engleski

Rudist mud mounds and biostromes from Upper Cre- taceous of Istria (Croatia)

Beside biostromes which are the most common paleoenviromental appearance of rudist congregations, in Upper Cretaceous of Istria rare rudist mud-mounds were investigated. Aim of this work is to present appearance of rudist congregations with respect to the lithofaces characteristics of paleoenvironment. Rudist congregations, which could appear within both mud mounds and biostromes in relatively shallow subtidal are result of interaction between accommodation space adequate for thriving of radiolitids and carbonate sedimentation rate. Shallowing and decrease of accommodation space are indicated in mud mounds by thin sheets of densely packed F-R with fragments of radiolitids at the top of beds, together with mud mound flanks which are visible as lamination. In case when radiolitid congregations throve in shallower subtidal paleoenvironment with less accommodation space they appear through biostromes.

Rudists, Mud mound, Biostrome, Upper Cretaceous, Istria, Croatia

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