|mhorn||Дата: Saturday, 28.07.2012, 11:38 | Сообщение # 1|
|Ballent S.C., Whatley R. (2012) New perspectives on the stratigraphical and temporal distribution patterns of Argentinian Jurassic marine Ostracoda // Revue de Paléobiologie, Vol. spéc. 11. P.169-185. |
The principal area for the recovery of Argentinean Jurassic marine Ostracoda is the Neuquén Basin, a large feature that spans the provinces of Neuquén, La Pampa, Río Negro and Mendoza. The Jurassic succession is very complete but not all is marine, some being continental clastic, evaporitic and volcanic in origin. At some levels, ostracods are very diverse and abundant, while other levels demonstrate low diversity but very high abundance. Generally, there is an increase in diversity with time but this is not steady and there are several reversions to low diversity. Recent works in West Australia and offshore western Australia, in certain Madagascan basins and in Kutch and Rajasthan in India, together with detailed synopses and analysis of faunas in these localities, in Europe and, importantly in Argentina, allow a better understanding of the principal components of the Neuquén faunas. The bi-hemispherical nature of important elements of the fauna is very clear, with certain key species being known for example, from the famous Mochras borehole in North Wales and from Neuquén, and other localities in between (Oligocythereis? mochrasensis). Other taxa, important in the local scheme of things are endemic to the Neuquén Basin; still other Argentinian taxa exhibit the third component of the faunas, those with gondwanine connections. The number of genera and species occurring in the basin and also, in Africa, Australia, Madagascar and India is impressive and all these are clearly indicated in the paper. Lastly, a new dimension is revealed by comparing the stratigraphical occurrence of certain of the more pandemic species. A number have their earliest occurrences in Neuquén, suggesting its importance as a locus of evolution from which species migrated out to other parts of the globe.
Middle Jurassic - Lower Cretaceous ammonites & aptychi