Tertiary palaeogeography and tectonostratigraphic evolution of the Northern and Southern Peri-Tethys platforms and the intermediate domains of the African–Eurasian convergent plate boundary zone

Abstract

The increasing effects of African–Eurasian convergence during the Tertiary resulted in the uplift and emergence of the Northern and Southern Peri-Tethys platforms. Palaeogeographic maps covering six selected time slices, including the Middle Eocene, late Early Oligocene, late Early Miocene, early Middle Miocene, early Late Miocene and Middle to Late Pliocene illustrate that environmental and depositional differentiations on the northern platform and along the bordering domains of the convergence zone were more pronounced than on the southern platform and its adjacent areas. The tectonic evolution of the northern platform included an overall eastward-directed trend in the onset of basin uplift and emergence, which started at about the Eocene–Oligocene transition, at 34 Ma. Tectonostratigraphic analyses indicate a striking contemporaneity of the events which defined the temporal and spatial development of both the domains of the convergent plate boundary zone and the bordering platforms. Five episodes of major regional change in palaeogeographic and tectonic setting are distinguished. They occurred in the Late Eocene (37–34 Ma), early Late Oligocene (30–27 Ma), latest Early to earliest Middle Miocene (17–15 Ma), early Late Miocene (9–8 Ma) and late Early to early Middle Pliocene (4–3 Ma). These episodes encompassed changes which were most probably induced by geodynamic events primarily related to the relative motions of the African/Arabian and Eurasian plates. In turn, the plate motions are assumed to have ‘triggered’ discrete steps in the regional kinematics and geodynamics that governed the palaeogeographic evolution of the Peri-Tethys platforms and the intermediate domains of the African–Eurasian plate boundary zone.

Introduction

The recently published Peri-Tethys Atlas (Dercourt et al., 2000a) includes a total of 24 palaeogeographic maps at a scale of 1:10 000 000 for the Late Palaeozoic to Pleistocene time interval. Seven of these maps and their accompanying explanatory notes concern the Tertiary (Meulenkamp et al., 2000a, Meulenkamp et al., 2000b). They reflect different stages of the evolution of the Northern and Southern Peri-Tethys platform areas at both sides of the African/Arabian–Eurasian convergent plate boundary, as summarised (Fig. 1) for the Early Eocene (early to middle Ypresian: 55–51 Ma), Middle Eocene (late Lutetian: 44–41 Ma), Early Oligocene (late Rupelian: 32–29 Ma), Early Miocene (early Burdigalian: 20.5–19 Ma), Middle Miocene (early Langhian: 16.4–15.5 Ma), Late Miocene (late Tortonian: 8–7 Ma) and Middle/Late Pliocene (Piacenzian/Gelasian: 3.4–1.8 Ma) in Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6, Fig. 7. Palaeogeographic reconstructions and tectonostratigraphic evaluations for some of the eastern and southern areas are relatively tentative due to less detailed information. For particular time intervals, the data available from some other parts of the area of study turned out to be insufficient for trustworthy reconstructions and analyses. The Tertiary evolution of the Peri-Tethys platforms was primarily controlled by the enhanced coupling of the African/Arabian, Apulian, Iberian, Eurasian and (in the easternmost part of the area of study) Indian plates (Dercourt et al., 1993, Dercourt et al., 2000a, Dercourt et al., 2000b (and references therein); Golonka et al., 2000). This large-scale development included the effects of the later, quasi-final stages of Alpine convergence and continent–continent collision on palaeogeography and sediment distribution patterns which followed upon the break-up of Pangaea in the early Mesozoic, the subsequent formation of the Neotethys and the inception of African–Eurasian convergence from the Cretaceous onward (Dercourt et al., 1986, Dercourt et al., 1993, Dercourt et al., 2000a, Dercourt et al., 2000b). The northward motion of the African block relative to Eurasia was fastest in the east, in accordance with the overall anticlockwise rotation of Africa/Arabia, whereas the position of the northern margin of the African Plate relative to Iberia remained fairly stable throughout the Cainozoic.

In this paper, we will summarise the palaeogeographic and palaeoenvironmental evolution of the Peri-Tethys Platform realms at either side of the African–Eurasian convergent plate boundary as inferred from Dercourt et al., 2000a, Dercourt et al., 2000b. More in particular, the tectonostratigraphic interrelations between the coeval development of the platform domains and the collision zone are explored in this paper. We will also attempt to relate some of the Tertiary episodes of major palaeogeographic change to specific geodynamic events in the collision zone.