Zmiany niektórych cech litologicznych osadów w dolnej części brzegu między klifem w Orłowie a Sopotem

Roman Racinowski

Abstract


CHANGES OF CERTAIN LITHOLOGIC FEATURRS OF DEPOSITS IN THE FORESHORE BETWEEN THE CLIFF AT ORŁOWO AND SOPOT

Summary

The paper presents the results of studies on sand-gravel material taken from the surf zone in an about 4 km long shore sector of the Gdańsk Bay, between the cliff at Orłowo and Sopot. The deposits of the tidal zone greatly differ from the material (boulder days) building up the cliff, and from the sands forming aggradation cones at the cliff base.
The first group of differences embraces the changes in deposits of the surf zone, which are characterized by a stabilized directional variability that is a result of dynamic activity of marine waters. It has also been ascertained that farther off the cliff, the gravels of 2–5 cm fraction change their form passing from spheroidal into discoidal. An increase in rounding degree of gravels takes place, too.
To the second group of differences belong the characteristics of the deposits from tidal zone, which are conditioned by the real dynamics of tidal waters, the character of deposits being to certain degree an exponent of intensity of flows and ebbs.
This concerns here the differentiation in grain size, the percentage of heavy minerals, and the ratio of heavy minerals having specific weight below 3.4 to those characterized by specific weight amounting to more than 3.4. The changes depend on the form of shore sector exposed to the activity either of feebler or of stronger energy of sea waters. The shore sectors exposed to stronger activity of swash and beckwasch are characterized in the surf zone by coarser sediment, greater content of heavy minerals, and considerable percentage of those that have specific weight higher than 3.4.
The third group embraces reactively smallest differences occurring between the continental material and deposits of surf zone. This concerns a small differentiation in mineral petrographic composition of sand fraction (contents of light components) and partly of gravel fraction, as well as slight changes in rounding degree of quartz grains.


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DOI: https://doi.org/10.7306/gq.v11i1.13525