Tafonomy of macroinvertebrates and Albian marine ingression as recorded by the Romualdo Formation (Cretaceous, Araripe Basin, Brazil) (original) (raw)
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Benthic macroinvertebrate fossils can be seen towards to the top of the Romualdo Member of the Santana Formation, in the Araripe Basin, Northeast Brazil, and can provide paleoenvironmental and paleobiogeographical information regarding the Cretaceous marine transgression which reached the interior basins in Northeast Brazil. We analyse taphonomic characteristics of macroinvertebrate concentrations of two outcrops (Torrinha and Torre Grande) within the municipality Araripina, Pernambuco, in order to enhance our understanding of the Cretaceous paleoenvironment in the western portion of the Araripe Basin. At the outcrop Torrinha, proximal tempestitic taphofacies were identified. These predominantly consist of ceritid, cassiopid, and later, naticid gastropods as well as undetermined bivalves. Given this lack of variability it can be deduced that there were no significant paleoenvironmental changes during the successive stages tempestitic sedimentation. In the Torre Grande outcrop distal to proximal tempestitic taphofacies were identified from the base to the top respectively pointing to a decrease in paleodepth. Asides from the macroinvertebrates present in Torrinha, there are also echinoids e unequivocal evidence for marine conditions. These occurrences appear to be restricted to Romualdo Member outcrops in the Araripina municipality (the Southeast portion of the Araripe Basin) confirming a previously published hypothesis suggesting that the Cretaceous marine transgression originated from the neighbouring Parnaíba Basin to the west. This study identified marine molluscs of a similar age to those in the Romualdo Member's equivalent rock units in the Parnaíba and Sergipe-Alagoas (SE-AL) basins suggesting a marine connection between these basins and the Araripe Basin during the Early Cretaceous.
Journal of South American Earth Sciences, 2015
Benthic macroinvertebrate fossils can be seen towards to the top of the Romualdo Member of the Santana Formation, in the Araripe Basin, Northeast Brazil, and can provide paleoenvironmental and paleobiogeographical information regarding the Cretaceous marine transgression which reached the interior basins in Northeast Brazil. We analyse taphonomic characteristics of macroinvertebrate concentrations of two outcrops (Torrinha and Torre Grande) within the municipality Araripina, Pernambuco, in order to enhance our understanding of the Cretaceous paleoenvironment in the western portion of the Araripe Basin. At the outcrop Torrinha, proximal tempestitic taphofacies were identified. These predominantly consist of ceritid, cassiopid, and later, naticid gastropods as well as undetermined bivalves. Given this lack of variability it can be deduced that there were no significant paleoenvironmental changes during the successive stages tempestitic sedimentation. In the Torre Grande outcrop distal to proximal tempestitic taphofacies were identified from the base to the top respectively pointing to a decrease in paleodepth. Asides from the macroinvertebrates present in Torrinha, there are also echinoids e unequivocal evidence for marine conditions. These occurrences appear to be restricted to Romualdo Member outcrops in the Araripina municipality (the Southeast portion of the Araripe Basin) confirming a previously published hypothesis suggesting that the Cretaceous marine transgression originated from the neighbouring Parnaíba Basin to the west. This study identified marine molluscs of a similar age to those in the Romualdo Member's equivalent rock units in the Parnaíba and Sergipe-Alagoas (SE-AL) basins suggesting a marine connection between these basins and the Araripe Basin during the Early Cretaceous.
