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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]

Palaeosols are common in sedimentary successions of continental origin, and notably they comprise the majority of the thickness of some accumulated successions of fluvial origin. Yet, detailed investigation of palaeosols and evaluation of their palaeoenvironmental significance are not routinely undertaken in detail in many sedimentological studies. A careful analysis of palaeosols may, however, reveal that sedimentary units, which appear similar if based solely on the facies analysis, indeed show strongly distinct palaeoenvironmental and depositional characteristics. This is the case of the upper portion of the Bauru Group, a 100–190 m-thick Maastrichtian red sandstone unit of fluvial origin, present over an area of c. 180,000 km2 in south-eastern Brazil. In this study, the palaeosols of this unit, which constitute 25–92 % of the succession by thickness, are used to decipher palaeoenvironmental climate conditions, sediment source areas, and relationships between pedogenic and depositional processes. Through the combined study of macroscopic, micromorphological, and geochemical aspects of the palaeosols and of facies analysis of the deposits, the upper portion of the Bauru Group succession is separated into three sectors: north-western, north-eastern, and south-eastern. Although these three areas are all characterised by similar lithology types and lithofacies, indicative of deposition in alluvial systems, the palaeosol analysis highlights that they were each characterised by different climate, different clastic source areas and different dynamics and interaction of the pedogenic and sedimentary processes. This research reveals the critical significance of the palaeosols for discriminating otherwise apparently similar depositional units. [Display omitted] • Palaeosols are significant proxies for stratigraphy and palaeoenvironmental studies. • The upper Bauru Group was considered a homogenous depositional system. • Palaeosols demonstrate the upper Bauru Group comprises three depositional systems. • Studies involving continental deposits cannot ignore the analysis of palaeosols. [ABSTRACT FROM AUTHOR]

The lateral and vertical distribution of sedimentary facies and ichnofacies in lacustrine systems records sensitive climatic variations and rates of subsidence. The Upper Jurassic–Lower Cretaceous lacustrine system of the Pastos Bons Formation in the Parnaíba Basin, northeastern Brazil, is an excellent opportunity to evaluate the depositional history of the post-CAMP thermal subsidence. This subsidence event succeeded the voluminous emplacement of mafic magma linked to the Central Atlantic magmatic province (CAMP), ∼201 Ma, forming a large subsiding area in West Gondwana. In this sense, this paper developed outcrop-based facies and ichnofacies analysis, allowing the interpretation of two depositional phases and four facies associations (FAs): 1) The lower depositional phase comprises lacustrine deposits showing an aggradational stacking pattern. FA1 - central lake records fibrous gypsum interbedded with fossiliferous shale beds, forming shallowing-upward cycles. 2) The upper depositional phase reveals a fluvio-lacustrine succession, forming a progradational stacking pattern. Central lake (FA1) comprises laminated mudstone and sandstone beds hosting a suite representative of Mermia ichnofacies, forming coarsening-upward cycles. Lakeshore (FA2) comprising mudstone beds, limestone lenses, and sandstone beds hosting a suite representative of Scoyenia ichnofacies, forming shallowing-upward cycles; and conglomerate lenses overlaid by sandstone beds hosting a suite representative of Skolithos ichnofacies, forming fining-upward cycles. A braided fluvial system (FA3) comprises conglomerate and sandstone beds, forming fining-upward cycles. Delta front (FA4) comprises mudstone lenses and sandstone beds hosting a suite representative of Skolithos ichnofacies, organized in coarsening-upward cycles. The fluvial discharge and wave activity oxygenated the water lake in the progradational phase, creating chemical and biological conditions that allowed the establishment of the epifaunal and infaunal benthic communities, represented by the well-preserved ichnological record. The decrease of the post-CAMP thermal subsidence rates (accommodation potential) related with the increase of the wet periods to the top of the succession (sedimentary supply) indicate a depositional evolution from underfilled to overfilled lake basin, during Upper Jurassic–Lower Cretaceous, in West Gondwana. [ABSTRACT FROM AUTHOR]