The Rocky Story about an Ecological Catastrophe 252 Million Years Ago

Alojz Demšar
Community engagement, Education, Cross-frontier collaboration, Youth oriented
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A few years ago near Žiri, Slovenia, geologists found a limestone layer that was formed during the Permian-Triassic extinction 252 million years ago. The catastrophe deserves particular attention, among other anomalies was also high increase of the temperature. Geological sites with a well-defined Permian-Triassic boundary are rare in Europe and the site will be preserved and presented by the local community and geologists to remind us of how vulnerable Earth and its inhabitants are.

In 2000, geologist dr. Bogdan Jurkovšek examined the Jarešca stream in Jarčja Dolina near Žiri. In the vicinity of the farm Lukač, he found a new limestone layer in the riverbed, which was previously revealed by the storm. Laboratory analyses have shown that the layers were formed 252 million years ago in the shallow sea, in the last period of the Paleozoic and at the beginning of Mesozoic (Permian-Triassic boundary). During that time, Earth's greatest catastrophe in the last 550 million years happened. Up to 96% of all marine invertebrate species   and 70% of genera of terrestrial vertebrate species probably disappeared in the great extinction of living beings. The extinction was most likely the result of volcanic eruptions in today's Siberia and China, which sent huge amounts of gases and dust into the atmosphere and sea. Earth's regulating mechanisms were denied. The temperature of the atmosphere and the seas increased. Aridity on the land and toxic hydrogen sulfite, as well as a lack of oxygen in the seas were probable causes of the extinction. There is still a lot of ambiguity about that time. Some of them were clarified by the exploration of the rock from the Jarča Dolina.
The investigation of the geological site was an international project of geologists from Slovenia, Croatia, USA and other countries and was published in scientific literature. Geologists guided a visit to the geological site during the European Heritage Days on September 30th, 2016.

European Dimension

In Europe, there are only a few geological sites where the Permian-Triassic boundary is precisely defined (Tesero and Bulla in Dolomites, Italy; Gartnerkofel in Carnic Alps, Austria; Jarčja Dolina in Slovenia). These locations are worthy of particular attention since they allow a clarification of events of the Permian-Triassic extinction.  An environmental disaster from a quarter of a billion years ago reminds us how vulnerable our Earth and its inhabitants are. A visit to a geological site and contact with rocks from the time of and Earth catastrophe is more convincing than listening to long explanations of the danger of global environmental changes. The preserved and presented geological site would attract school groups and other people interested in geology and ecology from Slovenia and other European countries.

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