Maastrichtian Species Research Articles

Les algues calcaires duMaastrichtien-Paléocène de la plate-forme de Gavrovo-Tripolitza (Grèce): Une floraison liée a un diastrophisme

In the Greek Gavrovo-Tripolitza carbonate platform, the carbonate sediments display a Maastritian-Paleoceneblooming of calcareous algae, contrasting with lack of these organisms during the previous and following periods. The Maastrichtian species Cymopolia tibetica (associated with a new species, of Permocalculus) never previously observed in the today's Mediterranean area, is exceptionnally present in a well known facies (with Rhapydionina liburnica); as for the Foraminiferal genus Loftusia which shows a roughly identical dispersal pattern and which is locally found in the same small area, this species seems to be in close dependence of a rudistid reefal facies, very scarce in present outcrops. Several of the Paleocene species are known from Tibet to Central America, displaying a geographical distribution which almost fits the Ranikothalia one; they flourished in most of the various environments all over the platform. This local blooming is taking place during the period when a large facies diversity and a variety of organisms substitute the monotonous lagoonal-confined facies and endemic biotas of the previous and following times. The common cause of these events seems to be a tectonic disorganization of the platform, leading to a temporary diversity of environments and a large input of open marine influence in the whole neritic domain. The algal blooming is supposed to depend upon the homogeneous chemistry of the waters resulting from the opening of the platform.

Brachylepas Woodward and Virgiscalpellum Withers (Cirripedia) from the Upper Cretaceous of Arkansas

Brachylepas americana n. sp. is described from abundant and well-preserved capitular and basal whorl plates from a littoral facies in the basal part of an Upper Cretaceous (upper Campanian) conglomerate questionably assigned to the Brownstown Formation in Hot Spring County, Arkansas. The new species resembles the European littoral Campanian–Maastrichtian species B. guascoi (Bosquet), and differs markedly from the only other known American species, B. angulosa Collins, from the Upper Cretaceous middle Ripley Formation of Mississippi. A few juvenile carinae of Virgiscalpellum may represent V. gabbi apertus Collins, previously known from the Ripley and basal Prairie Bluff Formations in Mississippi.

Late Maastrichtian Nannoplankton Provinces

IT has been known for some time that there was a sharp differentiation of late Maastrichtian faunal provinces with respect to planktonic foraminifera. Axelrod1 has presented evidence that this was also the case with some terrestrial megaphyta, for he found a rather abrupt southward shift for the coniferous vegetation of the northern hemisphere during this time. Before this provincialism was discovered, serious problems were encountered in long-range correlation by planktonic foraminifera, because the two late Maastrichtian species, Abathomphalus mayaroensis and Racemiguembelina fructicosa, are both restricted to the tropics (Fig. 1: A. mayaroensis is extremely rare in the two northernmost occurrences (Denmark and Sweden) shown).