Note on Upper Cretaceous ostracods from south-western Morocco

Cenomanian, Turonian and Coniacian ostracods from a borehole in the coastal zone of the Tarfayan Basin, south-western Morocco, display affinities with associations from Algeria, Tunisia and the Middle East as well as with the Iberian Peninsula. Relationships with central and southern West Africa are relatively slight, which could be a result of palaeoecological particularities.     

Periodicity in namurian sediments of derbyshire,england (a quantitative sedimentary analysis)

Five facies associations are present in the basin-filling Namurian sediments (Grindslow Shales and Kinderscout Grit) of the southern Central Pennine Basin of England. Visual study of sequences fails to disclose any pattern in the occurrence of facies. A simple mathematical statistical analysis shows that patterns do occur and approximate models can be proposed. The homogeneous siltstones (facies A) occur roughly in accord with a Poisson process model; the striped siltstones (facies B) of the sequence deviate from a renewal process model in many ways and may be most nearly approximated by some process showing trend in the rate of occurrence of events; the sharp-based sandstones (facies C) seem to occur in agreement with some type of renewal process, but not a Poissonian variety. The intervals between the sediment-building periods of these facies categories may be renewal processes of some kind, although all deviate from a simple Poisson model. Owing to the limitations of the data available only tentative conclusions can be drawn.     

Covariance structure and morphometric analysis—A contribution to paleogenetics

A method of analysis of covariance structure proposed by A. P. Dempster complements, in some respects, a recently suggested procedure by the author. The method is based on the comparison of ratios of generalized statistical distances and distancelike quantities. An analysis of septivariate data on the foraminiferTextilina mexicana (Cushman) shows general differences in covariance structure in which the sample rest linear discriminators also differ. This difference in covariance structure is thought to be genetic in origin. Two species of Middle Devonian brachiopods,Martinia inflata (Schnur) andUncites gryphus von Schlotheim), also show differences in covariance structure—the former slightly, the latter strongly. This is further analyzed forUncites by the author's methods and good agreement between the two approaches obtained.     

Geomagnetic reversal data statistically appraised

Standard methods of the statistical analysis of time series are applied to available data on geomagnetic reversals. The times between reversals from Kimmeridgian (148 m.y. BP) to Recent display pronounced trend with an increasing rate of occurrence parameter. This is not solely due to the Late Barremian to Late Coniacian quiet period, for significant trend exists in the observations running from Late Maastrichtian (67 m.y. BP) to Recent, although the size of the trend effect decreases steadily. From Middle Eocene (46 m.y. BP) onwards, the rate of occurrence of reversals becomes trend-free, forming some kind of a renewal process (excluding the Poisson process). A comparison of the sequences of times between normal, respectively, reversed polarities for the Early Eocene to Recent shows them to be almost identical. The selected intervals Kimmeridgian to Barremian, Eocene to Oligocene and Oligocene to Miocene are trend-free. The agreement between periods of pronounced non-stationarity in the frequency of reversals and epicontinental transgressions is briefly noted.