Changes in climate and palaeoenvironment during the Late Jurassic–Early Cretaceous in southern South America and western Antarctica

• Main Author: Brysch, Sven
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2018
• Subjects: 550; 550 Earth sciences; Antarc*; Antarctica; Antártica
• Online Access: https://archiv.ub.uni-heidelberg.de/volltextserver/25582/; https://archiv.ub.uni-heidelberg.de/volltextserver/25582/1/Dissertation_Brysch.pdf; https://doi.org/10.11588/heidok.00025582; https://nbn-resolving.org/urn:nbn:de:bsz:16-heidok-255829

The palaeoenvironmental changes of Upper Jurassic (Middle Tithonian) to Lower Cretaceous (Lower Albian) sediments are here analysed along a North-South transect following the southwestern margin of Gondwana (central Chile, Patagonia, and Antarctica). The focus of this high-resolution multidisciplinary study is paid to climatic perturbations, which are evident in palynofacies and lithofacies records as well as by presence/absence of the cold-water indicative mineral glendonite. In central Chile two sections corresponding to the Tithonian–Hauterivian Lo Valdés Formation were analysed from the Mendoza-Neuquén backarc basin. An uppermost Tithonian unit was identified which corresponds to a relatively low sea level and deposition in proximal to inner platform environments. This interval is followed by a transgressive interval in the Berriasian, leading to deep shelf to basin depositional settings. The early–Middle Valanginian shows again a relatively low sea level with inner platform to slope deposits, followed by a second transgressive phase in the Upper Valanginian to Hauterivian at the top of the sections, represented by deep shelf to basin deposits. Sedimentary organic matter (OM) in the sections is intensely altered by thermal degradation and mostly consists of terrestrial OM with only very minor amounts of marine OM. Calpionellids are found in the Berriasian interval, indicating warm, oxygen-rich conditions at least for the water column. Corresponding to both intervals of low sea level (uppermost Tithonian, early–Middle Valanginian) microscopic glendonite was identified in the insoluble sample residue. The occurrence of glendonites in these shallow marine shelf environments indicates cold water temperatures and thus provides evidence for significant climatic cooling in the latest Tithonian and early–Middle Valanginian. In Patagonia (Región de Magallanes y de la Antártica Chilena) drilled core cuttings of two wells were analysed reaching from the Tithonian to Berriasian and Hauterivian to Aptian (Sofia 1 core – ...