Academia.eduAcademia.edu

Figure 4 – uploaded by Eustoquio Molina

See full PDFdownloadDownload figure
Fig. 4. Stratigraphic distribution of planktic/benthic ratio (P/B) and diversity of planktic and benthic foraminifera

Figure 4 Stratigraphic distribution of planktic/benthic ratio (P/B) and diversity of planktic and benthic foraminifera

Related Figures (19)

Fig. 1. (A) Geological setting of the Betic Cordillera, (B) detailed geological setting of the studied section (star) close to Manilva village, (C) Banos de la Hedionda section includir the lithostratigraphic units, foraminiferal biozones and location of the samples.
Fig. 1. (A) Geological setting of the Betic Cordillera, (B) detailed geological setting of the studied section (star) close to Manilva village, (C) Banos de la Hedionda section includir the lithostratigraphic units, foraminiferal biozones and location of the samples.
Fig. 2. Macroscopic view of the lithostratigraphic units and microfacies. Capas Blancas Member (A) and (B), black radiolaritic shales (C) and (D), and Boquer6én Member (E) and (F). Scale bar 1 mm.
Fig. 2. Macroscopic view of the lithostratigraphic units and microfacies. Capas Blancas Member (A) and (B), black radiolaritic shales (C) and (D), and Boquer6én Member (E) and (F). Scale bar 1 mm.
Count data of planktic foraminifera from the Banos de la Hedionda section.
Count data of planktic foraminifera from the Banos de la Hedionda section.
Fig. 6. Planktic foraminiferal morphogroups and inferred life style including redox and trophic requirements.
Fig. 6. Planktic foraminiferal morphogroups and inferred life style including redox and trophic requirements.
the biconvex trochospiral (e.g., Gyroidinoides globosus, Charltonina australis, Charltonina sp., Gavelinella cenomanica and Gavelinella sp.) and cylindrical elongated morphogroups (e.g., Tritaxia gaultina, Laevidentalina spp., Praebulimina spp. and Marsonella oxycona) dominate (Fig. 10). Pseudospheric forms such as Ammosphaeroidina spp. are also common in the Capas Blancas Member. The epifaunal morphogroups are more abundant than infaunal ones (Fig. 11). A significant increase in the percentages of Charltonina australis (17.4%, BH-17), Gavelinella spp. (22.8%, BH-17) and Glomospira spp. (23.8%, BH-23) has been observed between 1 m and 1.5 m in the Capas Blancas Member (Fig. 10). Boqueron Member, and the Fisher-a index increases from 2.95 to 4.95 (Fig. 4). These values are lower than in the Capas Blancas Member. Assemblages in the Boqueron Member are dominated by biconvex trochospiral (Gyroidinoides beisseli and Gyroidinoides globosus), cylindrical (Praebulimina spp., Tritaxia gaultina and Pleurostomella spp.) and planoconvex trochospiral morphogroups (Stensioeina exsculpta). Infaunal forms are dominant relative to epifaunal ones (Fig. 11, Table 3). The lower part of this member is characterized by high proportions of species that were scarcer in the Capas Blancas Member, such as Gyroidinoides beisseli (24.6%), Praebulimina spp. (35.0%), Stensioeina exsculpta (17.5%), and Pleu- rostomella spp. (5.3%) (Fig. 10). Taxa such as Tappanina sp. (21.0%), Gaudryina spp., Gavelinella spp. and Lenticulina spp. are recorded immediately above the lowermost sample of the Boqueron Member (Fig. 10).
the biconvex trochospiral (e.g., Gyroidinoides globosus, Charltonina australis, Charltonina sp., Gavelinella cenomanica and Gavelinella sp.) and cylindrical elongated morphogroups (e.g., Tritaxia gaultina, Laevidentalina spp., Praebulimina spp. and Marsonella oxycona) dominate (Fig. 10). Pseudospheric forms such as Ammosphaeroidina spp. are also common in the Capas Blancas Member. The epifaunal morphogroups are more abundant than infaunal ones (Fig. 11). A significant increase in the percentages of Charltonina australis (17.4%, BH-17), Gavelinella spp. (22.8%, BH-17) and Glomospira spp. (23.8%, BH-23) has been observed between 1 m and 1.5 m in the Capas Blancas Member (Fig. 10). Boqueron Member, and the Fisher-a index increases from 2.95 to 4.95 (Fig. 4). These values are lower than in the Capas Blancas Member. Assemblages in the Boqueron Member are dominated by biconvex trochospiral (Gyroidinoides beisseli and Gyroidinoides globosus), cylindrical (Praebulimina spp., Tritaxia gaultina and Pleurostomella spp.) and planoconvex trochospiral morphogroups (Stensioeina exsculpta). Infaunal forms are dominant relative to epifaunal ones (Fig. 11, Table 3). The lower part of this member is characterized by high proportions of species that were scarcer in the Capas Blancas Member, such as Gyroidinoides beisseli (24.6%), Praebulimina spp. (35.0%), Stensioeina exsculpta (17.5%), and Pleu- rostomella spp. (5.3%) (Fig. 10). Taxa such as Tappanina sp. (21.0%), Gaudryina spp., Gavelinella spp. and Lenticulina spp. are recorded immediately above the lowermost sample of the Boqueron Member (Fig. 10).
