AN INFRAZONAL AMMONITE BIOSTRATIGRAPHY FOR THE KIMMERIDGIAN OF SPITSBERGEN

Abstract

An infrazonal ammonite-based biostratigraphy for the Kimmeridgian of Spitsbergen is reviewed in detail. The Bauhini Zone, bayi horizon, aff. beaugrandi and norvegicum horizon have been recognized in this area for the first time. The presence of separate decipiens and elegans horizons has been demonstrated for the Myklegardfjellet section. The Kimmeridgian ammonite succession of Spitsbergen resembles that of Franz Josef Land and consists mainly from Boreal cardioceratids and oppeliids. In contrast to East Greenland and the Norwegian Sea, the sub-Boreal aulacostephanids are restricted to a few narrow stratigraphic intervals. This difference suggests a very limited exchange by ammonite faunas through the Greenland-Norwegian Seaway during the Kimmeridgian. The evolutionary trend of Boreal oppeliid genus Suboxydiscites is briefly outlined.