Recycling and chemical weathering in tectonically controlled Mesozoic–Cenozoic basins of New Zealand

摘要: Sedimentation in molasse basins is controlled by tectonics, however, recycling and chemical weathering play a critical role the compositional evolution of sedimentary succession. The Cretaceous to Pliocene deposits Central Otago, New Zealand are excellent examples tectonically related that were governed effects recycling. Preserved fault-controlled floored flysch Otago Schist, clastic successions contain ubiquitous unconformities lithofacies consistent with alluvial, fluvial lacustrine depositional settings. Textural analysis sandstones establishes general quartz enrichment increased mixing angular well-rounded varieties up-section, history sediment Rare earth element (REE) patterns, which reflect upper crustal compositions, similar for flysch-type Schist (Permian–Early Cretaceous), palaeo-weathering profile, overlying deposits. development arenites also high degrees weathering, erosion schist basement, contains numerous veins. Although has occurred, SiO2 TiO2 do not consistently show negative correlation over time. This reflects previously deposited quartz-rich produced an inverse stratigraphy. CIA values range from 52 lithic-rich, coarse-grained polymictic conglomerate matrices, 93 pebble-rich arenites. Individual samples split into finer- coarser-grained pairs (<2·5φ 2·5 −1φ) analysed separately. results finer-grained higher REE abundances less SiO2, but Miocene–Pliocene have than their counterparts. These plot erratically on tectonic discrimination diagrams, implying using SiO2-poor more reliable geochemical analysis. Overall, petrographic indicate main factors controlling composition source composition, Studies this nature can be conducted Archaean affected allocyclic factors.