|mhorn||Дата: Saturday, 28.07.2012, 11:39 | Сообщение # 1|
|Stevens G.R. (2012) The Early Jurassic of New Zealand: Refinements of the ammonite biostratigraphy and palaeobiogeography // Revue de Paléobiologie, Vol. spéc. 11. P.187-204. |
The Aratauran and Ururoan stages of the New Zealand biostratigraphic sequence have been defined on the basis of the first appearance of the bivalve Otapiria marshalli (treChmann) (marking the base of the Aratauran) and the range zone of the bivalve Pseudaucella marshalli (treChmann) (marking the upper and lower boundaries of the Ururoan). The ammonite record preserved within Aratauran and Ururoan strata is fragmentary. However, correlation tie-points obtained from the ammonites indicate the probability that the Aratauran is of Hettangian-Sinemurian age and the Ururoan of Pliensbachian-Toarcian age. Two of the earliest divisions of the Hettangian (Tilmanni and Spelae Horizons) and the Laqueus Subzone of the Middle Hettangian appear to be absent. Otherwise, correlatives of all the remaining Hettangian subzones are represented. Correlatives of the earliest subzones of the Sinemurian (Conybeari and Rotiforme) are represented but the Bucklandi Subzone appears to be absent. A correlative of the Lyra Subzone is present but otherwise the remainder of the Sinemurian has no records in New Zealand. The Pliensbachian is represented by a single taxon of Juraphyllites correlated with the Margaritatus and Davoei Zones of the middle Pliensbachian. The sole representatives of the Toarcian consist of three taxa: Catacoeloceras, Zugodactylites and Harpoceras, correlating with the early Toarcian Crassum Subzone (Catacoeloceras) and the Fibulatum Subzone (Zugodactylites and Harpoceras). The ammonite assemblages indicate that strong faunal links existed with NW and Central Europe. Close links were also apparent with W. North America in the Hettangian-Sinemurian. Links with South America were less clear and similarly those with SE Asia. The presence of these faunal links may be interpreted to indicate that reasonably accessible faunal migration routes were available from W. Europe along the Tethyan seaway and also to W. North America, probably via the Hispanic Corridor and then transiting the embryonic Pacific Ocean to New Zealand and New Caledonia, then sited on the SE margin of Gondwanaland. The faunal links were strengthened and augmented by the various marine transgressive phases that occurred during rises in relative sea level, as the seaways became more accessible.
Middle Jurassic - Lower Cretaceous ammonites & aptychi