Dr Duncan Macgregor : Ongoing Research, Training and Consultancy on African Geology

Jurassic Paleotectonic and Paleogeographic Maps of Africa
Draft 1


an ongoing project using the plate model of Colin Reeves (www.reeves.nl)
Comments welcomed

Rhaetic/Hettangian 200Ma

Key Events/Points
•
•1. CAMP Plume volcanics centred on 200Ma (Mchone, 2000: Pevye, 2015)
•2. Newark. Nova Scotia and Moroccan Triassic rifts entering post-drift phase (Labails, 2010)
•3. It is unclear to how much of the developing Central Atlantic margin was a volcanic margin. It is generally thought that the extensive East Coast magnetic anomaly on the US margins ties to SDRs (Davis, 2018). In the African margin SDRs are reported as present off north Senegal (Petrosen, 2004) and Guinea Bissau/Demerara Plateau (Zinecker, 2020). Despite similar magnetic anomalies to the ECM to the north of Senegal, no SDRS have been reported and they seem to be absent off Morocco (Labails, 2010).
•4. Roberts et al report Morocco_Canaries as a hyperextended margin with true oceanic crust west of the Canaries and an abandoned hyperextended continental crust basin in between the islands and Morocco
•5. Africa rapidly moving northwards and climate warming
•6. Assumed topography associated with CAMP Plume



Pleinsbachian 185Ma

•1. Centre point in time of Karoo volcanics (Reeves. Peyve, 2015)
•2. SDRs in Mozambique assumed to be correlatable to these (Senkans, 2019)
•3. Breakup of Central Atlantic, initially slow (Pleinsbachian pillow lava ages in Canaries) (Sahabi, 2001 places this in latest Sinemurian)
•4.Roughly assumed age of breakup of most Eastern Mediterranean interpretations (Hinsbergen 2019, Handy, 2010)
•Paleomag data on Apulia shows potential for deviation from Africa at this time (Rosenbaum, 2004)
•Postdates interpreted rifts in Levantine Basin (Schattner, 2007)
•Ocean must predate Ligurian sea opening in Bajocian-Bathonian otherwise Adria is compressed
•Low heat flows in Ionian Sea suggest old ocean (Catalano, 2000)
•Postdates Triassic rifts in much of NE Africa
•Though questioned by rift history of e.g. Western Desert and deep marine environments in Sicily/Malta not till Aalenian (Catalano, 2013)
•5. Equator now in position from which it will not drift much until Late Cret

Bajocian 170Ma

•1. Opening of Ligurian Ocean, connected along Azores-Gibraltar transform to Central Med. Initiates a long term sinistral movement of Africa relative to Europe (Handy, 2010)
•2. Central Med spreading now extended to Senegal. Evidence for break-up of this age from seismic correlations on Blake Plateau (Sheridan, 1988)
•3. Eastern Med spreading possible terminating (to allow Ligurian to open), though this seems inconsistent with a major (second rift/?transtensional phase in the Western Desert, Dolson, 1998)
•4.Trangressions of this age in e.g. Tanzania suggest this is roughly the age of breakup of the Somali Basin/Ocean (Macgregor, 2018). Oblique slip at this time – no Davie Transform at this time (Phethean, 2016)
•5. Most datings in publications indicate volcanics/SDRs still dominate in Mozambique (Senkans, 2019)

Kimmeridgian 155Ma

•1. Following a major concentration of ocean opening enents between the Pleinsbachian and Bajocian, the Late Jurassic represents a generally more quiescent period, dominated by accelerated spreading of these oceans (Central Atlantic, Ligurian, Indian). Marked decrease overall in rift activity
•2. Sedimentation dominated in low paleolatitudes by platform carbonates, indicative of low sediment supply and ?hinterland topography
•3. High sea level with much of East Africa transgressed and even evidence for marine strata in Cuvette Centrale, again indicative of low topography
•4. Agulhas transform becomes active with transverse rifts in Agulhas Basin (Mcmillan, 1997), between Falklands and Maurice Ewing Bank, and southern Mozambique (Salman, 1995) – how coeval are these?
•5. There’s good geometrical reasoning for Limpopia to follow Antarctica fairly closely until about 138 Ma. At that time there is some upheaval that creates a new midocean ridge to the E of the Maurice Ewing Bank and south of Limpopia. This event also pushes Antarctica away from Africa (Reeves ‘sidestep’), temporarily deflecting it from its long-term trajectory (i.e. E-W. extension). This could be the cause of rifting in southern Mozambique