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The Jurassic-Cretaceous transition was marked by the fragmentation of the West Gondwana supercontinent and consequent opening of the Atlantic Ocean. This event resulted in extensive lava flows in the central portion of West Gondwana, composing the Central Atlantic Magmatic Province. In the Parnaíba Basin (NE Brazil), a large lacustrine system succeeded this event; nevertheless, the post-CAMP scenario and the influence of the decreasing isotherms in the Mesozoic sedimentation are poorly understood. In this sense, cyclostratigraphy and outcrop-based facies analysis were carried out in the lacustrine stratigraphic record, allowing the recognition of four paleoenvironments: central lake, sheet-like delta front, lakeshore and ephemeral fluvial channels, mainly organized in shallowing upward cycles. The upsection transition of thin black shales and limestones to thick oxidized mudstones and stratified sandstones reflects the evolution of underfilled to overfilled lake settings. The lacustrine succession is organized in four major depositional cycles, characterized by millimeter to centimeter-scale cycles, bounded by unconformities or flooding surfaces. The cycles define a retrogradational-progradational-retrogradational stacking pattern, with random and frequent changes in lithology and cycle thickness. Cyclostratigraphic data suggest that the upward increasing accommodation space was controlled by the post-CAMP thermal subsidence, as well as shifts in sedimentary supply and water inflow/outflow. The time span of this subsidence phase lasted from even before the CAMP magmatism (~200 Ma), affecting the whole deposition of the lacustrine succession, and was interrupted by the Cretaceous magmatic event (~126 Ma). Subsidence was also enhanced by crustal loading associated with thick subsurface Jurassic intrusions and probably influenced the whole basin, in consequence of flexural effects. • A lacustrine depositional system is defined by cyclostratigraphy and facies analysis. • Facies are mainly organized in shallowing upward cycles. • The lacustrine succession evolves from an underfilled to an overfilled lake system. • The cycles define increasing accommodation space upsection. • Geological and geophysical data suggest a post-CAMP thermal subsidence. [ABSTRACT FROM AUTHOR]

Fossil bonanzas called Konservat Lagerstätten provide geological windows to the ecology of ancient life communities. These deposits often occur as cluster of fossil localities with similar geographic locations, geological ages and facies, as the fossils were generally preserved during special periods and large-scale events in Earth history within environments with exceptional taphonomic conditions. This work applied petrological and geochemical analyses to evaluate the taphonomic pathway of a Konservat Lagerstätten in the Muzinho Shale, Upper Jurassic-Lower Cretaceous of the Parnaíba Basin, northeastern Brazil. These lacustrine deposits include interbedded limestones and fossiliferous black shales deposited in anoxic, non-euxinic and saline environment. Black shales contain articulated skeletons of fish fossils, characterised by three-dimensional preservation of the skeletal tissue. The polytypical assemblage includes diverse ontogenetic stages and is concentrated in a specific stratigraphic level. Mass mortality was triggered by anoxia probably established by stratified water column, high C flux and thermocline demise. The specimens are encased in kerogen-bearing siliciclastic laminae and cementstone microfacies, both microbially-induced. The fossils were cemented by eodiagenetic poikilotopic calcite that filled the skeletal articulation, including bone trabeculae and voids originally filled by bone marrow. The short distance, similar fossil assemblages, ages and coincident palaeoenvironments suggest that Muzinho Shale (Parnaíba Basin) and Crato Formation (Araripe Basin) compose a cluster of exceptional preservation in West Gondwana. Lava flows and outgassing related to the Central Atlantic Magmatic Province (CAMP) resulted in the subaereal exposure of volcanic plains, acid rains and subsequent CO 2 greenhouse crisis. CAMP-magmatism was especially voluminous in northern Brazilian basins, enhancing nutrient-rich waters and lacustrine eutrophication due to intensified chemical weathering in this area. Probably, other Konservat Lagerstätten remain unreported in West Gondwana. Despite similar causative events, the individual taphonomic pathways of Muzinho Shale and Crato Formation are very different, suggesting that in these cases local phenomena affected authigenesis and diagenesis. • Exceptionally preserved fossils are evaluated through petrography and geochemistry. • Three-dimensional preservation of bone tissue allows proposing a new Lagerstätte. • CAMP-related magmatism and intensified chemical weathering triggered eutrophication. • Similar location and geological data suggest clusters of exceptional preservation. • Despite similar taphonomic pathways, autogenic factors control fossildiagenesis. [ABSTRACT FROM AUTHOR]