H.-E. Reineck writes: This paper is very hypothetical, since this type of rhythmite is not known in recent sediments, either in ebb-tidal deltas or in shelf sediments. Such rhythmites would have to be deposited below wave base, and much of the shelf bottom is reached by waves, especially during storm surges. Usually jets from inlets and other channels in the peritidal area do not reach far into the shelf, except during storm surges when storm layers may reach up to 45 km from the mainland, and 35 km from the tidal flat border. In fairweather conditions jet sediments are separated in the nearshore area, sand being depositied in the coastal area and in ebb-tidal deltas, and mud on the shelf bottom.

I have never seen rhythmites in shelf sediments, except in storm layers (Aigner & Reineck 1982), and I suggest that the photographs in this paper (Figs 2 and 10) look very like lacustrine sediments, for instance those of Lake Constance (Reineck 1974).

G. E. Williams replies: My paper presents two related hypotheses: that the rhythmites described were deposited in a distal ebb-tidal delta to marine shelf setting below wave base, and that they encode palaeotidal periods. Both hypotheses would be confirmed if similar rhythmic laminae carrying tidal signals were to be found in modern distal ebb-tidal deposits. Özsoy (1986, p. 60) observed that ‘With regard to the transport and sedimentation processes, some of the basic tidal mechanisms have at times been overlooked in the past and too

This content is PDF only. Please click on the PDF icon to access.

First Page Preview

First page PDF preview
You do not currently have access to this article.