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The holes drilled during Leg 25 show a large degree of diversity. Each had its own objectives and revealed its own stratigraphic findings. They provided some understanding of the nature and age of the deposits and, possibly of the substratum. It is the purpose of this paper to place them in a regional setting and to compare them by enlarging the comparative framework. This wide geologic framework can provide useful data for the interpretation of seismic profiles. Holes will be compared in three ways, depending on the available data: (1) with data from onshore field observations (sedimentary fringe of African and Madagascar coastal "basins," and coastal boreholes) or from offshore observations (offshore boreholes); (2) with considerations linked to hypotheses about plate tectonics; and (3) with major geological or diastrophic events. This comparison covers a large area over which a great variety of sedimentary facies is represented. In most areas, published data are sparse. Also, the data which are available do not all have the same comparative value because they not only were obtained progressively as years went by, but also by different techniques. Within the limited space available, I have tried to avoid the two major pitfalls that can waylay any such undertaking, i.e., altering the data through diagrammatic formulating, and writing a report on regional geology. An attempt to avoid these dangers was made by limiting the comparisons to a certain number of crucial problems that concern the drilled sites. I have tried to overcome the handicap of not having direct personal knowledge about the regions involved by exchanging opinions and publications with various colleagues who have been kind enough to assist me and to whom I willingly extend my thanks. These include H. Besairie (Tananarive), G. Flores (Florence), G. Blant (Entreprise de Recherches et d'Activités Pétrolières, Paris), Compagnie Francaise des Pétroles (P. Burollet, Ph. Dufaure, Cl.de Lapparent, Ph. Trouvé), M Collignon (Gières, France), and A. Balduzzi (A.G.I.P., Milano). The biostratigraphic columns have been given for each site (Chapters 2-10). The distribution (and the recovery rates) of the cores, the paleontologic zones which have been recognized (planktonic and benthonic foraminifera and calcareous nannofossils), and the geochronologic scale are given in these columns. It was not possible, because of the time allowed, to write a paleontologic-taxonomic paper on the foraminifera and ostracod assemblages to be included in the Initial Report. However, many results are new because some drilled sequences were originally deposited in a particular realm (very austral for Site 245 for instance) and their monographic study would require much more time. Plates 1 through 11 illustrate the more important chronostratigraphic species which support the recognized conventional zones or chronostratigraphic determinations. Their purpose is essentially to justify the biochronostratigraphic data on which the delimitations of the drilled sequences and intercalated hiatuses are based. Also, they support the paleogeographic frame in which the sites and the surrounding sedimentary areas can be compared. The identified parts and the hiatuses of the stratigraphic columns are given in Figure 1, based on their actual range in the scale of "absolute" ages. The figure attempts to show, for each site, those parts of the stratigraphic column which were not recognized. They may thus correspond either to gaps, i.e., nondeposition or erosion, or they may correspond to condensed sequences, as it has been emphasized by Leclaire in the aforementioned chapter. Very probably both explanations must be considered, depending on the site, as it is evident that these "hiatuses" actually occur in very different paleogeographic environments. The hiatuses are included in a scale of measured ages in order to give the most accurate presentation of data possible. Moreover, the "absolute" age of the lower and upper limits of the hiatuses, as they can be deduced from the biochronologic data, is given. These determinations are the basic elements which enable sedimentation rates to be calculated.

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Comments on Leg 25 Sites in Relation to the Cretaceous and Paleogene Stratigraphy in the Eastern and Southeastern Africa Coast and Madagascar Regional Setting