The Kukruse bryozoan fauna seems to be rather specific, as the corresponding units [Lower and Upper Viivikonna
The samples were taken at the mines of Kukruse (the northern part of the deposit, 59[degrees]23' 27[degrees]23', closed 1967), Kivioli (the western part of the deposit, 59[degrees]20' 26[degrees]57', closed 1987) and Viru (the central part of the deposit, 59[degrees]18' 26[degrees]20', closed 2103), and in the eastern part of the deposit's open-casts at Sirgala (59[degrees]18' 27[degrees]46') and Viivikonna
In 1946 it obtained another oil shale mine, the Viivikonna
mine, which was supposed to supply oil shale to the gas plant to be established in Sillamae.
Formation of the Kukruse Regional Stage is the main stratigraphic unit containing oil shale (kukersite) in the Ordovician strata of Estonia (Fig.
Viljandi drill core, 373.3-374.3 m, the Kivioli Member of the Viivikonna
Formation, lower part of the Kukruse RS, lowermost Sandbian.
Advancing of Viivikonna
Section.--Tallinn: Maves AS, 2004.
Conodonts of the Kivioli Member, Viivikonna
Formation (Upper Ordovician) in the Kohtla section, Estonia.
Landscape researchers would be intrigued by a proposal to outline spatially the eastern open-cast mines, Narva, Sirgala and Viivikonna
with a total area of 300 k[m.sup.2] as a distinguished landscape district in the pattern of Estonian landscapes.
For supplying these power plants, the Viivikonna
surface mine was reconstructed and the Sirgala and Narva surface mines were opened.
2002) or from the Almelund Shale in Scania, and so direct correlation with the Viivikonna
Formation on the basis of these graptolites is not possible.
It is more expensive to ensure good quality in worse mining conditions (i.e., the Estonia underground mine and the eastern part of the Narva opencast mine) than in mines where conditions are better (i.e., the Viru mine and the Viivikonna
field in the Narva opencast mine).
It is represented in the Viivikonna
Formation (Sal), Kullsberg Limestone Formation (Kal), Lang&ra Formation (Ka4-Hi 1), and is especially abundant in the Boda Limestone Formation (Ka4-Hil).