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Legend of symbols used for sedimentological and ichnological structures, body fossils and abbreviations in Fig. 3.
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This study integrates ichnological and sedimentological data to interpret depositional environments of the mixed siliciclastic-carbonate fluvial to marine sediments of the Geirud Formation (Upper Devonian) in the central Alborz, northern Iran. Lithofacies analysis shows that these sediments are deposited in fluvial, tidal, shoreface, and shelf envi...
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... The D/C transition in the Eastern Alborz Range of the Tuye-Darvar section, is composed of the Jeirud Formation (Upper Devonian) and Mobarak Formation (Lower Carboniferous). Previous studies from this section have focused on sedimentology, and trace fossil analysis (Sharafi et al., 2014(Sharafi et al., , 2016. However, few biostratigraphic studies have been conducted on conodonts (Najjarzadeh, 1998;Najjarzadeh et al., 2020), but combined biostratigraphic and sedimentologic/ facies analysis is still lacking. ...
... The abundance of coarse-grained sediments and the remarkable thickness of intra-channel deposits, compared with the flood plain deposits (fine-grained), indicate the presence of shallow channels with low sinuosity, low base level, high sediment supply, and low accommodation space; as a result, this river is a braided one with sandstone-conglomerate bed load (Miall, 2006;Foix et al., 2013) (Figure 12). As well, this type of river has been reported from the Tuye-Darvar section by Sharafi et al. (2014). ...
The 1st order mass extinction at the
Devonian/Carboniferous transition, known
as the Hangenberg Crisis, is characterized by
major transgressive/regressive cycles which
led to widespread ocean anoxia during the
Hangenberg Black Shale Event, as well as to
a global major sea-level fall and the worldwide deposition of regressive Hangenberg
Sandstone equivalents. The Devonian/
Carboniferous transition at the Tuye-Darvar
section in the eastern Alborz Range is studied
in terms of conodont biostratigraphy, litho-,
microfacies and sequence stratigraphy. In order
to examine the biostratigraphical framework,
forty conodont samples were systematically
taken from the studied interval. Thirty-two
conodont species belonging to ten genera led to
the discrimination of twelve conodont zones,
ranging from the Pseudopolygnathus granulosus
Zone to the Scaliognathus anchoralis-Doliognathus
latus Zone. Due to facies, the conodont record
also exhibits some hiatuses. Field observations
and sedimentological and microfacies studies
led to the identification of thirteen facies types
from sub-tidal environments to the fully marine
environments, including seven microfacies
types. The sediments deposited in a mixed
carbonate-siliciclastic platform, revealed four
third-order sequences. The Hangenberg Black
Shale is not recorded in the Tuye-Darvar section as a result of depositional facies.
In comparison with other studied Devonian/
Carboniferous Boundary (DCB) sections of
the central and northern Iran, the Tuye-Davar
section suggests a tectonic position, which is
most likely placed on a separate tectonic block
... The D/C transition in the Eastern Alborz Range of the Tuye-Darvar section, is composed of the Jeirud Formation (Upper Devonian) and Mobarak Formation (Lower Carboniferous). Previous studies from this section have focused on sedimentology, and trace fossil analysis (Sharafi et al., 2014(Sharafi et al., , 2016. However, few biostratigraphic studies have been conducted on conodonts (Najjarzadeh, 1998;Najjarzadeh et al., 2020), but combined biostratigraphic and sedimentologic/ facies analysis is still lacking. ...
... The abundance of coarse-grained sediments and the remarkable thickness of intra-channel deposits, compared with the flood plain deposits (fine-grained), indicate the presence of shallow channels with low sinuosity, low base level, high sediment supply, and low accommodation space; as a result, this river is a braided one with sandstone-conglomerate bed load (Miall, 2006;Foix et al., 2013) (Figure 12). As well, this type of river has been reported from the Tuye-Darvar section by Sharafi et al. (2014). ...
