Navegando por Autor "Assine, Mario Luis"
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Item Cratonaia novaolindensis gen. et sp. nov. (Unionida, Silesunionoidea) from the Aptian of Brazil (Araripe Basin), and its implications for the early evolution of freshwater mussels.(2020) Silva, Victor Ribeiro da; Varejão, Filipe Giovanini; Matos, Suzana Aparecida; Fürsich, Franz Theodor; Skawina, Aleksandra; Schneider, Simon; Warren, Lucas Veríssimo; Assine, Mario Luis; Simões, Marcello GuimaraesThe fossil-rich carbonate deposits of the Aptian Crato Formation, Araripe Basin (Brazil) are one of the main Cretaceous Konservat-Lagerstatten of Gondwana, and have come to fame globally. However, in- € formation on fossils from deposits other than the famous laminites of the basal part of the unit is scarce. Herein, we describe the first bivalves of the suborder Silesunionidina Skawina and Dzik, 2011 in the order Unionida Gray, 1854 from South America. The specimens were collected from a 0.3e1-m-thick grey to yellow mudstone interval located 0.3 m above the laminated limestones of the lower part of the Crato Formation at Nova Olinda, State of Ceara. They comprise exquisite composite, internal and external -moulds, preserving key anatomical characters. Based on the analysis of muscle scars, hinge and orna- mentation, these bivalves are here assigned to a new genus and species, Cratonaia novaolindensis gen. et sp. nov. The presence of a series of small pedal elevator scars linearly arranged on the external wall of the umbonal cavity indicates that this is a member of the suborder Silesunionidina. The new form is the by far youngest representative of this group. Closely related bivalves were previously reported from Triassic deposits of Australia, Africa, Europe and potentially India. Detailed stratigraphic, sedimentological and taphonomic observations indicate that the new taxon thrived in a freshwater lake. The occurrence of Silesunionoidea in the Lower Cretaceous of South America indicates that the condition of the musculature in Mesozoic freshwater mussels needs to be established to assign them confidently at family level.Item 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 LuisSoft-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.Item Evidences of seismic events during the sedimentation of Sete Lagoas Formation (Bambuí Group – Ediacaran, Brazil).(2020) Okubo, Juliana; Warren, Lucas Veríssimo; Luvizotto, George Luiz; Varejão, Filipe Giovanini; Quaglio, Fernanda; Uhlein, Gabriel Jubé; Assine, Mario LuisThe Sete Lagoas Formation (Ediacaran), located in the central part of the São Francisco Craton (Brazil), consists of limestones and dolostones deposited in very shallow waters in the inner part of the carbonate platform. Four breccia types occur throughout the stratigraphic succession: evaporitic breccia with tepees, flat-pebble breccia, hydrothermal breccia and brecciated stromatolites. Here we combine a detailed sedimentological and strati- graphic analyses of the flat-pebble breccia in order to determine its origin and the processes and environmental conditions that originated these brecciated facies. The studied interval consists of a 20 m thick succession of tabular beds composed of flat-pebble breccia interbedded with laminated microbialites. In these breccia beds, the clasts are usually platy or oblate with angular edges and are mainly disposed horizontally within the sedi- mentary bed, suggesting that they were not transported or reworked. The presence of microbialite clasts with sharp edges and vertices in the Sete Lagoas flat-pebble breccia suggests that the lithification process started very early in diagenesis and, even the sediments exposed at the bottom were, at least, partially lithified. Some breccia levels show bidirectional imbrication and clast size analyses reveal a NE-SW long-axis clast orientation whereas square clasts tend to fill the space among oriented clasts. Breccia clasts are vertically oriented and show de- formation features increasing upwards, typically of deforming beds formed by ascendant expulsion of liquefied sediment. Disrupted layers or presenting folds and synsedimentary faults commonly occur confined between undeformed