Volcanoclastic and epiclastic diagenesis of sandstones associated with volcano-sedimentary deposits from the upper Jurassic, Lower cretaceous, Paraná Basin, southern Brazil

• Published in: Journal of South American earth sciences 2023-08, Vol.128, p.104466, Article 104466
• Main Authors: Rios, Fernando R., Mizusaki, Ana M.P., Michelin, Cassiana R.L., Rodrigues, Isaque C.
• Format: Article
• Language: English
• Subjects: Chalcedony cement; Contact diagenesis; Lava-sediment interaction; Paraná basin; Zeolite cement
• ISSN: 0895-9811; 1873-0647
• DOI: 10.1016/j.jsames.2023.104466

The opening of South Atlantic Ocean produced an immense volume of lava that covered an active aeolian system during Lower Cretaceous. The contact of Botucatu Formation sandstones with the Serra Geral volcanic flows generated a variety of volcano-sedimentary features and deposits. During volcanism, the temperature contrast between lava and wet or water-saturated sediments formed volcanoclastic features and related sedimentary deposits. In moments of magmatic quiescence, epiclastic deposits were generated due to the return of sedimentation. Volcanoclastic deposits include volcanic breccias with sandy matrix, and epiclastic deposits include conglomerates and conglomeratic sandstones with intraclasts. Quantitative petrography of the sandy matrix samples of these deposits was analyzed, in order to discuss the paragenesis of volcano-sedimentary interactions. Regular burial diagenetic processes were discussed for epiclastic sandstones and contact diagenesis processes for volcanoclastic sandstones. The original composition of volcanoclastic and epiclastic sandstones is heterogeneous. However, the main difference between them is the presence of textural fluidization indicators found in the volcanoclastic sandstones, along the lava-sediment interface. These textural characteristics indicate that the unconsolidated sediments were probably wet or saturated in water during the interaction with the volcanic flow. Epiclastic sandstones have infiltrated clays and neoformed smectites as their main diagenetic constituent due to alteration of available volcanic lithoclasts. For volcanoclastic sandstones, the formation of opal, chalcedony and megaquartz cements through burial is unlikely, due to the intergranular volume occupied by these cements, indicating near-surface early diagenetic conditions. Therefore, the mechanisms of dissolution and repreciptation of the siliceous fluids, incorporated in the system, formed mainly the chalcedony cementation. Furthermore, zeolite cementation, which occurs along the lava-sediment contact, is another important indicator of contact diagenesis for volcanoclastic sandstones. During telodiagenesis, the formation of secondary porosity by dissolution of volcanic lithoclasts and detrital K-feldspar grains was of great importance in volcanoclastic and epiclastic sandstones. •Diagenesis in a volcano-sedimentary context.•Epiclastic and volcanoclastic sandstones diagenesis.•Diagenesis during Upper Cretaceous and Lower Jurassic.•Contact diagenesis