Litologia i skład mineralny osadów z dna Basenu Gdańskiego

Abstract

W artykule przedstawiono rezultaty badań nad zmiennością składu mineralnego powierzchniowych osadów ilastych Basenu Gdańskiego z odległością od ujścia Wisły i linii brzegowej. Na podstawie zmienności składu mineralnego i chemicznego z głębokością osadu scharakteryzowano zmiany potencjału redukcyjno-oksydacyjnego i pH środowiska sedymentacji. Wydzielono poziomy o zróżnicowanej zawartości składników mineralnych. LITHOLOGY AND MINERAL COMPOSITION OF SEA FLOOR DEPOSITS IN THE GDAŃSK BASIN Clay sea-floor deposits of the Gdańsk Basin are characterized by low variability in mineral composition.The shares of quartz and clay minerals are 40% and 40–60%, respectively. Among clay minerals, the most important is illite whereas chlorite occurs in smaller amounts. Other, subordinate components include kaolinite, smectite, swelling chlorite and mixed-layer minerals. The deposits also yield carbonates (calcite, dolomite and siderite) and detrital minerals (feldspars, muscovite and glauconite).Smectite, present in material supplied by the Vistula River, undergoes transformation into chlorite and illite under the influence of sea water. The amount of smectite decreases along with distance from seashore at the advantage of the two minerals.The variability of deposits in the vertical is connected with increase in content and degree of crystallinity of illite and chlorite. The content of siderite and calcite is also changing, depending on oscillations in Eh and pH of the environment. Precipitation of siderite is related to its alkalization due to ingressions of water from the North Sea. On the basis of differences in content of some mineral components, there are differentiated horizons which are correlable with stratigraphic subdivision of the Baltic deposits.