Macrofloral and palynological criteria for recognising the Westphalian-Stephanian boundary
Cleal, Christopher J.; Dimitrova, Tatiana Kh.; Zodrow, Erwin L.
Newsletters on Stratigraphy Volume 39 Number 2-3 (2003), p. 181 - 208
published: Oct 2, 2003
ArtNo. ESP026003902010, Price: 29.00 €
The Cantabrian Stage is defined in Palencia, northern Spain, which is the only place known to have an essentially continuous stratigraphical record from the upper Westphalian D to the Barruelian ('Stephanian A'). The base of the Cantabrian Stage is positioned in the stratotype at the base of the Villaneuva Marine Formation, which immediately underlies the stratigraphically lowest non-marine strata containing Odontopteris cantabrica Zone macrofloras. The base of the O. cantabrica Zone is thus the effective index to the base of the Cantabrian Stage in non-marine facies. In the Cantabrian Stage stratotype, this biohorizon is marked principally by the lowest occurrence of Alethopteris bohemica. In other areas, however, A. bohemica does not occur in macrofloras of early Stephanian age. Other biostratigraphical criteria have had to be used, therefore, notably the increase in abundance of Alethopteris pseudograndinioides var. subzeilleri and the decline in abundance (sometimes extinction) of Mariopteris nervosa and A. pseudograndinioides var. pseudograndinioides. A short distance above this level, there is another and more distinct biohorizon (Biohorizon 3), which can be used as a guide to locating the base of the O. cantabrica Zone. This is defined by the stratigraphically lowest occurrences of Sphenophyllum oblongifolium, Odontopteris cantabrica, O. brardii, and Lobatopteris lamuriana, and the highest stratigraphical occurrence of Mariopteris nervosa. Biohorizon 3 also appears to coincide with first appearance of the relatively rare Schopfites dimorphus, a marked increase in abundance of Thymospora pseudothiessenii, and a lesser increase in abundance of Cadiospora magna. This palynological biohorizon is equivalent to the base of Peppers' Zone CP in Illinois and of Smith's Zone XII in southern Britain. Using these biostratigraphical criteria, it is possible to identify the base of the Cantabrian in the Sydney Coalfield (Nova Scotia), South Wales, and Central Bohemia.