Foraminiferal morphogroups as a tool to approach the Toarcian Anoxic Event in the Western Saharan Atlas (Algeria)

Reolid, Matías; Sebane, Abbés; Rodríguez‐Tovar, Francisco J.; Marok, Abbas

doi:10.1016/j.palaeo.2012.01.034

Cited by 74 publications

(32 citation statements)

References 83 publications

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“…Other fossil groups recovered from the residues used in the micropaleontological survey were gastropods, brachiopods, undifferentiated echinoderms, bivalves, and bryozoans (Table 1). The total number of benthic foraminiferal specimens identifi ed in the present study is signifi cant when compared to other faunas from comparable time intervals, such as those described by Reolid et al (2012), in which about 2,120 specimens were recovered from 22 samples (with 0.5 kg of residue analyzed), and Canales & Henriques (2008), in which 5411 specimens were recovered from 28 samples (with 0.3 kg of residue analyzed).…”

Section: Foraminiferamentioning

confidence: 51%

“…(Table 1). Species of Lenticulina, the second most abundant genus in the studied samples, are also considered r-selected generalists being characteristic of environments with moderate levels of dissolved oxygen (Bernhard, 1986;Koutsoukos et al, 1990;Canales & Henriques, 2008;Reolid et al, 2012). This dominance of r-selected strategists suggests the occurrence of stressing paleoenvironmental conditions (cf.…”

Section: Foraminiferamentioning

confidence: 95%

“…This dominance of r-selected strategists suggests the occurrence of stressing paleoenvironmental conditions (cf. Reolid et al, 2012), probably related to bottom-water oxygen levels.…”

Section: Foraminiferamentioning

confidence: 99%

“…In general terms, it can be suggested that r-selected strategists, such as species of Reinholdella and Epistomina, which are characteristic of oxygen-depleted environments (Sagasti & Ballent, 2002;Ballent et al, 2006;Reolid et al, 2012), dominate the studied assemblages, with special emphasis to Reinholdella sp. (Table 1).…”

Section: Foraminiferamentioning

confidence: 99%

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Benthic Foraminifera and Ostracoda from the Dalichai Formation (Aalenian–Bajocian) at Telma-Dareh, Alborz Mountains, Northern Iran

Kochhann¹,

Bergue

Falahatgar

et al. 2015

Rev. bras. paleontol.

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-Aalenian-Bajocian benthic foraminiferal and ostracode assemblages of the Dalichai Formation (lithologic unit III) at Telma-Dareh, Alborz Mountains (northern Iran) are presented herein. Twenty-four foraminiferal taxa were identifi ed, with the genera Reinholdella, Epistomina and Lenticulina as the dominant taxa. The dominance of r-selected strategists among foraminifera suggests the occurrence of stressing paleoenvironmental conditions, probably related to bottom-water oxygen levels, during the deposition of the studied strata. The foraminiferal assemblages studied herein are similar to other Boreal ones in paleobiogeographic terms. The ostracode assemblages present low abundance, low species richness and poor preservation, which did not allow any identifi cation at species level. A possible record of Majungaella is briefl y discussed due to its paleozoogeographic signifi cance. Cytherella, Paracypris and Pontocyprella are the richest genera with two species each.Key words: benthic foraminifera, ostracodes, Dalichai Formation, Alborz Mountains, Iran. RESUMO -Assembleias de foraminíferos bentônicos e ostracodes do intervalo Aaleniano-Bajociano correspondentes à Formação Dalichai (unidade litológica III), em Telma-Dareh, Montanhas Alborz (norte do Irã) são aqui apresentadas. Vinte e quarto táxons de foraminíferos bentônicos foram identifi cados, sendo os gêneros Reinholdella, Epistomina e Lenticulina dominantes. O predomínio de estrategistas-r entre os foraminíferos sugere a ocorrência de condições ambientais estressantes durante a deposição destes estratos, provavelmente relacionadas aos níveis de oxigênio nas águas de fundo. As assembleias de foraminíferos aqui estudadas são similares a outras descritas para o domínio Boreal. As assembleias de ostracodes apresentam espécimes mal preservados, baixa abundância e baixa riqueza. Um possível registro de Majungaella é brevemente discutido devido ao seu signifi cado paleozoogeográfi co. Cytherella, Paracypris e Pontocyprella são os gêneros mais ricos com duas espécies registradas cada.Palavras-chave: foraminíferos bentônicos, ostracodes, Formação Dalichai, Montanhas Alborz, Irã.

