• The first-order morphological elements on glaciated continental shelves are banks and longitudinal and transverse troughs. Many longitudinal troughs are located on bedrock boundaries or fracture zones, whereas transverse troughs often represent seaward continuations of fjords and glacial valleys on the hinterland. Most troughs have served as drainage routes for ice streams.

• The continental shelves are normally covered by less than 300 m of stratiform diamictons. The greatest thickness of glacigenic sediments occurs at the trough mouths.

• Many second-order morphological elements (e.g. morainal ridges/banks, streamlined forms, glacitectonic forms) are similar to the forms found in the terrestrial environment. Iceberg plough marks (normally at depths of less than 500 m, but locally up to 850 m depth) and iceberg turbate is typical for glaciated continental margins.

• TMFs are submarine fans at the mouths of troughs on presently or formerly glaciated continental shelves. TMFs are depo-centres containing kilometre-thick packages of sediments accumulated in front of ice streams draining ice sheets and ice caps. There is clearly reason to believe that many of the ancient diamicton records were deposited in a continental margin setting, particularly in TMFs.

• The main building blocks of TMFs are glacimarine debris flow deposits that might be as large as 2000 km3 and have a runout distance of up to 200 km. The debris flows were remobilized sediments from till deltas/grounding-zone wedges deposited by ice streams at the shelf break. The long runout distance might be due to hydroplaning.

• On steep continental slopes the glacigenic sediments might be transported directly to the deep sea by turbidity currents through channels and accumulate in deep-sea fans and/or drifts.

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Project Management Made Easy

Project Management Made Easy

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