Studies of distributive fluvial systems and their preserved successions envisage the distribution and orientation of architectural elements to be primarily controlled by channels radiating outward from fan apices, in many cases along an elongate basin margin. Conceptual models for such systems account for the downstream dynamics of the fluvial network, but with limited consideration of temporal geomorphic variations, resulting vertical organisation of architectural elements, or of the interplay of factors controlling system dynamics. To understand the external and internal architecture of distributive fluvial systems, and the factors that influence their sequential facies organisation, a sedimentary succession of the proximal portion of an Upper Cretaceous, semiarid, distributive fluvial system, located at the northeastern margin of the Bauru Basin (Southeast Brazil), has been analysed in detail. Three fining-and thinning-upward fluvial sequences are identified, forming an interval separated at the top and the bottom by two palaeosol profiles. Each sequence is formed of channel and floodplain deposits. Two types of channel deposits are identified. One is composed of stacked sets of small-scale dune deposits, suggesting perennial and steady fluvial regime, associated with more humid climate periods. The other is composed of large-scale sets indicative of flattened dunes associated with unsteady and fast-changing fluvial flow, formed in quasi-supercritical flow regime conditions, associated with drier climate periods. The vertical alternation of these two types of channel deposits records the accumulation of a fluvial succession that responded to high-frequency, climateinduced cyclic change in bounding conditions. Two palaeosol profiles, at the top and at the bottom of the succession, indicate temporary interruptions and cessation of the fluvial sedimentation, likely related to avulsion of the fluvial belt. Thus, the studied succession reveals high-frequency climateinduced allogenic sedimentary cycles that occur within a long-period autogenic geomorphologicinduced sedimentary cycle. This work suggests that the internal architecture of the channel deposits can be used as a climate proxy, and that climate and geomorphology act jointly as notable factors to control the vertical organisation of distributive fluvial systems.

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Coquinas constitute widespread deposits in lacustrine, estuarine, and shallow marine settings, where they are a valuable source of information on environmental conditions. Thick coquina successions were deposited in a series of lacustrine rift basins that formed along the Brazilian Continental Margin during the early stages of the opening of the South Atlantic Ocean, in the Early Cretaceous. In the Sergipe–Alagoas Basin, the coquina sequence, equivalent to the Morro do Chaves Formation, crops out in the Atol Quarry, and is considered a relevant analog for the economically important hydrocarbon reservoirs in the Pre-salt strata (Barremian to Aptian) of the Campos Basin (Pampo, Badejo, and Linguado oil fields), which occur only in the subsurface. The aim of this study is to generate a depositional and stratigraphic model through facies and stratigraphic analyses of a well core. These analyses allowed the geological characterization of the Morro do Chaves Formation and of its transition to the adjacent stratigraphic units, the Coqueiro Seco Formation above and the Penedo Formation below, contributing to the growing knowledge of sedimentation in rift basins and exploratory models in hydrocarbon-producing reservoirs. Facies analysis consists of sedimentological, taphonomic, and stratigraphic features of the rocks. Fourteen depositional facies were recognized, stacked into low-frequency and high-frequency, deepening-upward and shallowing-upward cycles driven by the interaction between climate and tectonism. A depositional model is presented, based on the correlation between well-core and outcrop data described in previous studies, providing insights into the spatial distribution of facies. The detailed analysis of facies and stacking patterns sheds light on depositional processes, paleoenvironmental conditions, and the evolution of the system through time, so we may better understand analogous deposits in the geological record.

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Studies of the palaeobiology of titanosaur eggs are significantly more common than studies of titanosaur-egg-bearing strata. Nevertheless, the latter provide significant insight into palaeoenvironmental conditions associated with the egg-laying behaviour. This study examines titanosaur-egg-bearing strata of the Upper Cretaceous Los Llanos Formation (La Rioja, Argentina) and relates them to the laying and preservation of titanosaur egg clutches. Los Llanos Formation is a predominantly sandstone succession throughout represented by palaeosol profiles. Five titanosaur egg clutches were recovered from the Bw horizon of an Inceptisol profile. This palaeosol type, named

Conceptual models developed from modern distributive fluvial systems (DFSs) show a predictable spatial variation of facies progression from the margin to the interior of continental sedimentary basins. The Upper Cretaceous Serra da Galga Member of the Marília Formation has recently been interpreted to be a result of DFS deposition in the intracratonic Bauru Basin. This paper describes the spatial variations in stratigraphic architecture from the proximal to medial regions of the studied DFS and presents the implications of the recorded changes for fluvial reservoir characterization. The proximal areas are dominated by amalgamated channel-fill deposits and weakly developed, well-drained palaeosol profiles with only sparse floodplain deposits. The medial areas display a reduction in channel-fill deposits, an increase in the preserved thickness of floodplain deposits and the occurrence of sheetflood deposits and well-developed, poorly drained palaeosols. This spatial trend is accompanied by changes in the net : gross ratios of the geological bodies, forming possible high net : gross reservoirs in the proximal areas and reservoirs with very variable net : gross ratios in the medial areas. This down-system change in preserved stratigraphic architecture is evidenced for the first time in the studied sedimentary succession and follows the same pattern of facies progression described from modern examples of DFSs.

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