[1][2] It was named for the Kačák Member of the Srbsko Formation in Bohemia, where it is represented by a black shale interval within a sequence of limestone.
This organic rich shale is found within a sequence of shallow water limestones forming the Srbsko Formation of the Prague Basin.
[5] The event has also been recognised at Eifel in Germany, Gorodenka (near Omsk, Russia) and in Ontario and New York State in eastern North America, all localities lying on the then continental shelf around the Old Red continent.
Further afield at the time of the event, on the continental shelf on the other side of the Rheic Ocean, it has been recognised in Morocco, Cantabria in northern Spain, the Carnic Alps and Graz Paleozoic in Italy and Austria, the Montagne Noire in France and in the Barrandian area of the Czech Republic.
[7] In the Horn River Group of Canada, the Kačák interval corresponds to an appearance of anoxic sedimentation and a termination of carbonate platform deposition.