beds. Other evidences of liquefaction and soft-sediment deformation are the injection structures, as flame and load cast-like features, in the base of the brecciated beds. These structures commonly penetrate the upper bed and disrupt the sedimentary layer immediately above promoting local brecciation. These features are found both in modern and ancient deposits of seismic influence, which suggests a similar origin for the Sete Lagoas flat-pebble breccia. Thus, the processes that led to the formation of the studied flat-pebble breccia are interpreted as seismically triggered, since: a) the breccia beds are laterally continuous and extend for several kilometers; b) the breccia beds are restricted to a 20 m thick stratigraphic interval; c) the clasts of the breccia are the same lithology of non-deformed beds below and above the interval of breccia; d) the interbedding of breccia beds and laminated microbialite beds is recurrent; e) the breccia beds are subhorizontal and present irregular upper and lower contacts; f) the presence of liquefaction structures and dyke injection. Thus, this seismic-trig- gered breccia deposits represent the product of the synsedimentary tectonism occurred within the São Francisco Craton during the terminal Ediacaran and correspond to a very well-defined local stratigraphic marker in the Bambuí Basin. The seismic activities could be related to the NW regional faults in the regional Paleoproterozoic basement of the study area, which were reactivated during the deposition of the Sete Lagoas Formation in the Ediacaran Period.Item High-resolution taphonomy and sequence stratigraphy of internally complex, bakevelliid-dominated coquinas from the Aptian Romualdo formation, Araripe Basin, NE Brazil.(2022) Rodrigues, Mariza Gomes; Varejão, Filipe Giovanini; Matos, Suzana Aparecida; Fürsich, Franz Theodor; Warren, Lucas Veríssimo; Assine, Mario Luis; Simões, Marcello GuimarãesThe Aptian Romualdo Formation (Araripe Basin, NE Brazil) was deposited in a restricted epeiric sea, during the opening of the South Atlantic Ocean, with a coeval record to that in the Brazilian Pre-Salt succession. The upper part of the Romualdo Formation encompasses the Highstand Systems Tract of a third-order stratigraphic sequence, and contains shell beds interbedded with shale, siltstone, and fine-grained sandstone. Based on distinct taphonomic features (shell sorting, fragmentation, abrasion, rounding, and orientation), sedimentological criteria (shell abundance, type of matrix, sedimentary structures, and presence/absence of quartz grains), and stratigraphic attributes (bed thickness, geometry, contacts), the paleoenvironmental conditions and the bed-by-bed accumulation history of the coquinas is disentangled. Eight carbonate microfacies were recognized, including ostracod carbonate mudstone, bivalve-gastropod wackestone, gastropod-bivalve packstone, bivalve-gastropod grainstone, bivalve-gastropod floatstone, bivalve-gastropod rudstone, bakevelliid floatstone, and bakevelliid rudstone, which are organized in six, cm-thick shell concentrations. Mudstone and wackestone facies mark the settling of carbonate muds without significant bottom currents and wave action, probably below storm wave base, whereas packstone, floatstone, and rudstone, with fragmented, rounded, and oriented shells, were deposited in agitated waters, between the fair-weather and the storm wave bases. Ripple cross-laminated grainstone is interpreted as high-energy facies deposited above fair-weather wave base. The shell beds are internally complex and consist of cm-scale alternations of microfacies differing in packing, sorting, and composition. They tend to fine upwards within dm-thick shell beds, generating shallowing-upward facies sequences. The concentrations, the uppermost one with in situ bakevelliid shells in the top, record high-frequency base level oscillations influenced by eustasy and climate changes. These bioclastic accumulations originated by the superposition of sedimentologic and primary biologic processes (e.g., post-deposition meiofaunal bioturbation). The cm-thick, low-diversity shell beds are excellent examples of multiple-event carbonate deposits generated in a siliciclastic-dominated, restricted epeiric sea, revealing high-frequency cycles in proximal to distal restricted marine settings.Item High-resolution taphonomy of the Lower Cretaceous “Amargosa Biota”, Central Tucano Sub-Basin, Bahia, Brazil : implications for the paleoenvironmental dynamics of a new Konservat-Lagerstätte.