McMurdo Sound Sediment and Tectonic Studies (MSSTS)

The main purpose of the MSSTS project is to obtain a record of the early history of the East Antarctic Ice Sheet and to date its initiation in the Ross Sea region. In addition, it was hoped to relate the offshore sedimentary sequence in McMurdo Sound to the strata cored inland of the Transantarctic Mountain Front and hence gauge the extent of late Cenozoic movement. Preliminary investigations were conducted in the 1978-1979 season to locate and determine the physical condition at two sites proposed for the drilling. For each site local bathymetry was determined and an access hole then opened for current measurements and sea floor sampling. The drill rigs were located on top of the sea ice and therefore measurements of the tides, ice thickness and deflection of sea ice near the rig were all measured. One site was cored for rock over 196m deep water. The drill reached a depth of 229.6m below the sea floor. 73 cores were collected with 44% recovery. Collected rock cores were described as soon as they were retrieved. The description comprised two elements, i) graphic log - used to show bedding features, location of fossils, pebbles and sample prints for petrographic or paleontological slides, ii) lithology. On average, one smear slide for petrographic study was prepared for each section of the core, though more may have been completed where the core was highly variable. The main value of the smear slide is in estimating proportions of biogenic components and in determining the proportion of biogenic to terrigenous material. In addition, paleontology and biostratigraphy were conducted and the core was photographed and sampled to maintain a record that can be sent to the science community. The core was analysed to detect any gas to ensure the safety of the drilling operation. After the core was retrieved and described, sonic velocity and density were also measured. Once drilling was completed, temperatures were measured down the drill hole. In addition, geophysical surveys were taken around the drill site area. An across sound survey was conducted at 5km intervals along six lines approximately normal to the axis of McMurdo Sound. At each beacon site (5km intervals) extensive piston coring, bottom photography, bathymetric and gravity surveys were conducted. However, electronic problems with the triggering of the camera prevented any underwater photography and the piston coring was only partially successful.