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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 64 (1980)

Issue: 5. (May)

First Page: 759

Last Page: 759

Title: Sand Dispersal at Norderneyer Seegat, West Germany: ABSTRACT

Author(s): Dag Nummedal, P. Shea Penland, Amy Maynard

Article Type: Meeting abstract


Norderneyer Seegat connects the North Sea and the Wattenmeer between the East Friesian Islands of Juist and Norderney. It is a high wave-energy mesotidal inlet. The mean tide range is 2.4 m and the estimated mean breaker height exceeds 1 m. The sediment dispersal pattern and resultant morphology differ significantly from those of mesotidal inlets investigated along the low wave-energy shores of the southeastern United States.

The seaward margin of the ebb-tidal delta consists of a nearly continuous arc of bars, the "reef-bow." These bars have segregated tidal flow; Previous HitfloodNext Hit dominates a broad ramp facing into the dominant waves (i.e., the west side), ebb dominates the narrow steep leeside margin. The bars migrate eastward through combined tide and wave action at an average rate of 400 m/year. Bar migration appears to be the dominant mode of inlet sediment bypassing.

The gorge section of the main inlet channel is ebb-dominated as a result of (1) water level-dependent inlet efficiency and (2) net water supply to the inlet drainage basin due to prevailing southwest winds.

Previous HitFloodNext Hit-dominated intertidal sand shoals abound in, and landward of, the inlet gorge. Ebb-dominated flanks occur on some of the shoals. The degree of Previous HitfloodNext Hit dominance increases landward, an effect which is attributed to the difference in celerity between the tidal wave trough and crest.

Both the mechanics of ebb-delta sand bypassing, and the occurrence of tidal-flat Previous HitfloodTop dominance, distinguish the dispersal pattern at Norderneyer Seegat from that at mesotidal inlets with lower wave energy. Stratigraphic models for tidal-inlet sequences must consider both tide range and wave energy.

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