Geochemical approach for decoding the paleoenvironmental and depositional evolution of a coastal lacustrine Konservat-Lagerstätte (Early Cretaceous, south-Central Pyrenees)

The lithographic limestone of La Pedrera de Meià (LPM) in south-Central Pyrenees (NE Spain) is considered one the best preserved lacustrine-coastal successions Early Cretaceous Europe, hosting a taxonomically diverse record Barremian biota. While this Konservat-Lagerstätte has been extensively surveyed for paleontological purposes, little known about paleoenvironmental and depositional conditions prevailing during formation fossil lagerstätte deposit. LPM made up homogeneous, dark gray to pale brown, faintly laminated 50 m-thick succession micrite-rich intervals. To shed light on environmental deposition, 303 rock samples were studied using multiproxy approach based different techniques including petrography, SEM-EDX, XRD, ICP-MS, XRF, Rare Earth Element distributions C O stable isotope geochemistry. combination sedimentological geochemical data reveals vertical shift facies from littoral profundal environments then returning conditions. Profundal are filament-rich mudstones originated situ precipitation micrite either through biotically mediated or physico-chemical processes undisturbed low energy settings, under anoxic conditions, characterized by presence transported terrestrial lacustrine organisms that exquisitely well-preserved. Littoral areas charophytes, smooth ostracods, miliolid foraminifera accumulated mud-rich indicating low/moderate-energy, shallow-water, relatively oxygenated Stable isotopic elemental geochemistry suggest hydrologically closed semi-closed system with restricted water circulation encouraging dysoxic sediments. Paleoproductivity proxies good correlation between catchment-derived siliciclastic discharge lake primary productivity peaks. Furthermore, decline terrigenous input coupled reduction meteoric entrance interpreted derived paleosalinity paleoredox analysis. Collectively, strontium/barium (Sr/Ba) ratios, sparse foraminifera, signatures indicate an increase salinity toward younger intervals infilling, although their ultimate causes unclear (i.e., increased evaporation, reduced sporadic marine inputs might explain our data). present work shows importance performing detailed geochemical-sedimentological studies better constrain unique paleohydrological associated exceptional preservation biotas deposits analogous settings.