Phanerozoic Cyclostratigraphy in North Africa: Case studies from Tunisia

Astronomical insolation forcing is an important driver of past and future climate and environmental change and acts on time scales from seasonality to millions of years. The amount of insolation the Earth’s surface receives affects, e.g., surface temperature, polar- and mountainous ice dynamics and oceanic circulation, which all shape Earth’s surface and climate variability on different time scales. Astrchronology is the field that uses geologic records of climate rhythms to quantify, with unprecedented accuracy, the transit of time through deep Earth history acting as powerful geo-chronometers for major geologic events.

Rhythmic sedimentary successions are very frequent in the geological records of North Africa, namely in Tunisia, which can often be attributed to cyclicities of orbital parameters driving Earth’s climate variability. Unlike Europe, China and USA, where cyclostratigraphic studies have extensively been carried out, examples of significant studies in North Africa are scares (e.g., Ben Ameur et al., 2022; Omar et al., 2021; Omar & Yaich, 2022; Thibault et al., 2016). Other studies were carried out but have almost exclusively been done using very classic and weakly significant paleoclimate proxies. Southern, central and northern Tunisia, where strongly cyclic sedimentary series were developed from the Ordovician to the Holocene, provides a powerful candidate for cyclostratigraphy with many Formations that were deposited during these times, and are amenable for integrated stratigraphy.

In this study, we investigate the feasibility of cyclostartigraphy on Phanerozoic cyclic strata in North Africa from outcropping series and well-logging data, covering a wide variety of paleoenvironments from continental deposits to deep basin sequences through hemi-pelagic sediments. The targeted geologic intervals are thoroughly chosen from Paleozoic, Mesozoic, Cenozoic and Quaternary. The main objectives are to (1) develop floating orbital scales for several Phanerozoic sedimentary rocks constituting potential source rocks feeding most of Tunisian petroleum reservoirs, (2) highlight currently under-investigated geologic intervals for cyclostratigraphy in Tunisia and (3) testify the most advanced techniques for astrochronology to decode the orbital periodicities potentially recorded within the studied sections.

 

Ben Ameur, Mariem et al. 2022. “Middle to Late Holocene Sedimentary Filling History of the Sebkha El Melah in South-Eastern Tunisia.” Sedimentology 69(5): 2348–66.

Messaoud, Jihede Haj, Nicolas Thibault, Chokri Yaich, and Johannes Monkenbusch. 2020. “The Eocene ‐ Oligocene Transition in the South ‐ Western Neo ‐ Tethys ( Tunisia ): Astronomical Calibration and Paleoenvironmental Changes Paleoceanography and Paleoclimatology.” : 1–25. https://doi.org/10.1029/2020PA003887.

Omar, Hamdi, Anne Christine Da Silva, and Chokri Yaich. 2021. “Linking the Variation of Sediment Accumulation Rate to Short Term Sea-Level Change Using Cyclostratigraphy: Case Study of the Lower Berriasian Hemipelagic Sediments in Central Tunisia (Southern Tethys).” Frontiers in Earth Science 9(March): 1–20.

Omar, Hamdi, and Chokri Yaich. 2022. Advances in Science, Technology and Innovation Orbital Tuning of the Berriasella Jacobi Ammonite Zone in Central Tunisia (Southern Paleotethys). Springer International Publishing. http://dx.doi.org/10.1007/978-3-030-72547-1_42.

Thibault, Nicolas et al. 2016. “The End-Cretaceous in the Southwestern Tethys (Elles, Tunisia): Orbital Calibration of Paleoenvironmental Events before the Mass Extinction.” International Journal of Earth Sciences 105(3): 771–95.