Lateral Variabilities of Carbonate Cycle Patterns in the Latemàr Lagoon, Triassic, Italian Dolomites

Sven O. Egenhoff¹ and Arndt Peterhaensel^2
1 Technische Universitaet Bergakademie Freiberg, Freiberg, Germany
² University of Cambridge, Cambridge, United Kingdom

The well-known, cyclic carbonate succession of the Middle Triassic Latemàr Massif in the Italian Dolomites reveals significant cycle pattern discrepancies when tracing the platform's interior strata. Additional marine flooding surfaces bounding individual small-scale shallowing-upward cycles were detected near the tepee belt, i.e. the backreef area representing the maximum elevation of the Latemàr lagoon. These spatially restricted intermittent emergence and marine flooding surfaces have been produced by low-amplitude sea-level fluctuations that are exclusively recorded on this elevated zone. It is postulated that such generated alternations of submergence and intermittent subaerial exposure have favoured tepee formation. Sediment collecting in the bucket-shaped tepee megapolygons further expedited shallowing-upward of small-scale cycles. Conversely, deeper parts of the lagoon remained largely unaffected by low-amplitude sea-level oscillations: marine flooding surfaces disappear and cycles amalgamate. It is concluded that tepee structures are generally confined to topographically elevated areas where low-amplitude sea-level fluctuations were recorded, i.e. the so-called “intracyclic zone”. Tepees and lateral increase of cycle numbers are good indicators for a subtle palaeorelief on the Latemàr platform top. Lateral cycle pattern variations should be commonplace in shallow carbonate build-ups throughout the geological record, where a palaeorelief existed in the platform interior.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005