The 1st order mass extinction at the Devonian/Carboniferous transition, known as the Hangenberg Crisis, is characterized by major transgressive/regressive cycles which led to widespread ocean anoxia during the Hangenberg Black Shale Event, as well as to a global major sea-level fall and the worldwide deposition of regressive Hangenberg Sandstone equivalents. The Devonian/Carboniferous transition at the Tuye-Darvar section in the eastern Alborz Range is studied in terms of conodont biostratigraphy, litho-, microfacies and sequence stratigraphy. In order to examine the biostratigraphical framework, forty conodont samples were systematically taken from the studied interval. Thirty-two conodont species belonging to ten genera led to the discrimination of twelve conodont zones, ranging from the Pseudopolygnathus granulosus Zone to the Scaliognathus anchoralis-Doliognathus latus Zone. Due to facies, the conodont record also exhibits some hiatuses. Field observations and sedimentological and microfacies studies led to the identification of thirteen facies types from sub-tidal environments to the fully marine environments, including seven microfacies types. The sediments deposited in a mixed carbonate-siliciclastic platform, revealed four third-order sequences. The Hangenberg Black Shale is not recorded in the Tuye-Darvar section as a result of depositional facies. In comparison with other studied Devonian/Carboniferous Boundary (DCB) sections of the central and northern Iran, the Tuye-Davar section suggests a tectonic position, which is most likely placed on a separate tectonic block.
... The siltstones and thin sandstones were deposited during relatively high-energy conditions and the development of traction currents of the lower flow regime (e.g. Nouidar and Chellai 2001;Fabuel-Perez et al. 2009;Sharafi et al. 2014Sharafi et al. , 2022a. Occasional thin coal layers formed in small ponds/swamps with slack water on the delta plain (e.g. ...
... Interpretation: Sandstones with sharp/ erosional convex base are interpreted as distributary channels of the delta plain (e.g. Sharafi et al. 2013Sharafi et al. , 2014Bayet-Goll and Neto de Carvalho 2015;Ponte et al. 2019). Structureless and mediumto thick-bedded sandstone layers display a high sedimentation rate, emphasised by their sharp/erosional bases (e.g. ...
... Structureless and mediumto thick-bedded sandstone layers display a high sedimentation rate, emphasised by their sharp/erosional bases (e.g. Sharafi et al. 2014;Bayet-Goll and Neto de Carvalho 2017;Bayet-Goll et al. 2022). The shell concentrations at the base of the sandstones are considered to be lag deposits. ...
... The pluri-dm height of tidal dunes of FA4a suggest that they were deposited in shallow marine waters (Dalrymple and Rhodes, 1995) that would be equivalent to proximal middle ramp to inner ramp sedimentary environments. This is in accordance with the occurrence of Paleophycus ichnofossiles formed mainly in middle shoreface depositional environments (Gérard and Bromley, 2008;Sharafi et al., 2014). The monospecificity of the ichnofaunal assemblage indicates a stressed environment (e.g. de Gibert and Goldring, 2007;Malpas et al., 2005) that agrees with tidal dominated environments. ...
To assess the influence of growing salt structures on facies distribution, stratal pattern, and thickness trends, this paper provides the tectonostratigraphic framework of the outstandingly exposed Cotiella minibasins (South-Central Pyrenees, Spain). Based on detailed analysis of field cross-sections, our results showcase the syn-halokinetic upper Coniacian-lower Santonian Cotiella minibasins infill (1.5-3 km thick) records four shallow-marine depositional sequences, made of mixed siliciclastic-carbonate stratigraphic sequences. This infill is subdivided in three tectonostratigraphic units, identified by using large and small-scale halokinetic structures (i.e. wedges, megaflaps) and variations in facies associations, thicknesses, stratal patterns from the salt wall flanks to the central part of the minibasins. The first unit records the onset of salt movement with overlying laterally continuous sheet-like sedimentary layers and progressive facies transitions over distances of kms. The influence of halokinesis on sedimentation patterns was minor, and only impacted thickness trends and depocenters localization. The second unit records salt evacuation at the surface with the presence of salt-wall derived detritus, the rapid downbuilding and a increase of sand-rich facies proportions. The stratal pattern is characterized by sheet like layers, laterally discontinuous over distances of 300 to 600 meters downdip to the salt wall. Topographically elevated salt walls likely amplified tidal currents, implying sand-rich facies accumulation along the salt wall margin. The halokinesis influence on sedimentation, thickness trends and depocenter localization was significant. The third unit records the end of the salt evacuation stage, marking a brutal decrease of sand-rich facies , likely controlled by regional controls such as eustacy and tectonics. The influence of halokinesis on sedimentation patterns, thickness trends, large-scale geometries and depocenter localization was significant. Our work indicates that distinguishing these large-scale tectonostratigraphic units and their characteristics is of prime importance to understand the archetypal facies distribution, thickness and stratal patterns along salt structures margins.
