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Zuschin, Martin1, Mathias Harzhauser2, Oleg Mandic1
(1) University of Vienna, A-1090 Vienna, Austria 
(2) Natural History Museum Vienna, Vienna, Austria

ABSTRACT: Changes in the Composition of Miocene Marine Mollusk Assemblages of the Central Paratethys in Relation to Tectonic Events and Relative Sea Level Changes

The Central Paratethys Sea extended in the Miocene along the northern margin of the (Proto) Mediterranean Sea, from which it was separated by a land mass including the Eastern Alps, the Dinarids and the Macedonian Massif. Major changes of its rich mollusk record correlate well with the regional geotectonic development forced by the Alpine orogenesis. Global climate and sea level fluctuations additionally modulated regional paleogeography and water circulation patterns. 
The interplay of these parameters resulted in two successive metacommunity cycles. These cycles start with an initial phase of diversification by faunal migration from neighboring seas, then pass a stage of restriction that culminates in severe extinction crises. Each cycle terminates in the autochthonous evolution of highly endemic Paratethys faunas. 
The first cycle starts with the Eggenburgian (early Burdigalian) marine transgression. In the Late Eggenburgian the typical large-sized, warm water fauna became replaced by species invading the Central Paratethys from the (Proto) Mediterranean region through the reactivated Swiss Molasse. This highly diverse, large-sized fauna reflects tropical to subtropical conditions and persisted into the Early Ottnangian. During the Late Ottnangian (middle Burdigalian) a regional sea level fall isolated and partially disintegrated the Paratethys, leading to the first major extinction and to an autochthonous evolution of endemic genera. 
A new marine flooding initiated the second cycle, which started in the Karpatian (late Burdigalian). The connection via the Trans-Tethyan Trench Corridor resulted in the replacement of the endemic fauna by new, marine mollusks of Mediterranean type. The spectacular diversification of that fauna coincided with the Middle Miocene climatic optimum during the Early Badenian (Langhian). In the Late Badenian, restrictive conditions developed and the Sarmatian (Serravalian) was characterized by increasing isolation of the Central Paratethys, which was reflected in severe changes in water chemistry. The major extinction involved the fully marine elements, whereas an endemic fauna developed uniformly throughout the Paratethys.


AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.