Search results for "Structural geology"
showing 10 items of 48 documents
Sedimentary dynamics and structural geology of pre-rift deposits of the interior basin of Gabon
2002
Abstract Recent studies combining field data (facies and paleocurrent analyses, structural surveys), sub-surface data (core analyses, well logs, seismic sections) and palynological data provide insight into the sedimentary dynamics of pre-rift deposits of the interior basin of Gabon and their structural and paleoclimatic setting. These sedimentary deposits belong to the Noya, Agoula and M’vone series of Late Precambrian to Jurassic age. Although these deposits are potential sources of petroleum, they are partly known because of poor outcrop in a wet equatorial climate, low density and uneven distribution of exploration wells and poor seismic survey coverage. The pre-rift deposits reflect fl…
A Framework of Microtectonic Studies
1998
From their first use in the last century, thin sections of rocks have been an important source of information for geologists. Many of the older textbooks on structural geology, however, did not treat microscopic aspects of structures, while petrologists would describe microscopic structures as, for example, lepidoblastic or nematoblastic without paying much attention to kinematic and dynamic implications. During the last decades, however, structural geologists learned to profit from the wealth of data that can be obtained from the geometry of structures studied in thin section, and metamorphic petrologists have appreciated the relation of structural evolution on the thin section scale and m…
Collapse structures in the Permian of the Saar-Nahe area, Southwest Germany
1971
Volcanic breccias near an intrusive rhyolite dome in the Permian Saar-Nahe trough of southwest Germany have been identified as complex pipe-like subsidence-structures occupying the site and immediate neighbourhood of “explosive” volcanoes.
Rb-Sr geochronology in favour of polymetamorphism in the Pan African Damara belt of Namibia (South West Africa)
1978
New Rb-Sr whole rock age data are reported from two metasedimentary sequences of the Damara Supergroup in the central Pan African Damara belt of Namibia (South West Africa).
Deformation and metamorphism at the base of the Helgeland nappe complex, northwest of Grong (Northern Norway)
1984
Pelites, carbonate-silicate rocks and mafic rocks occurring at the base of the Helgeland nappe complex northwest of Grong (N. Norway) were subjected together with the crystalline basement to medium grade metamorphism and threefold deformation during Caledonian times.
The Nahe Caldera — A resurgent Caldera in the permocarboniferous Saar Nahe basin, SW-Germany
1984
In the Saar Nahe basin, SW-Germany, a large resurgent caldera complex of Lower Permian age was recognized recently, for which the name „Nahe Caldera” is proposed.
Areal extent and first U-Pb age of the Pre-Damaran Abbabis complex in the central Damara belt of South West Africa (Namibia)
1978
The Proterozoic Abbabis Complex emerges from beneath the metasediments of the Late Precambrian Damara Supergroup within mantled gneiss domes and anticlinoria over a wide area in the central granite zone of the Pan African Damara belt. U-Pb dating of composite-, size-, and non-magnetic fractions of metamict zircons from two samples of Abbabis granite-gneiss from the farm Abbabis yielded a concordia intercept age of 1925 −280 +330 Ma. It is speculated that the Abbabis basement rocks are continuous under the Damaran metasedimentary cover and may link up with the Franzfontein basement inlier of similar age. This conclusion supports the ensialic character of the northeastern branch of the Damara…
Interaction between seismicity and deformation on different time scales in volcanic areas: Campi Flegrei and Stromboli
2019
We study oscillations recorded at Stromboli and Campi Flegrei by different sensors: seismometers, strainmeters and tiltmeters. We examine both the high-frequency (>0.5 Hz) portion of the spectrum and very long period signals up to tidal scales. In this context, seismicity and deformation are investigated on different time scales (from minutes to days/years) in order to identify the basic elements of their interaction, whose understanding should provide new insights on the predictive models. In this work, the strict relation of tides and volcanic processes is shown. At Stromboli, indeed the transition from the stationary phase to the non-stationary phase seems to have a tidal precu…
Integration of onshore and offshore seismic arrays to study the seismicity of the Calabrian Region: a two steps automatic procedure for the identific…
2014
Abstract. We plan to deploy in the Taranto Gulf some Ocean Bottom broadband Seismometer with Hydrophones. Our aim is to investigate the offshore seismicity of the Sibari Gulf. The seismographic network optimization consists in the identification of the optimal sites for the installation of the offshore stations, which is a crucial factor for the success of the monitoring campaign. In this paper, we propose a two steps automatic procedure for the identification of the best stations geometry. In the first step, based on the application of a set of a priori criteria, the suitable sites to host the ocean bottom seismic stations are identified. In the second step, the network improvement is eval…
Distribution of radioactive elements in three progressively metamorphosed pelite series of the Bohemian Massif
1980
The variations of the content of radioactive elements in pelitic rocks in dependence on the grade of metamorphism were studied in three regions of the Bohemian Massif with a different character and age of metamorphism. The concentrations of Th, U and K were determined by gammaspectrometric method, the major elements Si, Ti, Al, Fe, Mn, Ca, K, P by the X-ray fluorescence method. An increasing mobility of radioactive elements was found with the help of variation diagrams in the higher stages of metamorphism, the migration being apparent especially for Th and usually starting in the garnet or biotite zone. A significant negative correlation of both Th and U content with the content of SiO2 was…