Volume 18 (2001)
CHALK DEPOSITION IN LAKE KRUKLIN (NE POLAND) AS A RESULT OF
DECAICIFICATION OF THE LAKE CATCHMENT
Institute of Geological Sciences, Polish Academy of
Sciences, ul. Twarda 51/55, 00-818 Warszawa,
Poland, tel. +48-22-6978811, fax.
+48-22-6206223; e-mail: firstname.lastname@example.org
Lacustrine chalk is very common in post-glacial lakes of northern
Poland. In the deposit of Lake Kruklin (NE Poland) carbonates occur as a layer 2-3
m thick. Samples for laboratory studies were collected from three
profiles in SW part of the deposit. Mineral composition of the sediments
was determined using differential thermal analysis (DTA) and
thermogravimetry analysis (TGA), while the age was determined on the basis of pollen analysis. The sediment profiles represent an age of early Holocene. Calcite is the major component
of lacustrine chalk. It forms small crystals (<10 mm), sometimes grouped in aggregates, or present as bioclasts.
Calcium carbonate precipitated from lake water. Chemical
weathering of glacial and fluvioglacial material of the lake catchment is the main
source of ions, transported to the
lake mainly by groundwater.
Formation of the Kruklin lacustrine chalk deposit must have required
300-350 kg of dry weight calcium carbonate to be carried away from each
square meter of the lake catchment. If only top one-meter layer of
glacial sediments had been decalcified, it should have contained
13-22 percent of calcium carbonate. The
results of petrographic analysis show this
value to be possible.
Key words: Kruklin Lake, lacustrine chalk,
decalcification, Holocene, NE Poland