Nowe stanowiska laminowanych osadów jeziornych na Pojezierzu Kaszubskim

Abstract

New sites of laminated lake sediments in Kashubian Lakeland.A b s t r a c t . Annually laminated lake sediments are a very valuable source of paleoecological information because they provide a precise timescale in calendar years and limited post-depositional disturbances. They are formed in specific conditions that enable not only the formation but also preservation of lamination, hence they rarely occur. The goal was to find lakes with annually laminated sediments in Kashubian Lakeland which can provide new high-resolution paleoenvironmental and paleoclimatic data for this part of Europe. Based on statistical analyses including catchment geology and topography, morphometric lake basin features and hydrological parameters, a pre-selection of 22 lakes with water depths ranging from 15 to 35 m was carried out. Gravity cores (30–90 cm long) were obtained from 18 of these lakes during a field survey in 2006. The cores were split lengthwise, photographed digitally and examined carefully. Four of the lakes studied show distinct alternations of pale and dark laminae. For three lakes (Kramsko Duże, Kramsko Małe and Borowo Wielkie) such laminations were restricted to sections of the cores only. Lake Suminko was deemed the most promising site with its laminations covering the entire taken core. In all the cases, biochemical varves were developed with pale spring/summer layers composed of autochthonous carbonates and dark fall/winter layers made of organic detritus and minerogenic particles.