RRS James Cook JC018
Cruise summary report
| Cruise Info. | |
| Ship name (ship code) | RRS James Cook (740H) |
| Cruise identifier | JC018 |
| Cruise period | 2007-12-03 — 2007-12-16 |
| Status | Completed |
| Port of departure | St. John's, Antigua and Barbuda |
| Port of return | St. John's, Antigua and Barbuda |
| Purpose | Research |
| Objectives | The major objective of this cruise was to test the hypothesis that early diagenetic alteration of recent, subaerial, volcanogenic material in the submarine environment has a significant impact on the global biogeochemical cycles. To this end, NERC funded a 13 day research cruise around Montserrat. The island of Montserrat was chosen as it has been the site of active volcanism since 1995, with ~90% of the products this phase of volcanism already having been transported to the surrounding ocean. In addition, there is a wealth of data concerning volcanic activity on Montserrat, enabling the results of our study to be placed in a well constrained context.
During this cruise we sought to collect sediments from the seafloor using various coring devices (gravity core, box core, mega core). Pore waters were extracted from the sediments (collected from box cores and mega cores) by centrifugation. These pore waters were preserved for transport back to Southampton University and subsequent geochemical analysis. Pore water profiles of dissolved oxygen and redox conditions were measured on board ship using micro electrodes. In addition, DGT and DET gel probes were also deployed in sediments recovered from box cores and mega cores. These probes were fixed and returned to Portsmouth University for subsequent analysis. To complement the pore water studies, a limited number of water column samples were taken using the combined rosette and CTD. A secondary objective of the cruise was to map the distribution of volcanogenic material in the upper 1 metre of sediments around the island. This work augments cruise 123 of the James Clark Ross, which used vibro-cores to take long (up to 8 m) cores to study the history of volcanism on Montserrat. However, the vibro-cores do not preserve the upper sediments that contain products of the most recent phase of volcanism. A related aspect of this sedimentological work involved scientists from Plymouth University. This objective was to study the foraminiferal faunal assemblages within the sediments to establish the origin and age of volcanogenic and carbonate turbidites and to examine the nature of early foraminiferal colonisation of volcanogenic sediments. The study of volcanogenic sediment distribution also included swath bathymetry surveys of underwater features related to subaerial and submarine collapse events. |
| Chief scientist | Martin R Palmer (National Oceanography Centre, Southampton) |
| Project | Early Diagenesis of Volcanic Ash in the Oceans |
| Coordinating body | School of Ocean & Earth Science, University of Southampton |
| Cruise report |  (0.62 MB) |
| Ocean/sea areas | |
| General | Caribbean Sea |
| Specific | Caribbean Sea around Montserrat |
| Track charts | (0.04 MB) |
| Measurements | |
| Physical oceanography | |
| CTD stations | Quantity: number of profiles = 10 Description: CTD profiles and dissolved oxygen measured and samples taken for dissolved Mn |
| Chemical oceanography | |
| Oxygen | Quantity: number of profiles = 10 Description: Dissolved oxygen was measured in samples taken from CTD |
| Geology and geophysics | |
| Core - soft bottom | Quantity: number of cores = 53 Description: Sediment cores taken and pore waters extracted and sediments sub-sampled for geochemical analyses at Southampton University |
| Multi-beam echosounding | Quantity: number of surveys = 2 Description: Swath surveys were taken in two areas to obtain an accurate measure of the sea floor bathymetry |
