Paleomagnetism of the Cretaceous Galula Formation and implications for vertebrate evolution

摘要: Abstract This study uses magnetostratigraphy to help constrain the age of paleontologically important Galula Formation (Rukwa Rift Basin, southwestern Tanzania). The formation preserves a Cretaceous vertebrate fauna, including saurischian dinosaurs, putative gondwanatherian mammal, and notosuchian crocodyliforms. With better dating, its fossils fill temporal gap in our understanding evolution continental Africa, enabling evaluation competing paleobiogeographic hypotheses concerning faunal exchange throughout Gondwana during Cretaceous. Paleomagnetic samples for this were collected from Namba (higher section) Mtuka (lower members underwent stepwise thermal demagnetization. All displayed strong normal magnetic polarity overprint, maximum unblocking temperatures at approximately 690 °C. Three short reversed intervals identified Member, whereas Member lacked any clear reversals. Given relatively limited existing constraints, one interpretation correlates Chron C32. An alternative correlation assigns reversals recently proposed near end Normal Superchron (Chron C34), time that is traditionally interpreted as having stable polarity. lack supports deposition within C34. These data suggest no older than Late (Cenomanian-Campanian), with less well constrained middle (Aptian-Cenomanian). paleomagnetic results are supported by application fold reversal tests stability, poles (246.4°/77.9°, α95 5.9°) (217.1°/72.2°, 11.1°) closely matching apparent polar wander path Africa confidently indicate Creteceous assignment Formation, unit has yielded key crocodyliform (e.g., Pakasuchus; Rukwasuchus) dinosaur Rukwatitan; Shingopana) eastern Africa.