... (b) Decrease in the tectonic-generated subsidence during HST stage and consequent decrease in accommodation space; progressively filling-shallowing trend of the sedimentary basin and formation inner ramp deposits with development of the filled to overfilled basin. HST, highstand system tract; TST, transgressive system tract changes; it could, however, also be affected by eustatic sea-level changes (allogenic factor) or prevailing sedimentary process controlling sediment distribution (autogenic factor) in various parts of the depositional system (Folkestad & Satur, 2008;Pomar et al., 2012;Sharafi et al., 2014Sharafi et al., , 2019Zecchin et al., 2006). As mentioned in the previous chapter, the carbonate platform of Tirgan Formation was influenced by wave-induced currents in the middle ramp and tideinduced currents in the inner ramp setting (mainly shoal) (Figure 9) (Figures 13-15); see models proposed by Catuneanu (2006) and Neto and Catuneanu (2010). ...
... The sheltered lagoon zone, which is protected from high-energy to normal marine currents and waves by the shoals, is commonly recognized by muddominated facies having low diversity and a prevalence of allochems(Barnaby & Ward, 2007;Flügel, 2010;Pomar, Bassant, Brandano, Ruchonnet, & Janson, 2012). The grain-supported facies (FB3-FB5) consist of coarse-grained skeletal and non-skeletal elements, dominated by ooids, intraclasts, and diverse marine fauna (echinoderms, serpulids, brachiopods, elongated orbitolines); they periodically display water circulation or connection to open waters(Bayet-Goll et al., 2014Bover-Arnal et al., 2009;Palma, L opez-G omez, & Piethé, 2007;Sharafi et al., 2012Sharafi et al., , 2021Sharafi, Mahboubi, Moussavi-Harami, Mosaddegh, & Gharaie, 2014). FB3-FB5 facies were deposited in the semi-restricted part of the lagoon environment, given the presence of microboring and micrite coating, diverse ...
The carbonate‐dominated successions of the Tirgan Formation (Latest Barremian‐Early Aptian) in the Kopet‐Dagh Basin (Iran) were studied to decipher the tectonic and eustatic sea‐level effects, as well as the autogenic influence on lateral and vertical facies changes, depositional environment, and sequence stratigraphy of the tide‐wave‐dominated sediments at the northern margin of the Neo‐Tethys Ocean. Fourteen facies were identified in the studied sequences, here grouped into five facies associations according to the depositional setting: tidal flat (A), lagoon (B), shoal (C), shallow open‐marine (D), and deep‐open marine (E). A third‐order depositional sequence, including a transgressive system tract (TST) and a highstand system tract (HST) was also identified, along with several medium‐ and small‐scale, thickening‐ and shallowing‐upward cycles (parasequences). The development of the depositional sequence and parasequences of the studied successions of the Tirgan Formation were controlled by interactions between allogenic (tectonic and eustasy) and autogenic factors (wave and tidal hydrodynamic regimes). The allogenic factors mainly affected the stacking pattern and parasequence development of the TST deposits in the lower part of the Tirgan Formation, characterized mainly by the deep‐open marine association. Autogenic factors display a main influence on the stacking pattern and formation of the HST deposits and related parasequences, characterized by shallow open‐marine‐lagoon–shoal associations developed in the upper part of the Tirgan Formation. The tectono‐sedimentary model for the evolution of the tide‐wave‐dominated carbonate platform represented by the Tirgan Formation may be useful for further studies on sedimentary basin evolution or palaeogeographic reconstructions of the Neo‐Tethys margin.
