Description: Expedition 311 of the Integrated Ocean Drilling Program (IODP) to northern Cascadia recovered gas-hydrate bearing sediments along a SW-NE transect from the first ridge of the accretionary margin to the eastward limit of gas-hydrate stability. In this study we contrast the gas gas-hydrate distribution from two sites drilled ~ 8 km apart in different tectonic settings. At Site U1325, drilled on a depositional basin with nearly horizontal sedimentary sequences, the gas-hydrate distribution shows a trend of increasing saturation toward the base of gas-hydrate stability, consistent with several model simulations in the literature. Site U1326 was drilled on an uplifted ridge characterized by faulting, which has likely experienced some mass wasting events. Here the gas hydrate does not show a clear depth-distribution trend, the highest gas-hydrate saturation occurs well within the gas-hydrate stability zone at the shallow depth of ~ 49 mbsf. Sediments at both sites are characterized by abundant coarse-grained (sand) layers up to 23 cm in thickness, and are interspaced within fine-grained (clay and silty clay) detrital sediments. The gas-hydrate distribution is punctuated by localized depth intervals of high gas-hydrate saturation, which preferentially occur in the coarse-grained horizons and occupy up to 60% of the pore space at Site U1325 and 〉 80% at Site U1326. Detailed analyses of contiguous samples of different lithologies show that when enough methane is present, about 90% of the variance in gas-hydrate saturation can be explained by the sand (〉 63 µm) content of the sediments. The variability in gas-hydrate occupancy of sandy horizons at Site U1326 reflects an insufficient methane supply to the sediment section between 190 and 245 mbsf.

Description: In situ sediment temperature and sediment thermal conductivity measurements were made with the GEOMAR heat flow probe (6m total length) during Expedition MSM57 on board the R/V MARIA S. MERIAN at the Svalbard margin. Two sub-regions were visited: Vestnesa Ridge and Svyatogor Ridge. A total of eleven deployment sequences were performed. The first deployment was used to defined individual sensor offsets to a reference temperature (data file available in section source data set). Deployment sequence 2 - 8 were conducted around pockmarks on Vestnesa Ridge, and deployment sequence 9 - 11 are at pockmarks across Svyatogor Ridge. During each deployment sequence several individual stations were visited as detailed in Bohrmann et al., (2017) (see datasets listed in this publication series below). From the individual measured temperature records, thermal gradients and in situ thermal conductivity values are derived using the technique described in Villinger and Davis (1986). We report here our initial results as well. Initial results and further details of the deployments can be found in the cruise report by Bohrmann et al. (2017).

Description: Long-term monitoring over 1 year revealed high temporal variability of gas emissions at a cold seep in 1250 m water depth offshore Vancouver Island, British Columbia. Data from the North East Pacific Time series Underwater Networked Experiment observatory operated by Ocean Networks Canada were used. The site is equipped with a 260 kHz Imagenex sonar collecting hourly data, conductivity-temperature-depth sensors, bottom pressure recorders, current meter, and an ocean bottom seismograph. This enables correlation of the data and analyzing trigger mechanisms and regulating criteria of gas discharge activity. Three periods of gas emission activity were observed: (a) short activity phases of few hours lasting several months, (b) alternating activity and inactivity of up to several day-long phases each, and (c) a period of several weeks of permanent activity. These periods can neither be explained by oceanographic conditions nor initiated by earthquakes. However, we found a clear correlation of gas emission with bottom pressure changes controlled by tides. Gas bubbles start emanating during decreasing tidal pressure. Tidally induced pressure changes also influence the subbottom fluid system by shifting the methane solubility resulting in exsolution of gas during falling tides. These pressure changes affect the equilibrium of forces allowing free gas in sediments to emanate into the water column at decreased hydrostatic load. We propose a model for the fluid system at the seep, fueled by a constant subsurface methane flux and a frequent tidally controlled discharge of gas bubbles into the ocean, transferable to other gas emission sites in the world's oceans.