Fig. 8. Percentages of planktic foraminiferal genera across the studied interval.
Fig. 8. Percentages of planktic foraminiferal genera across the studied interval.
Fig. 9. Benthic foraminiferal species in the Los Banos de la Hedionda section: A, Spiroplectammina roemeri (BH-0). B, Plectina pinswagensis (BH-0). C, Ammodiscus sp. (BH-0) D, Arenobulimina sp. (BH-0). E, Lingulina sp. (BH-0). F, Saracenaria sp. (BH-0). G, Hemirobulina sp. (BH-0). H, Tristix sp. (BH-0). I, Stensioeina exsculpta. J—K, Charltonina australis (BH-0) L, Bolivinopsis spectabilis (BH-1). M, Ammosphaeroidina sp. (BH-1). N, Gaudryina pyramidata (BH-3). O—Q, Gyroidinoides globosus (BH-18). R, Gyroidinoides beisseli (BH-18). S—T Valvulineria sp. (BH-24). U—V, Globorotalites sp. (BH-25). W—X, Gyroidinoides subglobosus (BH-88). Scale bars: 0.1 mm.
Fig. 9. Benthic foraminiferal species in the Los Banos de la Hedionda section: A, Spiroplectammina roemeri (BH-0). B, Plectina pinswagensis (BH-0). C, Ammodiscus sp. (BH-0) D, Arenobulimina sp. (BH-0). E, Lingulina sp. (BH-0). F, Saracenaria sp. (BH-0). G, Hemirobulina sp. (BH-0). H, Tristix sp. (BH-0). I, Stensioeina exsculpta. J—K, Charltonina australis (BH-0) L, Bolivinopsis spectabilis (BH-1). M, Ammosphaeroidina sp. (BH-1). N, Gaudryina pyramidata (BH-3). O—Q, Gyroidinoides globosus (BH-18). R, Gyroidinoides beisseli (BH-18). S—T Valvulineria sp. (BH-24). U—V, Globorotalites sp. (BH-25). W—X, Gyroidinoides subglobosus (BH-88). Scale bars: 0.1 mm.
Count data of benthic foraminifera from the Banos de la Hedionda section.
Count data of benthic foraminifera from the Banos de la Hedionda section.
Fig. 10. Stratigraphic distribution of selected benthic foraminiferal species.
Fig. 10. Stratigraphic distribution of selected benthic foraminiferal species.
event within the R. cushmani Biozone reflects an ecological replacement of opportunistic taxa, with Gavelinella as the first colonizer and Glomospira and Praebulimina as the last ones reaching maximum percentage peaks (Fig. 10). Globorotalites sp., Pleurostomella spp. Spiroplectammina roemeri, Glomospira spp. and Praebulimina spp. (samples BH-17 to BH-23), which point to decreased sea-bottom water oxygenation (Fig. 14) (e.g. Gebhardt et al., 2010; Reolid et al., 2015). Gavelinella has been interpreted in the literature as a low-oxygen tolerant genus (Sliter, 1975; Koutsoukos et al., 1990; Gertsch et al., 2010), and it occurs in shales with a high concentration of organic matter (Holbourn et al., 2001). Globorotalites peaked in abundance under stressful condi- tions after the Cretaceous/Paleogene impact event (Alegret, 2007; Alegret et al., 2012). The interpretation of dysoxic conditions is supported by a small peak in the Ugr values (Fig. 12). This minor
event within the R. cushmani Biozone reflects an ecological replacement of opportunistic taxa, with Gavelinella as the first colonizer and Glomospira and Praebulimina as the last ones reaching maximum percentage peaks (Fig. 10). Globorotalites sp., Pleurostomella spp. Spiroplectammina roemeri, Glomospira spp. and Praebulimina spp. (samples BH-17 to BH-23), which point to decreased sea-bottom water oxygenation (Fig. 14) (e.g. Gebhardt et al., 2010; Reolid et al., 2015). Gavelinella has been interpreted in the literature as a low-oxygen tolerant genus (Sliter, 1975; Koutsoukos et al., 1990; Gertsch et al., 2010), and it occurs in shales with a high concentration of organic matter (Holbourn et al., 2001). Globorotalites peaked in abundance under stressful condi- tions after the Cretaceous/Paleogene impact event (Alegret, 2007; Alegret et al., 2012). The interpretation of dysoxic conditions is supported by a small peak in the Ugr values (Fig. 12). This minor
