Rheology of Natural Sediments and Its Influence on the Settling of Dropstones in Hemipelagic Marine Sediment

• Published in: Earth and space science (Hoboken, N.J.) Vol. 7; no. 3
• Main Authors: Knappe, E., Manga, M., Le Friant, A.
• Format: Journal Article
• Language: English
• Published: Hoboken John Wiley & Sons, Inc 01.03.2020; American Geophysical Union/Wiley; American Geophysical Union (AGU)
• Subjects: Clay; dropstones; IODP340; Laboratories; Marine sediments; mud rheology; Ocean floor; Particle size; Quartz; Rheology; Salinity; Sciences of the Universe; Sediment yield; Sediments; Terrestrial environments; thixothropy; Viscosity; Volcanoes; Yield stress; Lesser Antilles; Salton Sea
• ISSN: 2333-5084; 2333-5084
• DOI: 10.1029/2019EA000876

We investigate the rheology of naturally occurring hemipelagic marine sediment and compare measurements to another naturally occurring sediment from a terrestrial mud volcano and literature values. The hemipelagic marine sediment, collected by IODP 340, has a median grain size of 5.5 microns, is poorly sorted, and contains 31% clay, including smectite. The yield stresses and consistency are calculated by applying a range of shear stresses and shear rates using a cone‐and‐plate rheometer. A Herschel‐Bulkley model is fit to measured shear stresses and shear rates to calculate the yield stress and consistency. These measurements are performed at a range of particle concentrations and show that the hemipelagic sediment has a yield stress at particle concentrations as low as 10%. Increasing particle concentration increases the yield stress and consistency. We apply our results to show that natural pumice clasts need to have a radius greater than about 1 cm in order to settle through hemipelagic sediment on the sea floor. Most recovered pumice clasts from IODP 340 are thus preserved in the same horizon in which they were deposited. Key Points We obtain a new data set of rheology measurements from naturally occurring hemipelagic sediment and a terrestrial mud volcano Comparison with existing measurements indicates that particle composition influences yield stress and consistency Most pumice clasts recovered from IODP 340 are stratigraphically in place and thus date the occurrence of eruptions