(2022) Souza, T. G. L.; Silva, Suzana Aparecida Matos da; Varejão, Filipe Giovanini; Rodrigues, Mariza Gomes; Ribeiro, Alexandre Cunha; Freitas, Bernardo Tavares; Warren, Lucas Veríssimo; Assine, Mario Luis; Simões, Marcello GuimarãesWe report the Amargosa Biota from the middle part of the Lower Cretaceous Marizal Formation (Central Tucano Sub-Basin, NE Brazil), as a new Konservat-Lagerstatte ̈ . Exceptionally preserved fossils are confined to the lower part of an up to 15-m-thick, mud-dominated succession, named Amargosa Bed. Seven bedding planes (L0-L6) with distinct sedimentological and taphonomic attributes were identified in the type section (Amargosa Village, Euclides da Cunha County, Bahia State), distributed in an ~1-m-thick succession of well-laminated claystone, mudstone, siltstone, and very fine-grained sandstone. These contain ostracods, spinicaudatan carapaces, palae- monid shrimps, fish, and comminuted plant remains. Fossils occur in high concentration on at least four bedding planes (i.e., L2, L3, L5, and L6), forming polytypical assemblages that are dominated by one of the fossil groups. Assemblages are formed mainly by autochthonous to parautochthonous elements, representing variable, but limited, temporal mixing. A key attribute of some fossil-rich strata (L3, L5, and L6) is the preservation of poorly biomineralized organisms and/or of complete soft-bodied parts, which are typically prone to destruction due to rapid decay or bioturbation. The polytypical nature of these fossil assemblages, interbedded with non- fossiliferous intervals, suggests mass mortality events, probably caused by abrupt changes in water parameters (anoxia, salinity, pH, among others). The dark greenish gray color (yellowish when weathered), and the finely laminated nature of the claystone, siltstone, and mudstone containing members of the Amargosa Biota indicates that the benthic infaunal life was absent or, at least, very scarce in a locally, relatively deep, oxygen-poor lake bottom. Anoxia and high salinity, linked with local semi-arid conditions during the Lower Cretaceous may have played key roles in the exceptional preservation of some fossils (shrimps, fish). Finally, our data provide a more comprehensive understanding of the temporal distribution of taxa and taphonomic processes associated with the complex genesis of the fossil-bearing interval of the Amargosa Bed in its type locality.Item 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 GuimarãesHot 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.Item Macroinvertebrates of the Capivari marine bed, late Paleozoic glacial Itararé Group, northeast Paraná Basin, Brazil : paleoenvironmental and paleogeographic implications.(2020) Simões, Marcello Guimarães; Neves, Jacqueline Peixoto; Taboada, Arturo César; Pagani, Maria Alejandra; Varejão, Filipe Giovanini; Assine, Mario LuisA 2-m-thick silty shale bed within the Taciba Formation, Itararé Group, Paraná Basin, State of São Paulo, southeastern Brazil, records marine sedimentation in a siliciclastic-dominated, low-energy, shelf setting, during a short-lived deglacial event. The bed is located 100–150 m below the base of the lower Permian, post-glacial Tatui Formation. The marine assemblage is dominated by rhynchonelliform brachiopods, with subordinate bi- valves, gastropods and crinoids, recording the highest phylum-level diversity so far identified within a given fossil-bearing horizon in the uppermost portion of the Itararé Group. Two new species are described, one bra- chiopod Biconvexiella saopauloensis and one gastropod Peruvispira brasilensis. Additionally, shells of Lyonia ro- chacamposi, Rhynchopora grossopunctata, Quinquenella rionegrensis, Phestia tepuelensis, Streblopteria aff. S. lagu- nensis, Limipecten capivariensis, Praeundulomya cf. subelongata and Mourlonia (Woolnoughia)? sp. are identified. Crinoid columns were assigned to øPentaridica