Cretaceous Research, 2019
The Cretaceous (upper Aptian) Romualdo Formation of the Araripe Basin, northeastern Brazil, is a marine-influenced, predominantly fine-grained siliciclastic unit. In the eastern part of the basin, it corresponds to a depositional sequence composed of two transgressive-regressive cycles. Low-diversity benthic macrofaunas document high-stress conditions. Their palaeoecological and taphonomic analysis allows for the detailed reconstruction of the palaeoenvironments and of the temporal changes in the palaeoecosystem. The transgressive part of the lower cycle is a black shale with calcareous concretions that contain excellently preserved fishes and other vertebrates (the famous "Santana fossils"), but apart from abundant ostracods and rare decapod crustaceans, benthic faunal elements are very rare due to anoxic to dysoxic conditions. A low-diversity parautochthonous molluscan fauna of small bivalves and gastropods records fluctuating dysoxic conditions during early regression. Towards the top of the measured sections (late regression), thin gastropod shell beds become conspicuous. At the top of the sections decimetre-thick shell concentrations show signs of reworking and a greater marine influence (transgressive part of the upper cycle). The distribution pattern of three benthic associations and two assemblages is almost equally shaped by three environmental parameters: The low overall species diversity, small size of the fauna, and the lack of stenohaline elements suggest lowered and fluctuating salinity conditions. Fluctuating redox conditions with anoxia to dysoxia, identified especially in the lower parts of the succession, and substrate were the other two factors shaping the faunal distribution. The late Aptian sedimentary and faunal history of the eastern part of the basin indicates restricted marine influence, coupled with increasing freshwater input during phases of sea-level lowstand, and low-energy conditions offshore, which led to widespread anoxia, especially in the lower part of the formation. Thus, palaeoecological analyses are an excellent tool to disentangle the various environmental parameters that shaped the palaeoenvironments of the basin, to understand more closely its Fossil-Lagerstätten, and to corroborate and fine-tune the sequence stratigraphic framework.
Palaeogeography, …, 2005
The Romualdo Member of the Santana Formation (Araripe Basin, northeastern Brazil) is famous for the abundance and the exceptional preservation of the fossils found in its early diagenetic carbonate concretions. However, a vast majority of these Early Cretaceous fossils lack precise geographical and stratigraphic data. The absence of such contextual proxies hinders our understanding of the apparent variations in faunal composition and abundance patterns across the Araripe Basin. We conducted controlled excavations in the Romualdo Member in order to provide a detailed account of its main stratigraphic, sedimentological and palaeontological features near Santana do Cariri, Ceará State. We provide the first fine-scale stratigraphic sequence ever established for the Romualdo Member and we distinguish at least seven concretion-bearing horizons. Notably, a 60-cm-thick group of layers (bMatracãoQ), located in the middle part of the member, is virtually barren of fossiliferous concretions. Moreover, a sample of 233 concretions shows that (i) the stratigraphic distribution of the concretions is very heterogeneous and their density varies from 0.8 to 15 concretions/m 3 ; (ii) concretions have a preferential, bimodal orientation pattern (major NW-SE axis and secondary cN-S axis) throughout the section, suggestive of permanent palaeocurrents of low energy; (iii) few concretions yield the well-preserved vertebrates that have made the Romualdo Member so famous, and those are mainly restricted to four stratigraphic horizons; (iv) only six fish taxa were recovered, the most common being Vinctifer and Tharrhias, followed by Cladocyclus, whereas Brannerion, Calamopleurus (=Enneles) and Notelops are rare. No tetrapod was found in the sample; (v) there is a strong stratigraphic control in the distribution of these taxa and one can distinguish at least three major
The latest Pragian to the early Eifelian succession of the Devonian of the eastern border of the Paraná Basin (Brazil) is approached integrating taphonomy and sequence stratigraphy, providing new insights to the analysis of intracratonic siliciclastic Paleozoic seas. The high-resolution study of six outcrops revealed a mud-prone succession, composed predominantly of distal tempestites, with minor preservation of foreshore/shoreface depositional systems, and permitted the acquisition of sensible fossil and sedimentary data in relation to environments within the general depositional tendencies of the lowstand (LST), trangressive (TST) and highstand (HST) systems tracts of the succession. The LST has fragmented fossils preserved that indicate proximity to the shoreline; also, can preserve fossils that live in the foreshore/shoreface zone by proximal obrution events. In general, the TST records an epoch of moderate to high faunal diversity, low rates of sedimentation, with occurrence of obrution deposits in its middle part. Concretions with phosphatic animals can be preserved at the maximum transgressive surface, where the calcareous shells are preferentially dissolved. Stringers and rosette orientations below storm wave base are explained by flow lifting of distal muddy turbidity currents. The HST presents higher faunal diversity, with abundance of fragmented valves; sedimentation rates are moderated. Specific lingulid taphofacies displayed a very good correlation with the environmental conditions in each depositional environment. The lingulid taphofacies could be used as a more sensible tool in order to analyze environmental conditions in ancient seas. Therefore taphonomic signatures and biofabrics of the fossils (their occurrences and diversities) showed correlation with the general principles of sequence stratigraphy, and seem to be controlled by the system tracts where they were preserved.
