Permo-Triassic Maps of Africa

Africa is reaching the end of the Palaeozoic Wilson Cycle, with the Hercynian tectonism near its end and Cape Fold Belt activity at an early stage. Late Hercynian movements are setting off shear zones into the African and Iberian continents (Doblas, 1991: Hoepffer et al, 2005 ) and the most likely model for the Djeffara (DJ) and Sicani (SI) rifts is that these are narrow transtensional features, not unlike those developed in southern Africa. These are infilled with shallow to deep marine strata tortuously connected through to Neotethys (Muttoni et al, 2009), which has yet to propagate into Africa, as suggested by the lack of evidence for basinal development in the Eastern Mediterranean.  The model adopted here for the Cape Fold Belt (CFB)  is that of Linol and de Wit (2021), who suggest that there was double subduction below Patagonia, including consumption of the Agulhas Ocean (AO)  separating Africa and Patagonia. The fold belt is growing at this time, though the paroxysm of activity was later.  The pre-drift position of the Falkland Islands is disputed but the fit supported here, mainly based on Kimmeridgian facies and tectonic correlations places it south of Natal, necessitating a bend in the Cape Fold Belt as it enters South Africa offshore. This is supported by some lineaments in that area.

Southern and East African lineaments are after Macgregor (2018), who differentiates two phases of Permo-Trias rifting in southern Africa. The first of these is initiated in the Stephanian and reaches peak activity at this time (Catuneanu et al, 2005).  Narrow transtensional and deep half grabens are developed along the ‘Southern Trans Africa Shear’ from the Morondava Basin (MO) to the Aranos Basin (AB) of Namibia (Orpen et al, 1989, Miller, 2008). Another set of dip slip rifts, typified by the Rukwa (RU) rift, runs perpendicular to the main trend through Zambia and Tanzania. This constitutes a very similar pattern to the later association of Cretaceous rifts with the Central African shear. There is no clear connection to lineaments in South America but an intersect with the Cape Fold Belt is likely (Visser & Praekelt, 1995), perhaps in the current offshore.

A large deep marine inlet or brackish lake is developed in the Great Karoo (GK) Basin (Bastos et al, 2021, Visser, 1995), in which the anoxic Whitehill Shale is deposited in the transition between an underfilled marine and filled non-marine basin. This passes into thick non-marine, often deep lacustrine sections, in the STASS rifts (Catuneanu et al, 2005).  Periodic marine transgressions affect the Morondava Basin (MO), likely sourced from the north (Wescott & Diggens, 1998), where Iranian fragments are detaching from Somalia and Oman.

At this time the South Pole is located in Antarctica and Africa is entirely in the southern hemisphere, ranging from the paleoequator to approx 60 deg S. As would be expected for such a range, sedimentological descriptions indicate a wide range of environments ranging from humid tropical in Morocco (Olsen, 2000)  to cool temperate peat bog in the coal belt (Cairncross, 2001) . Climate has warmed progressively from a glacial episode in the latest Carboniferous and continues to changes with time over the Permian as Africa rapidly moves northwards (Visser, 1995) . Most topography is interpreted to be associated with a series of broad folds across North Africa that run parallel to the Hercynian belt that were the sites of later deep erosion represented by the Hercynian subcrop pattern. The Permian rifts of southern Africa may or may not have had high rift shoulders

Neotethys may now be propagating into at least the northeastern part of the Mediterranean. This is evidenced by the outcropping of Late Triassic oceanic basalts in Cyprus (Lapierre et al 2006) and in Turkey (Robertson and Parlak, 2013). Events in Israel are however often younger than those to the north and the North Eratosthenes Transform (NET) is speculated to form a limit to the Neotethyan ocean at this time. Areas south of this transform are likely to be rifting at this time, with an estimated date of initiation of 240Ma (Jagger et al, 2018). Widespread carbonate deposition characterises the northern and north-eastern margins of the African (including Arabian) plate, though with an increasing proportion of deepwater facies (Dercourt et al, 2000).

There is a large expansion or initiation of rifting in the Atlas (AT) rifts (Le Roy & Pique, 2001: Manspeizer, 1988) and in the Newark (NE) rifts and presumably their NW African conjugates, as well as in offshore Sicily (Catalano et al, 2013).  More gentle sag-like extension occurs in the Triassic Basin (TB) of Algeria , while rifting has also tentatively been interpreted on seismic in the Gulf of Sirt (GOS) and northern Cyrenaica areas (Gillard, 2017, PESGB Africa Conference presentation) . Rifting may thus be occurring over a wide belt from the Levantine Basin (LB) of Israel to Senegal at this time and many authors thus consider this the peak rifting period of North Africa  (Jagger et al, 2018).

Many of the rifts in southern Africa now seem to be in a phase of passive fill by fluvial redbeds (Macgregor (2018). Following a stratigraphic hiatus in the Ladinian which could mark the final movements on the Cape Fold Belt (CFB), the Great Karoo (GK) Basin appears to enter an overfilled phase (Catuneanu et al, 2005)

Africa is now moving rapidly northwards, which as Africa is fixed on these maps, is shown as a southern migration of paleolatitude belts.  The plotted data points on indicator minerals such as evaporites seem to indicate at least seasonal aridity over most of the continent (Boucot et al, 2013), with humid episodes around the NW African rifts (Olsen, 2000: Manspeizer, 1988) and in southern Africa. Many authors believe that parts of the Carnian were more humid than other Late Triassic eras. On the margins of the Great Karoo (GK) basin, the flora and fauna of the Molteno Formation (Cairncross, 2001) indicate warm temperate conditions with semi-humid and humid periods allowing marshlands to form. There are no indicators of the existence of any significant topography, though this interval is generally beyond the AFTA ‘clock’, so this may due to a lack of any surviving evidence in rocks of this age.