sp. (a genus based on elements of the columnal). This is the first systematic description of members of the Eurydesma-Lyonia fauna in the northeastern part of the Paraná Basin, Brazil. The overwhelming majority of brachiopods belong to Biconvexiella saopauloensis, followed by Rhynchopora grossopunctata. The record of Lyonia rochacamposi closely resembles that of the uppermost part of the Taciba Formation in southern Brazil. Hence, the Capivari marine fauna correlates approximately with that of the upper part of the Taciba Formation. Lyonia rochacamposi also indicates correlation with Permian units of the Sauce Grande-Colorado (Argentina), Huab (Hardap shale of the Dwyka Group), Aranos area (Namibia), southwest Africa, and the Carnavon (Western Australia) basins. These correlations support a latest Asselian-earliest Sakmarian age for the fauna.Item Marine or freshwater? : accessing the paleoenvironmental parameters of the Caldas Bed, a key marker bed in the Crato Formation (Araripe Basin, NE Brazil).(2021) Varejão, Filipe Giovanini; Silva, Victor Ribeiro; Assine, Mario Luis; Warren, Lucas Veríssimo; Matos, Suzana Aparecida; Rodrigues, Mariza Gomes; Fürsich, Franz Theodor; Simões, Marcello GuimarãesThe Aptian Crato Formation is world renowned for its well-preserved fossils in microbially-induced laminated limestones, which are regarded as one of the main Cretaceous Konservat-Lagerstätte of the geological record. Detailed stratigraphic investigation and mapping of the up to 90-m-thick Crato Formation at the eastern border of the Araripe Plateau allowed recognition of a regionally persistent fossil-bearing muddy interval, herein defined as the Caldas Bed. At its type locality, it is defined as an up to 2-m-thick coarsening-upward succession of grey/green mudstone and interbedded sandy siltstone and claystone. The 0.85- to 2-m-thick interval was recognized in several localities along the outcrop belt, and it is bounded by sharp, lower (Konservat-Lagerstätte limestone) and upper (sandstone and heterolithic facies) contacts. Despite pre vious literature data suggesting the presence of marine mollusks, the bed contains freshwater bivalves, small gastropods, spinicaudatans, plant remains, trace fossils, and rare ostracods. The Caldas Bed records benthic paleocommunities representing a short-term isochronous regional freshening event, marked by abrupt changes in sedimentation pattern, bathymetry, salinity, oxygenation and water chemistry.Item Mixed siliciclastic–carbonate sedimentation in an evolving epicontinental sea : aptian record of marginal marine settings in the interior basins of north-eastern Brazil.(2021) Varejão, Filipe Giovanini; Warren, Lucas Veríssimo; Simões, Marcello Guimaraes; Buatois, Luís Alberto; Mángano, María Gabriela; Rumbelsperger, Anelize Manuela Bahniuk; Assine, Mario LuisThe Aptian evaporitic transitional sequence (sag phase) of the Brazilian mar- ginal basins records the first connection between the Central and South Atlan- tic oceans in the equatorial area. During this phase, lacustrine carbonate reservoirs and giant salt deposits developed in the southern basins of Santos and Campos, forming world-class petroleum reservoirs. The sag succession is also well-preserved in the interior rift basins of north-eastern Brazil, where upper Aptian strata are represented by a continuous section. This contribution presents an interpretation of the evolution of a third-order depositional sequence comprising lacustrine limestones, marine siliciclastic facies and evaporite deposits of the intracontinental Araripe Basin. The Lowstand Sys- tems Tract is characterized by fluvial deposits filling accommodation gener- ated during the syn-rift phase. The overlying deposits comprise marine facies with preservation of dinoflagellates and marine ichnotaxa, evidencing marine deposition in bayhead delta settings. The transgressive surface is represented by limestones, including the Konservat–Lagerstatte € laminites, onlapping the basement rocks. Above, tide-dominated bay deposits with distinct subtidal, intertidal and supratidal portions are recorded. The Maximum Flooding Sur- face is a dark shale below foreshore to shoreface facies, marking the beginning of the Highstand Systems Tract, culminating with deposition of evaporites (gypsum and anhydrite). The stratigraphic architecture and palaeocurrents measured in different facies associations suggest that marine waters reached the basin from the south. The data unequivocally records late Aptian marine ingressions of an incipient South Atlantic Ocean over the interior basins of north-eastern Brazil, while lacustrine conditions were still prevailing in the Pre-Salt sag units of the Santos and Campos basins.Item New freshwater mussels (Bivalvia, Unionida) with potential trigonioidid and hyriid affinities from the Early Cretaceous of Brazil.