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Grahn, Y. 1995. Lower Silurian Chitinozoa and biostratigraphy of subsurface Gotland. GFF 117 (1), 57-65. | DOI | DETAILS
|Title||Lower Silurian Chitinozoa and biostratigraphy of subsurface Gotland|
|Source type||article in journal|
Early Silurian (Llandoverian ‐ earliest Wenlockian) chitinozoans from the subsurface of Gotland are described from the File Haidarborrningen 1, Rosendalborrningen 1, and Närborrningen 1 boreholes. Twenty‐five species from ten genera, of which eight species are in open nomenclature, have been encountered. One species, Gotlandochitina magnifica Nestor 1982b, is given the name Ramochitina nestorae nomen novum. The oldest Silurian beds on Gotland belong to strata coeval with the upper part of the M. cyphus graptolite zone. On southern Gotland there is a gap within the Lower Silurian corresponding to the interval between the M. gregarius and M. spiralis graptolite zones, and on northern Gotland beds corresponding to the M. convolutus graptolite zone are probably missing. The Llandoverian‐Wenlockian transition on Gotland is situated within the upper part of the Lower Visby Beds, but the exact level of the boundary cannot be distinguished by chitinozoans. Red beds occur between the M. sedgwickii and M. spiralis graptolite zones in sediments deposited in comparatively shallow water on northern Gotland, and in the upper M. cyphus graptolite zone in sediments deposited in somewhat deeper water on south Gotland.
New taxa described