Research-paper
Tegulated Inoceramids and Maastrichtian Biostratigraphy
Dhondt, Annie Valerie
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Abstract
The author demonstrates that in non-Tethyan deposits of the Northern Hemisphere, Lower and Upper Maastrichtian strata can be distinguished by using inoceramid species which have often been assigned to the genus Tenuipteria and which are characterised by a tegulated ('tile-like') ornamentation. Spyridoceramus tegulatus (VON HAGENOW), an equivalve species, has been recorded from the Early Maastrichtian and from the earliest Late Maastrichtian; its geographic distribution ranges from the Western Interior of North America to the European 'Schreibkreide' deposits, over the Russian platform, to Central Asia, and it has also been found in the Arctic and Far Eastern deposits of the USSR. This distribution pattern is easiest to explain through a northern, almost Arctic seaway. Tenuipteria argentea (CONRAD), an inequivalve species, has only been recorded in deposits of Late Maastrichtian age. Its distribution ranges from the North American Gulf Coast, to the European 'Schreibkreide', over the Russian platform into Central Asia and lies generally along the southern margin of the Chalk Sea (or along the northern margin of the Tethys?).