Abstract: Productional Fingerprinting of Carbonate Platforms

John J.G. Reijmer, Arnout J.W. Everts

Compositional analysis of calciturbidites was used as a tool, in order to establish the relationship between the production of sediments on the carbonate platform-top, and the progradation/retrogradation of the platform as registered at the toe-of-slope. Two independent examples were researched. The first dataset consists of five successions within a sequence of Middle to Late Triassic calciturbidites from the Dolomites (Pico di Vallandro/Durrenstein, Italy). The second dataset comprises five successions of the Vercors carbonate platform (Early Cretaceous, SE France).

In both case studies toe-of-slope sediments display significant differences in their composition depending on their geometry of progradation. Prograding intervals show a distinct input of limeclasts and platform-margin grains (framebuilding biota, reef foraminifers and others). During retrogradation lagoonal grains (platform interior biota, ooids, oncoids, pellets), and basinal grains (radiolaria, pelagic bivalves and others) were more frequently encountered, while the platform margin input was subdued.

In the Triassic the long-term trends of composition clearly matched the prograding/retrograding geometries visible in outcrop. In the Cretaceous the compositional fingerprints showed that both prograding and retrograding units have equivalents on the platform top.

So, in both examples the composition logs reflected the environmental conditions and sea-level stand on the carbonate platform. They also could be used for the construction of time lines between the platform and the basin.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994