Search for dissertations about: "geochronology"

Showing result 21 - 25 of 53 swedish dissertations containing the word geochronology.

2. 21. Geography and geometry of pre-Caledonian western Baltica: U-Pb geochronology and Palaeomagnetism

   Author : Emma Rehnström; Berggrundsgeologi; []
   Keywords : NATURVETENSKAP; NATURAL SCIENCES; Physical geography; geomorphology; pedology; cartography; climatology; Fysisk geografi; geomorfologi; marklära; kartografi; klimatologi; Fennoscandia; correlations; Baltica; Early Palaeozoikum; palaeogeography; orthogneisses; nappes; palaeomagnetism; U-Pb geochronology; Caledonian orogen; Scandinavia;

   Abstract : In an attempt to reconstruct the pre-Caledonian cratonic margin of Fennoscandia, U-Pb geochronological and geochemical investigations have been performed on allochthonous orthogneisses in the northern Swedish Caledonides. The crystalline basement of the nappes have also been examined to further constrain the continuation of various chronologically defined orogenic belts. READ MORE

4. 22. Crustal evolution of the Arabian–Nubian Shield : Insights from zircon geochronology and Nd–Hf–O isotopes

   Author : Fitsum Girum Yeshanew; Victoria Pease; Martin J. Whitehouse; Robert J. Stern; Stockholms universitet; []
   Keywords : NATURVETENSKAP; NATURAL SCIENCES; Gondwana; Arabian–Nubian Shield; Azania; zircon U–Pb–O–Hf isotopes; Nd isotopes; Cambrian Sandstones; juvenile; pre–Neoproterozoic; reworking; Geology; geologi;

   Abstract : The Arabian–Nubian Shield (ANS) represents a major site of juvenile Neoproterozoic crustal addition on Earth and documents Neoproterozoic tectonics bracketed by two supercontinent cycles, namely the fragmentation of Rodinia and the amalgamation of Gondwana. There is general consensus that the ANS formed by juvenile magmatic arc accretion and subsequent shield–wide post–tectonic magmatism. READ MORE

5. 23. Precambrian Crustal Evolution of the Rehoboth Province, Southern Africa

   Author : Valby van Schijndel; Göteborgs universitet; []
   Keywords : NATURVETENSKAP; NATURAL SCIENCES; Rehoboth Province; Rehoboth Basement Inlier; Kaaien Terrane; Dwyka Diamictite; U–Pb; Sm–Nd; Lu–Hf; Ar–Ar Geochronology; Oxygen isotopes; Zircon; Baddeleyite;

   Abstract : This thesis uses U-Pb, Sm-Nd Lu-Hf, Ar-Ar and Oxygen isotope data on well-documented rock samples, to investigate crustal evolution of the Precambrian Rehoboth Province of Southern Africa. This province is defined by its smooth magnetic character, reflecting deep magnetic basement in contrast to the adjoining mobile belts and the Kaapvaal Craton. READ MORE

6. 24. Assembly of the Caledonian Orogenic Wedge, Jämtland, Sweden

   Author : Hagen Bender; Uwe Ring; Bjarne SG Almqvist; Rob Strachan; Stockholms universitet; []
   Keywords : NATURVETENSKAP; NATURAL SCIENCES; collisional orogeny; Scandinavian Caledonides; Seve Nappe Complex; Köli Nappe Complex; in-sequence thrusting; out-of-sequence thrusting; imbrication; nappe stacking; orogenic wedge assembly; Rb–Sr geochronology; rock magnetism; anisotropy of magnetic susceptibility; Geology; geologi;

   Abstract : Collisional orogeny creates the largest mountain belts on Earth. The Caledonides of Scandinavia are a deeply eroded, ancient mountain belt, which today exposes a deep section through the former orogenic interior. READ MORE

7. 25. Geochronology of the Oklo and Bangombé fossil natural fission reactors : tracing the effects of geological events

   Author : Lena Zetterström Evins; Ian Williams; Stockholms universitet; []
   Keywords : NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; Historisk geologi; Geology; geologi; geokemi; Geochemistry;

   Abstract : Thesis to be publicly defended for the degree of Doctor of Philosophy, in lecture room De Geersalen, Svante Arrhenius väg 8a, Stockholm, Friday February 1, 2002 at 10.00 am. Two billion years ago, natural fission reactions took place in the Oklo and Bangombé uranium ores in Gabon, West Equatorial Africa. READ MORE