Search results for " Cretaceo"
showing 3 items of 23 documents
Geochimica e petrografica di black shales del Livello Bonarelli, sezione di Novara di Sicilia (Monte Peloritani), Sicilicia nord-orientale: Implicazi…
2000
Black shales ad alto potenziale petrolifero, alternati ritmicamente a marne e argilliti, affiorano in associazione con Argille Varicolori (Cretaceo-Paleogene) nei pressi di Novara di Sicilia (Monti Peloritani, Sicilia nord-orientale) costituendo l’espressione sedimentaria di un evento anossico con diffusione globale (OAE2), riferibile al Cenomaniano superiore. I depositi corrispondenti a tale evento sono individuati come “Livello Bonarelli”. In detta successione, le alternanze black shales-marne-argilliti si estendono per uno spessore di circa 11 metri passando verso il basso ad alternanze irregolari di calcari marnosi, marne chiare, marne scure, argilliti e calcareniti (spessore ca. 9 m) c…
Hafnium-neodymium isotope evidence for enhanced weathering and tectonic-climate interactions during the Late Cretaceous
2022
<p>Over million-year timescale the carbon cycle evolution is driven by mantle CO<sub>2</sub> degassing (source) and by continental weathering that drawdowns atmospheric CO<sub>2</sub> through silicate weathering reactions (sink). Based on a novel geochemical proxy of chemical weathering intensity (i.e. using measurements of Hf and Nd isotope ratios in clay-size fractions of sediments) and clay mineralogy, we discuss the links between tectonic, continental weathering and climate evolution during the late Cretaceous. That period records the very first step of the last greenhouse to icehouse transition and is concomitant to …
Concreções calcárias da formação Santana, bacia do Araripe: uma proposta de classificação.
2007
18 pages; The calcareous concretions of the Santana Formation have been known since 1800 thanks to the work of João da Silva Feijó (1800). Their study was promoted internationally by the report of von Spix and von Martius (1823-1831), and their richness in fossil fishes led Silva Santos to name them “ichthyoliths” in 1950. Here we propose a classification for the various types of calcareous concretions that occurred in the Santana Formation (Late Cretaceous, Araripe Basin). We consider their geographic distribution and we propose a terminological uniformization for the descriptions of that material. This will serve future statistical, geographical, geochemical and taphonomical studies that,…