Fig. 11. Relative abundance of benthic foraminiferal inferred microhabitats across the studied interval.
Fig. 11. Relative abundance of benthic foraminiferal inferred microhabitats across the studied interval.
Differentiation of morphogroups according to test shape, and inferred life style compared with previous interpretations (outsoukos et al., 1990; Hart, 1996; Bak et al., 1997) Note: Koutsoukos et al. (1990) for assemblages from oxygen depleted environments across the Cenomanian/Turonian boundary.
Differentiation of morphogroups according to test shape, and inferred life style compared with previous interpretations (outsoukos et al., 1990; Hart, 1996; Bak et al., 1997) Note: Koutsoukos et al. (1990) for assemblages from oxygen depleted environments across the Cenomanian/Turonian boundary.
Table 3 (continued ) geochemical proxies) was also documented across the Toarcian Oceanic Anoxic Event by Reolid et al. (2012a). A significant decrease in the diversity of benthic foraminifera occurs towards the top of the Capas Blancas Member, and is congruent with the progress of the unfavourable conditions at the seafloor.
Table 3 (continued ) geochemical proxies) was also documented across the Toarcian Oceanic Anoxic Event by Reolid et al. (2012a). A significant decrease in the diversity of benthic foraminifera occurs towards the top of the Capas Blancas Member, and is congruent with the progress of the unfavourable conditions at the seafloor.
Fig. 12. Stratigraphic fluctuations of geochemical redox proxies and U- and Mo-based proxies (enrichment factor and authigenic content) The lack of benthic foraminifera in the black radiolaritic shales and the occur sample (BH-4! of the black s ple BH-49 (F relatively dee rence of planktic foraminifera only in the lowermost 9) point to adverse conditions during sedimentation hales. Low-diversity planktic assemblages from sam- ig. 4) are characterized by opportunist taxa from p waters (Muricohedbergella delrioensis, Fig. 6), which indicate poorly oxygenated waters and eutrophic conditions (Fig. 14). Non-opportunist intermediate-dwellers (Praeglobo- truncana) and 2002) have al abundant Marginotruncana (K-strategists; Petrizzo, so been identified in this sample, whereas no deep- dweller specialists such as Rotalipora and Thalmanninella have been observed. The fact that Marginotruncana sigali first occurred in the lower part of the black radiolaritic shales is difficult to interpret. We argue that this species, which was considered as a specialist taxon by Pet rizzo (2002), may have been adapted to oxygen-
Fig. 12. Stratigraphic fluctuations of geochemical redox proxies and U- and Mo-based proxies (enrichment factor and authigenic content) The lack of benthic foraminifera in the black radiolaritic shales and the occur sample (BH-4! of the black s ple BH-49 (F relatively dee rence of planktic foraminifera only in the lowermost 9) point to adverse conditions during sedimentation hales. Low-diversity planktic assemblages from sam- ig. 4) are characterized by opportunist taxa from p waters (Muricohedbergella delrioensis, Fig. 6), which indicate poorly oxygenated waters and eutrophic conditions (Fig. 14). Non-opportunist intermediate-dwellers (Praeglobo- truncana) and 2002) have al abundant Marginotruncana (K-strategists; Petrizzo, so been identified in this sample, whereas no deep- dweller specialists such as Rotalipora and Thalmanninella have been observed. The fact that Marginotruncana sigali first occurred in the lower part of the black radiolaritic shales is difficult to interpret. We argue that this species, which was considered as a specialist taxon by Pet rizzo (2002), may have been adapted to oxygen-
Fig. 13. Stratigraphic distribution of %CaCOs, total sulphur (TS), total organic carbon (TOC), and geochemical palaeoproductivity proxies (Ba/Al and P/Ti ratios).
Fig. 13. Stratigraphic distribution of %CaCOs, total sulphur (TS), total organic carbon (TOC), and geochemical palaeoproductivity proxies (Ba/Al and P/Ti ratios).
Related topics:
Oceanic Anoxic EventsTrophic ConditionsCenomanian/Turonian boundary event (CTBE)Redox conditions
580 California St., Suite 400
San Francisco, CA, 94104
© 2025 Academia. All rights reserved