Description: In situ sediment temperature and sediment thermal conductivity measurements were made with the GEOMAR heat flow probe (6m total length) during Expedition MSM57 on board the R/V MARIA S. MERIAN at the Svalbard margin. Two sub-regions were visited: Vestnesa Ridge and Svyatogor Ridge. During each deployment sequence several individual stations were visited as detailed in Bohrmann et al., (2017). Raw-data have the extension ".TOB" and are tab-delimited ascii files with data labels and units in top rows. Note: Temperatures in the raw files are not corrected for sensor Offsets from reference. Tose Offsets are included in the individual penetration files. Within each deployment sequence, the total record is split into individual penetration files, one penetration file per station visited. Naming convention is as follows: H1602P01.pen.dat for penetration 1 of deployment sequence H1602. Each Penetration file has complete header information on the measurement and performance. Note: temperatures are reported in values of mili-degrees Celsius). From the individual measured temperature records, thermal gradients and in situ thermal conductivity values are derived using the technique described in Villinger and Davis (1986). We report here our initial results as well. For each penetration, a results-file is included with in situ temperature and conductivity reported as function of Depth. Naming convention of the results files is as follows: H1602_P01_results.dat with "H1602" as deployment sequence, "P01" as penetration number. If the heat pulse was not generated, only the decay of frictional heating was used to define in situ temperature. Thermal conductivity was assumed to be constant for all depths in those instances. Here, we used a value of 1.25 for the assumed thermal conductivity. Initial results and further details of the deployments can be found in the cruise report by Bohrmann et al. (2017).

Description: In situ sediment temperature and sediment thermal conductivity measurements were made with the GEOMAR heat flow probe (6m total length) during Expedition MSM57 on board the R/V MARIA S. MERIAN at the Svalbard margin. Two sub-regions were visited: Vestnesa Ridge and Svyatogor Ridge. During each deployment sequence several individual stations were visited as detailed in Bohrmann et al., (2017). Raw-data have the extension ".TOB" and are tab-delimited ascii files with data labels and units in top rows. Note: Temperatures in the raw files are not corrected for sensor Offsets from reference. Tose Offsets are included in the individual penetration files. Within each deployment sequence, the total record is split into individual penetration files, one penetration file per station visited. Naming convention is as follows: H1603P01.pen.dat for penetration 1 of deployment sequence H1603. Each Penetration file has complete header information on the measurement and performance. Note: temperatures are reported in values of mili-degrees Celsius). From the individual measured temperature records, thermal gradients and in situ thermal conductivity values are derived using the technique described in Villinger and Davis (1986). We report here our initial results as well. For each penetration, a results-file is included with in situ temperature and conductivity reported as function of Depth. Naming convention of the results files is as follows: H1603_P01_results.dat with "H1603" as deployment sequence, "P01" as penetration number. If the heat pulse was not generated, only the decay of frictional heating was used to define in situ temperature. Thermal conductivity was assumed to be constant for all depths in those instances. Here, we used a value of 1.25 for the assumed thermal conductivity. Initial results and further details of the deployments can be found in the cruise report by Bohrmann et al. (2017).

Description: In situ sediment temperature and sediment thermal conductivity measurements were made with the GEOMAR heat flow probe (6m total length) during Expedition MSM57 on board the R/V MARIA S. MERIAN at the Svalbard margin. Two sub-regions were visited: Vestnesa Ridge and Svyatogor Ridge. During each deployment sequence several individual stations were visited as detailed in Bohrmann et al., (2017). Raw-data have the extension ".TOB" and are tab-delimited ascii files with data labels and units in top rows. Note: Temperatures in the raw files are not corrected for sensor Offsets from reference. Tose Offsets are included in the individual penetration files. Within each deployment sequence, the total record is split into individual penetration files, one penetration file per station visited. Naming convention is as follows: H1604P01.pen.dat for penetration 1 of deployment sequence H1604. Each Penetration file has complete header information on the measurement and performance. Note: temperatures are reported in values of mili-degrees Celsius). From the individual measured temperature records, thermal gradients and in situ thermal conductivity values are derived using the technique described in Villinger and Davis (1986). We report here our initial results as well. For each penetration, a results-file is included with in situ temperature and conductivity reported as function of Depth. Naming convention of the results files is as follows: H1604_P01_results.dat with "H1604" as deployment sequence, "P01" as penetration number. If the heat pulse was not generated, only the decay of frictional heating was used to define in situ temperature. Thermal conductivity was assumed to be constant for all depths in those instances. Here, we used a value of 1.25 for the assumed thermal conductivity. Initial results and further details of the deployments can be found in the cruise report by Bohrmann et al. (2017).

