PaleoAngola na Geological Society of America

O nosso trabalho do Projecto PaleoAngola, que em Portugal envolve a Faculdade de Ciências e Tecnologia e o Museu da Lourinhã, está em força no congresso de geologia dos Estados Unidos, GSA, Geological Society of America - Annual Meeting, a decorrer de 20 a 27 de Outubro em Denver, Colorado. Apresentamos as seguintes três comunicações científicas sobre os vertebrados fósseis de Angola:

Vista panorâmica de Bentiaba.

A marine vertebrate assemblage from the Campanian-Maastrichtian boundary at Bentiaba, Angola

A single, geographically and temporally restricted horizon, Bench 19, at the Campanian-Maastrichtian boundary at Bentiaba, Angola, preserves a dense concentration of skeletons and isolated elements representing sharks, rays, bony fish, three species of turtles, two species of plesiosaurs, and at least seven species of mosasaurs. Nearly all of the amniote specimens show evidence of scavenging by sharks. 

Polcyn, M. J., Jacobs L. L., Mateus O., Schulp A. S., Strganac C., Araújo R., Graf J. F., Vineyard D., & Myers T. S. (2013).  A marine vertebrate assemblage from the Campanian-Maastrichtian boundary at Bentiaba, Angola. Geological Society of America Abstracts with Programs. Vol. 45, No. 7,

Cabinda revisited: age and environment of new Cenozoic vertebrate fossils from northern Angola

In the early 20th century, Belgian naturalists reported Paleocene and Eocene sharks, the bothremydid pleurodiran turtleTaphosphrys (formerly Bantuchelys), and a neosuchian and the dyrosaurid crocodyliform Congosaurus from coastal outcrops near Landana in the northern province of Cabinda, Angola. In 1935, rare and fragmentary mammals were reported from strata at Malembo Point, south of Landana, and originally considered to be Miocene in age. 

Jacobs, L. L., Myers T. S., Gonçalves A. O., Graf J. F., Jacobs B. F., Kappelman J. W., Mateus O., Polcyn M. J., Rasbury E. T., & Vineyard D. P.(2013).  Cabinda revisited: age and environment of new Cenozoic vertebrate fossils from northern Angola. Geological Society of America Abstracts with Programs. Vol. 45, No. 7.

Late Cretaceous marine reptiles and cooling at the South Atlantic coast inferred through stable oxygen isotopes of Inoceramus from the Namibe Basin, Angola

Strganac, C., Jacobs L. L., Ferguson K. M., Polcyn M. J., Mateus O., Schulp A. S., & Morais M. L. (2013).  Late Cretaceous marine reptiles and cooling at the South Atlantic coast inferred through stable oxygen isotopes of Inoceramus from the Namibe Basin, Angola. Geological Society of America Abstracts with Programs. Vol. 45, No. 7.

The opening of the South Atlantic Ocean enhanced global ocean circulation and contributed to the transition from warmer temperatures during the middle Cretaceous to cooler climates characterizing much of the Cenozoic. We present δ18O values derived from bivalve shells to elucidate nearshore temperature change in southern Angola during the Late Cretaceous development of the South Atlantic Ocean. Inoceramus and other bivalve shells were recovered from marine sediments at Bentiaba, Angola, that overlie non-marine redbeds deposited during the initial rifting of Africa and South America. The section is anchored by a radiometric age of 84.6 Ma on an intercalated basalt and the δ13C stratigraphy derived from shells is correlated to global carbon isotope events from the Late Cenomanian to Early Maastrichtian. The δ18O stratigraphy derived from shells indicate an overall increase from -4.5‰ in the Late Cenomanian to -1.2‰ in the Late Campanian, which is a similar trend observed in oxygen isotopes in foraminifera globally. Assuming a constant oceanic δ18O value, the change in oxygen isotopes reflects cooling of ~15° for the shallow marine environment at Bentiaba. Early to Late Campanian inoceramids yield the highest δ18O values, between -1‰ to -2‰, and are offset by about +1‰ from published records for benthic foraminifera and bathyal Inoceramus at Walvis Ridge. This offset in δ18O values indicate a temperature difference of ~5° between coastal and deeper water offshore Angola prior to the latest Campanian. The stratigraphic distribution of marine reptile fossils coincides with cooler temperatures at Bentiaba implied by more positive δ18O values derived from bivalves. A diverse marine reptile fauna has been recovered from Bench 19 that was deposited at the Campanian-Maastrichtian Boundary during a time of increased global ocean connectivity and circulation of cooler productive high latitudinal waters. This pattern aligns with the larger context of the mosasaur record, which indicates productivity driven evolution accompanied by an increase in size disparity, in diversity, and in niche differentiation.

O Projecto PaleoAngola envolve várias instituições científicas entre as quais:

• Southern Methodist University, Dallas, EUA
• Depart. de Ciências da Terra, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa,
• Natuurhistorisch Museum Maastricht, Maastricht, Netherlands, 
• Faculdade de Ciências, Universidade Agostinho Neto,Angola
• Museu da Lourinhã

Estes e outros artigos sobre Angola estão disponíveis aqui.