ABSTRACT The biostratigraphic zonation of Barremian – Aptian shallow-water carbonate systems has a low resolution due to the slow evolutionary rate of most species living in these environments. A notable exception to this are the orbitolinid foraminifers, which show relatively rapid evolutionary trends mainly in the embryonic structures, and can thus be used for high-resolution dating of these strata. Here a revised orbitolinid biostratigraphic zonation scheme is presented for the eastern Arabian Plate. This zonation is based on published work and new research on orbitolinid-rich successions in shallow-water carbonate platform environments and intra-shelf basin margins. A subdivision into six zones and three subzones is proposed for the Barremian and Aptian, using the evolutionary lineages Montseciella (= ex- Dictyoconus ) arabica – Rectodictyoconus giganteus, Eopalorbitolina – Palorbitolina and Praeorbitolina – Mesorbitolina . In this paper we also introduce a new species, Palorbitolina ultima , which represents the advanced development of Palorbitolina lenticularis . This revised zonation was derived from a unique database covering the eastern Arabian and northeastern African plates including offshore Abu Dhabi, Ethiopia, southwest Iran, Oman, Somalia and Yemen. As a result, a revision of the age assignment of the Dariyan Formation in southwest Iran is proposed. In addition, examples of biostratigraphic zonations, which constrain regional (sequence) stratigraphic correlations are: (1) the regional appearance of the short range, Late Barremian species Montseciella arabica , that allows to correlate a third-order sequence in a low-angle, carbonate ramp system over a distance of 4,000 km; (2) the assemblage of Palorbitolina and Praeorbitolina species that characterise the late Early Aptian maximum flooding event; and (3) the subsequent appearance of different Mesorbitolina species that characterise the regressive Upper Aptian deposits.

ABSTRACT The lateral transition from carbonate platforms to intra-shelf basin in Aptian – Early Albian times is documented along a regional transect in the excellent exposures of the Zagros Mountains. An integrated dataset, including carbonate carbon-isotope curves, and ammonite and planktonic foraminifera biostratigraphy constrains the regional correlations, and forms the basis for an age revision of the Kazhdumi and Dariyan formations. Of particular importance in this study is the Kuh-e-Bangestan section, wherein a continuous succession of Aptian – Albian intra-shelf basinal deposits was used to erect a detailed ammonite and planktonic foraminifera biostratigraphic zonation scheme, in combination with a carbon-isotope curve and organic-matter measurements. Key observations are: (1) the oldest Kazhdumi intra-shelf deposits are of Early Aptian age ( D. deshayesi Zone), indicating a time-equivalent initiation of the Kazhdumi and neighbouring intra-shelf Bab Basin. (2) The presence of well-developed organic matter-rich sediments in the N. nolani and H. jacobi zones is interpreted as equivalent to part of the OAE1b set. (3) The presence of an exceptionally well-developed Upper Aptian – Lower Albian succession (80 m thick) shows a clear positive carbon-isotope excursion and a faunal crisis, with the turn-over of the planktonic foraminifera assemblage (only small and low diversity Globigerinelloides and Hedbergellids ) and the total absence of ammonites. A composite carbon-isotope curve is proposed based on sections measured in both the platform and basin settings. This curve deserves attention because it has an expanded Upper Aptian - Lower Albian section, which is well dated (ammonites, planktonic foraminifera and orbitolinids).

Abstract: Numerical ages have been derived from the 87 Sr/ 86 Sr values of well-preserved rudist shells from localities in Salento (S Italy)and Lefkas (Ionian Islands, Greece). Samples are from the platform margin (Salento) and from the toe of slope (Lefkas) of the former Apuliancarbonate platform. Rudists from both localities yielded a latest Maastrichtian age (66.4 Ma), and their rudist associations are the mostspecies-rich so far reported from the Mediterranean region so close to the Cretaceous-Paleogene (K-P) boundary. The abundance of large-size recumbent morphotypes of a taxon similar to Pseudosabinia is remarkable. Generally, the latest Maastrichtian rudist morphotypes ofthe Caribbean and of the Mediterranean region are very similar, although the faunas are highly endemic on the genus level. When comparedto the Turonian-Campanian, the increased abundance of aragonite in the shells of the dominant rudist taxa, and the higher abundance ofother originally aragonitic skeletal components, is discussed with respect to the major-ion composition of Cretaceous seawater. The nowwell-documented existence of species-rich rudist associations on both sides of the Atlantic argues for a catastrophic rather than a gradualextinction of the group.

Abstract During Aptian to Albian times a major influx of terrigenous material from the emerged Arabian Shield led to the deposition of the Nahr Umr Formation within the intracratonic Bab Basin. This argillaceous facies interfingers in northern Oman with sediments shed from reefal complexes. We studied a 100 km transect across the zone of facies intercalation extending from the margin of the Neo-Tethys (northern Jabal Akhdar) into the fringes of the Bab Basin in northern Oman (Foothills). The age of formation boundaries and key beds and surfaces in a reference section (Wadi Bani Kharus; I) was dated by use of the graphic correlation method. Graphic correlation indicates that the Nahr Umr Formation is of uppermost Aptian to Upper Albian age. Two types of stratigraphic markers were recognized: limestone marker beds, successions, and disconformity surfaces. Calcareous marker beds are probably related to increased carbonate production during sea-level lowstands. Investigations of the geochemistry (stable isotopes, fluid inclusions) and sediment petrography of limestones beneath disconformities revealed that they are of combined submarine and subaerial origin. Evidence for a subaerial exposure stage is recognized along the basin margin (northern and southern Jabal Akhdar) but is found less frequently in the basinward settings of the Foothills. Marker-bed successions and disconformity surfaces are correlated throughout the sections and indicate coeval deposition of the Nahr Umr Formation in northern Oman.