The northern part of the N–S-trending basin of the Limagne graben, located in the northern part of the Massif Central (France), contains Oligocene and Miocene calcareous lacustrine deposits. The area is known for its stromatolite reefs surrounded by marl, clay and uncemented carbonate sand with oncolites. Because the origin of the carbonate accumulated by cyanobacteria has long been debated, the clayey deposits associated with the stromatolites were analysed using XRD, SEM and K–Ar dating methods. The results show a monotonous assemblage of carbonates, dioctahedral smectite, illite–smectite (Reichweite) R=0, glauconitic illite and abundant orthoclase. Detrital minerals such as quartz and detrital illite are found near the basin's borders but are very scarce in its central part, indicating a lack of detrital input from the regional basement. Hence, the abundant orthoclase found in all the clayey deposits of the Limagne Basin cannot be linked to erosion of the surrounding Hercynian basement. The SEM analysis showed the orthoclase crystals to have a tabular morphology with sharp boundaries and to be embedded within a clay matrix, whilst the K–Ar dating of the orthoclase and glauconitic illite yielded ages ranging from 90 to 66±2Ma, i.e. Turonian to Maastrichtian. These two results clearly indicate that the fill of the Limagne Basin, composed mainly of carbonate, clay and orthoclase, must have been partly due to the erosion of an Upper Cretaceous sedimentary blanket once covering the Massif Central basement. This cover was probably constituted of chalk, dioctahedral smectite, I/S and glauconitic illite, associated with authigenic orthoclase and flint. Flints are found reworked in the alluvial formations of the Late Pliocene Lower Bourbonnais sands and clays (‘Sables et argiles du Bourbonnais’) and in the Pleistocene terraces. Moreover, relicts of the Upper Cretaceous cover were preserved during the sedimentary filling of the Cenozoic Limagne Basin. Authigenic orthoclase of similar shape has been described in the Chalk Group of the Paris Basin and from localities in northern France and Belgium. The mineral is rare in the Turonian chalk but increases rapidly at the base of the Coniacian to Campanian chalk; it has also been noted that the number of orthoclase crystals increases as the quantity of clastic components decreases. Similar orthoclase crystals were found associated with dioctahedral smectite in the decarbonated residues of the Coniacian to Santonian chalk from Fécamp and Etretat (northern France). Moreover, our results are consistent with other data from within and around the Paris Basin, such as the palaeogeography and facies distribution of the Chalk formations, the residual flints in the clay-with-flints of the southern Paris Basin and around the Morvan, and apatite fission-track thermochronology data from the Hercynian basement of the Massif Central and the Morvan. All these data indicate a major connection between the Paris Basin and the Tethys, and an extensive palaeocover on the Massif Central and Morvan basement.

A new assemblage of marine vertebrates from northern Saudi Arabia, east of the Nafud, leads us to reconsider the age of the top unit of the Aruma Formation, the Lina Member, hitherto referred to the Maastrichtian. This assemblage contains the remains of a dozen selachian and actinopterygian fishes, as well as those of a giant sea turtle representing a new dermochelyid taxon. It suggests a Late Paleocene to Early Eocene age for this unit. This new dating and a revision of the stratigraphic position of the Lina Member demonstrate the existence, on a regional scale, of an important hiatus at the K-T boundary.

During the Cenozoic, in the western Paris Basin, atmospheric weathering of the chalks with flints of the Upper Cretaceous led to the creation of clay with flints. A reconstitution of the chalks lost to dissolution is proposed and is based on the determination of the age of the parent chalks of the clay with flints and the quantification of the thickness of dissolved chalk. The chalks affected by weathering range in age from Turonian to Maastrichtian, thus confirming the deposition of calcareous sediments in the western Paris Basin up to the Maastrichtian. Chalk weathering took place in situ, as indicated by the preservation of the stratigraphic succession of the chalk in the clay with flints profiles. Weathering led to the dissolution of 20–200 m of chalk, with regional variations. The weathering rate varies between 2.1 and 14.5 m/Ma.

In Oman, the sedimentary basins located along the edges of the Oman Mountain chain show continuous sedimentation at the K/T boundary. Two distinct sedimentary palaeoenvironments have been analysed. In the northwestern flank of the Oman Mountains (near Buraymi), the K/T boundary occurs within hemipelagic deposits; whereas in the Abet basin (southeastern flank), it occurs within confined carbonate platform facies. The negative partial derivative(13)C shift and the positive iridium anomaly, which characterize the global geochemical events of the K/T boundary in marine sections, have been detected in Oman. Moreover this isotopic signature is nor the only event recorded in these sections. Some other important shifts have been recognized in the Upper Maastrichtian and Lower Danian sediments. These shifts are related to some palaeogeographical events such as platform flexuration which correspond to some regional tectonic reajustments.

Two new sites, revealing a record of the events at the K/T boundary, have been recently discovered in the Oman Mountains at the eastern end of the Arabian plate. In the Buraymi Basin. located at the northwestern flank of the chain, the KIT boundary is intersected by a basinal facies succession, whilst in the Sur area, the transition is illustrated within a confined carbonate platform sequence. This period exhibits important palaeoenvironmental and biotic changes which originated from the conjunction of multiple factors. These came together over differing intervals of time, i.e., long period of time, short time scale and instantaneous event. At the scale of the long period of time (4 Ma) stretching from late Maastrichtian to the Danian (P1c), the Oman Mountains recorded profound modifications in terms of their palaeogeographic context, undoubtedly linked to plate reorganisation. This was initially shown by the emersion of the rudist platforms and the flooding of the margins in the late, but not terminal, Maastrichtian. This first tectonic event introduced an hemipelagic and a turbiditic sedimentation. As a consequence, this episode created, at the southern limb of the chain, the confined Murka sub-basin characterised by a carbonate platform sedimentation. Because the transition terminal Maastrichtian-earliest Danian correspond to a period of tectonic quiescence, the sedimentation persisted through the K/T boundary without any notable modification. A second tectonic episode in the Danian P1b/P1c interval, accentuated the flooding of the plate margins where basin deposits were accumulating. The renewal of planktic foraminifera took place in stages suggesting a gradation of palaeoecological conditions spread over a short time scale (1 to 2 Ma). This gradation is marked by the succession of three waves of extinction which took place from the late Maastrichtian to the KIT boundary. Diversity of the benthic foraminifera then increased progressively from subzone P1b onwards, showing the re-establishment of the ecosystem in P1c. The iridium anomaly detected at the WT boundary at both sites would tend to reinforce the hypothesis of a meteorite impact. the effects of which would have added to these events that unfolded over a longer rime scale.

A regional survey on residual clay-with-flints (= "RS") in Northwestern Paris Basin gaves the opportunity to study new outcrops crossing chalky plateaux and interfluves. Flints are sampled in these "RS" covering chalk and in "paleo-RS" reworked at the base of Thanetian deposits. They supply Upper Maastrichtian microfauna. The deposition of chalk with flints until the Upper Maastrichtian is thus confirmed in the Western Paris Basin as well as in neighbouring basins. Weathering processes caused their ulterior occultation.