Wednesday, June 4, 2014

Highlights—Calling Out Megaclasts

Although the expanded Udden-Wentworth (U-W) grain-size scale is an important tool for classifying the size of sedimentary particles, existing terminology at the coarse end of the scale is problematic. In this paper, Terry and Goff review how several terms used to define size ranges on the U-W scale also have shape applications on particle form diagrams, which can lead to confusion. To resolve this issue, the paper proposes abandoning shape-related terms and replacing them with a new incremental system based on meso- and macro- prefixes to classify large boulder size ranges. The value of the modification is that both size and shape classification of very coarse sediments can now be accomplished simultaneously without overlap or confusion in nomenclature.

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