--> Abstract: The Latemàr—A Matter Of Competence; #90063 (2007)
[First Hit]

Datapages, Inc.Print this page

The Latemàr—A Matter Of Competence

 

Egenhoff, Previous HitSvenTop O.1, Arndt Peterhaensel2 (1) Colorado State University, Fort Collins, CO (2) Universitaet Potsdam, Potsdam, Germany

 

The bucket morphology characteristic for many modern tropical carbonate platforms develops, if the tropical seafloor moves into and remains long enough within a favorable window where rates of production of bound carbonate and accommodation space are in balance. “Empty buckets” form as a consequence of stress-induced strongly deviating growth between frame-built metazoan margin and starved lagoon. Only glacially-induced high-amplitude sea-level rises create sufficient accommodation space to enable their formation. Tropical carbonate platforms during interglacial or greenhouse times, in contrast, are thought to develop filled bucket morphologies with metazoan reefs confining a shallow lagoon. We postulate that in the absence of major frame-builders, for example following global faunal crises, a microbially-induced and cement-reinforced tepee belt assumes the role of energy barrier on many ancient carbonate platforms of greenhouse times. The post-extinction Triassic Latemàr platform in the Italian Dolomites is a case in point. Competence of its marginal part rendered by intermittent tepee formation provided protection for incompetent shallow lagoonal material and prevented wave-driven off-platform transport. An intermittently established hydraulic head between the ocean and the restricted lagoon supplied large quantities of marine water percolating from the open sea into the sediment/rock body of the tepee belt. Moving along boundaries of cm- to dm-scale layers, these fluids produced ample amounts of fortifying early cements. In contrast to the conventional model, this relief- and margin-maintaining process is active during phases of falling accommodation. Once established, the tepee belt becomes an integral part of platform geometry buffering the impact of sea-level changes and subsidence.

 

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