Mapping og bioclastic sediments - data, methods and confidence

Abstract

MAREANO has shown that acoustic mapping with limited ground truthing is a powerful tool for mapping biogenic mounds and associated bioclastic sediments. Standard Quaternary geology maps show the genesis of surficial sediments, i.e. the origin of the sediments and how they have been deposited. In MAREANO, maps of bottom sediment genesis (where bioclastic sediment is one of many sediment classes) are complementary to the maps of bottom sediment grain size. Bioclastic sediments (BS) is a common term used to describe all carbonate sediments resulting from dead organisms and includes a range of grain sizes and origins, from silt to gravel clasts, coral rubble and dead coral blocks. BS normally have a minerogenic component, either coming from in situ deposits, traction currents along the seabed, or deposition from suspension. Many biogenic mounds are wholly or partly covered by living corals and other organisms, but these are not considered part of the bioclastic sediment. In this report, we have defined biogenic mounds based on morphology; i.e. they are structures which can be mapped from bathymetric data.