Permo-Triassic Palaeogeographic and Paleotectonic Maps of Africa

Draft 2 Feb 22
An ongoing project using the plate model of Colin Reeves (
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Kungurian 275Ma

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 (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, which has yet to propagate into Africa, based on 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 (2016), 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.

 Macgregor (1992) differentiates two phases of Permo-Trias rifting in southern Africa, with the first of these initiated in the Stephanian and with peak rifting in the Kungurian. Narrow transtensional half grabens are developed along the ‘Southern Trans Africa Shear’  from the Morondava Basin (MO) to the Aranos Basin (AB) of Namibia  Another set of more typical dip slip rifts typified by the Rukwa (RU) rift, runs at a right angle to the main trend through Zambia and Tanzania. There is no clear connection to lineaments in South America but an intersect with the Cape Fold Belt is likely.

A large deep marine inlet or brackish lake is developed in the Great Karoo (GK) Basin, 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.  Periodic marine transgressions affect the Morondava Basin (MO), likely sourced from the north, 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 20 deg S. As would be expected, sedimentological descriptions indicate a wide range of environments ranging from humid tropical to cold temperate peat bog in a wide coal belt.

Induan 250 Ma

 The last of the collisions that assemble Pangea occurs as the main phase of the Cape Orogeny  (Linol and de Wit, 2016) . Distal compression is seen as far away as the Cuvette Centrale (CC). The Great Karoo (GK)  Basin moves into a filled stage, characterized by non-marine sediments (Catuneanu et al, 2005) .  A general expansion of the Permo-Triassic rifts of southern and eastern Africa occurs around this time, with much more activity in north-east Africa (Macgregor, 2017). The main rift event in the Ogaden (OG) Basin is, for instance, of Early Triassic (Induan) age, during which a thick deep lacustrine shale (Bokh Shale) was deposited, time equivalents of which are seen in Kenya  and in the Middle Sakamena Formation of the Morondava Basin (MO).  The correlation of Triassic rifts between Tanzania and Madagascar is an important element in defining the original fit between Africa and Madagascar (Reeves, 2016). Reeves fit has been slightly relaxed here for ease of display. Madagascan rifts again show more marine influence at this time than do the African ones, due likely to a marine inlet likely pulsating southwards from Tethys, perhaps through the Somalian offshore rifts mapped by Davidson et al (2018)

In North Africa the Djeffara (DJ) Rift is still subsiding while other seemingly isolated set of rifts is forming in the Maragh (MA)  Basin and Hameimat (HA) Basins of Libya (Gras and Thusu, 1996 ). The Palymrides (PA) Basin of Syria (Brew et al 2001) rifts as a precursor to opening of part of the Eastern Mediterranean and such activity could extend offshore into the Levantine Basin. The first rift that preceeds Central Atlantic breakup occurs within the Argana (AR) Valley of Morocco (Frizon et al, 2008). Local rifting also occurs in the Sabratah (SA) Basin offshore Libya as part of a gradual step northwards of rift activity on this area through the Permo-Trias (Reeh, 2015)

Aridity is interpreted for all data points north of a warm temperate zone that covers the Cape Fold Belt and Permo-Triassic graben belt. Particularly interesting is an interpreted change in Moroccan paleoclimates from humid tropical to arid within a belt that is equatorial on both the Kungurian and Induan levels (Olsen et al, 2000).

Carnian 230Ma

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 (Bosch et al 2007) and in Turkey (Robertson and Parlak, 2015). 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.

There is a large expansion or initiation of rifting in the Atlas (AT) rifts 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) . 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, 2017). 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, 2015).

Africa is now moving rapidly northwards, which as Africa is fixed on these maps, is shown as a   southern migration of paleolatitude belts.  The data points seem to indicate at least seasonal aridity throughout the continent, with humid episodes around the NW African rifts 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 well known flora and fauna of the Molteno Formation (Cairncross et al, 2001)  indicate warm temperate conditions with semi-humid and humid periods allowing marshland to form