Most of the work was carried out during several field trips. After a long-lasting prospection phase, during which we opened as many profiles as possible, we decided to select the nine most representative LPS for detailed geochemical and granulometric analyses and dating (Fig. 2). Archeological investigations were actually never planned, but we always kept an eye out for potentially interesting findings. The chronological framework is ongoing work by the means of optically stimulated luminescence (OSL) and infrared-radiofluorescence (IR-RF) dating (OSL – Huntley et al., 1985; IR-RF – Trautmann et al., 1998, 1999; Frouin et al., 2017) as a joint effort of four different laboratories located at the University of Bayreuth (Germany), the Max Planck Institute for Evolutionary Anthropology in Leipzig (Germany), the Université Bordeaux Montaigne (France) and the University of Freiburg (Germany).

Figure 3Selection of artifacts from the TB-1 profile.

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Figure 4Stone artifact in its position found in TB-1 on a paleosol.

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The original aim of the project was the reconstruction of paleoenvironmental conditions during loess sedimentation and soil formation phases. In this short communication, however, we focus on lithic artifacts found by chance during fieldwork. The chronology is still preliminary and allows only a rough temporal framework. However, our still-ongoing luminescence dating indicates that the lithic artifacts can be attributed to the marine isotope stage (MIS) 6 or older. Stone artifacts made of fine-grained flint (Fig. 3) were found on top of a paleosol in two locations (Fig. 4; for orientation see Fig. 2; TB-1 is 33.48162^∘ N, 10.00782^∘ E, and MT-02 is 33.51820^∘ N, 9.99644^∘ E). Combining both locations, the collection comprises 23 unretouched complete flakes larger than 2 cm, which are cortical, partially cortical and noncortical. We also found stone artifacts in a couple of other sections (20 complete flakes and flake fragments), albeit without exact stratigraphic context (the artifacts were washed out and transported downslope). The location of the artifacts found on paleosols is shown in Fig. 2. The age attribution has to be corroborated by further luminescence dating efforts, but even the possible minimum chronological placement in MIS 6 renders these findings the oldest stone tools ever found in Tunisia (see Aouadi-Abdeljaouad and Belhouchet, 2017). Currently, the oldest reported Middle Stone Age deposits in Tunisia originate from Oued El Akarit, about 30 km north of Gabès, dated to around 80 ka (thermoluminescence on flint artifacts; Reyss et al., 2007). Ages older than this are also presented in Reyss et al. (2007) but highly questioned due to severe dosimetric problems. In a subsequent publication, we plan to provide more detailed contextual information on the as yet provisional chronology presented here. Nevertheless, our preliminary findings suggest that the Matmata loess region as an extraordinary sedimentary archive could potentially play a major role in reconstructing past environmental conditions of human mobility and survival in central northern Africa in this period.

No data sets were used in this article.

DF wrote the text, corrected the text several times, is the PI of the team and took part in two field trips. SK is responsible for dating activities in the Bordeaux lab and elaborated some figures and was involved in the revision process. YT coordinates our work in Tunisia and took part in some field trips. MP took part in all field trips and did his Master's thesis in this area. We changed some figures that we took out of his thesis. GM took part in all field trips and did his Master's thesis in this area. We changed some figures that we took out of his thesis. MB coordinated the project and took part in almost all the field trips. JMRE and FDdO realized all the clay mineral analyses. CS was responsible for dating in Bayreuth and took part in field trips. TL was responsible for dating and took part in a field trip. ZR was responsible for archeological determinations and took part in a field trip. AF was responsible for dating activities in Freiburg. SM was the project leader in Tunisia; he took part in every field trip and was the second leader of the project. Finally he did all the preparation work for this express report.

The authors declare that they have no conflict of interest.

This research has been supported by the DAAD.

The article processing charge was funded by the Quaternary scientific community, as represented by the host institution of EGQSJ, the German Quaternary Association (DEUQUA).

This paper was edited by Christopher Lüthgens and reviewed by Eduard Pop and one anonymous referee.