Quaternary Geochronology, 2015

In the present study, we applied the IRSL 50 C dating method to both K-and Na-feldspar coarse grains from interglacial coastal deposits in north-eastern Tunisia. We used the yellow IRSL 50 C signal of Nafeldspars and the blue IRSL 50 C signal of K-feldspars. The key-sites for this study are at El Hajeb (Sahel area) and Dar Oufa (Cap Bon Peninsula). These deposits belong to the "Douira Unit" which has previously been assigned to marine isotope stage (MIS) 7 on the basis of amino acid ratios and chronostratigraphic evidence.

In this study thermally transferred (TT) OSL and post-IR elevated temperature IRSL (290 C) (pIRIR 290 ) dating are applied to deposits covering coastal terraces on the Cap Bon peninsula, Tunisia. Both methods perform well under standard performance tests; dose recovery tests using a modern analogue show that doses relevant to our study can be recovered accurately. Residual signals in the modern analogue for both signals are very small (w2 Gy). For the younger (<250 ka) deposits reasonable good agreement of the ages is observed between both methods, and in addition with standard quartz OSL dating. Systematic discrepancy in ages is found for the older sediments. The TT-OSL underestimate (compared to the pIRIR 290 ages) is most likely due to the short lifetime of the TT-OSL trap; we estimate a lifetime of w0.7 Ma at 19 C (mean ambient air temperature of the study area). This is the first time this lifetime has been derived from geological data and it is within the range of previously published laboratory estimates. This result suggests that TT-OSL is not likely to provide a significant extension of the age range beyond that available from other methods. Our preferred pIRIR 290 ages suggest that the geological setting on Cap Bon is not as simple as previously suggested.

Quaternary Geochronology, 2012

In this study thermally transferred (TT) OSL and post-IR elevated temperature IRSL (290 C) (pIRIR 290 ) dating are applied to deposits covering coastal terraces on the Cap Bon peninsula, Tunisia. Both methods perform well under standard performance tests; dose recovery tests using a modern analogue show that doses relevant to our study can be recovered accurately. Residual signals in the modern analogue for both signals are very small (w2 Gy). For the younger (<250 ka) deposits reasonable good agreement of the ages is observed between both methods, and in addition with standard quartz OSL dating. Systematic discrepancy in ages is found for the older sediments. The TT-OSL underestimate (compared to the pIRIR 290 ages) is most likely due to the short lifetime of the TT-OSL trap; we estimate a lifetime of w0.7 Ma at 19 C (mean ambient air temperature of the study area). This is the first time this lifetime has been derived from geological data and it is within the range of previously published laboratory estimates. This result suggests that TT-OSL is not likely to provide a significant extension of the age range beyond that available from other methods. Our preferred pIRIR 290 ages suggest that the geological setting on Cap Bon is not as simple as previously suggested.

Geomorphology, 2009

Morphostratigraphic and sedimentological studies were undertaken in the Cap Bon peninsula, north-eastern Tunisia. These studies have identified a series of middle to late Pleistocene–age marine deposits discontinuously cropping out on three raised platforms (Pf I, Pf II and Pf III). These stepped marine platforms (terraces) were related to the interplay between Pleistocene sea-level changes and progressive uplift movement during Quaternary period. We present here a description of facies organization and stratigraphic characteristics of the platform deposits, and their relation with eustatic and climatic variations. All the marine platforms unconformably overlie a Mio-Pliocene and Quaternary slope succession. The sedimentary sequences represented by mixed carbonate and siliciclastic bodies are related to the succession of highstand shorelines and contrasting climate conditions. The intercalated soils and calcretization occurred during episodes of relative sea-level fall. The oldest platforms (Pf I and Pf II), found at an elevation of about + 100 m and + 60 m respectively, have so far no equivalent in the northern, in the eastern or in the southern coasts of Tunisia. They are correspondingly attributed to MIS 11/13 and MIS 9/11. The youngest and lowest platform (Pf III) attains an altitude of + 40 m and shows three high-frequency cycles of sea-level rise and fall, probably associated with Marine Isotope Stage (MIS) 5e and MIS 7.

Quaternaire, 2009

A sedimentological and fauna analysis of Quaternary deposits at two sites located on the south-eastern littoral of the Cap Bon peninsula (Tunisia) provides new details about sea-level changes. Two shallowing-upward sequences separated by an erosion surface occur above the present sea level at several locations along the south-eastern shoreline of Cap Bon peninsula. Each sequence has a distinctive sedimentology and fauna content. The older one is especially rich in quartz grains and lithic fragments and is associated with shallow marine fauna in the lower member which would indicate a high relative sea level. The younger sequence is dominated by carbonates such as pellets, oolithes and mollusk fragments. The fauna of its lower marine member is rich in "Senegalian fauna" such as the Strombus bubonius LAMARCK. This biomarker, revealed at other locations in Tunisia (e.g., Sahel region, Jorf and Jerba Island) and at many sites around the Mediterranean Basin (Spain, France, Italy, Greece, Lebanon, and Egypt), indicates warm sea water. Both units include paleosols, colluviums and dunal members indicating respectively a wet phase followed by a drier phase. The vertebrate fauna discovered in the dunal deposits of the carbonate unit provides more information on the development of a savannah occurring with trees in the Cap Bon land at the post-Tyrrhenian.

This work reports for the first time evidence for an Ediacaran glaciation in Morocco on the West African Craton that we have named the Bou-Azzer glaciation. It is represented by glacially eroded surfaces and sedimentary features observed in Precambrian outcrops in two inliers of the Anti-Atlas Belt. The commonly accepted stratigraphic framework constrains the glacially eroded surfaces to post-date a regionally defined D2 deformational age known to be between 605 and 595 Ma. A minimum age for the glaciation is less certain but likely pre-dates the end of Ouarzazate Group deposition at 560 Ma. This age range permits two possible correlations to glacial events known from elsewhere: the Bou-Azzer glaciation could be equivalent to the Gaskiers glaciation (∼580 Ma), which has not been recognised previously in the West African Craton, or it could be a late Ediacaran glaciation (∼560 Ma), which has been suspected in different places on the Craton.

Boreas, 2010

The chronology of coastal dunes (aeolianites) along the western littoral of the Cap Bon peninsula (northeastern Tunisia) was investigated using an optical dating technique to examine their tentative correlation with the Marine Isotope Stage (MIS) record. These dunes, formed under a northwesterly wind regime and supplied by sand from the shore, are an indicator of sea-level and climate changes. We obtained optically stimulated luminescence ages for these aeolianites ranging from 112±10 to 53±2 ka and clustering around the last interglacial period (∼125–75 ka), implying that the former stratigraphic allocation of these dunes is inaccurate. The optical chronology suggests dune formation during MIS 5 in association with a sea level lower than today but higher than the glacial sea-level lowstand.