ORIGIN OF THE CONCRETIONARY LIMESTONES IN THE ISTANBUL DEVONIAN SUCCESSION

Abstract

Nodular limestone occurrences are widely present in the Devonian - aged sediments of the İstanbul region. This nodular units have been developed in the blue-grey coloured micritic limestones and marls alternation. The occurrences seen in the Lower-Middle Devonian strata are larger and the ones observed in the Upper Devonian sediments are smaller. The laboratory and field findings indicate that the nodules were developed within the. limestone-marl intercalation in which the thickness of the individual beds varies from 2-3 mm. to 5-6 cm. during the early diagenesis compaction, and loading and, later, by means of presure-solulion effects and, in part by tectonic deformation. No effects of organic activities and transportation have been detected. The size, shape and the order of the nodules are found depending on the thickness ratio of the individual beds in the limestone-marls intercalations.