Ammonites and ammonite stratigraphy of the Bimammatum Zone and lowermost Planula Zone (Submediterranean Upper Oxfordian) at Bobrowniki and Raciszyn in the Wieluń Upland, central Poland

Abstract

Abstract. An extensive collection of ammonites made bed by bed from sections in the Submediterranean Upper Oxfordian of the Wieluń Upland, Central Poland, is described and used as a basis for a chronostratigraphical interpretation of the deposits. The ammonites are mostly of Submediterranean character and enable the recognition of the Bimammatum Zone, including the Bimammatum and Hauffianum
subzones, as well as the lowermost Planula Zone distinguished here as a new biostratigraphical horizon – the matyjai horizon – based on the occurrence of Subnebrodites matyjai Wierzbowski et Głowniak sp. nov. The Submediterranean ammonites are mostly oppeliids with Taramelliceras (Taramelliceras) [M] – Glochiceras (Lingulaticeras) [m] the most numerous, as well as Taramelliceras (Richeiceras) and Taramelliceras (Metahaploceras) [M] – Glochiceras (Coryceras) [m]. The profusion of ammonites of these two groups in the stratigraphical interval studied provides new information on their evolution, and two new oppeliid species, Taramelliceras (Taramelliceras) zelcense Wierzbowski et Głowniak sp. nov. and Glochiceras (Lingulaticeras) bobrownikiense Wierzbowski et Głowniak sp. nov., are described here. Subboreal and Boreal ammonites are not common in these sections, but are nevertheless important for correlation. Subborealammonites of the family Aulacostephanidae are represented by the genus Vineta [M], including its newly recognized microconchiate counterpart, Vineta [m], and a newly established genus Vielunia [M] Wierzbowski et Głowniak gen. nov., with type species Vielunia dzalosinensis Wierzbowski et Głowniak sp. nov. The latter genus includes ammonites previously referred in the area of study to Ringsteadia, and with a microconchiate counterpart assigned to Prorasenia [m]. The Boreal ammonites comprise late cardioceratids assigned to Amoeboceras (Plasmatites). These ammonites indicate that the deposits in question from the Submediterranean Bimammatum Zone up to the Planula Zone correlate with the Subboreal and Boreal lowermost Kimmeridgian (Baylei Zone, and Bauhini Zone, respectively).