8 of the samples, these were sent for isotopic analysis. These results may tell us about the nature of shallow gas in the Adriatic Sea and its association with shallow and seafloor acoustic properties, as well as recent sediment accumulation rates and TOC.
DE: 0935 Seismic methods (3025)
DE: 1050 Marine geochemistry (4835, 4850)
DE: 3000 MARINE GEOLOGY AND GEOPHYSICS
DE: 3022 Marine sediments--processes and transport
DE: 4219 Continental shelf processes
SC: Ocean Sciences [OS]
MN: 2003 Fall Meeting