Sand waves and other bedforms in lower Cook Inlet, Alaska
- 1 January 1977
- journal article
- research article
- Published by Taylor & Francis in Marine Geotechnology
- Vol. 2 (1), 291-308
- https://doi.org/10.1080/10641197709379785
Abstract
Lower Cook Inlet in Alaska has high‐ tidal currents that average 3–4 knots and normally reach a peak of 6–8 knots. The bottom has an average depth of about 60–70 m in the central part of the inlet that deepens toward the south. Several types of bedforms, such as sand waves, dunes, ripples, sand ribbons, and lag deposits form a microtopography on the otherwise smooth seafloor. Each bedform type covers a small field, normally a few hundred to a few thousand meters wide, and usually several kilometers long parallel to the tidal flow. High‐resolution seismic systems, side‐scan sonar and bottom television were used to study these bedforms. Large sand waves with wavelengths over 300 m and wave heights up to 10 m were observed. Fields of ebb‐oriented or flood‐oriented asymmetric bedforms commonly grade into more symmetric shapes. Several orders of smaller sand waves and dunes cover the flanks of the very large bedforms. The crest directions of both size groups are normally parallel, but deviations of up to 90° have been observed; local deviations may occur where smaller forms approach the crests of the larger sand waves. Bottom television observations demonstrated active bedload transport in a northerly direction on crests and midflanks of southward asymmetric large sand waves, but not in their troughs. Movement of bedload occurs in the form of small ripples. Although the asymmetry of the large bedforms suggests that migration has taken place in the ebb or flood directions, the very low surface angles (2.5°‐8°) of these bedforms do not indicate regular movements. The large bedforms are probably relict features, or they migrate only under severe conditions, whereas active sand transport by ripples and smaller sand waves and dunes moves bedload back and forth with the tides. An understanding of such movements is essential for determining design criteria for offshore installations and in benthic‐faunal studies.Keywords
This publication has 8 references indexed in Scilit:
- Seismic profiles of Lower Cook Inlet and Kodiak Shelf, R/V Sea Sounder, June-July 1976Open-File Report, 1976
- Preliminary report on the surface and shallow subsurface geology of Lower Cook Inlet and Kodiak Shelf, AlaskaOpen-File Report, 1976
- BED CONFIGURATIONSPublished by Society for Sedimentary Geology ,1975
- Depositional Sedimentary EnvironmentsPublished by Springer Nature ,1973
- Sand waves in the North Sea off the coast of HollandMarine Geology, 1971
- Sand waves in the southern bight of the North SeaMarine Geology, 1971
- Sand ribbons of European tidal seasMarine Geology, 1970
- Shape and size trends for sand waves in a depositional zone of the North SeaGeological Magazine, 1970