Charakterystyka warunków sedymentacji osadów Zalewu Puckiego na podstawie analizy minerałów ciężkich

Abstract

CHARACTERISTICS OF SEDIMENTARY CONDITIONS IN THE PUCK EMBAYMENT IN THE LIGHT OF ANALYSIS OF HEAVY MINERALS Summary In the recent bottom deposits of the Puck Bay Lagoon there occurs a very differentiated set of heavy minerals. The most abundant are three kinds of heavy minerals: garnets, amphiboles, and opaque minerals. Other minerals, like: epidote, zoisite, zircone, rutile, kyanite, staurolite, biotite and chlorite there occur in much smaller amounts. The differentiation of heavy minerals concentrations shows some connections with the type of bottom deposits. The biggest heavy minerals concentrations occur in medium sands and in verigrained sands with gravel. Whereas the smallest ones occur in aleurithic deposits. Variable concentrations of garnets and amphiboles, reflect conditions, in which sediments were deposited. There were established three groups of the deposits with the respect to differentiated concentrations of garnets and amphiboles: 1. Medium sands and varigrained sands with gravel, where the garnets prevail to amphiboles. They occur to the depth of 2 m. These sediments were deposited in an active environment with superiority of erosional conditions or it is possible that after the deposition they were modified by currents. 2. Fine sands and fine .sands with silts containing almost equal amounts of garnets and amphiboles. They occur on the depth from 2 m to 4 m, and represent a transitional environment. 3. Sandy - aleurithic and aleurithic sediments with the amphiboles prevailing to garnets and with notable admixture of biotite and mineral aggregates. These sediments represent an environment with superiority of accumulational processes and they mainly occur below the depth of 4 m (Kuźnicka Hollow and Rzucewska Hollow). The composition of heavy minerals, which occur in the sandy deposits in the northern part of the Puck Bay Lagoon, they were enriched in heavy minerals by strong streams which disrupted the Hel Peninsula during the extremely high water level increase in the Baltic Sea.