Abstract
Reefs developed simultaneously during the latest Sandbian/earliest Katian global Guttenberg Isotopic Carbon Excursion (GICE) in several places across Baltoscandia. Latest Sandbian/earliest Katian patch reefs are also described from the Vasalemma Formation of northern Estonia. The Saku Member of the Vasalemma Formation was previously considered as a proximal facies related to the reefs. However, the Saku Member clearly post-dates the GICE interval and ranges from the latest Keila to Rakvere in terms of regional stages. Some small reefs occur in direct proximity to the stratotype of the Saku Member. New delta C-13 data from the stratotype section and the adjacent reefs indicate that these reefs developed before the deposition of the Saku Member during the GICE interval. The chemostratigraphic data support the hypothesis of a short-time Baltoscandian reef growth event that terminated during the GICE interval.
Highlights
Latest Sandbian/earliest Katian patch reefs are described from the Vasalemma Formation of northern Estonia
The Saku Member of the Vasalemma Formation was previously considered as a proximal facies related to the reefs
New δ13C data from the stratotype section and the adjacent reefs indicate that these reefs developed before the deposition of the Saku Member during the Guttenberg Isotopic Carbon Excursion (GICE) interval
Summary
Late Ordovician reefs were first reported from northern Estonia by Raymond (1916). These reefs occur as distinctive bodies with diameters of up to 50 m and thicknesses of up to 15 m within the Vasalemma Formation (Fig. 1). New δ13C data from the stratotype section and the adjacent reefs indicate that these reefs developed before the deposition of the Saku Member during the GICE interval.
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