Turkish Journal of Earth Sciences

The development of Nummulites Banks within the Compressional Tectonically Controlled Tertiary Basin of Gürün Autochthone, Eastern Taurus, SW Sivas (Turkey)






The investigated area is located at nortwestern part of Eastern Taurus, on the Gürün autochthone. The limestones described a Nummulites banks and contemporaneous rock units situated on Tertiary uplift and in the Tertiary basin at behind of uplift. Tertiary basin, developped locally over rock units of Akdere basin which deposited on Mesozoic carbonate platform during Late Cretaceous-Early Paleocene and folded, uplifted during late Paleocene-Early Lutetian. This Nummulite bank Tertiary (Lutetian) unit (Demiroluk Fm.) is represented by tectonically controlled shallow-marine, shoeline and offshore facies. The conglomerate/breccia is at the lower part and transsionally Nummulit-Alveolina bearing limestone at the upper part. The three have types of facies assemblages has distinguishe; Facies-1: Conglomerate/breccia (Bio-litoclastic packstone-grainstone), Facies-2: Nummulit-Alveolina bearing wackestone-packstone, Facies-3: Pelagic mudstone-wackstone. In addition, Facies-2: is divided into two microfacies; Facies-2a and Facies-2b comprising Nummulited bearing wackstone-packstone and Alveolina bearing wackstone-garinstone respectively. The facies 1, 2 and 3 deposited in fore-bank slope, fore-bank, bank-rim and back-bank local basins. The Nummulites banks and comtempraneous underlying and overlying rock units undergone pre-and post-depositional different diagenetic events. the calcit and micritic cement developed within and intergrain areas and the syntaxial overgrowth has been developed on the echinoids which characterize the marine and fresh water pheratic environments. During the late diagenetic stage, the pressure solutions formed and caused the rock to have stylotic-fractured structure.

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