Annotated record of the detailed examination of Mn deposits from DSDP Leg 40 (Hole 361)

From a structural and morphological point of view, the continental margin of southwestern Africa is a middle-aged "pull-apart" or "passive-type" margin which was initially created during the breakup of the supercontinent of Gondwanaland in the Mesozoic. The most important objective of the Leg 40 expedition was the attainment of strata laid down when the newly formed ocean was very young and only a few hundred kilometers wide. Site 361 was drilled at the fall of continental platform into the Cape Basin, to a sub-sea floor depth of 1314 meters and yielded sediments that range in age from upper Eocene to lower Aptian and possibly slightly older

Environmental Gradients in Carbonate Sediments and Rocks Detected By Correspondence-analysis - Examples From the Recent of Norway and the Dinantian of Southwest England

Continuous sedimentary gradients are only crudely expressed by standard facies and microfacies methods which are more appropriate to situations where changes occur in relatively discrete steps. In carbonate sediments and rocks, continuous gradients are often represented by the arrangement of component grain types in a relay, that is, a systematic shifting of the relative importance of the components. Subdivision of such relays into (micro)facies can only be arbitrary. Correspondence analysis is shown to be useful for detecting, isolating and describing relays. Particular use is made of the arch effect in which samples and components from data sets with a strong unidimensional structure (a relay) plot in the form of an arch in the plane of the first two factor axes. A relay index, indicating the position of samples in the relay, can be extracted from the analysis and plotted on maps and stratigraphic logs to reveal details of the sedimentary gradient in areal and/or stratigraphic context. Examples are given from: (i) Recent shallow-marine carbonate sediments from northern Norway, illustrating a relatively simple depositional setting where surface sediments are viewed in plan; and (ii) Lower Carboniferous carbonates of southwest England, representing a more complex regional study of a particular stratigraphic interval viewed in cross-section. In both examples the relays can be related to identifiable environmental gradients

The Gulf: Facies Belts, Physical, Chemical, and Biological Parameters of Sedimentation on a Carbonate Ramp

The Holocene of The Gulf, also referred to as the Arabian or Persian Gulf, is frequently cited as a classic example of a mixed carbonate-siliciclastic ramp system for an arid climate. This notion of a ramp is supported by the recognition that The Gulf area has a dominant shallow water carbonate/evaporite basin fill from the Permian to today despite a complex tectonic history (Alsharhan and Kendall 2003). The current depositional setting is that of a proximal foreland ramp (Burchette and Wright 1992; Evans 1995; Kirkham 1998). Walkden and Williams (1998), however, argue that since The Gulf has been above sea level for over much of the past 2.5 Ma, and since it is in tectonic, eustatic and depositional disequilibrium it should not be considered a ramp. Despite this controversy, the Holocene sedimentary fill of the current Gulf has been and will continue to be used as a model for a carbonate ramp. This interest in the area is hightened by the fact that is one of the few places in which Holocene dolomite and evaporites form.https://nsuworks.nova.edu/occ_facbooks/1039/thumbnail.jp