2016
(DBio-UFSCAR), who have both become great friends while advising me in my dissertation. Their humility and dedication are inspiring; their passion for Science is contagious; and their willingness to give students freedom of thought is fruitful. I have always had invaluable help during my research and own them my academic growth. I acknowledge the Brazilian Council for Scientific and Technological Development (Process 154062/2014-6) for having provided my masters scholarship, and the Post-Graduation Program in Geochemistry and Geotectonics of the Institute of Geosciences of the University of São Paulo for logistics and financial support. I also thank the post-graduation secretaries for full support during my masters. My sincere thanks also goes to Professor Thomas Rich Fairchild (IGc-USP), whose witty comments and sharp criticism make research routine lighter but, nevertheless, a high-quality enterprise. Professor Luiz Eduardo Anelli (IGc-USP) has always inspired me with insightful discussions. I also thank Professor Juliana Moraes de Leme Basso and Professor Paulo Eduardo de Oliveira (both from the IGc-USP) for having provided classroom assistant scholarships, and Ivone Cardoso Gonzales, Josefa Francisca Ferreira and all trainees of the Palaeontological Scientific Collection of the IGc-USP for their prompt help with infrastructure issues, facilitating research activities enormously. Samuel "Samuca" has always helped in dangerous rock cutting and Renato Carvalho in skilful thin-section preparation. I am also very grateful to Prof. Dr. Marcia de Almeida Rizzutto (IF-USP), Dr. Douglas Galante (LNLS), Prof. Dr. Fabio Rodrigues (IQ-USP), Prof. Dr. Adriana de Oliveira Delgado (UFSCAR), Rafael Parra Ribeiro (UNESP Sorocaba), and Prof. Dr. Elidiane Rangel (UNESP Sorocaba), who have made a great effort in both teaching and helping me with analytical techniques since the very early stages of my research. I am thankful to Izabel Ladeira ("English for You") for language revision, to Professor Mario Luis Assine (IGCE-UNESP), who have kindly provided a vectorized version of a map of the Araripe Basin, and to Bruno Becker Kerber (PPGERN-UFSCAR) for the palaeoenvironmental diagram of the Crato palaeolake. I would like to thank my family, including my parents Ana and Julio, my brothers Guilherme and Mariana, my aunts Amália and Izabel, my uncle Hugo, and my grandmothers Lourdes and Rosa, for their kindness, inspiration and support throughout my life.
Paleoenvironmental evolution of the Aptian Romualdo Formation, Araripe Basin, Northeastern Brazil
The tectonic evolution of the Equatorial Atlantic Gateway (EAG) throughout the early Cretaceous had global implications. This break-up of western Gondwana has played a significant role in causing, or amplifying, environmental changes due to its influence on ocean chemistry, nutrient distribution, water mass circulation, and bottom waters ventilation. However, the timing of its establishment and the areal extent of this oceanic gateway is still poorly constrained. Marine settings were recorded by the black shales of the Romualdo Formation (Late Aptian), Araripe Basin-Northeastern Brazil, which are known worldwide for their fossil content and importance for paleogeographic reconstructions of Gondwana. In this contribution, we present multiproxy analyses, combining macro-and micropaleontological, as well as sediment compositional data to evaluate paleoenvironmental conditions during the deposition of sedimentary strata assigned to the Romualdo Formation. We investigate the ~100-m-thick succession of the Sobradinho Section, which is the most complete exposure of the Romualdo Formation. Increased abundances of ostracods, the occurrence of agglutinated benthic foraminifera, bakevelliid bivalves, and cassiopid gastropods coincide with levels of relatively high paleosalinity estimates based on the Sr/Ba (strontium/barium) and S/TOC (sulfur/total organic carbon) ratios. These levels correspond to a transgressive system tract and the lower interval of a highstand systems tract. Throughout the section, black shales occur intercalated with sparse sandstone and calcarenite levels, and the deposition of these black shales is associated with dysoxic to anoxic bottom water conditions, as suggested by the V/Cr (vanadium/chrome) ratio. The occurrence of stagnant bottom water conditions may explain the mass mortality of ostracods in the lower interval of the succession. The upper part of the highstand system tract in the studied section was deposited in coastal environments and is characterized by coarser-grained siliciclastic-dominated facies (high log(Zr/Rb) (zirconium/rubidium) ratio), as well as increased phytoclasts and terrigenous (high magnetic susceptibility) contents.
