Sedimentary cyclicity and micropaleontological investigations in the upper triassic shallow marine carbonate successions (Central and Western Taurides, Turkey)

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Tezin Türü: Doktora

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Mühendislik Fakültesi, Jeoloji Mühendisliği Bölümü, Türkiye

Tezin Onay Tarihi: 2008

Öğrenci: BURCU COŞKUN TUNABOYLU

Danışman: DEMİR ALTINER

Özet:

Shallowing-upward meter-scale cycles (parasequences) consisting of megalodont-bearing limestones or clay levels at the bottom and fenestral limestones, breccias, stromatolites or vadose pisoids at the top constitute the basic working units of the Upper Triassic successions in the Central and Western Taurides. These cycles are mainly represented by subtidal through supratidal carbonate facies and known as Lofer cycles in the literature. The presence of breccias, mud cracks, dissolution vugs and vadose pisoids indicates subaerially exposed conditions at the top of the cycles. Shallowing-upward meter-scale cycles are interpreted as 4th and 5th order cycles in this study. Megalodont-bearing limestones of the subtidal zone are characterized by wackestones/packstones with abundant involutinids. However, involutinids are poorly represented in the intertidal-supratidal zone. To determine the relationship between cyclicity and foraminifers, the vertical variation of benthic foraminifer abundance has been analysed in the cycles. This analysis leads us to conclude that the foraminiferal abundance decreases from subtidal through supratidal zone. Furthermore, cluster analysis was performed in order to delineate the relation between the biofacies and foraminiferal associations. Micropaleontological analysis of the uppermost Triassic carbonates reveals the presence of restricted platform foraminiferal associations in the studied successions. Foraminiferal associations discovered in the samples belong to the Upper Norian (Sevatian)-Rhaetian Triasina hantkeni assemblage zone. Detailed examination of peritidal carbonates in the Central and Western Taurides against the studies, which claimed that the Dachstein-type platform carbonates are characterized by the transgressive models, should be explained by regressive models.