Fossil Palaeoweathering Profiles and their Relation to Deformation at Basement-Cover-Interfaces : Case studies from Israel, Sweden and Spain

• Main Author: Angerer, Thomas
• Format: Doctoral or Postdoctoral Thesis
• Language: German
• Published: 2007
• Subjects: 550; 550 Earth sciences; Fennoscandian
• Online Access: https://archiv.ub.uni-heidelberg.de/volltextserver/7413/; https://archiv.ub.uni-heidelberg.de/volltextserver/7413/1/dissertation_angerer_print.pdf; https://archiv.ub.uni-heidelberg.de/volltextserver/7413/2/dissertation_angerer_view.pdf; https://doi.org/10.11588/heidok.00007413; https://nbn-resolving.org/urn:nbn:de:bsz:16-opus-74135

Detachment horizons are associated with basement-cover-interfaces in many regions of compressive or extensional regimes. The fabric evolution and alteration of ancient fossil palaeoweathering profiles and their relation to deformation at basement-cover-interfaces are the object of this thesis. Three cases of palaeoweathered granite and one case of folded sedimentary basement rocks are investigated by means of structural, mineralogical, whole-rock geochemical and magnetic susceptibility analyses. In the case study Negev, South Israel, the deformed Roded Granite (Pan-African basement) weathered under warm and humid to (semi-) arid conditions to a saprock-saprolite-laterite sequence, buried beneath Cambrian red beds. The laterite was compacted beneath 2.8 ± 0.1 km overburden to 73% of its original thickness (plane strain). In the case studies Långviken and Hara, Central Swedish Caledonian margin, the deformed Revsund Granite (Fennoscandian basement) weathered in a temperate to cold climate to weathering-breccias, which were buried beneath sequences of Vendian conglomerates and Cambrian black shales, respectively. Caledonian detachment tectonics overprinted and duplicated the autochthonous weathering-breccia in basement slices under anchizonal cataclasis. In the case study Narcea Antiform, Cantabrian Mountains in North Spain, sedimentary basement rocks, folded during the Cadomian orogeny, weathered moderately without significant textural changes in an arid climate and were buried beneath Cambrian siliciclastics. The Variscan Orogeny overprinted the rocks under regional anchimetamorphic conditions. It reactivated the angular unconformity, locally under higher metamorphic conditions causing ductile quartz deformation. The intensity of weathering features, which are preserved in all cases, is a function of proximity to the unconformity. Hydrolysis of Na-feldspar and chlorite is the predominant chemical weathering process, leading to clay precipitation, whole-rock Al-enrichment and Na-, Ca-leaching. SiO2-dissolution and ...