Abstract
The Oligo-Miocene Numidian Flysch of northern Tunisia has long been divided into three distinct lithostratigraphic units considered as vertically superimposed: the lower unit or the “Zouza member”, the middle unit or the “Kroumirie member” and the upper unit or the “Babouch member”. According to this reconstruction the two first members are mostly Oligocene in age and only the third member was assigned as early Miocene in age. In this study, we present new biostratigraphic data, based on planktonic foraminiferal analysis, demonstrating that both the Zouza and the Kroumirie members are Oligocene–early Miocene in age and are, therefore, coeval. Four distinct facies associations have been identified within the Numidian Flysch including: (a) massive sandstones; (b) conglomerate; (c) an interbedded mudstone–sandstone association; and (d) a mudstone facies association. Slide-slump units and injectionite sands occur within the more mud-rich associations. The likely depositional setting is a muddy slope–apron system, cut locally by sand-rich channels, which fed channel-terminal lobe deposits. Paleocurrent data support strongly a flow from N and NW. Modal analysis, demonstrates that the Numidian sandstones are quartz-arenite type (QFL, 97.25:1.25:1.5) derived from middle to high grade-metamorphic and granitic rocks. Zircon geochronology, yielding ages of 514 ± 19 Ma from Tunisia and 550 ± 28 Ma from Sicily, would support the basement terrain that crops out along the Algerian coast and forms part of Calabro–Peloritani–Kabylian zone, as the most likely parental source of the Numidian Flysch for both Sicily and Tunisia. Zircon data from the Fortuna Formation yields ages of 1698 ± 67 Ma, which is more compatible with an African craton source ( Fildes et al., 2009). Structural consideration of the basal contact of the Numidian Flysch with the underlying Tellian rocks, as well as newly interpreted seismic data; confirm the allochthounous position of the Numidian complex and its displacement southward. Facies comparison with the equivalent Oligo-Miocene Bejaoua siliciclastic deposits outcropping towards the south shows that the Numidian complex is an “out-of-sequence thrust unit” and that the two Oligo-Miocene sedimentary systems are quite distinct and were sourced from wholly different source regions.
Highlights
Resedimented carbonates interbedded with basinal facies are described in Tethyan Middle Jurassic carbonate stratigraphy, as demonstrated by the Vajont limestone (Bosellini et al, 1981), Jabalcuz Formation (Ruiz-Ortiz, 1982) and Hawasina complex (Blechschmidt et al, 2004))
Incorporating new field and laboratory analysis this paper enhances this interpretation. It can be shown without reasonable doubt that the Cutri Formation was deposited in a carbonate base-of-slope environment on the palaeowindward side of a Mid-Jurassic Tethyan platform
Based on laterally extensive outcrops, this study builds on previous work carried out on the sedimentology of Jurassic carbonate deposits found on the island of Mallorca (Fig. 1)
Summary
Resedimented carbonates interbedded with basinal facies are described in Tethyan Middle Jurassic carbonate stratigraphy, as demonstrated by the Vajont limestone (Bosellini et al, 1981), Jabalcuz Formation (Ruiz-Ortiz, 1982) and Hawasina complex (Blechschmidt et al, 2004)). Based on laterally extensive outcrops, this study builds on previous work carried out on the sedimentology of Jurassic carbonate deposits found on the island of Mallorca (Fig. 1). Topography based on CNIG (División 672-IV Artá) and map is displayed in EPSG code: 23031. This study incorporates new field and laboratory analysis which enhances this interpretation From this analysis, it can be shown without reasonable doubt that the Cutri Formation was deposited in a carbonate base-of-slope environment on the palaeowindward side of a Mid-Jurassic Tethyan platform. It can be shown without reasonable doubt that the Cutri Formation was deposited in a carbonate base-of-slope environment on the palaeowindward side of a Mid-Jurassic Tethyan platform Key evidence such as laterally extensive exposures, abundant deposits of calciturbidtes and debris flows amongst hemipelagic deposits strongly support this interpretation
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