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Section: Foraminiferamentioning

confidence: 51%

Section: Foraminiferamentioning

confidence: 95%

“…This dominance of r-selected strategists suggests the occurrence of stressing paleoenvironmental conditions (cf. Reolid et al, 2012), probably related to bottom-water oxygen levels.…”

Section: Foraminiferamentioning

confidence: 99%

Section: Foraminiferamentioning

confidence: 99%

See 2 more Smart Citations

Benthic Foraminifera and Ostracoda from the Dalichai Formation (Aalenian–Bajocian) at Telma-Dareh, Alborz Mountains, Northern Iran

Kochhann¹,

Bergue

Falahatgar

et al. 2015

Rev. bras. paleontol.

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“…Studies carried out in different sections in the upper Toarcian-lower Aalenian of the Lusitanian Basin, located in the distal, middle and inner part of the platform (Canales andHenriques, 2008, 2013;Canales et al, 2010Canales et al, , 2014Figueiredo et al, 2010a;Henriques and Canales, 2013), confirm this fact, as to this genus corresponds the higher values of relative abundance in almost all the analyzed assemblages. The high values of this genus, corresponding to a lenticular morphogroup (Nagy, 1992;Tyszka, 1994a;Reolid et al, 2008Reolid et al, , 2012Reolid et al, , 2013, indicate that the studied assemblages developed in oxic environmental conditions. This reinforces previous interpretations supported by the taxonomical composition analysis at suborder level.…”

Section: Taxonomical Composition Of the Assemblagesmentioning

confidence: 91%

Foraminifera of the Toarcian-Aalenian boundary from the Lusitanian Basin (Portugal): a paleoecological analysis

Figueiredo

Canales

Henriques

2014

Journal of Iberian Geology

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A detailed study carried out on 37 well preserved benthic foraminiferal assemblages sampled throughout the upper Toarcian-middle Aalenian in two well calibrated sections representing different facies within the Lusitanian Basin (Portugal) -the Maria Pares and the Zambujal de Alcaria sections -allows interpreting the past environmental conditions. Several mathematical indexes related to diversity, which enable establishing the particular conditions to which the assemblages were submitted, were applied. All the studied assemblages are characteristic of the Jurassic carbonate platforms of the Boreal Realm, in which the genus Lenticulina usually dominates. The suborder Lagenina is the most abundant, but taking the second more abundant suborder into account, the comparison between coeval sections in the Lusitanian Basin allows the recognition of a regional gradient ranging from the distal part of the platform (Murtinheira) towards the transitional and proximal parts of the shelf (sections of Maria Pares and Zambujal de Alcaria respectively). The relative abundance values, as well as the obtained data from the diversity indexes indicate that the studied assemblages are relatively abundant and diverse, reflecting general appropriate paleoenvironmental conditions for their development. The detailed analysis of the data allows the identification in both sections of three different episodes, traducing particular environmental conditions: unstable (Mactra Subzone-lower part of the Opalinum Subzone), favorable and stable (lower part of the Opalinum Subzone-upper part of the Comptum Subzone), and unfavorable (upper part of the Comptum Subzone-lower Bradfordensis Subzone). These data are consistent with previous results obtained in the sections of Murtinheira and São Gião, located in the Northern Lusitanian Basin and corresponding to the distal and transitional parts of the platform respectively, and they aimed at contributing to a better understanding of the paleoecological conditions prevailing within the Lusitanian Basin during the Early-Middle Jurassic times.Keywords: Benthic foraminifera, Lower-Middle Jurassic boundary, Portugal, paleoecology, diversity index, Paleoenvironmental gradient Resumen Se ha realizado el estudio detallado de 37 asociaciones de foraminíferos bentónicos bien preservados, registradas en materiales del intervalo estratigráfico Toarciense superior-Aaleniense medio en dos secciones bien calibradas que representan diferentes facies dentro de la Cuenca Lusitánica (Portugal) -Maria Pares y Zambujal de Alcaria -permitiendo realizar interpretaciones de las condiciones paleoambientales. Para ello, se han aplicado varios índices matemáticos relacionados con la diversidad, que permiten establecer las condiciones ambientales concretas en las que se desarrollaron dichas asociaciones. Todas las asociaciones estudiadas son características de las plataformas carbonatadas jurásicas del Dominio Boreal, en las que predominan los representantes del género Lenticulina. El suborden Lagenina es el más abundante,...

