Foraminiferal biostratigraphy and sequence stratigraphy of peritidal carbonates at the Triassic–Jurassic boundary (Karaburun Peninsula, Western Turkey)

Abstract

Continuous shallow marine carbonates spanning the Triassic–Jurassic boundary are exposed in the Karaburun Peninsula, Western Turkey. The studied section (Tahtaiskele section) consists of Upper Triassic cyclic shallow marine carbonates intercalated with clastics overlain by Lower Liassic carbonates. Based on the microfacies stacking patterns, three main types of shallowing-upward cycles have been recognized. Cycles are mostly composed of subtidal facies at the bottom, intertidal/supratidal facies and/or subaerial exposure structures at the top. The duration of the cycles suggests that cycles were driven by the precessional Milankovitch rhytmicity. In the sequence stratigraphic frame of the Tahtaiskele section 4 sequence boundaries were detected and globally correlated. The first sequence boundary is located at the Alaunian–Sevatian boundary nearly coinciding with the first appearance of Triasina hantkeni. The second falls in the Rhaetian corresponding to a major sea level fall which led to the invasion of forced regressive siliciclastic deposits over the peritidal carbonates. The third occurs close to the T/J boundary and the fourth lies slightly above the base of the Jurassic. In the studied section, extinction, survival and recovery intervals have been recognized based on the stratigraphic occurrence patterns of benthic foraminifera and algae. Foraminifers became nearly totally extinct in the inner carbonate shelves at the Triassic–Jurassic boundary and an interval of approximately 0.5my passed before the begining of the recovery of Jurassic foraminifera.