... In the last years, ichnological features and particularly ichnofabrics have been widely applied as a tool in paleoenvironmental reconstructions (e.g., Taylor and Goldring 1993;Taylor et al. 2003;Bayet-Goll et al. 2015, 2018a, 2018bSharafi et al. 2016Sharafi et al. , 2019Sharafi et al. , 2020Sharafi et al. , 2021 give few examples). The main controls on the distribution, diversity and behaviour of the trace makers, and then on ichnofabric features in marine environments are considered to be nutrient supply, hydrodynamic energy, salinity, rate of sedimentation, pore space, bottom water oxygenation, substrate consistency and water turbidity (Seilacher 1967;Bromley and Ekdale 1984;Gingras et al. 2008;Sharafi et al. 2014Sharafi et al. , 2016Sharafi et al. , 2021Bayet-Goll et al. 2020;Rodríguez-Tovar et al. 2019, just to give few examples). Herein, integrative ichnological and sedimentological analyses reveal a valuable strategy in sedimentary basin research, improving paleoenvironmental (ecological and depositional) interpretations. ...
... In the studied section Chondrites is characterised by small straight to slightly curved branched burrows with burrow tunnels diameter of 2.5-4 mm and a burrow system width of 50-70 mm and different infilling sediments (composition and colour) with respect to the host rock. Chondrites as a fodinichnion trace fossil is commonly interpreted as associated with low oxygen-level conditions in low energy depositional settings like lower shoreface, offshore, prodelta and outer ramp to basin (Fürsich 1998;Uchman and Krenmayr 2004;Sharafi et al. 2014Sharafi et al. , 2021Rodríguez-Tovar et al. 2019;Reolid and Reolid 2020). Chondrites is also considered to be related to the activity of the chemo-autotrophic organisms (Seilacher 1990;Fu 1991; See recent review in Baucon et al. 2020). ...
... Taenidium is a typical component of the Scoyenia ichnofacies, being indicative of a transitional zone between terrestrial and nonmarine aquatic environments. It is also associated with shallow marine deposits (Sarkar et al. 2009;Rodríguez-Tovar et al., 2016;Sharafi et al. 2021), although has also been reported from deep marine, lower to middle shoreface and middle to outer ramp environments (Sharafi et al. 2014;Bayet-Goll et al. 2018b). ...
This study integrates ichnological and sedimentological data to interpret depositional environments in the carbonate sediments of the Mobarak Fm. (Lower Carboniferous) in the Alborz Mountains of northern Iran. Seven ichnofabrics including Thalassinoides (Th), Zoophycos‒Phycosiphon (Zo-Ph), Skolithos‒Thalassinoides (Sk-Th), Zoophycos‒Diplocraterion (Zo-Di), Thalassinoides‒Rhizocorallium (Th-Rh), Zoophycos‒Arenicolites (Zo-Ar) and Chondrites‒Phycosiphon (Ch-Ph) have been identified in the studied succession. Th ichnofabric is characterised by the dominance of the deposit-feeding trace fossils, revealing low sedimentation rate and activity of the organisms in a loose substrate. Vertical succession of the Zo-Ph, Sk-Th and Zo-Di ichnofabrics indicates change in the firmness of the substrate. Th-Rh and Zo-Ar ichnofabrics reveal two different energy phases including a lower energy condition with the activity of deposit-feeders and a higher energy phase identified by the activity of suspension-feeders. Ch-Ph ichnofabric is characterised by low diversity and low abundance of trace fossils that were identified in black, limy shale, displaying a long lasting outer ramp setting with low energy, low sedimentation rate, and dysoxic-anoxic conditions of the substrate. Ichnological features of the Mobarak Fm. are controlled by subsidence-inducing changes in the accommodation space of the depositional system dictating variations in paleoenvironmental conditions such as oxygen levels and hydrodynamic energy.