(2020) Silva, Victor Ribeiro da; Varejão, Filipe Giovanini; Matos, Suzana Aparecida; Rodrigues, Mariza Gomes; Fürsich, Franz Theodor; Skawina, Aleksandra; Schneider, Simon; Warren, Lucas Veríssimo; Assine, Mario Luis; Simões, Marcello GuimaraesTwo new taxa of freshwater mussels (Bivalvia: Unionida) from the Aptian Crato Formation of the Araripe Basin, NE Brazil, are described. The fossil bivalves are confined to 30- to 130-cm-thick bioturbated mudstones overlying the fossil-rich laminated limestones of the Crato Formation Konservat- Lagersta ̈tte. Individuals are often preserved with closed or splayed articulated valves, some of them potentially in life position, forming an autochthonous to parautochthonous assemblage. Monginellopsis bellaradiata nov. gen., nov. sp. shares key characters with the Trigonioidoidea: (i) the anterior pedal retractor muscle scar is clearly separated from the anterior adductor muscle scar; (ii) the shell has fold- like radial ribs on the posterior half; (iii) a right valve anterior tooth has a striated facet. Araripenaia elliptica nov. gen., nov. sp. is the most abundant and widely distributed unionid of the Crato Formation. Its ornament of anterior inverted V-shaped riblets, and central and posterior radial and sub-radial riblets resembles modern and fossil Hyriidae from the Americas, but also Trigonioidoidea from Eurasia. Its dentition of two smooth anterior pseudocardinals and two smooth posterior laterals in each valve provides no further clues for systematic assignment; muscle scars are not preserved. Assignment to the Hyriidae would make Araripenaia the oldest member of this family known from South America. Moreover, this bivalve assemblage of trigonioidoidids, hyriids, and previously reported silesunionoids suggests palaeobiogeographic links to other areas in both Gondwana and Laurasia.Item 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 LuisThe 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.Item Short-lived “Bakevelliid-Sea” in the Aptian Romualdo Formation, Araripe Basin, northeastern Brazil.(2020) Rodrigues, Mariza Gomes; Matos, Suzana Aparecida; Varejão, Filipe Giovanini; Fürsich, Franz Theodor; Warren, Lucas Veríssimo; Assine, Mario Luis; Simões, Marcello GuimaraesNew Aptian (Lower Cretaceous) bakevelliid bivalves are described for the Romualdo Formation, Santana Group, Araripe Basin, northeastern Brazil. Together with the other known member of the family Bake- velliidae, already recorded from the unit (i.e., Aguileria dissita), the new bivalves (Araripevellia musculosa gen. et sp. nov., Aguileria romualdoensis sp. nov., and Gen. et sp. indet.) indicate that the Romualdo bakevelliid fauna was more diverse than previously realized. Bakevelliid-rich carbonates, some with specimens preserved in situ, are restricted to the upper third of this unit, a stratigraphic interval yielding also echinoderm-, gastropod- and stromatolite-bearing limestones. These pteriomorphian bivalves were widely distributed in the Romualdo Formation and are a testimony of the short-lived Bakevelliid-Sea that flooded the whole Araripe Basin during the Aptian. Notably, Aguileria romualdoensis sp. nov. closely resembles Aguileria renauxiana from the Cenomanian Woodbine Formation, Texas, US. In addition, Aguileria dissita is also recorded in the upper AptianeAlbian Riachuelo Formation of the Sergipe-Alagoas Basin. Together with other macroinvertebrates (i.e., gastropods, echinoderms, bivalves) the bakevelliid fauna of the Romualdo Formation can be tightly correlated with that of the Riachuelo Formation, sup- porting a paleogeographic scenario with a marine ingression flooding the Araripe Basin from the southeast, probably via the seaway developed in the Reconcavo-Tucano basin area. Finally, sedimento- ^ logic, stratigraphic and paleontological data indicates that the fate of the bakevelliids in the Romualdo Formation was linked to the onset of continentalization of the Araripe Basin.Item So close and yet so far : U–Pb geochronological constraints of the Jaibaras Rift Basin and the intracratonic Parnaíba Basin in SW Gondwana.