By: Simone Burzacott-Gorman
Meet Kim Picard, Marine Geoscientist working for Geoscience Australia. Kim’s role on Investigator this voyage is to sample the sea floor to identify differences between the multi-beam sonar backscatter (the hardness of the sea floor). On the sonar, some areas appear to be harder than others, its Kim’s job to ‘ground truth’ the data being collected with the geology on site. Kim is particularly interested in understanding what looks to be a large ancient dune. In this area Kim will collect 3 very precise samples at different aspects on the dune, using the Smith Grab to determine the morphology of the area. Some of the sites are looking through the stratigraphy of the area (the sub bottom profiler) and in a couple of areas the geologists can see through the profile to the deep layer which they are most interested in collecting as these areas will provide greatest insights into the geomorphology.
At each sampling location Kim will collect a sample from the top 2cm of the profile, record substrate colour (using Munsell Soil Colour Book), grain size and angularity. Soil colour indicates how anoxic, organic, or rich the substrate is. Grain size can be indicative of geomorphology. Weathering and sorting of grain size can be indicative of movement, glaciation and river flow. The samples will then be further reviewed by Geoscience Australia with lasers to determine accurate grain size.
The Smith Grab is set and launched by the crew of Investigator and winched over the side of the vessel. The deepest site will take a sample at 75 metres. Once retrieved, Kim photographs the sample inside the grab with a sampling identification code placed within the frame. The grab is emptied into a trough and carried very carefully so as not to disturb the substrate layering, into the Lab. Once in the Lab Kim conducts the colour and grain size test and retrieves a sample. Biologicals inside the sample are then identified as these critters provide further indications of substrate and seafloor ecology. In the samples, many tiny crabs were identified.