T237 Insights from Microfossils and Their Modern Analogs: From Traditional and Emerging Approaches, to Critical Re-Evaluations (Posters)

Wednesday, 18 October 2023
8:00 AM - 5:30 PM
Hall B

ORGANIC WALLED MICROFOSSILS FROM WET PEPERITES IN THE PARANÁ-ETENDEKA INTERTRAPS

Paper number: T237-1
Program: Technical Sessions
Time: 8:00 AM – 5:30 PM

Authors

Abstract

Large igneous provinces (LIPs) have significant global environmental and biospheric impacts, including triggering mass extinctions. While LIPs offer valuable sedimentological and geochemical records of intense geological activity in deep time, their igneous origin limits their contribution to understanding ancient life. In this study, we present the first paleontological evidence of organic walled microfossils extracted from wet peperites, which are volcanoclastic rocks formed by the interaction of lava and subaqueous sediments. These peperites were found in the early Cretaceous Paraná-Etendeka intertraps of the Paraná basin in Brazil. The Paraná-Etendeka LIP was a continental flood basalt formed approximately 132 million years ago in South America and Namibia, releasing large quantities of sulfur dioxide, methane, and hydrogen fluoride into the atmosphere. The recovered microfossils from the wet peperites include pollen grains, spores, various sporomorphs, acritarchs, and other unidentified organic remains (possible tardigrade eggs). Organic-walled microfossils were also discovered in volcanoclastic sandstones and interpillow sandstones. Most microfossils exhibited pale yellow to dark colors and exhibited two degrees of preservation potential. Some microfossils displayed ornamentations such as ridges or saccis, while others had iron oxide inclusions or coverings identified as hematite. The distribution and preservation of organic-walled microfossils varied within the primary volcaniclastic deposits, with wet peperites containing better-preserved specimens compared to heterolhitic sandstones, dry peperites, and interpillow deposits. Our findings provide the first view of the extinct biodiversity of the Paraná basin during the early Cretaceous, a period characterized by intense magmatism. The microfossil assemblages support a regional paleoclimatic transition from arid to more humid conditions likely influenced by volcanic activity. This study highlights the potential of wet peperite rocks as valuable sources of paleobiological data and underscores the importance of sampling volcaniclastic units previously considered unfossiliferous due to their igneous origin.

Geological Society of America Abstracts with Programs. Vol. 55, No. 6

doi: 10.1130/abs/2023AM-390656

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