Pliocene Basalts Research Articles

Geology of a portion of the north wall of the Puerto Rico Trench

Rocks dredged from the north wall of the Puerto Rico Trench represent a thick accumulation of rock types consisting of siliceous mudstones, cherts, basalts, serpentinites and minor amounts of volcanic wackes, carbonaceous material and limestones, all of which formed in a submarine environment. A tentative stratigraphie sequence of the north wall in ascending order is Cenomanian limestone, Upper Cretaceous siliceous mudstones and cherts, Upper Cretaceous-Eocene limestones, Upper Cretaceous-Eocene serpentinites, Eocene-Pliocene siliceous mudstones and cherts, pre-Pliocene volcanic wackes, Pliocene basalts and Pliocene-Recent unconsolidated sediments. Two main fault patterns are apparent in the area of study and trend east-west and northwest-southeast. The east-west faults are older and are terminated by those trending northwest-southeast. Magnetic susceptibility, remanent magnetism and Qn values obtained from the rocks indicate that permanent polarization is responsible for the geomagnetic anomalies measured at sea.

Paleomagnetism of Pliocene Basalts from the Southwestern U. S. A.

Paleomagnetism of Pliocene Basalts from the Southwestern U. S. A.

Caracteres mineralogiques et chimiques des ordanchites de la vallee de la Santoire (massif du Cantal)

Abstract Ordanchite is relatively rare in the volcanic rocks of the Cantal massif of the Auvergne region of France. It occurs as short, thin coulee flows overlain by the last Pliocene basalt flows, and also as blocks in pyroclastic deposits. It is more siliceous and alkaline than the ordanchite of the Mont Dore massif adjacent on the north, and resembles phonolite and basalt.

Quelques particularites de la partie nord-ouest du volcan cantalien (region des Rhues et de la Sumene)

Abstract The Miocene basalts at the base of Cantal volcano are exposed at approximately uniform heights in the valleys of the area, indicating that there ought to be a branching internal basaltic lava flow with an origin and extent similar to the upper Pliocene basalts of the plateaus. The igneous breccias in the Auzers area exhibit an abnormal thickness of 170 meters. The northwest part of the Moussage lava field, formed of the plateau basalts, is overlain by the Suc du Rond flows indicating that the Suc du Rond basalts, and not those of the plateau, represent the last phase of the Cantal eruption.

The geology of the Cape Rodney — Kawau district, Auckland

Summary Five lithological groups overlain by Recent deposits are recognised. Otaian (Oligocene) sandstones and mudstones with associated andesitic agglomerates overlie argillaceous limestones of probable Bortonian (Eocene) age. These strata, with gently undulating or horizontal attitudes lap on to highly-sheared, siliceous claystones resting on a basement of deformed Mesozoic greywackes and argillites which contain interbedded spilites, chert bodies and ores of manganese, iron and copper. The interrelations and origin of the spilitic lavas, chert bodies and copper are discussed. The basement rocks have attained a grade of regional metamorphism equivalent to the chlorite-1 zone of the Otago Schists. The sequence is intruded and overlain locally by Pliocene Basalts.

L'evolution du magmatisme dans le geosynclinal dinarique au Mesozoique et au Cenozoique

Abstract The inner and outer zones of the Dinaric Alps of Yugoslavia are compared. With the exception of Triassic porphyrites and quartz porphyrites and small upper Cretaceous rhyolite masses, the outer zone has few igneous rocks. The inner zone, however, was the scene of more extensive magmatic activity, represented by lower and middle Triassic porphyrites, Jurassic gabbros, melanophyres, and diabases, Oligocene and Pliocene granodiorites, andesites, dacites, and quartz monzonites, and late Pliocene andesites, basalts, and leucite basalts.

Observations sur le volcanisme et le glaciaire de la region des Rhues (Haute- Auvergne)

Abstract The first part of the paper deals with the volcanic complex of the Limon plateau in the upper Auvergne region, France. Successive eruptions of Miocene basalts, andesites and their breccias, phonolites, and finally Pliocene basalts took place. A new volcanic center has been located in the region. The second part concerns Pleistocene glaciation in the region and its effect on drainage, particularly on the course and profile of the Dordogne.