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Ocean Observation: From Microfluidics to Global Scale
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The importance of in-situ measurements of turbidity currents: the limitations of grain-size and upscaling in flume experiments
Tuesday 8th @ 1410-1430, Conference Room 7
Guilherme Bozetti* , Visua-Log Geology Consulting, AB39 2PR, Stonehaven, United Kingdom;
University of Aberdeen, Department of Geology & Petroleum Geology, AB24 3UE, Aberdeen, UK
Presenter Email: g.bozetti@visua-log.com |
| Submarine gravity flows, including turbidity currents, are the main sediment transport mechanism recognised on the Earth’s surface, responsible for redistributing more sediments than any other sediment flow process. Although turbidity currents play a major role shaping the bottom of our oceans and large lakes, direct measurements of their properties are extremely rare, and important properties such as sediment concentration and density stratification have never been directly acquired.
In an attempt to diminish uncertainties regarding turbidity currents properties, flume experiments have been carried out extensively for the past 30 years, and their results upscaled to dimensions encountered in nature. However, making predictions of natural gravity-flow processes based on turbidity current behaviours produced in experiments in tanks that range from 5 to 25 metres, with very limited grain-size range, and extremely restricted duration is rather concerning, and some major issues should be addressed:
i) there has never been reliable experiments on turbidity currents produced with grain-sizes greater than 0.5 mm, leaving a huge grey area when it comes to the behaviour of the flows transporting larger grain-sizes; ii) in such a short duration of the experiments, there is not enough time for a series of well-known phenomena such as water entrainment and flow rheology transformation to be observed; iii) the vast majority of the experiments are unimodal in terms of grain-sizes, not representing, even within the finer grain fraction, the effects of a series of grain-sizes within the same flow interacting one another.
For a precise understanding of the sediment transport mechanisms, direct monitoring observations of gravity-driven flows, now available due to recent technological advances in monitoring sensors, moorings, and autonomous data recovery, should be combined with cores and seismic data to link flow and deposit character. Experimental and numerical models play a key role in understanding specific properties, but the better the knowledge of natural properties of these events, better models can be produced, generating results that are more reliable.
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