Particle settling velocity is a fundamental parameter in sedimentology and engineering, and has accordingly received much attention in the literature. Grain properties, such as shape and drag coefficient, which affect terminal settling velocity, also control the threshold of initiation of motion and sediment entrainment into suspension. Terminal settling velocity therefore provides insights into sediment dynamics in modern and past depositional environments and is important for marine engineering works. Despite the global importance of resedimented carbonates the study of particle hydrodynamics is strongly biased towards terrigenous sediments. This paper presents a review of the settling hydrodynamics of carbonate grains and associated particle properties, such as shape, grain size and density. For carbonate grains these parameters are more complex than for siliciclastic counterparts due to their common biogenic origin, introducing a wide range of morphologies, densities and abrasion products as a result of the skeletal nature of such grains. This review includes an extensive database of published composition-specific settling velocities, as well as densities of common carbonate constituents. The database includes corals, coralline red algae, bivalves, brachiopods, gastropods, Halimeda green algae, bryozoans, crinoids, echinoderms, Alcyonarian spicules, numerous benthic and planktic foraminifers, and fecal pellets. Grain density as a function of skeletal structure and mineralogy exerts another control on settling velocity, with unclarity in density definitions hampering effective communication in the literature. The variation in single-grain hydrodynamic behaviour implies careful application of previously proposed equations for the prediction of settling velocity of bulk sand. Despite a firm basis there is a need for additional systematic composition-specific investigations to enable the adequate prediction of carbonate particle hydrodynamics due to the broad spectrum of forms and densities. Emerging technologies such as automated particle velocimetry, computational fluid dynamics, machine learning and microtomography provide exciting avenues for future understanding of the hydrodynamic behaviour of particles with the complexity of natural carbonate grains.
Bibliographical noteFunding Information:
We are grateful for the extensive and helpful comments provided by Stephen Lokier and four anonymous reviewers as well as the careful handling of the manuscript by Editor Chris Fielding. We are indebted to Siim Sepp from www.sandatlas.org ; Carol Hopper Brill, Kate Clover and Leo Kenney from http://www.splendidsands.com ; and Alain Couette from www.arenophile.fr for kindly providing magnificent photos of diverse carbonate sediments in Fig. 1 . Brett Metcalfe is thanked for his kind assistance during SEM analysis. We also thank Elias Samankassou for help with identification of carbonate grains in the SEM images. This study was inspired by the master projects of MdK, RdB and Jonathan Kranenburg at Vrije Universiteit Amsterdam, which was made possible through funding to JR provided by Vrije Universiteit Amsterdam, and TOTAL E&P Recherche Développement (Pau, France) under contract number FR00008062. We greatly appreciate the support from Jean Borgomano (now at Aix-Marseille University ), Patrick Sorriaux and Emmanuelle Poli from TOTAL in obtaining funds. The College of Petroleum Engineering & Geosciences at King Fahd University of Petroleum & Minerals is thanked for funding through Aramco Chair Professor start-up funds.
© 2021 Elsevier B.V.
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- Hydrodynamic behaviour
- Particle shape
- Settling velocity