Search results for "Acritarch"
showing 3 items of 3 documents
Challenges in defining the base of Cambrian Series 2 and Stage 3
2017
Formal subdivision of the Cambrian System into four series and ten stages is in progress. The base of Cambrian Stage 3 (provisional), which is conterminous with the base of Cambrian Series 2 (provisional), is expected to be placed at a horizon close to the first appearance of trilobites, which marks the onset of the largest phase of the Cambrian explosion. Conceptually, an ideal boundary position would be marked by a significant and globally recognizable bioevent that divides the lower part of the Cambrian System into a sub-trilobitic Terreneuvian Series and a trilobite-dominated Series 2. If the level is to be identified principally through biostratigraphic means, its position also needs t…
Palynological variations and sedimentary cycles in the Jurassic from the Paris basin
1995
Abstract Two studies, one on Hettangian dolomitic cap rocks over “Gaz de France” gas storage reservoir rocks at Sologne, and the other on two separate sections in Dogger formations in Burgundy, conducted at the Palynology Laboratory of Strasbourg, illustrate that a palynological approach can lead to a considerable refinement of knowledge in sequence stratigraphy. The palynological study of the dolomitic cap rocks at Sologne dates them as Hettangian, distinguishes microfloristical assemblage types within the sequence, and establishes palynofacies variations with basin evolution. The evidence suggests that palynological variations in the Hettangian rocks are attenuated, reflecting restricted …
Miocene lithological, foraminiferal and palynological data from the Belverde borehole (Portugal)
2021
XVIII Jornadas de Paleontología, 2002 Preliminary data on litho stratigraphy and biostratigraphy of the Belverde borehole (http://www. dct.Jct.unl.pt/ SondagemISondagem/colunalindex_col.html) is presented. The borehole attained 619,77 m of depth, crossing 130 m of Plio-Pleistocene and 460 m of Miocene dep osits. Main lithologies are fine sands , marl s and biocalcarenites. A coral reef was recognized in the lower part of the borehole (530-585 m). Gamma ray, neutrons and sonic diagraphies were obtained. Eight 87Sr/86Sr isotopic ages (H. Elderfield, Cambridge University)and the presence of some of the main planktonic foraminifera markers were used to establish the chronostratigraphic framewor…