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  21.05.2020, 07:00h


How it all began: fossil travertine

Outside the present-day course of the Krka River, in the area of the river's previous course near Knin that which was active during the time of the river’s geological development, we find travertine about 125,000 years old – fossil travertine.

The process of travertine building began in the Pleistocene, the last ice age, and with occasionally interruptions has lasted until the present day. After the end of the last glacial period, call the Würm period, the climate began warming and the flow of water slowed, creating the conditions for the settlement of mosses, algae and other organisms that take part in the travertine building process. The Pleistocene travertine in the Krka River Valley and its tributaries is up to 20 metres higher than the present-day riverbed, indicating the height at which the river flowed during that period. This travertine is called dead travertine, or fossil travertine.

Most of the travertine at the waterfalls is less than 10,000 years old. The creation of travertine deposits in the post-Würm period began at Skradinski buk waterfall, Roški slap waterfall and other falls along the river’s course, creating Visovac Lake and other accumulations in the canyon sections of the present-day Krka. The active travertine falls of the river, as sections of the barrier that lie within the current watercourse, are biodynamic formations that continue to grow under the travertine building processes, and so they are called “live” travertine.

Travertine is important for understanding the creation of the present-day appearance of the Krka River. It is represented in two variations – the hard, hollow travertine at the barriers, and the dusty-pelite travertine on the lake bottom. The remnants of travertine barriers are also found at different relative heights in comparison to the current riverbed, which is also important in explaining the rate at which the Krka River cut through the landscape.

The former flow of water over time is best seen in the example of the Krčić River. The Krčić is the source of the Krka River, in the morphogenetic sense, and today represents its first tributary. It springs in the foothills of Mt. Dinara at an elevation of 375 metres, and runs over a length of 10,5 km. During periods of heavy rain or snowmelt in the mountains inland, the Krčić is a torrential river, while it dries out during the summer. If it did not dry out during summer, the Krčić would not exist as its current concept and the source of the Krka would be where the source of the Krčić is today, in the foothills of Mt. Dinara, which legend says is the place where the Krka is born. However, people recognised the seasonal water regime of the Krčić River and gave it is name. In the recent geological past, due to the colder climate and higher levels of precipitation, it did not dry out, and the Krka and Krčić formed the same course. Evidence of its previous regime is visible in the remnants of the vast travertine deposits found within the Krčić valley, high above the present-day flow.