PLANT SUBSTRATE INTERACTIONS PRESERVED IN PALEOSOLS FROM CAPACETE FORMATION, SANFRANCISCANA BASIN, MINAS GERAIS, BRAZIL

PLANT SUBSTRATE INTERACTIONS PRESERVED IN PALEOSOLS FROM CAPACETE FORMATION, SANFRANCISCANA BASIN, MINAS GERAIS, BRAZIL

Plant-related sedimentary structures remain poorly documented in the geological record, despite the widespread occurrence of root traces and in situ plant stumps in numerous Brazilian geological units. Vegetation-induced sedimentary structures (VISS) form when plants act as hydrodynamic obstacles in fluvial environments, altering flow patterns, reducing turbulence and velocity, and generating deformed bedding around progressively buried trunks. These interactions demonstrate how vegetation impacts sedimentary and weathering processes through substrate colonization and stabilization. This study investigates plant-sediment interactions through ichnofabric analysis of root traces and VISS in fluvial deposits and paleosols of the Campanian Capacete Formation (Sanfranciscana Basin, SE Brazil). Results indicate that rhizohaloes were produced by shrub vegetation colonizing proximal floodplains with elevated water tables, as evidenced by redoximorphic features associated with rhizoliths and paleopedological features. In contrast, large root casts are linked to trees occupying distal floodplain. In distal floodplain associated with rhizoliths asymmetrical, upturned and folded beds that are interpreted as VISS associated with root casts imply the former presence of standing trees that were progressively buried, degraded, and partially preserved. Crevasse-splay deposits migrated into these distal tree-colonized areas, burying vegetation that withstood exceptional flooding and survived initial burial. This process reflects the alluvial plain progressive infilling and suggests plant recovery after flood events. The rhizohaloes and root casts represent two different taphonomic pathways associated with water table behavior and soil development. The Capacete Formation preserves diverse plant-substrate interactions, including rhizoliths, paleosols, and VISS linked to standing trees. Root casts associated with VISS provide critical evidence of vegetation-sediment interactions and biogeomorphological processes even in the absence of plant fossils. FAPESP 22/16353-9; FAPEMIG APQ-00458-21