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Microfacies and stable isotope features of the Lower–Middle Jurassic carbonate rocks of Western Saharan Atlas (Aïn Ouarka area, Algeria)

2021

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The Jurassic Lower Carbonate Group in the Aïn Ouarka area of Western Saharan Atlas, Algeria, is represented by six formations, from base to top: Hettangian Chemarikh Dolostone, Early Sinemurian–Pliensbachian Aïn Ouarka Limestone, Toarcian Aïn Rhezala Limestone, Aalenian–Late Bajocian Raknet El Kahla Limestone Breccia, Late Bajocian Theniet El Klakh, and Late Bajocian–Bathonian Tifkirt Limestone formations. From the microfacies analysis, six microfacies types (MF1–MF6) have been recognized and grouped into three associations developed during a transgressive–regressive cycle: (a) inner ramp facies association; (b) middle ramp facies association; and (c) outer ramp facies association. The mineralogical analysis of the carbonate rocks reveals that they contain mostly low‐Mg calcite associated with ankerite, pyrite, and other detrital minerals such as quartz, chlorite, illite, feldspar (albite), and a few clay minerals. These minerals could be related to the deep fluid and hydrocarbon circulations during deposition. The isotopic data display a variation of δ13C isotopic values between −5.14‰ and +2.21‰ (VPDB) and between −8.12‰ and −4.95‰ for δ18O values (VPDB). The set of δ13C values is similar to the signature of marine dissolved inorganic carbon. First of all, the positive values of δ13C show that the origin of carbon is not from the organic‐rich zone (microbial zone), but probably derived from pore‐water and/or biogenic carbonate precursors. On the other hand, the negative values of δ13C indicate that the carbon may result from organic sources linked to the sulphate reduction bacteria activity, or by a heightened volcanic and/or hydrothermal activities releasing light carbon (12C). The negative δ18O values are not consistent with marine water ambient temperature, but with a possible influence of diagenesis or increasing of temperature by hydrothermal water. This hydrothermal activity is controlled by synsedimentary faults during the Early Jurassic and related to a late pulse of the Central Atlantic Magmatic Province (CAMP) volcanism and by regional volcanism during the Middle Jurassic (Bajocian–Bathonian).

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Foraminiferal morphogroups as a tool to approach the Toarcian Anoxic Event in the Western Saharan Atlas (Algeria)

Cited by 74 publications

References 83 publications

Benthic Foraminifera and Ostracoda from the Dalichai Formation (Aalenian–Bajocian) at Telma-Dareh, Alborz Mountains, Northern Iran

Benthic Foraminifera and Ostracoda from the Dalichai Formation (Aalenian–Bajocian) at Telma-Dareh, Alborz Mountains, Northern Iran

Foraminifera of the Toarcian-Aalenian boundary from the Lusitanian Basin (Portugal): a paleoecological analysis

Microfacies and stable isotope features of the Lower–Middle Jurassic carbonate rocks of Western Saharan Atlas (Aïn Ouarka area, Algeria)

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