graywacke
or grey·wacke
Geology. a dark-gray coarse-grained wacke.
Origin of graywacke
1Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2024
How to use graywacke in a sentence
The strata consist of greywackes, flags and shales with seams and zones of graptolite shale which yield fossils sparingly.
In the second place, there is no proof that the ancient greywackes are not deoxidized sediments.
Climatic Changes | Ellsworth HuntingtonAs a rule greywackes are not fossiliferous, but organic remains may be common in the finer beds associated with them.
In some districts the greywackes are cleaved, but they show phenomena of this kind much less perfectly than the slates.
By increasing metamorphism greywackes frequently pass into mica-schists, chloride schists and sedimentary gneisses.
Scientific definitions for graywacke
[ grā′wăk′, -wăk′ə ]
Any of various dark gray, coarse-grained sandstones that contain abundant feldspar and rock fragments and often have a clay-rich matrix. Graywackes are thought to originate in environments where erosion, transportation, and deposition happen so quickly that minerals and rock fragments do not have sufficient time to break down into finer constituents.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
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