The volcanic rocks of the Catoca Diamond Mine, northeastern Angola, were formed in an eruption ~118 million years ago. Above these rocks, researchers discovered Early Cretaceous mammalian, crocodilian, and sauropod dinosaur footprints in crater lake sediments. These footprints are among the relatively few vertebrate fossils from the Cretaceous Period (145-66 million years ago) found in Sub-Saharan Africa. The ~118 million-year-old age, which is the maximum age of the footprints, is provided by the uranium and lead isotope ratios in the zircon crystals from these volcanic rocks. The presence of dinosaur footprints limits the minimum age to 66 million years ago. Detrital zircons from the sediments were collected for uranium-lead dating because these lake sediments may contain not only the ~118 million-year-old zircons but also zircons from younger eruptions, which could more precisely constrain the maximum age of these sediments. Forty zircons have been analyzed from this sediment sample, yielding an age range of 2.9 billion years ago to 150 million years ago. None of these zircons was ~118 million years old. Work is currently underway to find more zircons and to determine why no ~118 million-year-old zircons have been found in the lake bed sample.
Jackson, Yasmin; Economos, Rita; Jacobs, Louis; Mateus, Octávio; Gonçalves, António O. (2021) "When Dinosaurs Walked Through Diamonds: Constraining the Age of Early Cretaceous Footprints in Volcanic Crater Sediments," SMU Journal of Undergraduate Research: Vol. 6: Iss. 1, Article 1. DOI: https://doi.org/10.25172/jour.6.1.1 Available at: https://scholar.smu.edu/jour/vol6/iss1/1
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