Regional Monitoring of Natural Environment 2004, No 5, 213-234
MORPHOLOGY OF QUARTZ GRAINS FROM RELICT RESIDUAL DEPOSITS OF THE TERRA ROSSA AND TERRA FUSCA TYPE FROM THE HOLY CROSS MTS. AND THEIR MARGIN
Quartz grains from relict residual deposits of limestones located in the Holy Cross Mts. and their margin were analysed. The non-carbonate residual deposits of the terra rossa type as the residuum of Devonian limestone could have developed at the Permian/Triassic boundary, or in the Tertiary in a hot climate with dry and humid periods. The terra fusca residual deposit, in turn, as a residuum of Tertiary limestones, developed during the oldest interglacial of the Quaternary. In relation to the general characteristics of these residual deposits the evolution of quartz grains isolated from the non-carbonate residuum of the limestones is analysed. It was assumed that under different magnifications the quartz grains reveal features of chemical weathering typical of a neutral environment. Features pointing to an alkaline environment, when the quartz grain is still within the limestone, were observed to a much smaller degree. Amorphous silica may cement quartz grains, pass into crystalline forms (opal) or in certain physical-chemical conditions sodium-calcium aluminosilicates – zeolites – can be formed. Such recrystallisation is one of the stages of diageneis, when stable minerals are formed and the grain undergoes overgrowing.