(2021) Cerri, Rodrigo Irineu; Warren, Lucas Veríssimo; Varejão, Filipe Giovanini; Silva, Alex Joaquim Choupina Andrade; Lana, Cristiano de Carvalho; Assine, Mario LuisSeveral sag-type basins apparently developed from rift systems, but there is no consensus about how and if these grabens influenced the sedimentation of the post-rift thermal subsidence phase. The Ediacaran Jaibaras Rift Basin is one of the best-exposed sedimentary records among the NE Brazil late Precambrian – early Cambrian rift system, cropping out at the eastern margin of the intracratonic Parnaíba Basin and extending below it towards the west. Here we present detrital zircon U–Pb ages of rocks from the Jaibaras (Aprazível Formation) and Parnaíba (Ipu Formation) basins, in order to understand the provenance patterns, maximum depositional ages (MDA) and age relationship between these units. The MDA for the Aprazível Formation (c. 499 ± 5 Ma) indicates a Cambrian age for the upper part of the Jaibaras Basin. The bulk U–Pb data indicate that the Ipu Formation started to deposit during late Cambrian and/or Early Ordovician time, despite its MDA (c. 528 ± 11 Ma) being older than that of the Aprazível Formation. Detrital zircon provenance suggests that the primary source areas for the early deposits of the Parnaíba Basin were mountains related to the Brasiliano Orogeny to the south and SE (e.g. Rio Preto and Riacho do Pontal metamorphic belts). Finally, our data emphasize the key change in source areas from the rift to the initial deposition of the intracratonic phase, indicating major depositional style changes between both basins after the Gondwana assembly.Item Taphonomy and ontogeny of the brachyuran crab Exucarcinus gonzagai, from the Lower Cretaceous (Aptian) Romualdo Formation, Araripe Basin, NE Brazil.(2021) Matos, Suzana Aparecida; Castilho, Antonio Leão; Prado, Ludmila Alves Cadeira do; Bondioli, João Guedes; Varejão, Filipe Giovanini; Custódio, Michele Andriolli; Fürsich, Franz Theodor; Assine, Mario Luis; Simões, Marcello GuimarãesBrachyurans played important ecological and evolutionary roles in the marine benthic communities of the past and were the components of the Mesozoic Decapod Revolution. Therefore, the search for their fossil remains is fundamental to understanding the composition, diversity, and ecological structure of Mesozoic marine benthic communities. Brachyuran remains are uncommon in the decapod record of the Aptian Romualdo Formation in the Araripe Basin. In this context, we recorded and described new occurrences of Exucarcinus gonzagai, preserved in shales from the middle portion of the Romualdo Formation, near the city of Jardim in the State of Cear´a. Comparisons between these new specimens and former specimens from the Exu locality, State of Pernambuco, including the type material, allowed us to recognize, for the first time, three distinct ontogenetic stages (i.e., informally referred as I, II, and III). Throughout ontogenetic development, the carapace becomes wider and spinier. Stage III carapaces exhibit a large number of grooves, although the grooves are poorly impressed, and some are pitted. Growth also resulted in better-developed orbital lobes and fissures. In addition, the preservation of some anatomical structures is highly influenced by the carapace fossilization process (i.e., molds or cuticles), including the tubercles, grooves, and spines. Unfortunately, those characters that can vary according to onto genetic development or fossilization are commonly used in the systematic and phylogenetic decisions of the group. Hence, it is advisable to consider these changes whenever possible to avoid the erection of taphotaxons and mistaken phylogenetic decisions.Item Unraveling the origin of the Parnaíba Basin : testing the rift to sag hypothesis using a multi-proxy provenance analysis.