Navegando por Autor "Alessandretti, Luciano"

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Evaluation of distinct soft-sediment deformation triggers in mixed carbonate-siliciclastic systems : lessons from the Brazilian Pre-Salt analogue Crato Formation (Araripe Basin, NE Brazil).
(2022) Varejão, Filipe Giovanini; Warren, Lucas Veríssimo; Simões, Marcello Guimarães; Cerri, Rodrigo Irineu; Alessandretti, Luciano; Santos, Mauricio Guerreiro Martinho dos; Assine, Mario Luis
Soft-sediment deformation structures (SSDSs) are ubiquitous in several depositional sedimentary environments and can be triggered by autogenic- and allogenic-related mechanisms. SSDSs identification in the geological record is more frequent in siliciclastic deposits, from which the most accepted models were developed. Given the fact that carbonate rocks have rapid diagenesis, which results in changes in the rheological behavior of defor- mational processes in short time, these are excellent facies for exploring past deformational mechanisms in a given sedimentary basin. Here, we describe distinct SSDSs developed in mixed carbonate-siliciclastic successions deposited in an Early Cretaceous lacustrine depositional system (carbonate-dominated) subjected to recurrent epicontinental marine ingressions (siliciclastic-dominated). Deformation occur in some siliciclastic intervals but it is more common in carbonate beds. Facies associations analysis combined with detailed outcrop description of the SSDSs allowed the recognition of seismic- and non-seismic-generated structures. Two km-scale, laterally continuous carbonate beds, characterized by deformation-bearing horizons, are interpreted to be the result of seismic shocks. Conversely, most of the recognized SSDSs cannot be confidentially interpreted as seismites. Autogenic triggers and criteria for accessing the origin of deformation mechanisms in both carbonate- and siliciclastic-dominated settings are alternatively proposed. Assessing such criteria is fundamental for differ- entiatte the timing and range of deformation and are here discussed in the context of the offshore petroleum reservoirs in the Brazilian Pre-Salt successions, where lacustrine carbonates were probably subjected to a similiar superposition of syn-sedimentary seismicity and later events of salt-tectonics and hydrotermalism.
Late Permian siliceous hot springs developed on the margin of a restricted epeiric sea : insights into strata-confined silicification in mixed siliciclastic‐carbonate successions.
(2022) Varejão, Filipe Giovanini; Warren, Lucas Veríssimo; Alessandretti, Luciano; Rodrigues, Mariza Gomes; Riccomini, Claudio; Assine, Mario Luis; Cury, Leonardo Fadel; Faleiros, Frederico Meira; Simões, Marcello Guimarães
Hot springs are sources of carbonate minerals in modern settings; however, few fossil structures are recorded in successions older than the Quaternary due to their enhanced erosional potential. >4500 siliceous mounds are recognized in a well-defined level from the upper part of the Permian Teresina Formation (Parana ́ Basin, SE Brazil). Additionally, a new mound level is here reported for the first time about 15 m below the main occur- rence. Remarkable lithological, mineralogical, paleontological and geochemical features characterize the mounds of both levels, pointing to a hydrothermal origin. Therefore, these structures are here called as hot springs. These were originated subaerially, on the margins of a closing epeiric sea developed on a large intra- continental sag basin. Hydrothermal fluids were sourced from deep circulating basin waters that erupted through intraplate deep-rooted faults. Our data suggests that these hot springs were active during distinct cycles of base level variations. Strata-confined silicification was enhanced during periods of high evaporation and hydrother- mal exudation. Finally, the vertical and lateral facies associations of the Permian hot spring succession are compared with modern sites, and implications for the recognition of syn-depositional hydrothermally precipitated silica in ancient sedimentary basins are discussed.
Sedimentary evolution of distributive fluvial systems within intraplate tectonic active basins : case study of the Early Cretaceous Araripina Formation (Araripe Basin, NE Brazil).
(2021) Warren, Lucas Veríssimo; Andrade, André Santiago Martins de; Varejão, Filipe Giovanini; Promenzio, Paloma; Santos, Mauricio Guerreiro Martinho dos; Alessandretti, Luciano; Assine, Mario Luis
The Lower Cretaceous Araripina Formation records deposition in a distributive fluvial system that is a part of the post-rift sequence of the Araripe Basin, NE Brazil. Following the opening of the Brazilian Equatorial Margin, the reactivation of regional faults of the Paleoproterozoic basement resulted in tectonic subsidence and formation of a regional-scale DFS. The Araripina Formation is an up to 40-m-thick succession of rhythmically interbedded sandstone and mudstone, organized in two depositional sequences separated by a regional disconformity. We recognized and grouped nine sedimentary facies into six facies associations that we interpreted as deposits of meandering channels, ribbon channels, minor channels, floodplain, lateral and terminal splays, and distal floodplain. The lower sequence facies associations suggest deposition in the medial to distal part of a distributive fluvial system in a tectonically active, interior basin subjected to episodic flooding. The periodic inundations were responsible for activating ephemeral channels and producing sheetfloods, followed by deposition of lateral and terminal splays in distal flooded areas. Syn-sedimentary deformation structures are present in rhythmite facies (truncating surfaces, load structures, injectite and convoluted folds) in the upper part of the lower sequence. The upper sequence was formed after a period of intense tectonic activity in a large distal floodbasin dominated by suspension. The deposition culminates in an interval with pedogenetic deposits cross-cut by a regional disconformity with the upper Exu Formation. Paleocurrent data from both depositional sequences indicate paleodepositional slope towards southeast and east with source-areas located to the northwest and west. This pattern is similar to that observed in the lower Santana Group and opposite to the westward direction of sedimentary transport in the overlying Exu Formation implying significant change of source region, basin topography and continental paleodrainage in the Araripe Basin after the Albian.
Uplifting mountains and shaking deserts : volcano-tectonic earthquakes revealed by soft-sediment-deformation structures in Upper Cretaceous aeolian deposits.
(2023) Alessandretti, Luciano; Warren, Lucas Veríssimo; Varejão, Filipe Giovanini; Rassi, Raul; Santos, Mauricio Guerreiro Martinho dos; Silva, Mariana N. M.; Honorato, Fernando Resende; Estrada, Michele Jessica Teixeira; Cunha, João V. O.
During the last stages of Gondwana fragmentation, large regions of the newly formed South American continent were covered by extensive deserts. Some parts of this continental landmass were synchronously affected by pronounced tectonism and magmatism, which were responsible for reshaping the regional topography. In this context, the southwestern part of the Sanfranciscana Basin in central Brazil is a key area for understanding this particular period in the geodynamic evolution of the South American continent. Aeolian deposits of the Posse Formation in the basin occur in direct association with volcanic rocks of the Upper Cretaceous Mata da Corda Group. Here, we report evidence of synsedimentary magmatism in direct association with soft-sediment-deformation structures, including flame structures, load casts and pseudonodules, water-escape structures, convolute lamination, faults, breccias, and clastic dikes, developed exclusively in aeolian sandstone and siltstone facies. The deformation features are interpreted as indicative of liquefaction, fluidization, and brittle behavior of the loose to partially lithified, wet sandy–silty sediments. The Late Cretaceous aeolian sedimentation is contemporaneous with the uplift of the Parana ́ıba High and associated magmatism in the Minas–Goia ́s Alkaline Province. In this context, these significant volcano-tectonic activities are considered to have triggered ductile to brittle deformation in the reported aeolian deposits.