Saturday, 19 July 2014

Glorious Mud.

We have been coring in the Traenadjupet region, and have seen some fabulous examples of a range of processes recorded in the mud. We are hopeful for some great results from these cores, though this will take some time to work up, but in the meantime, here are a few examples of some of the wonderfully colourful and exciting mud cores we have taken recently:

This layer has been described as the Pistachio Green horizon after its distinctive colour. This was the first core we found it in, though it has appeared in several others. The exact chemistry and mineralogy of the layer will be part of the post cruise work, but this is an unusual colour, and will unfortunately fade over time.

This very unusual deposit looks remarkabaly like a butterfly, but is in fact a series of mud boulders that were caught up in a submarine landslide. The mud would have been partially consolidated at the time, and the layers ripped up and rolled into boulders, which we have then cored through.

This picture is a close up of one of these contorted mud boulders, and shows that the sequences of colours is symmetrical across the pale brown horizon. When interpreted as having symmetry, andthe fact that these layers terminate against the side of the core, we can be sure that they are boulders of mud and not an artefact of the coring process, which can sometimes cause disturbance to the layers, as seen below:

The darker mud visible in the centre of the core is running from top to bottom, and there are very few processes that can produce this type of feature. It could be bioturbation, the traces left behind by burrowing fauna that are infilled by sediment, but in our current location in very deep water, this is too large a burrow to be possible. This is unfortunately a product of suction at the base of the core, which can cause mud from the base to be injected upwards into stratigraphically higher layers. This limits the usefulness of the core, but is normally confined to the lower sections.

The unusual black block in the lower core is a boulder of peat that was caught in the flow. It is surrounded by clasts of mud set in a sandy matrix, typical of the type of deposit left by a large submarine landslide. The peat boulder is spongy and soft, and will be useful for us to determine where the flow originated as it should contain macrofossils and pollen.

This wonderful striped section is from a deep basin core, and each of the layers represents a very distal deposit from the submarine landslide. Cores like this one have the deposits separated by a thin section of hemipelagite: "normal" marine sedimentation whcih contains forams and potentially other material that will allow us to date each event. These long basin records are one of the key objectives of the project, areas that capture a long record will allow us to assess how frequently landslides happen, whilst the cores taken on top of the landslides are helping us to understand what makes some landslides tsunamigenic or not.

This final picture shows some very pretty laminations, couplets of sediment that will be part of our research into sedimentation patterns on the margin. They appear only in certain locations and within small sections of core, and are potentially the result of seasonal/cyclic changes in sediment source or the energy of the current.


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