Origin of hummocky and swaley cross-stratification— The controlling influence of unidirectional current strength and aggradation rate

Abstract

Research Article| December 01, 2006 Origin of hummocky and swaley cross-stratification— The controlling influence of unidirectional current strength and aggradation rate Simone Dumas; Simone Dumas 1Department of Earth Sciences, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada Search for other works by this author on: GSW Google Scholar R.W.C. Arnott R.W.C. Arnott 1Department of Earth Sciences, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada Search for other works by this author on: GSW Google Scholar Geology (2006) 34 (12): 1073–1076. https://doi.org/10.1130/G22930A.1 Article history received: 25 Apr 2006 rev-recd: 27 Jul 2006 accepted: 29 Jul 2006 first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Simone Dumas, R.W.C. Arnott; Origin of hummocky and swaley cross-stratification— The controlling influence of unidirectional current strength and aggradation rate. Geology 2006;; 34 (12): 1073–1076. doi: https://doi.org/10.1130/G22930A.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract A series of wave-tunnel experiments was conducted to investigate the conditions under which hummocky and swaley cross-stratification form. Isotropic 3-dimensional (3-D) hummocky bed forms were generated under long wave periods (∼8–10 s) and moderate oscillatory velocities (Uo ∼50–90 cm/s) with very weak (< 5 cm/s) to no unidirectional flow. Hummocks became anisotropic with the addition of only a small unidirectional current (5–10 cm/s), and began to resemble unidirectional dunes when the unidirectional current was increased above 10 cm/s. Synthetic aggradation of the hummocky bed forms at high (4.2 mm/min) and low (1 mm/min) rates generated stratification resembling hummocky and swaley cross-stratification, respectively. Based on these findings, we suggest that hummocky cross-stratification optimally forms above (but near) storm wave base where aggradation rates during storms are high enough to preserve hummocks but unidirectional current speeds are sufficiently low to generate low-angle, isotropic cross-stratification. Swaley cross-stratification is also hypothesized to be deposited by an aggrading hummocky bed between fair-weather and storm wave base, but in shallower water where aggradation rates are low enough to cause preferential preservation of swales. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.