The Sidi Khalif Formation at Jebel Meloussi locality (central Tunisia) is one of the most suitable section for this purpose. In central Tunisia (Southern Tethys margin), Figure 1A the Lower Cretaceous (Berriasian) stratigraphic record offers a scenic exposure of strata, extremely amenable for stratigraphic investigations. (2020) because the proposed GSSP does not meet at least four of the five geological requirements for a GSSP. However, their work has immediately been criticized by Granier et al. (2020) have proposed the locality of Tré Maroua (Hautes-Alpes, SE France) as a GSSP for the Berriasian stage. Some other studies (e.g., Vennari et al., 2014) proposed a completely different chronostratigraphic model for the base of the Berriasian at 139.55 ± 0.09 Ma.
The Berriasian base is defined as follow: In GTS2012, a working definition of the base of magnetic Chron M18r ( Wimbledon et al., 2011) was used to place the Jurassic-Cretaceous (J–K) boundary whereas in the GTS2016, the Jurassic/Cretaceous working group favored a slightly older level in the middle of Chron M19n at the “explosion” of small, globular Calpionella alpina (base of Calpionellid Zone B).
The Cretaceous is the only system/period of the Phanerozoic that has not yet been defined by a basal GSSP. In addition, we applied the DYNOT and ρ1 methods for seal-level change modeling to reconstruct a local eustatic profile which matches the previously published local and global eustatic charts. The inferred floating ATS was tuned to the La2004 astronomical solution. The identification of Milankovitch cycles in the record also allowed to propose a floating astronomical timescale of the studied section, with ~4 long eccentricity cycles (E 405) extracted, which points to a duration estimate of ~1.6 Myr with an average sediment accumulation rate (SAR, after compaction) of 2.77 cm/kyr. The application of these spectral analysis techniques revealed a pervasive dominance of E 405-kyr and e 100-kyr cycles showing that the climate turnover across the early Berriasian-middle Berriasian seems to had been governed by the long and short orbital eccentricity cycles. We performed multiple spectral analyses and statistical techniques on the magnetic susceptibility signal, such as Multi-taper Method, Evolutive Harmonic Analysis, Correlation Coefficient, Time-optimization, and Average Spectral Misfit to obtain an optimal astronomical model. Elemental data using X-Ray fluorescence analyses was acquired from 19 samples to prove the reliability of the MS signal on recording the past paleoclimatic changes. Six hundred and twenty two samples were measured for magnetic susceptibility and carbonate content as paleoclimate proxies for the detection of potential Milankovitch cycles. High-resolution magnetic susceptibility and % CaCO 3 records (5 to 10 cm sampling interval) are used to track astronomical cycles from a Lower Berriasian record from central Tunisia. 3Sedimentary Petrology Laboratory, Liège University, Liège, Belgium.
2Laboratory of Georessources, Materials Environment and Global Change, Faculty of Sciences of Sfax, University of Sfax, Sfax, Tunisia.1Department of Geological Engineering, National Engineering School of Sfax, Sfax University, Sfax, Tunisia.Hamdi Omar 1,2 *, Anne-Christine Da Silva 3 and Chokri Yaich 1,2
0 kommentar(er)