... Environmental conditions (i.e., ecological and depositional) such as energy level, salinity, light, turbulence and nutrient supply associated with fluvial, wave and tide processes significantly influence proximal shallow-marine environments (e.g., delta, estuary, shallow carbonate systems), the living biota therein, and even effect the variably different settings of a concrete distinct sedimentary environment (e.g., Fürsich 1998;Zonneveld et al. 2001;Buatois et al. 2002;Rodríguez-Tovar et al. 2007;Sarkar et al. 2009;Dashtgard et al. 2010;Gingras et al. 2012;Sharafi et al. 2012Sharafi et al. , 2013Sharafi et al. , 2014Sharafi et al. , 2016Bayet-Goll et al. 2018, 2020. For example, in the tide-dominated estuary and delta systems, repeated salinity changes, especially in the delta plain and distributary channels, and a generally high sedimentation rate, especially in the distributary channels and delta front, tend to reduce the diversity and abundance of tracemakers and then trace fossils (Sharafi et al. 2014Bayet-Goll et al. 2016. ...
... Environmental conditions (i.e., ecological and depositional) such as energy level, salinity, light, turbulence and nutrient supply associated with fluvial, wave and tide processes significantly influence proximal shallow-marine environments (e.g., delta, estuary, shallow carbonate systems), the living biota therein, and even effect the variably different settings of a concrete distinct sedimentary environment (e.g., Fürsich 1998;Zonneveld et al. 2001;Buatois et al. 2002;Rodríguez-Tovar et al. 2007;Sarkar et al. 2009;Dashtgard et al. 2010;Gingras et al. 2012;Sharafi et al. 2012Sharafi et al. , 2013Sharafi et al. , 2014Sharafi et al. , 2016Bayet-Goll et al. 2018, 2020. For example, in the tide-dominated estuary and delta systems, repeated salinity changes, especially in the delta plain and distributary channels, and a generally high sedimentation rate, especially in the distributary channels and delta front, tend to reduce the diversity and abundance of tracemakers and then trace fossils (Sharafi et al. 2014Bayet-Goll et al. 2016. In shallow carbonate systems, in spite of the prevalence of normal marine conditions, such as normal salinity, considerable decrease in diffusion of the fresh water from hinterland and low terrigenous sediment supply, the activity of the tidal and/or wave-induced currents and/or a generally high hydrodynamic energy level can exert physic-chemical stresses on the living tracemakers community determining changes in their diversity, abundance, activity and/or behavior in different parts of depositional environment, such as lagoon, sandy shoals, mid-and outer ramp (Bayet-Goll et al.2016. ...
... The thick package of the green-gray shale (FA) of the lower part of the formation with a few marine fossils (brachiopods and bivalves) displays predominant stable and low energy conditions in the deepest part of the basin below storm wave base (SWB) (Fig. 10) (Bassi and Nebelsick 2010;Sharafi et al. 2012;Moosavizadeh et al. 2015), occasionally disturbed by storm waves which are represented by intercalated thin-bedded sandy limestone (sandy intraclast floatstone). In absence of generalized evidence of high-energy and low oxygen conditions affecting benthic habitat, the sporadic nature of the fossils and the lack of trace fossils in this association probably reflect low nutrient supply to sea bottom in this part of the basin (Sharafi et al. 2014;Bayet-Goll et al. 2016). ...
