--> Abstract: Differential GPS-Mapping Reveals Lagoonal Paleorelief of the “Layer-Cake” Latemàr Buildup, Dolomites, Northern Italy; #90063 (2007)

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Differential GPS-Mapping Reveals Lagoonal Paleorelief of the “Layer-Cake” Latemàr Buildup, Dolomites, Northern Italy

 

Peterhänsel, Arndt1, Gordon Schlolaut1, Ines Voigt1, Uwe P. Baaske1, Sven O. Egenhoff2, Maria Mutti1 (1) Universität Potsdam, Golm, Germany (2) Colorado State University, Fort Collins, CO

 

Many isolated carbonate platforms display systematic spatial facies patterns often with subconcentric belts following the contours of the buildup margin. In modern platforms, this non-randomness in lateral facies distribution is unequivocally related to a topographic gradient resulting from differential growth. However, invoking a paleorelief for ancient carbonate platforms often relies only on mapping-out facies followed by their bathymetrical interpretation.

 

We have used differential GPS measurements to corroborate a conventional lateral facies reconstruction of the cyclic lagoonal interior of the Middle Triassic Latemàr. Individual horizons from different stratigraphic levels were mapped down to decimeter accuracy over extensive parts of the platform interior. Three-dimensional visualization of these layers with PETREL software reveals decreasing paleodepths towards a tepee belt in the backreef zone. The persistence of this paleotopographic high throughout cyclic platform evolution argues for a higher amount of carbonate fixation and growth in the tepee belt area likely related to sediment trapping in tepees and inter-tepee depressions and favored by cementation and microbial growth. It implies that despite lagoon-wide shallowing-upward either (1) accommodation space had not been entirely filled in the lower parts of the lagoon, or (2) relative sea level dropped and exposed the lagoon thereby preserving the paleorelief, or (3) after filling accommodation space, cementation processes allowed the tepee belt to build up further into the subaerial zone. This study not only directly measures paleotopography within a fossil carbonate buildup but also postulates that cement-controlled tepee margins may have the ability to grow upward beyond normal marine accommodation.

 

AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California