Description: In situ sediment temperature and sediment thermal conductivity measurements were made with the GEOMAR heat flow probe (6m total length) during Expedition MSM57 on board the R/V MARIA S. MERIAN at the Svalbard margin. Two sub-regions were visited: Vestnesa Ridge and Svyatogor Ridge. During each deployment sequence several individual stations were visited as detailed in Bohrmann et al., (2017). Raw-data have the extension ".TOB" and are tab-delimited ascii files with data labels and units in top rows. Note: Temperatures in the raw files are not corrected for sensor Offsets from reference. Tose Offsets are included in the individual penetration files. Within each deployment sequence, the total record is split into individual penetration files, one penetration file per station visited. Naming convention is as follows: H1606P01.pen.dat for penetration 1 of deployment sequence H1606. Each Penetration file has complete header information on the measurement and performance. Note: temperatures are reported in values of mili-degrees Celsius). From the individual measured temperature records, thermal gradients and in situ thermal conductivity values are derived using the technique described in Villinger and Davis (1986). We report here our initial results as well. For each penetration, a results-file is included with in situ temperature and conductivity reported as function of Depth. Naming convention of the results files is as follows: H1606_P01_results.dat with "H1606" as deployment sequence, "P01" as penetration number. If the heat pulse was not generated, only the decay of frictional heating was used to define in situ temperature. Thermal conductivity was assumed to be constant for all depths in those instances. Here, we used a value of 1.25 for the assumed thermal conductivity. Initial results and further details of the deployments can be found in the cruise report by Bohrmann et al. (2017).

Description: In situ sediment temperature and sediment thermal conductivity measurements were made with the GEOMAR heat flow probe (6m total length) during Expedition MSM57 on board the R/V MARIA S. MERIAN at the Svalbard margin. Two sub-regions were visited: Vestnesa Ridge and Svyatogor Ridge. During each deployment sequence several individual stations were visited as detailed in Bohrmann et al., (2017). Raw-data have the extension ".TOB" and are tab-delimited ascii files with data labels and units in top rows. Note: Temperatures in the raw files are not corrected for sensor Offsets from reference. Tose Offsets are included in the individual penetration files. Within each deployment sequence, the total record is split into individual penetration files, one penetration file per station visited. Naming convention is as follows: H1605P01.pen.dat for penetration 1 of deployment sequence H1605. Each Penetration file has complete header information on the measurement and performance. Note: temperatures are reported in values of mili-degrees Celsius). From the individual measured temperature records, thermal gradients and in situ thermal conductivity values are derived using the technique described in Villinger and Davis (1986). We report here our initial results as well. For each penetration, a results-file is included with in situ temperature and conductivity reported as function of Depth. Naming convention of the results files is as follows: H1605_P01_results.dat with "H1605" as deployment sequence, "P01" as penetration number. If the heat pulse was not generated, only the decay of frictional heating was used to define in situ temperature. Thermal conductivity was assumed to be constant for all depths in those instances. Here, we used a value of 1.25 for the assumed thermal conductivity. Initial results and further details of the deployments can be found in the cruise report by Bohrmann et al. (2017).

Description: In situ sediment temperature and sediment thermal conductivity measurements were made with the GEOMAR heat flow probe (6m total length) during Expedition MSM57 on board the R/V MARIA S. MERIAN at the Svalbard margin. Two sub-regions were visited: Vestnesa Ridge and Svyatogor Ridge. During each deployment sequence several individual stations were visited as detailed in Bohrmann et al., (2017). Raw-data have the extension ".TOB" and are tab-delimited ascii files with data labels and units in top rows. Note: Temperatures in the raw files are not corrected for sensor Offsets from reference. Tose Offsets are included in the individual penetration files. Within each deployment sequence, the total record is split into individual penetration files, one penetration file per station visited. Naming convention is as follows: H1607P01.pen.dat for penetration 1 of deployment sequence H1607. Each Penetration file has complete header information on the measurement and performance. Note: temperatures are reported in values of mili-degrees Celsius). From the individual measured temperature records, thermal gradients and in situ thermal conductivity values are derived using the technique described in Villinger and Davis (1986). We report here our initial results as well. For each penetration, a results-file is included with in situ temperature and conductivity reported as function of Depth. Naming convention of the results files is as follows: H1607_P01_results.dat with "H1607" as deployment sequence, "P01" as penetration number. If the heat pulse was not generated, only the decay of frictional heating was used to define in situ temperature. Thermal conductivity was assumed to be constant for all depths in those instances. Here, we used a value of 1.25 for the assumed thermal conductivity. Initial results and further details of the deployments can be found in the cruise report by Bohrmann et al. (2017).