This study integrates ichnological and sedimentological data to interpret depositional environments of the carbonate sediments of the Tirgan Formation (Lower Cretaceous) in the eastern Kopet-Dagh Basin, north-east Iran. Lithofacies analysis shows that these sediments were deposited in inner ramp, middle ramp and offshore (outer ramp) environments. Five ichnoassemblages are identified in the sediments that consist of Thalassinoides, Thalassinoides–Rhizocorallium, Planolites–Rhizocorallium, Arenicolites–Diplocraterion, and Arenicolites. Th, Th-Rh and Pl-Rh with low diversity and abundance of the trace fossils formed during waning phase of storms in a predominantly medium to high-energy hydrodynamic regime. High sedimentation rate and mobile substrate condition featuring a shallow-marine setting. Ar–Di ichnoassemblage, consisting of horizontal and vertical traces of deposit and suspension feeders, respectively, portray two different phases. A predominantly high energy phase with instable substrate is displayed by the vertical traces, while a minor omission phase, associated with a decrease in sedimentation rate or non-deposition, is indicated by the horizontal structures. Arenicolites ichnoassemblage with low bioturbation index and low ichnodiversity is related to a semi-sheltered area of lagoon environments with periodically marine water circulation. The study of the ichnological attributes in the studied successions indicates the presence of a shallowing up-ward trend in the storm‒tide-dominated ramp sequence. Ichnoassemblage development is largely controlled by depositional and ecological conditions, e.g., the stability of substrate, hydrodynamic regime (wave and tide), and food abundance, which altogether control the substrate colonization. Based on an integrated ichnological and sedimentological approach, we characterize the depositional environment, deciphering allogenic and autogenic environmental controls on the trace fossil distribution on a passive margin depositional setting.
... Achieved results in this research provide valuable information of the distribution of the bio/ facies associations, lifestyle and manner of the prevailing organisms (benthic, feeding and suspension feeding) and their reaction to the dominated sedimentary processes and changes in the sedimentary environment conditions in the various parts of the carbonate systems and their controlling factors. ( Sharafi et al., 2012( Sharafi et al., , 2013Bayet-Goll et al., 2018 Sharafi et al., 2012Sharafi et al., , 2013Sharafi et al., , 2014Sharafi et al., , 2016Bayet-Goll et al., 2016, 2018 .) ...
The Carboniferous sedimentary sequence at the Mighan section with 450 m thickness are studied with respect to the microfossils specially foraminifers and biozones. Based on the stratigraphic distribution of the index species, the age of the Mobarak Formation in the studied section is identified as the Late Tounaisian (Ivorian)- middle Visean (Moliniacian). With studying and identification of the foraminifers, Tounaisian- Visean stages boundary and their evolution trend until the end of the Lower Carboniferous sedimentation are studied. Five foraminifer biozones, GZ1-GZ5, are introduced for the Mobarak Fm. in the studied locality, which can be compared to the Belgium and the north France biozones, respectively. The most important ecologic and environmental factors that directly affect the distribution, abundance and lifestyle and the mode of preservation of biota and trace fossils are consist of oxygen level, light, salinity and nutrients during the deposition of the carbonate sediments of the Mobarak Formation. Achieved results in this research provide valuable information of the distribution of the bio/ facies associations, lifestyle and manner of the prevailing organisms (benthic, feeding and suspension feeding) and their reaction to the dominated sedimentary processes and changes in the sedimentary environment conditions in the various parts of the carbonate systems and their controlling factors.
... Arenicolites is rather common throughout the Phanerozoic (H€ antzschel 1975). It was documented from the Upper Devonian of Iran (Sharafi et al. 2014) and USA (New York State: Corbo (1979) and West Virignia: Bjerstedt (1987)). Arenicolites isp. ...
... The specimens have been collected in the grey micaceous and dolomitic sandstone (U32) and in the grey micaceous sandstone from the Heid des Gattes quarry and in the greenish micaceous and arkosic siltstone of the N eblon quarry (alluvio-lagoonal and tidal lagoonal environments after Thorez and Dreesen 1986). Diplocraterion is known from the Upper Devonian of Ireland (Higgs and Higgs 2015) and Iran (Sharafi et al. 2014). Fillion and Pickerill (1990) provided a summary of the occurrences of the Diplocraterion ichnospecies throughout the Phanerozoic. ...
