Portal de Periódicos da CAPES

A transitional Ediacaran–Cambrian biota in the Abenójar anticline (Iberian Massif, Spain)

2018; Spanish National Research Council; Volume: 74; Issue: 2 Linguagem: Inglês

1988-3250

J. Haynes Simon,

Paleontology and Stratigraphy of Fossils

espanolSe describe una secuencia conteniendo una biota transicional ediacarica–cambrica, en el valle del arroyo de las Navezuelas, anticlinal de Abenojar (Grupo Ibor, Zona Centroiberica, Espana). La secuencia empieza con capas siliciclasticas de grano fino conteniendo Vendotaenia antiqua y moldes de Cloudina cf. hartmannae, uno de los primeros animales con esqueleto mineralizado. Continua con carbonatos con Cloudina fosfatizadas, coincidiendo en muestra de mano con Vendotaenia antiqua y con protoconodontos semejantes a Protohertzina unguliformis, lo cual sugiere una edad ediacarica terminal o cambrica basal. Las capas detriticas sobre este nivel contienen pistas fosiles simples de organismos sedimentivoros. Sobre un estrato superior de carbonatos con pequenos vendotenidos se ha hallado un conjunto de pistas fosiles de aspecto cambrico, incluyendo Treptichnus pedum y madrigueras ornamentadas semejantes a la superficie ventral de Psammichnites. El hallazgo de protoconodontos es nuevo para la transicion Ediacarico–Cambrico en Europa, y esta es la tercera vez a escala mundial que este tipo de fosiles tipicamente cambricos son hallados junto con cloudinidos, tipicamente ediacaricos, lo cual sugiere que la transicion Ediacarico–Cambrico fue biologicamente mas gradual de lo que se pensaba anteriormente. EnglishA sequence with a transitional Ediacaran–Cambrian biota is described from the Navezuelas stream valley, in the Abenojar anticline (Ibor Group, Central Iberian Zone, Spain). The sequence starts with fine-grained siliciclastics containing Vendotaenia antiqua and moulds of the early skeletal fossil Cloudina cf. hartmannae. These beds are followed by carbonates with Cloudina co-occurring at hand sample level with Vendotaenia antiqua together with protoconodonts similar to Protohertzina unguliformis, suggesting a terminal Ediacaran or lowermost Cambrian age. The detrital beds above this level have simple trace fossils of deposit feeders. Above an upper carbonate bed with tiny vendotaenids there is a trace fossil assemblage of Cambrian aspect, including Treptichnus pedum and ornamented burrows resembling the ventral surface of Psammichnites. The occurrence of protoconodonts is new to the Ediacaran–Cambrian transition in Europe, and this is the third time worldwide that these typically Cambrian fossils are found co-occurring unambiguously with the typically Ediacaran cloudinids, which suggests that the Ediacaran–Cambrian transition was biologically more gradual than previously thought.