Cyclicity of Middle Jurassic calciturbidites of the Travnik Formation, Bovec Basin, NW Slovenia

Abstract

We investigate calciturbidite cyclicity using statistical method based on time-series analysis (Fourier analysis) of bed thickness patterns. This method was applied to four members of the Jurassic calciturbidite-dominated Travnik Formation of the Bovec Trough outcropping in three adjacent and correlated sections. Our study has shown that the Fourier analysis of calciturbidite bed thicknesses is not successful for reconstruction of cyclicity in erosional upper slope depositional environments (Member 3). On the contrary, the method shows meaningful results for lower slope and distal basin floor depositional setting (Members 1, 2, 4). Here we detected variability of cyclicity in the same time frame of deposition and also subtle lateral variation of the stacking pattern between different sections. Each section contains regional lowfrequency cycles common to all sections, and superimposed specific “local” high-frequency cycles. Tectonic factors have an influence on the low frequency, and other factors, such as the local topography, climate, different position on a depositional lobe or magnitude of the turbidite event, can force the high-frequency cycles. We calculated nine cycles for Bajocian and Bathonian (Members 1 and 2), and also nine cycles from Early Callovian to Middle/Late Oxfordian (Member 4). Due to the erosional nature of the Member 3 (Bathonian to Early Callovian) sedimentary environment, reliable comparison to Jurassic sea-level variations was not possible.