Publication authorized by the Director, Bureau of Economic Geology, The University of Texas at Austin.
Formation of Storm Deposits by Wind-Forced Currents in the Gulf of Mexico and the North Sea†
- S.-D. Nio,
- R. T. E. Shüttenhelm and
- Tj. C. E. Van Weering
Published Online: 29 JUN 2009
Copyright © 1981 The International Association of Sedimentologists
Holocene Marine Sedimentation in the North Sea Basin
How to Cite
Morton, R. A. (1981) Formation of Storm Deposits by Wind-Forced Currents in the Gulf of Mexico and the North Sea, in Holocene Marine Sedimentation in the North Sea Basin (eds S.-D. Nio, R. T. E. Shüttenhelm and Tj. C. E. Van Weering), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444303759.ch27
- Published Online: 29 JUN 2009
- Published Print: 23 DEC 1981
Print ISBN: 9780632008582
Online ISBN: 9781444303759
- advective processes involving lateral sediment transport;
- graded sequences and well-sorted sand beds;
- poststorm processes - storm-surge ebb;
- proximal and distal unitts;
- broad sub-aerial plain
Textural variations, sedimentary structures, and vertical sequences preserved in shelf storm beds from the Gulf of Mexico are remarkably similar to published examples from the North Sea. In both areas, interlaminated and graded sands and muds characterize proximal and distal deposits. Proximal deposits, which are dominantly composed of sand, are first influenced by strong unidirectional currents, which may later give way to storm waves. Advective processes involving lateral sediment transport are also responsible for finer grained distal beds deposited in deeper water below wave base.
The formation of graded shelf deposits by storm runoff from coastal lagoons and adjacent barriers was first proposed by Hayes (1967). Since then, many sedimentologists studying ancient shelf deposits have appealed to storm-surge ebb as a mechanism for explaining size sorting and vertical succession of sedimentary structures found in shallow marine sand and mud sequences. However, re evaluation of topographic and geomorphic data for the type area (Padre Island and Laguna Madre) in conjunction with flood data for Hurricane Carla indicates that storm-surge ebb, as defined by Hayes, was probably not responsible for the graded bed deposited during Carla.
Judging from nearshore current data for recent storms, large-scale bottom flows produced or augmented by wind forcing are the most likely explanation for graded shelf deposits. Highest current velocities on the shelf, of the order of 2 m sec−1, are recorded shortly after the greatest wind stress is applied. These wind-driven currents occur near or within the bottom boundary layer and are directed alongshore or offshore. In storm-dominated basins such as the Gulf of Mexico, breaking waves and orbital velocities are important for assisting in sediment entrainment, but unidirectional bottom flows produced by wind forcing are probably the most important mechanism for shelf sediment transport. In other areas, such as the North Sea, which is characterized by substantially higher wave activity and stronger tidal currents than is the Gulf of Mexico, wind forcing can temporarily alter the tidal component and significantly increase the bottom current velocities.