Biostratigraphy of Lower Cretaceous microfossils from the Araripe basin, northeastern Brazil
Geobios, 2002
A biostratigraphic study was carried out in the Lower Cretaceous Araripe basin, northeastern Brazil, allowing the recognition of several chronostratigraphic units: the Dom João (Jurassic?-Lower Cretaceous?), the Rio da Serra (Neocomian) and the Alagoas (Aptian/Albian) local stages. For the first time a large hiatus between the Rio da Serra and Alagoas local stages is carefully documented. The palynomorphs and the ostracode associations throughout the Jurassic?-Aptian/Albian sequence allow the interpretation of the paleoenvironmental evolution of the Araripe basin which otherwise confirms that a polycyclical sedimentation occurred in the basin, being one of the controlling factors on the distribution of ostracodes and palynomorphes. © 2002 É ditions scientifiques et médicales Elsevier SAS. All rights reserved.
First evidence of marine influence in the Cretaceous of the Amazonas Basin, Brazil
Cretaceous Research, 2006
An integrated investigation emphasizing sedimentological and ichnological studies of Cretaceous deposits of the Alter do Chão Formation, exposed in the western Amazonas Basin, was undertaken with the aim of determining depositional environments. Four facies associations attributed to upper shoreface, foreshore, delta mouth bar, and lower/middle shoreface-prodelta depositional environments were recognized. The upper shoreface deposits were deposited by storm flows. They are interbedded with highly bioturbated sandstones displaying Thalassinoides, Planolites and Diplocraterion traces. The foreshore deposits, which are coarser-grained than the shoreface strata, are characterized by tabular sandstones with planar or trough cross-lamination/stratification, wavy/flaser lamination, and parallel lamination. These strata also contain an abundance of trace fossils. The delta mouth bar deposits comprise upward-coarsening beds displaying a lobed geometry. The lower/middle shoreface-prodelta settings consist of well-stratified, very fine-grained sandstones and mudstones deposited mostly by storm wave action. A wave-dominated delta system that prograded into a marine-influenced basin is supported for the study area. Therefore, in contrast to previous interpretations, it seems that a widespread transgression during the Cretaceous would have resulted in the submergence of large continental areas in the north of Brazil, affecting sediment deposition even in the innermost portions of the intracratonic Amazonas Basin.
Invertebrate ichnofossils from the Adamantina Formation (Bauru Basin, late Cretaceous), Brazil
Revista Brasileira De Paleontologia, 2006
The Bauru Group is a sequence at least 300 m in thickness, of Cretaceous age (Turonian-Maastrichtian), located in southeastern Brazil (Bauru Basin), and consists of three formations, namely Adamantina, Uberaba and Marília. Throughout the Upper Cretaceous, there was an alternation between severely hot dry and rainy seasons, and a diverse fauna and flora was established in the basin. The ichnofossils studied were found in the Adamantina Formation outcrops and were identified as Arenicolites isp., ?Macanopsis isp., Palaeophycus heberti and Taenidium barretti, which reveal the burrowing behavior of the endobenthic invertebrates. There are also other biogenic structures such as plant root traces, coprolites and vertebrate fossil egg nests. The Adamantina Formation (Turonian-Santonian) is a sequence of fine sandstones, mudstones, siltstones and muddy sandstones, whose sediments are interpreted as deposited in exposed channel-bars and floodplains associated areas of braided fluvial environments.