(2020) Cerri, Rodrigo Irineu; Warren, Lucas Veríssimo; Varejão, Filipe Giovanini; Marconato, André; Luvizotto, George Luiz; Assine, Mario LuisSyneclises are long-lived sedimentary basins characterized by complex subsidence and erosion histories. The premise that these geotectonic units evolve from initial rifting processes following thermal (or flexural) subsidence is widespread in the geologic sciences and, to this day, remains a controversial issue. Seeking to test this hypothesis, we proceeded a novel multi-proxy provenance study aiming to identify differences (and/or similarities) in the sedimentary signal and source areas of the Jaibaras (rift) and Parnaíba (sag) basins. We conducted a detailed analysis of trace elements geochemistry of detrital rutile grains, macroscopic gravel composition and paleocurrents from the sedimentary deposits of the Aprazível Formation (Ediacaran - Cambrian, top of Jaibaras Basin) and the Ipu Formation (Ordovician, basal unit of Parnaíba Basin). Our data reveal that important changes in source areas occurred between the end of the rifting and the beginning of the sag phase, reinforcing the hypothesis that the evolution of the Jaibaras and Parnaíba basins were not genetically related. Our results demonstrate that conglomerates of the rift sequence are predominantly composed of volcanic, sedimentary, and metamorphic angular to sub-angular clasts, pointing to diverse, nearby source areas. Contrastingly, conglomerates of the initial sag sequence have greater sedimentary maturity, with dominant rounded vein quartz clasts and other minor source contributions, which suggest distant source areas, showing a consistent paleocurrent direction towards NW. Indeed, the detrital rutile trace elements geochemistry demonstrates that the source areas of these two units were distinct, revealing an important decrease in the input of granulite facies and metamafic grains in the sag basin comparing with the rift succession. In conclusion, as well as paleomagnetic and geochronological studies, the provenance methods using a multi-proxy approach proved to be an effective and powerful technique for distinguishing modifications in the sedimentary signal between rift-to-sag sequences.Item Using detrital zircon and rutile to constrain sedimentary provenance of Early Paleozoic fluvial systems of the Araripe Basin, Western Gondwana.(2022) Cerri, Rodrigo Irineu; Warren, Lucas Veríssimo; Spencer, Christopher J.; Varejão, Filipe Giovanini; Promenzio, Paloma; Luvizotto, George Luiz; Assine, Mario LuisThe Early Paleozoic of the NE Brazilian sedimentary basins are key to understanding the primeval depositional environments and paleogeography of Western Gondwana after its final assembly. In this context, determining the sedimentary provenance of the Early Paleozoic Cariri Formation (basal unit of the Araripe Basin) may improve paleogeographic reconstructions and stratigraphic correlations. Despite the Araripe Basin being one of the best-studied interior basins of northeastern Brazil, the Cariri Formation lacks detailed geochronological and sedimentary provenance analyses, which hamper precise definitions of its depositional age, sedimentary source areas and paleogeography. Considering this scenario, we performed a combined multiproxy approach, including sedimentologic and stratigraphic analysis, detrital zircon U–Pb dating and provenance studies based on trace elements in detrital rutile. The maximum depositional age for the Cariri Formation suggests that its sedimentation started after the Late Cambrian. Detrital zircon ages and detrital rutile provenance indicate that the primary source areas for the Cariri Formation fluvial system were the orogenic terranes related to the Brasiliano Orogeny, located at the SE of the Borborema Province (e.g., Sergipano Belt), with secondary, but also important, the contribution of Cambrian sources. Records of this event are also found in northern Africa, where units related to the Neoproterozoic East African-Antarctic and Pan African orogens provided sediments for basin-scale fluvial systems.