... The specimens have been collected in the greenish micaceous and arkosic siltstone from the Heid des Gattes quarry, in the reddish micaceous and arkosic sandstone and the grey micaceous and calcareous sandstone from the Thomas quarry (tidal lagoonal and alluvio-lagoonal environments after Thorez and Dreesen 1986). Various ichnospecies of Helminthopsis are known from the Upper Devonian of Iran (Sharafi et al. 2014) and Algeria (Bendella and Mehadji 2015). ...
Ichnofossils from the type locality of the Famennian are here described and figured for the first time. The siliciclastic supratidal alluvial to proximal subtidal deposits of S Belgium yield a diverse ichnofauna composed of Arenicolites ispp. (two morphotypes), Chondrites intricatus, Diplocraterion isp., Dolopichnus gulosus, Gordia marina, Helminthopsis isp., Lockeia cordata, L. siliquaria, Palaeophycus tubularis, P. sulcatus, Planolites isp., Protovirgularia obliterata, P. cf. rugosa, P. isp. and Psammichnites implexus. As a whole, these 16 ichnospecies and 11 ichno-genera form the typical assemblage of the Cruziana ichnofacies where Palaeophycus is largely dominant. However, the Belgian Famennian displays a large range of lithofacies corresponding to various environments in which distinct ichnofossil assemblages are identified. Arenicolites isp. collected from sabkha-type primary dolomite indicates the probable colon-isation of hypersaline environment by Arenicolites tracemakers as early as the Late Devonian. The type material of Crossochorda marioni Dewalque, 1881 is revised and attributed to Protovirgularia obliterata and P. cf. rugosa.
... Low sedimentation rate, nutrient-rich with colonization by benthic macrofauna during fair weather intervals. Mainly low-energy hydrodynamic regime where food particles accumulate, in lower shoreface to transition zone lower shoreface-offshore (MacEachern et al., 2010;Sharafi et al., 2014). ...
Pragian to Givetian successions in the Canindé group, Parnaíba Basin (Brazil), present phosphorites, ironstone and organic rich sediments that globally coincide with greenhouse conditions and an increase in continental weathering, ocean oxygen levels and black shale deposition events. These facies are associated with the evolution of the northern Gondwana epeiric sea margin of the Rheic Ocean and can tell us how ocean chemistry changed and the paleoceanographic factors involved in this particular transition of the ocean record. We conducted an integrated study based on sedimentology, sequence stratigraphy, petrography, scanning electron microscopy and X-ray diffraction to understand the paleoenvironmental, stratigraphic and diagenetic controls. Lithofacies stacking patterns indicate that deposition occurred during marine transgressions resulting in four depositional sequences. Late Eifelian and Givetian maximum flooding surfaces are represented by phosphogenesis and francolite precipitation associated with condensed zones. Pragian-Emsian to Givetian ironstones were represented by authigenic coated phosphatic ironsilicate (odinite, chamosite/clinochlore, francolite) and siderite precipitation. These are related to normal regressions under lowstand and highstand systems tract. Oxic waters prevailed and episodic upwelling is interpreted as the source of nutrients that maintained Fe, Si and P supply on a storm-influenced to storm-dominated shelf with an additional source of iron also associated with river discharges. Phosphorite was formed in a stratified ocean, near storm wave base, under anoxic (sulfide reducing bacteria microbial communities) and suboxic conditions (productivity fueled by recycled P). Shallower anoxic conditions (near the fairweather wave base) existed, possible related to a shift in the locus of upwelling, and then resumption to oxic conditions indicate that water column stratification was not a stable feature due to variations in base level, ventilation, terrigenous or marine contribution and progressive microbial degradation. At the beginning of late Eifelian transgression, an event of increased delivery of continental flux and eutrophication can also be proposed. The link between organic-rich intervals and third order black shale events (Daleje, Chotěc and Kačak) suggests that extinction events can be tracked by analyzing sections in South America. Global correlation with ironstone precipitation and organic rich sediments shows that stepped periods of C sink conditions probably contributed to the ocean oxygenation.
