Quaternary Seismostratigraphy and Tectonosedimentary Evolution of the North Tunisian Continental Margin

Abstract

Northern Tunisia contains the poorly defined boundary between the Nubia and Eurasian plates. Offshore north Tunisia, the continental margin is interpreted to be part of the North Africa collisional fold and thrust belt system, linking the Maghrebian and the Sicilian-Apennine chains. The Tunisia margin deforms by a slow NW-SE trending convergence resulting in a diffuse deformation zone with scarce and scattered seismicity, in contrast to the neighboring regions of north Algeria and north Sicily. The complex recent evolution of this region is poorly known due to the paucity of studies, particularly offshore in the north Tunisian continental margin. Here, we present the seismostratigraphic analysis of the last~1.8 Ma tectonosedimentary evolution of this area. The seismostratigraphic analysis supports that individual Quaternary depocenters developed syntectonic to faulting and that faulting influenced sedimentation patterns. We identify an abrupt variation in the sediment accumulation rates (SARs) coeval to a change in the strata geometry of the units located near faults at 402 ± 5 ka (mid-Middle Pleistocene), supporting a change in the rate of faulting associated to contraction tectonics. This change indicates that deformation is controlled by the NW-SE convergence between Nubia and Eurasia, probably accelerated at the end of extension in the Tyrrhenian back-arc. Therefore, the current driving mechanism in the Central Mediterranean is possibly lithospheric collision between Nubia and Eurasia.

Active Tectonics of the North Tunisian Continental Margin

“…A significant normal fault together with conjugated faults and transparent deposits, possibly representing MTDs, and tilted strata, occur on the hanging‐wall to the main fault, corresponding to the eastern flank of the high (Figure 13a and 13b). The MTDs support recent sudden slip of faults, although are covered by a thin undisturbed sediment veneer, indicating some elapsed time since the last fault slip causing sliding, or that the fault has not slip since approximately 146 kyr (age derived from the seismostatigraphy; Camafort, Gràcia, & Ranero, 2020). Toward the south‐west, the fault corridor may link to or dissect the Resgui Bank (Figures 11 and 12).…”

“…The highly orthogonal attitude of the Hayat fault with respect to the Nubia‐Eurasia convergence vector and strongly tilted strata at the forelimb of the Bizerte Ridge, suggests that Hayat fault is likely a major fault accommodating much of the convergence between the plates on the studied area (Figure 4). Furthermore, slip on the Hayat fault appears to control the topographic evolution of the northern sector, and is responsible of its uplift (Camafort, Gràcia, & Ranero, 2020).…”

“…Fault‐related structures are more significant toward the east (Figure 8a), indicating that the Hayat fault grows toward the west (Figure 8b). Using the margin seismo‐stratigraphy (Camafort, Gràcia, & Ranero, 2020) and assuming that the noncontourite strata were deposited fundamentally with a subhorizontal attitude, the current layering geometry supports an uplift‐rate estimated as approximately 0.24 mm/yr for the last 471 kyr, due to slip on the Hayat reverse fault. Assuming a 45° dip for the Hayat fault, this uplift‐rate would correspond to 0.33 mm/yr slip‐rate during the last 471 kyr.…”

“…Location is shown in Figures 11 and 12. Ages of horizons are shown in Figure 8b and taken from Camafort, Gràcia, and Ranero (2020).…”

A 1‐Million‐Year Record of Environmental Change in the Central Mediterranean Sea From Organic Molecular Proxies

“…A closer inspection to seismic profiles in the area revealed smooth, continuous strata surrounding the LC07 location, that is, an absence of abrupt geological features (Camafort et al, 2020). We therefore interpret this interval as a winnowed lag deposit as in Dinarès-Turell et al (2003) and Camafort et al (2020), an event probably caused by the removal of the fine sediment fraction due to strong bottom currents and an invigorated MOC. Extreme aridity (and hence stronger MOC) was indeed reported during glacial MIS 16 at Tenaghi Philippon (NE Greece) through the increased abundance of grassland pollen (Tzedakis et al, 2006).…”