Stratigraphy and depositional history of the Cretaceous carbonate successions in the Spil Mountain (Manisa, W Turkey)

Abstract

The Bornova Flysch Zone (western Turkey) consists of huge Mesozoic limestone and ophiolite blocks embedded into sheared siliciclastic sedimentary rocks of Maastrichtian−Paleocene age. The limestone blocks, which range in age from Late Triassic to Cretaceous, are considered to be olistoliths or deformed and sliced platform parts. In the Spil Mountain, two successions of Cretaceous carbonates are tectonostratigraphically differentiated: (1) a Lower Cretaceous and Campanian(?)−Maastrichtian relatively autochthonous succession showing sedimentary transition to the Bornova Flysch, and (2) a Cenomanian(?)−lower Campanian allochthonous succession overthrusted to the flysch. These successions represent separate parts of the same platform. The autochthonous succession bears Lower Cretaceous peritidal carbonates at its base and is named Unit 1. The succession is often composed of fenestral mudstone and algal wackestone microfacies. Unit 2 disconformably overlies Unit 1 and consists of platform-derived litho and bioclastic packstones of Campanian(?)−Maastrichtian age. This unit reveals a typical thinning and fining upward sequence, finally passing into pelagic wackestones of Unit 3. The two aforementioned units record a platform drowning event, which occurred rapidly based on the presence of planktonic foraminifera within matrix of basal breccia. Carbonate deposition ceased due to the input of siliciclastic sediments during the late Maastrichtian−Paleocene. The allochthonous succession consists of two vertically superimposed units: (1) Cenomanian(?)−Santonian rudistid limestones (Unit 4) deposited in restricted platform environments and (2) Santonian−lower Campanian pelagic limestones (Unit 5) indicating open platform to slope conditions. The Spil Mountain Cretaceous carbonate sequences are correlated with those in peri-Mediterranean platforms. They show close similarities to the Bey Dağları (western Taurides) carbonate sequences in stratigraphy and facies. Paleontological and sedimentological analyses and the microfacies enable us to reconstruct a paleoenvironment evolution and a facies model for the Spil Mountain carbonate deposits during the Cretaceous period.